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Hypothesis: Fused filament fabrication (FFF) method is widely used in additive manufacturing due to its benefits, such as ease of use, cost-effectiveness, and availability. The mechanical properties of polylactic acid (PLA) printed by the FFF method can be significantly improved by combining them with nanomaterials such as nanoclay and optimizing the printing process parameters such as printing temperature and raster angle.Methods: In order to investigate and optimize the multi-objective 3D printing process of PLA nanocomposite samples reinforced by nanoclay, the response surface method (RSM) was used as one of the methods of design of experiments. Nozzle temperature (190, 210 and 230°C), raster angle (0, 45 and 90°) and nanoclay weight percentage (0, 2 and 4% by wt) were studied to optimize output responses. Melt mixing of PLA with nanoclay particles was done using a twin-screw extruder machine and a granulator machine. The composite granules of PLA were prepared with 2 and 4% (by wt) of nanoclay. The prepared composite granules were entered into a single-screw extruder and composite filaments were produced.Findings: The analysis of parameter participation in the density data reveals that the weight percentage of nanoclay and the nozzle temperature exhibit the most substantial influence, while raster angle has the least impact. Conversely, when considering tensile strength results, the weight percentage of nanoclay is the dominant factor, while the interaction between the weight percentage of nanoclay and raster angle has the smallest influence among the parameters under investigation. The multi-objective optimization results revealed that the optimal process conditions to achieve maximum strength are a nanoclay weight percentage of 4% (by wt), a nozzle temperature of 230°C, and a raster angle of about 25.5°. The tensile strength of the parts produced is 33.78 MPa, and their density is at least 1.089 g/cm3.

Hypothesis: The technology of preparing materials with desired dielectric constants is used in designing and manufacturing telecommunication equipment. Foaming of the polymers is an effective method to reduce their dielectric constant further, as the influence of the microstructural characteristics of the expanded polystyrene foams is important for their dielectric characteristics and mechanical properties. This article focuses on the effect of cell wall thickness of the expanded polystyrene foams on their dielectric constant, loss factor, hardness and resilience.Methods: Many samples of the expanded polystyrene foam with different porosity and overall thickness values were prepared using a specific thermal procedure in a programmable oven. At first, the physical properties such as density and porosity of the expanded polystyrene foams were measured. Next, their microstructural characteristics such as the average cell wall thickness of the expanded polystyrene foams were investigated using a scanning electron microscope. The dielectric constant and loss factor of the samples were assessed with a vector network analyzer with a lens horn antenna. The mechanical properties of the expanded polystyrene foams were evaluated according to Shore D hardness, and the value of mechanical energy stored in them was measured by a resilience tester.Findings: By increasing cell wall thickness in samples at equal overall thickness, the dielectric characteristics such as dielectric constant and dielectric loss factor increase by 12% and 53%, respectively. Moreover, the mechanical properties such as hardness and resilience reveal an increase of 40 and 42%, respectively, due to the increase of cell wall thickness in samples at the same overall thickness. While the dielectric constant and the dielectric loss factor decrease with the reduction of the overall thickness at the same cell wall thickness, the variation of the overall thickness depicts no effect on the hardness and resilience.

Traditional anti-corrosion coatings only act as a passive barrier on the metal substrate and have no active protective function if the coating on the surface is damaged. Recent smart anti-corrosion coatings can greatly increase the lifespan of the coating. On the other hand, self-healing technology in polymer coatings is a preventive method to progress of corrosion process on the surface of metals. This technique has been developed in order to prevent the growth and propagation of cracks in the early stages and to repair the damage automatically without external intervention. The increasing trend of published scientific articles shows that the use of anti-corrosion smart polymer coatings with self-healing capability has received much attention. In this type of coatings, corrosion inhibitors and healing agents can be loaded together or separately in spherical or nanofiber micro-carriers. In the case of damage of the coating surface, the anti-corrosion as well as healing processes trigger simultaneously to prevent the corrosion progress of the metal surface. The purpose of this study is to review novel epoxy-based coatings with self-healing and anti-corrosion properties. For this purpose, the self-healing mechanisms, methods of implementation of self-healing materials and anticorrosion agents on the coating have been reviewed and categorized. The use of polymer microcapsules with core-shell structures in the form of spherical particles or electrospun nanofibers in self-healing coating has been described. Various nanofiber systems have been classified in terms of the location of restorative and anticorrosion materials, the type of polymer shell and core materials, the electrospinning methods of nanofibers, and the method of dispersing within the coatings, for simultaneous anti-corrosion and self-healing properties. Finally, the recent studies on the coatings containing conductive and/or green nanofibers have been reviewed.

Perovskite solar cells (PSCs), despite the stability challenges they face, have made significant progress. It is predicted that this trend will continue due to the progress in composite engineering and the materials that make up the layers. It is expected to continue to achieve high performance and long-term stability in these cells. One of the key components and layers in PSCs is “electron transporting material” (ETM), playing a crucial role in electron transfer, extraction, and cell efficiency. ETMs are categorized into various types based on their constituent materials, including inorganic, organic, and polymer-based ETMs. Polymeric ETMs are of particular importance due to their unique properties and considering the limitations in other types of ETMs. Fullerene derivatives, which are organic ETMs, lack adequate electron mobility and solubility. However, in polymeric ETMs, the ability to connect different functional groups to their central core creates significant changes in the photovoltaic parameters of the cell. By choosing polymeric ETMs, potential advantages such as high electron mobility, easy purification, suitable solubility for processing during layer deposition, and desirable stability can be achieved. Polymeric ETMs with various central cores such as naphthalenediimide (NDI), perylenediimide (PDI), and bithiopheneimide (BTI) have been widely used in reverse PSCs due to their high electron mobility and the absence of additives. Among them, the highest efficiency (20.43%) relates to a cell containing the PDI-core polymer PPDIN6. Additionally, researchers use n-type polymers to modify, create effective interlayer connections, and improve the photovoltaic parameters of reverse PSCs. This review article highlights that the selection of polymeric ETMs along with specific central cores can lead to meaningful changes, resulting in desirable performance and stability in PSCs.

Hypothesis: Fibers with low melting point have high bonding strength with other fibers, and in addition, they have a controllable melting temperature and good processability. Currently, these fibers are used in production of non-woven fabrics for textile, medical and agricultural applications. In this study, melt spinnability of two grades of low melting point co-polyester in high speed spinning has been investigated. Also, structural, rheological and physical properties of the resulting filament yarn have been studied.Methods: The properties of polymeric chips were investigated, and for this purpose, differential scanning calorimetry analysis, melting point determination test, drying conditions and rheological analysis were carried out. Then filament yarns produce, and their properties were investigated. Linear density, yarn tensile properties, melting temperature, thermal shrinkage, rheological properties, X-ray diffraction, differential scanning calorimetry, optical birefringence index and surface longitudinal cross-section were analyzed.Findings: The results of thermal analysis of polymeric chips with low melting point analysis showed that the used polymers are not crystalline and their melting point is about 176°C. The temperature 60°C for 24 h is enough to dry the chips, and the melt of these materials has a viscous behavior. Both low melting point co-polyesters grades were spun by melt spinning process. But only one of them had a suitable spinnability. After melt spinning, as-spun yarns were drawn because it was necessary to produce no brittle filaments. The results of the investigation of the properties of as-spun and drawn yarns showed that the best conditions for melt spinning of the copolyester yarn is as follows: the optimum extrusion temperature of 230°C and the take-up speed of 2500 m/min. All samples have no crystalline region, the polymer chains are oriented, and the phenomenon of rheological instability, such as melt fracture during melt spinning, which disrupts the cross-sectional area of the fibers, has not occurred.

Hypothesis: first, poly ether sulfone (PES)-based nanofiltration (NF) membranes were prepared through the phase inversion-immersion precipitation technique. Then, the surface of the membranes made of polymethyl methacrylate (PMMA)-graphene oxide nanoplates (GO NPs) was modified using dip-coating technique. The effect of the active coating layer on the morphology, physical-chemical properties, and antifouling performance and separation ability to remove metal ions from wastewater was studied.Methods: The properties of prepared membranes were studied by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) analysis. Also, the effect of the formed active layer on the physio-chemical properties of the membrane including water contact angle, water content, flux and sodium sulfate rejection, porosity, mean pore size, heavy metal rejection and anti-fouling performance was investigated. Findings: The obtained results revealed that the surface-modified membrane with 1 % (by wt) MM-0.5% (by wt) GO-NPs had a more appropriate separation performance and better antifouling properties compared to other membranes. SEM images of the cross-sectional area of the membranes showed the formation of a relatively uniform layer on the membrane surface, which became more dense with increase in the amount of GO-Nps. The performance of the modified membrane in the removal of Cu and Cr heavy metal ions was also evaluated and compared with the pristine membrane. The removal percentage of Cu and Cr ions was 51.4% and 49.3% for the neat membrane, whereas it was 81.7% and 75.3% for the superior modified membrane, respectively. Moreover, the total fouling resistance was measured to be 23% for the virgin membrane, while it was 13.2% (Pvalue

Hypothesis: Considering water quality problems and strict rules established for drinking water treatment, there is an urgent need to use more effective and economical methods to remove natural organic matter from water. Meanwhile, membrane processes are one of the effective methods to remove these pollutants. In this way, in order to prepare a membrane with a high ability to remove pollutants, in the present study, the production and optimization of poly(vinyl chloride) (PVC) membranes with poly(ethylene glycol) (PEG) additives have been carried out.Methods: PVC microporous membranes were prepared by nonsolvent-induced phase separation method. Influential parameters in the membrane fabrication, including the concentration of PVC and PEG and the composition of the coagulation bath were optimized using the response surface methodology (RSM). Meanwhile, tensile strength and porosity were considered as responses.Findings: The obtained results showed that all the membranes had an asymmetric structure with finger like pores. It was also found that the tensile strength of the membranes increased with the increase in PVC concentration. The lowest tensile strength was related to the membrane made of 10.30% (by wt) of PVC, while the membrane made of 18.7 % (by wt) of PVC had the highest tensile strength. In addition, for the optimum membrane in which the concentration of PVC was 17.52% (by wt), the concentration of PEG was 5.87% (by wt) and the volume fraction of ethanol in the coagulation bath was 0.27, the tensile strength and porosity of the membranes were obtained as 5 MPa and 80.57, respectively. Furthermore, in the following, titanium dioxide nanoparticles (TiO2) were used to prepare the composite membrane under the aforementioned optimum conditions. The obtained results showed that the optimum membrane containing 2% (by wt) of nanoparticles had the highest humic acid separation efficiency with a value of 80%.

Today, the economic growth of countries depends on the supply of energy resources. In most countries, these resources include coal, oil, natural gas, and nuclear energy. However, the use of these resources faces various challenges, including the depletion of fossil fuel resources, environmental pollution and an escalating price. In order to reduce global reliance on finite natural resources and environmentally destructive fuels, many efforts have been made to replace them with renewable resources, such as solar energy, water, wind, and etc. Batteries are one of the most potential technologies for this purpose. Lithium batteries have become increasingly important energy storage systems in our daily lives, which play a significant role in electronics and electric vehicles. However, their practical applications are plagued by the safety issues from liquid electrolytes, especially when the batteries are exposed to mechanical, thermal, or electrical abuse conditions. Polymer electrolytes are being proposed as an alternative liquid electrolyte for building safer lithium batteries. In this review article, polymer electrolytes are divided into two large categories of solid polymer electrolytes and gel polymer electrolytes. The characteristics and properties of solid polymer electrolytes and gel polymer electrolytes are presented at the first. Then, the recent progress of common polymers, namely, poly(ethylene oxide), poly(methyl methacrylate), polyacrylonitrile, poly(vinylidene difluoride) and poly(vinylidene fluoride-hexafluoropropylene) copolymer, biopolymers (cellulose, polyurethane, polycaprolactone), polycarbonate and polysiloxanes as polymer host of polymer electrolytes will be discussed. Finally, we will discuss remaining challenges and future perspectives of the polymer electrolytes for high-performance lithium batteries. We hope that this paper can provide useful information for the development of new polymer electrolytes with excellent properties for use in lithium batteries.

Hypothesis: This study constituted the effect of chitosan-zeolite active nanocomposite layer formation on the morphological, physico-chemical and separation properties, as well as the anti-fouling performance of the polyethersulfone-based nanofiltration membrane.Methods: The nanofiltration-based membrane was prepared by phase inversion method and its surface was modified through the dip-coating technique in the polymeric solution. The properties of the prepared membranes were investigated by Fourier transform infrared (FTIR) analysis, scanning electron microscopy (SEM), 3D surface images, contact angle, water content, pure water flux, salt and heavy metal rejection and anti-fouling performance techniques. Findings: The FTIR analysis results confirmed the formation of the chitosan/zeolite nanocomposite layer on the polyether sulfone-based membrane. Moreover, the scanning electron microscopy images of the surface and cross-section of the prepared membranes showed the formation of an active layer on the membrane surface. The results of surface analysis showed that the surface modification reduced the surface roughness of the membrane. In addition, the use of zeolite nanoparticles on the surface layer caused to an increase in the membrane water content. The pure water flux of bi-layer modified membrane showed an increase in water content of > 54% compared to the virgin membrane. The sodium sulfate salt rejection was measured > 70% for the bi-layer modified membrane. The chromium rejection increased from 69% for the virgin membrane to > 95% for the modified bi-layer membrane. The water contact angle results exhibited that the surface hydrophilicity of the membrane increased with the surface modification. The modified membranes showed superior antifouling ability as the flux recovery ratio increased from 85% to 93.6% and the irreversible resistance decreased considerably to 6.4%.

Hypothesis: In recent years, scientists and researchers have been looking for new and advanced materials for use in various fields, including drug delivery and biotechnology. One of the attractive materials that has been considered in this field is chitosan-based bionanocomposite hydrogel beads. Chitosan-based bionanocomposite hydrogel beads have attracted attention as carriers in drug delivery systems due to their inherent properties such as excellent biocompatibility, high swelling, and high storage capacities.Methods: First graphene quantum dots (GQDs) were prepared by the pyrolysis method, and then their magnetic properties were obtained using iron nanoparticles (MGQD). Next they were coated with chitosan hydrogel (CS-MGQD) and finally loaded with methotrexate (MTX/CS-MGQD). This unique combination of the properties of chitosan hydrogel, the magnetic properties of graphene quantum dots, and the ability to adjust drug release has been able to create an important milestone in the field of drug delivery research and the compatibility of drugs with the biological environment. Through various analyses, including FTIR to analyze the spectra of the functional groups, XRD to identify the crystal structure, and SEM to examine the morphology of the samples, the success of the synthesis and formation of the desired compound was confirmed.Findings: The fabricated CS and CS-MGQD hydrogel beads were loaded with about 84% and 64% MTX, respectively. The results of the swelling behavior and drug release behavior showed that the hydrogel beads experience pH-dependent swelling and release of MTX. In addition, investigating the effect of MGQD concentration on swelling behavior and drug release showed that CS-MGQD has favorable stability and controllable drug release in an acid environment. Also, the Weibull kinetic model was found to be the best-fitting model for the release of MTX from CS-MGQD at pH 5. These findings suggest that the prepared magnetic bionanocomposite hydrogel beads have a good potential for pH-sensitive implantable drug delivery in the treatment of cancerous tissue.

Hypothesis: One of the existing challenges in the foam production industry is to achieve the desired mechanical and thermal insulation properties required, which are directly related to cellular density, size, and distribution of bubbles. Therefore, predicting the bubble size distribution in each foam production system significantly contributes to the final properties of the desired foam. Nucleation, growth, coalescence of bubbles, and their final stabilization are influential stages in the ultimate properties of the foam that should be considered in predicting the bubble size distribution and laboratory testing phase.Methods: Initially, a modified classical nucleation model was used for predicting cell nucleation, and then a population balance model was employed to predict the size distribution of bubbles in a batch system for the production of polystyrene foam. The modeling of this process was one-dimensional, and changes in bubble diameter were included as the characteristic variable of the system's equations. The foam production stage was carried out at temperatures of 70°C, 90°C, and 110°C, under a pressure of 20 MPa, and the consolidation stage was performed within 0.1 s and 1 s and without consolidation. To calculate the average cell size and size distribution, SEM images and software tools such as Axiovision.v4.82.SP2 and SPSS 26 were used, and the results were compared with the modeling outcomes.Finding: Using the bubble size distribution obtained from modeling, the average bubble size at a saturation temperature of 70°C and a consolidation time of 1 s was 4.3 µm. With an increase in temperature from 70°C to 90°C, the average bubble size increased to 36.7 µm due to the higher rate of gas diffusion into the bubbles. With an increase in the amount of gas in polystyrene, the free volume increased, and glass transition temperature decreased. At 110°C, the average size of bubble cells increased to 78.1 µm. Since this temperature was higher than the glass transition temperature of polystyrene, in addition to the high gas diffusion rate into the bubble cells, the growth process did not stop, and gas diffusion and coalescence between the bubbles continued. Finally, the model predictions were compared with experiments under various conditions and demonstrated acceptable agreement.

Unsaturated polyester resins (UPRs) including ortho, iso, bisphenolic and vinylester are the most widely used thermosetting polymeric resins in the form of coating and matrix in the industry, making up around three quarters of all thermoset resins used in the industry. The major advantages of UPRs include low cost, low viscosity, good mechanical properties and chemical resistance, lightness, low moisture absorption, curing without the formation of volatiles, and simple processing with conventional processing methods. UPRs have been used in a wide variety of applications including composites, coatings, sealants, chemical and fuel storage tanks, and high-performance components for the construction, marine and land transportation, and electrical industries. However their high shrinkage after curing, low fire resistance and environmental pollution due to volatile styrene have limited their use. In the past decades, the use of nanofillers in polymers to form polymer nanocomposites has attracted attention due to the ability to combine the advantages of nanofillers and polymers. In addition, the development of nanocomposites of UPRs has made these resins desirable for current and emerging applications that require high specific strength, electromagnetic shielding and improved thermal stability. However, due to the high tendency of nanoparticles to agglomerate, the main challenge in the preparation of nanocomposites is to achieve a homogeneous distribution of nanofillers in the matrix, which is the main key to achieving the desired properties. Therefore, the aim of this study is to evaluate extensive research in this field and to recognize the existing limitations related to the manufacture of these nanocomposites. For this purpose, firstly, the types of nanofillers are categorized and the mixing of nanofillers with UPRs is introduced. Then, the effect of adding nanofillers on the properties of these nanocomposites is reviewed according to the research works done in this field.

Due to environmental concerns and considering the petroleum resources, the bio-based materials have recently attracted more attention both in academia and industries. In addition to environmental sustainability and renewability, the bio-based adhesives have shown some competing advantages with respect to fossil-based products. This article covers the advantages and challenges of bio-based adhesives. The main advantages of bio-based adhesives include their less greenhouse gas emission, lower volatile organic compounds (VOC), lower environmental and human toxicity. The bio-based adhesives show higher tendency to biodegradability, which may be considered as their strong aspect compared to fossil-based resources. The bio-based materials may be incorporated in adhesive formulation through direct usage of biopolymer, in the form of building blocks and/or reactive monomer, and in the form of adhesive formulation additives. In bio-based adhesives, the pioneering technologies belong to fabrication of paper and different wooden products using starch and/or protein-based adhesives. The main goal was to remove as much as possible the harmful emitting formaldehyde gases during fabrication and product service life. The modification of bio-resource materials through introduction of new functionalities in the molecular architecture may bring some specific properties. There are many reports on the effect of various vegetable oils on the improved hydrophobicity in epoxy and polyurethane adhesives. The bio-based vegetable oils and cashew nut shell liquids now have acquired reliable position in adhesive and coating market. Recent investigations on some specific bio-resource structures such as lignin and tannin with complex structures have shown promising results for the improved thermal and antibacterial activities in adhesive formulation. In order to make a strong decision on the effectiveness of the bio-based adhesives, much investigations on different biological/economical aspects of bio-based materials are needed to achieve this goal.

Cellulose, as one of the most abundant natural polymers with a wide spectrum of applications, has drawn the attention of many researchers. In this regard, cellulose-base structures such as cellulose nanocrystals (CNCs) and nanocomposites are known as materials widely used in many fields. Therefore, development, production and use of cellulose-based structures by gaining the relevant insights are progressively increasing. In the present paper, the latest developments in the field of various extraction techniques of CNCs, their properties and dispersion methods in epoxy matrix to obtain desired mechanical properties in cellulose nano-crystals/epoxy nanocomposite structures are reviewed. First, cellulose nanocrystals are introduced as one of the most promising biodegradable and abundant nanomaterials widely used in various industries. The various production techniques of cellulose nanocrystals are briefly reviewed. Based on the various applications of cellulose nanocrystals in many fields, cellulose acid hydrolysis as one of the most practical and low-cost methods for cellulose nanocrystals preparation is described in details. In this regard, the source of cellulose, time and temperature of the acid hydrolysis, the concentration and type of acid as important factors of the hydrolysis process are investigated. Reinforcing epoxy-based nanocomposites using cellulose nanocrystals is the subject of another section. Dealing with problems associated with cellulose nanocrystals agglomeration phenomenon, the main challenge to achieve a homogeneous dispersion of cellulose nanocrystals within the epoxy matrix, is also thoroughly discussed. In this regard, various methods of chemical surface modification of cellulose nanocrystals are investigated. Finally, considering the investigated cases, the debate on the issue of appropriate methods for dispersing cellulose nanocrystals in the epoxy-based resin is comprehensively covered. It can be said that based on growing demands for high performance cellulose nanocrystals/epoxy nanocomposite structures, research on this field is ongoing. Therefore, in the present review, by providing a comprehensive discussion on the latest researche works conducted in this field, it has been attempted to present the new achievements of researchers and approaches to overcome the involved challenges. The most important achievement of researchers is the emphasis on selection of appropriate dispersion medium considering the cellulose nanocrystals surface energy to produce nanocomposites with suitable mechanical and thermomechanical properties.

Hypothesis: Today, due to the widespread use of coarse particle suspensions in chemical industry, the tendency to study the rheological behaviour of suspensions has increased significantly. One of the most important research fields is the study on friction of particles between them and the shear thickening behavior of their suspensions. In high-filled suspensions, the viscosity and the thickness of shear are proportional to the thickness of the suspended particles. Methods: This research is based on the syntheses of smooth particles (styrene/acrylic acid copolymers) and rough particles (silica-coated styrene/acrylic acid copolymers), with a volume proportion of 20%, 34% and 49% in the ethanol/water solution. The initial critical shear rate of suspension thickening regions was obtained in different ratios of rough and smooth particles. In addition, experimental and semi-empiric models such as Herschel Barclay and Gopalakrishnan have been used to describe the relationship between suspension rheology and microstructure. Findings: It was observed that with the increase in roughness of the composition of the same percentage of particles, a more severe shear thickening behavior occurs in smaller amounts of rough particles. It was also observed that hydro-clusters were formed in samples that contain the highest proportion of suspension composition and consist of 100% coarse particles with the lowest amount of Peclet. An increase in the amount of rough particles leads the system to an increase in viscosity at lower shear rates. Furthermore, the adaptation of the Gopalakrishnan model to experimental data clearly shows that an increase in roughness leads to a reduction in the critical value of Pe at the beginning of the shear thickening zone and a stronger shear thickness behavior in the system.

Hypothesis: The curing process for phenolic resin composites is always carried out under press or autoclave pressure, as water by-products are released during curing process. As a result, when phenolic composite parts are formed using the vacuum bag-only method, the costs of the mold and challenges of the pressure vessels would be eliminated, and a significant step is taken in easier manufacture of these parts.Methods: For the purpose of comparing the two methods, phenolic laminates were prepared using 3 bar pressure autoclave and vacuum bag-only methods. In order to investigate the effects of thickness on different properties, the samples were subjected to bending tests, short beam strength tests, void percentage tests, and fractured surface morphology tests.Findings: As the sample’s thickness increases, the flexural modulus increases while the flexural strength and short beam strength decrease. Furthermore, the modulus, bending strength, and strength of the short beam in the autoclave sample have increased by 27%, 17%, and 17%, respectively, compared to the vacuum bag-only sample. Morphological studies also showed that more void content was formed in the vacuum bag samples and the resin-fiber interaction was reduced compared to the autoclaved samples. A decrease in the bonding between resin and fibers and in the penetration of resin between fiber strands has also been observed with increasing thickness. Samples with a thickness of 1 mm had a void content of 3.5 ± 1% and in samples with a thickness of 9 mm, it was 15% ± 1%.

Hypothesis: Solid/liquid phase change materials (PCMs) are among the materials used to store thermal energy. By nanoencapsulating these materials, the problem of leakage during melting can be solved and the thermal efficiency of the system can be increased. In previous studies, researchers have used complex and expensive methods to prepare nanocapsules of PCM. In this work, in order to simplify and reduce the time and costs of the synthesis process, the difference in the solubility parameter of the core and shell materials at different temperatures and the sequence in phase separation have been used for the synthesis of PCM nanocapsules.Methods: In order to make the desired PCM nanocapsule, the difference in solubility parameters of polyethylene glycol, polystyrene and toluene at temperatures of 5, 25 and 80ºC has been used. In fact, this difference in the solubility parameter creates a homogeneous solution of these three substances at a temperature of 80ºC. By decreasing the temperature to 25°C, primary cores are formed and solid polyethylene glycol nanoparticles are completely separated. Further, by decreasing the temperature to 5ºC, polystyrene is separated from the solution and completely covers the nanoparticles of polyethylene glycol. In this way, using the sedimentation with temperature gradient method, polyethylene glycol nanoparticles were first synthesized, and polyethylene glycol nanoparticles were coated with polystyrene deposition. Also, to increase the thermal conductivity of the shell and the thermal efficiency of the PCM system, carbon nanoparticles have been used in polystyrene shells. Findings: Examining and evaluating the morphology of the synthesis PCM system in this work confirmed the creation of a polyethylene glycol/polystyrene core/shell nanocapsule. The thermal energy absorption efficiency of the heat transfer fluid prepared from these nanoparticles at the applied temperature of 55ºC is about 17% more than that of water.

Hypothesis: The skin is the largest organ and outer covering of the body, which acts as a barrier against microbial invasions as well as mechanical and chemical damage. But, sometimes the skin does not have the ability to regenerate the tissue on its own. In this context, tissue engineering (TE) is a promising and reconstructive solution for repairing serious skin tissue damage. This article refers to the importance of electerically conductive scaffolds based on tragacanth gum (TG) for skin TE owing to non-toxicity, metabolic compatibility, and the non-hazardous nature of its degradation products as well as the effect of electerical conductivity of the sacffold in performance of skin TE.Methods: Electroconductive nanofibrous hydrogel scaffolds composed of tragacanth gam-polyaniline blend (TG-B-PANI) and poly(vinyl alcohol) (PVA) were fabricated with a weight ratios of 30:70 and 20:80 by electrospinning method. Their physicochemical and biological properties for skin TE application were studied by various experiments. Findings: The fabricated scaffolds were tested using FTIR, SEM, TGA, UV-Vis, and cyclic voltammetry (CV). SEM images indicated the achievement of uniform fibers within their nano-scale domain. The cytocompatibility and cells proliferation characteristics of the scaffolds were approved by MTT assay using L929 mouse fibroblast cells. The fabricated scaffolds exhibited excellent hemocompatibility and human serum albomin adsorption capacity. The fabricated scaffolds showed proper physicochemical and biological properties for skin TE. The scaffold made with 20% (wt) of TG-B-PANI showed higher potential in adhesion and proliferation of L929 mouse fibroblast cells than those of scaffold with 30% (wt) of the above polymeric blend.

In recent years, the performance of perovskite solar cells (PSCs) has made a significant growth of about 25.5%. Nonetheless, the long-term stability of these cells for industrial production is still a major concern. One of the important reasons for the instability and degradation of the perovskite layer is its sensitivity toward moisture, oxygen, lack of resistance to ultraviolet light, electric fields, and temperature. In this context, hole-transporting materials (HTMs) play a key role in the construction of a stable inverted perovskite solar cell, including regulating the growth and crystallization of the perovskite and creating a water-repellent surface with a suitable structure. Naturally, the function of a hole-transporting layer depends on the type of perovskite solar cell configuration, and it is discussed in detail in the relevant section. In recent decades, researchers have focused on developing stable HTMs based on additive and non-additive semi-conducting polymers. Polymers have unique properties such as adjustable molecular weight, easier mobility of the hole compared to organic compounds, and suitable conductivity under additive-free conditions for 3D printing applications at an industrial scale. In addition, the cost-effectiveness of synthesis steps and potential interlayer displacement during the manufacturing process has made attraction and innovations in this area. Therefore, this article evaluates and analyzes the performance and mechanism of hole-transporting layers based on p-type semi-conducting polymers and the effect of various component structures of polymer systems on the inverse perovskite solar cell system. Polymers such as, pol(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), and (poly(3-hexylthiophene) (P3HT) have received most of the research and experimentation, with PTAA being the most desirable and efficient option, reaching over 25% efficiency.

Hypothesis: Some adducts were prepared from three kinds of DGEBA-based epoxy resins, phthalic anhydride and an alkanol amine accelerator, as a latent accelerator for one-pot epoxy/dicy systems. These adducts come with two kinds of accelerators: DMP-30 A, which is lab-grade and Ax-10, which is industrial-grade, as well as DGEBA based epoxy resins Epikote 828, Epiran 06 and ML 504. The adduct made of Epikote 828 and DMP-30 A was considered as a reference. It seems that it might be possible to prepare a new efficient latent accelerator with change of epoxy resin and accelerator.Methods: For this purpose, four different adducts with resins and accelerators and four different epoxy/dicy mixtures with four adduct types and AX-10 accelerator and one with no adduct as a reference were prepared. Measuring the melting point, viscosity build-up versus time, gelation time, non-isothermal differential scanning calorimetry (DSC) and glass transition temperature characterization and also lap shear, interlaminar shear strength, transvers tensile and scanning electron microscope (SEM) were used to study the latent properties of the prepared adducts in the epoxy/dicy system and find its effect on mechanical properties of the final composites and all were compared with references.Findings: Melting point of all adducts is above room temperature, so they are solid at room temperature. The results show that the adducts containing the industrial accelerator in one-pot epoxy/dicy system has lower gel time at high temperature, higher viscosity changes at ambient temperature and pot life and has made no significant change in cure temperature. The mechanical properties of the composite made with an adduct consisting of ML 504 resin are accompanied by a decrease in the related values. In general, the adduct made with Epiran 06 or Epikote 828 resin and industrial accelerator is an efficient and new latent accelerator and is suitable for preparing one-pot epoxy/dicy systems.

Hypothesis: The effect of incorporation of carbon black nanoparticles (CB) and nano-precipitated calcium carbonate (NPCC) on wear behavior, thermal behavior and morphology in polyacetal (POM)-based nanocomposite gears has been studied. Polyacetal is one of the widely used engineering materials for manufacturing the gears. Nevertheless, heat resistance and relatively low crack impact strength and sensitivity to UV are the major disadvantage of POM. Adding carbon black nanoparticles into the polyacetal can simultaneously increase the tensile strength and toughness and increase the UV resistance of the polyacetal. In addition, the presence of NPCC in the POM/CB can lead to improvements in CB dispersibility, increase of wear and thermal resistance.Methods: POM/CB/NPCC nanocomposite gears containing 0.42% (by wt) carbon black and different fractions (1.5%, 3% and 4.5% all by wts) of NPCC were produced by utilizing a twin-screw extruder and injection molding machine. Morphology and nanostructure were investigated by applying scanning electron microscopy. The gear performance of nanocomposites was examined by applying a gear test rig. Gear tests were performed in the mode constant loading. The temperature and wear of the gears were evaluated in the gear tests. Findings: The simultaneous addition of both types of nanoparticles to polyacetal led to a reduction in the amount of wear by 58% compared to pure polyacetal. The temperature of the gear surface, in the same number of revolutions, was reduced using CB and NPCC nanoparticles. The decrease in the temperature of the nanocomposite tooth surface compared to pure POM was attributed to the increase in storage modulus and improvement in elastic behavior, decrease in damping ratio, as well as decrease in friction coefficient and increase in heat transfer in presence of nanoparticles. The use of 4.5% (by wt) of NPCC nanoparticles caused cracks and expansion of wear and material flow in the gear pitch zone.

Hypothesis: Chemical cross-linked shape memory polyurethanes (CSMPUs) can have various applications in different fields such as medicine, where mechanical behavior and shape memory are improved in these samples compared to linear shape memory polyurethanes. Shape memory polyurethanes consist of at least two different phases. The first phase, which is in the form of a net point, is responsible for maintaining the permanent shape of the shape memory polyurethane. In contrast, the second phase, also known as shape memory switches, temporarily fixes the temporary shape of the polyurethane by crystallinity. The aim of this research is the synthesis of linear and star polycaprolactones (PCLs) in the first step and the synthesis of CSMPUs using linear and star PCLs in the second step, as well as the investigation and comparison of hydrogen-bonding indices through -C=O groups and -NH CSMPU samples that were synthesized using glycerol as the initiator of the soft segment or the chain extender of the hard segment.Methods: Linear and star polycaprolactones (PCLs) were synthesized using ring-opening polymerization (ROP) of caprolactone, and shape memory polyurethanes with chemical cross-linking (CSMPU) were synthesized using a two-step pre-polymerization method. By changing the molar ratios of the functional groups, the weight percentage of the hard segment in polyurethane samples was kept constant at 10%.Findings: The hydrogen-bond index is decreased with the introduction of glycerol as a chain extender. Also, the degree of crystallinity in CSMPU samples is decreased compared to those of pure PCLs. With the increase of chemical cross-linking the crystallinity of CSMPU samples is decreased. In addition, in the studies of mechanical behavior no significant difference was observed in the presence of glycerol in the soft segment or the hard segment.

Hypothesis: Due to the alternating hydroxyl and secondary amine groups, the polymer poly(1-(2-((3-amino-2-hydroxypropyl)amino)ethyl)-1'-ethyl-[4,4'-bipyridine]-1,1'-diium) (poly(AHAEBD)), is highly prone to complex formation. In this case, iron (III) was selected for complexation with poly(AHAEBD) due to its effective role in metabolic activities in the body then, anticancer effects of the synthesized compounds were evaluated on human breast cancer cells (MCF-7). Methods: 1,1'-Bis(2-aminoethyl)-[4,4'-bipyridine]-1,1'-diium (BABD) was prepared from the reaction of 4,4'-bipyridine and 2-aminoethyl. The polymer, (poly(AHAEBD)), was synthesized from the reaction of BABD and epichlorohydrin, and then complexed with iron (III) to prepare ([Fe(poly(AHAEBD)2].Na3). The structure of the synthesized compounds was confirmed using Fourier transfer infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR) spectroscopy, field emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), and gel permeation chromatography (GPC). The effects of [Fe(poly(AHAEBD)2].Na3, poly(AHAEBD), and cisplatin as a reference were evaluated on MCF-7 cell line using the MTT assay. Findings: The IC50 values for the polymer complex [Fe(poly(AHAEBD)2].Na3 (0.53 µg/mL), cisplatin (2.68 µg/mL), and poly(AHAEBD) (1.14 µg/mL) were obtained, indicating the superior performance of this polymer complex in inhibiting cancer cell growth compared to cisplatin as well as displaying the effect of complex formation with iron in increase the cytotoxicity compared to poly(AHAEBD). The impact of the synthesized polymer on the MCF-7 cancer cell line, on one hand, as well as the effect of increased iron levels in stopping the growth of cancer cells, and on the other hand, it has resulted in the effective performance of this complex polymer in stopping the growth of cancer cells in in vitro tests. Based on the results obtained, this polymer complex can be considered as a potential candidate for further investigation as an anticancer drug.

Hypothesis: In elastomeric composites, interfacial phenomena such as the effect of reinforcing filler on molecular dynamics of the rubber chain in the interphase and the way of rubber-filler interaction are the source of strain energy change or viscoelastic loss of the composite in highly filled rubber compound. To obtain a preliminary approximation of how the strain energy is influenced by interfacial phenomena, including stiffness, loss and the quality of this region, in this research, the finite element microstructural model was created in two-dimensional and three-dimensional mode and the effective characteristic changes in mechanical properties were studied. The effect of the change in stiffness of the interphase and the change in viscoelastic nature, the amount of contact between the rubber-filler in completely bonded and frictional sliding states were modeled.Methods: The solution styrene butadiene rubber composites reinforced with silica were prepared by melt mixing. For this purpose, rubber was mixed with silica and silane coupling agent in an internal mixer. Then the masterbatch was mixed with the curing system on a two-roll mill and finally the sample was cured under pressure at 160°C.Findings: In agreement with the modeling results, the composite tensile test showed that the most important controlling parameter is the type of rubber-filler connection in the interphase. The simulation results showed that considering the interphase region with frictional sliding greatly reduces the stress transfer from the matrix to the particle. But in the case of the completely bonded interphase region, due to the complete transfer of stress from the particle to the matrix, the mechanical properties showed a significant deviation compared to the experimental results. Also, the 3D models provided better predictions than the 2D ones.

Hypothesis: Hydrophobic silicone rubber is used as coatings that create hydrophobic properties for different surfaces. Silicone rubbers have high chemical and physical stability. Hydrophobic properties and resistance to creeping flow are unique features of silicone rubber coatings. The purpose of this research is to synthesize and assess silicone rubber and alter its surface wettability by roughening and modifying the surface using materials with low surface energies.Methods: Silicone rubber was first synthesized by hydrosilylation method in presence of a platinum catalyst, and subsequently coated onto polytetrafluoroethylene (PTFE) sheet as an example of a low surface energy substrate. In order to create roughness on the surface, industrial sandpapers were used of having grit sizes of 120, 220, and 400. In the next step, low surface energy silicon nanofilaments (SNF) were used to modify the desired surface, which were decorated on the surface of the sample through vapor deposition method. Findings: The SEM images show that the roughness density on the surface of the samples created by a 400-grit sandpaper is higher than that of a 220-grit sandpaper, and this sandpaper is also higher than that of a 120-grit sandpaper. Increasing the roughness density increases the static water contact angle (WCA) because in this case the Wenzel model is no longer dominant, and the hydrophobic mechanism follows Cassie Baxter theory. Due to the highest degree of roughness density created on the surface, the PTFE substrate treated with a 400 grit sandpaper was used for the next stage of silicone rubber coating and finally for the growth of SNF on top of the silicone layer. Applying SNF coating on the sample surface leads to a significant increase in the WCA (~159°). This hydrophobicity enhancement after SNF coating can be attributed to the low surface energy of the coating and the increase in roughness caused by the random growth of nanofilaments.

Hypothesis: A nanocomposite layer including graphene nanosheets could be used to enhance the barrier properties of high density polyethylene through a layer-by-layer assembly method. Planar graphene nanoparticles help to decrease the gas permeability of polyethylene substrates by making a tortuous pathway for gas molecules transmittance.Methods: Two different methods were used to increase the barrier properties of high density polyethylene and the results were compared with each other. In the first method, a thin film of polymer nanocomposite including graphene oxide nanoparticles and polyvinyl alcohol was coated on the surface of high density polyethylene film using a film applicator. The effective variables in this method were the weight fraction of graphene oxide particles in polyvinyl alcohol and thickness of the nanocomposite layer. In the second method, a layer-by-layer assembly was used. Chitosan solution acted as a positive charge and graphene oxide suspension in water was utilized as a negative charge.Findings: In high density polyethylene samples coated by polyvinyl alcohol nanocomposite (10 micrometers), the oxygen transmittance rate decreased drastically to 3 cm3m2 bar. This decrease was expected due to the structure of polyvinyl alcohol and its inherent barrier properties. By adding graphene oxide into polyvinyl alcohol, the permeability values showed a slight decrease and reached 0.8 cm3 m2 bar.Statistical analysis based on the surface response method for the layer-by-layer method showed that permeability depends on pH, number of bilayers and graphene concentration. At high pH, the graphene oxide sheets take on a smoother and more stretched shape and are more likely to aggregate, which increases permeability.

Hypothesis: Determination of the parameters of the material models for rubber compounds is usually carried out under simple modes such as uniaxial tension. These models are typically consisted of hyper-viscoelastic and stress-softening equations. However, due to the complicated behaviors of rubbery materials, the effectiveness and accuracy of such models under combined loads of tension, compression, and shear should be verified.Methods: Three rubber compounds were prepared based on SBR reinforced by three different amounts of carbon blacks and underwent uniaxial cyclic under two loading/unloading rates and volumetric tests. The experimental data were used for the determination of parameters of three complex material models using a nonlinear curve fitting method. These models were selected based on the results of our previous findings. We have verified the uniaxial condition of the chosen test method and sample size using finite element method. The computed parameters were employed to simulate cylindrical rubber samples prepared from the same compounds through the finite element method using Abaqus code under compressive-contact loads. The predicted results were next compared with their experimentally measured data.Findings: The results showed that the effectiveness of a material model in the prediction of stress-strain or stress-time behavior of a rubber compound under a simple load case does not necessarily guarantee that the same level of accuracy is obtained for the other loading modes, especially for highly filled compounds. It is shown here that to obtain accurate results in such cases, in addition to hyper-viscoelastic and stress softening equations, the material model should include proper terms to consider the effect of the filler-filler interactions into account, especially for highly carbon black-loaded compounds. It is found that the best model is the one in which the viscoelastic behavior of the filler-filler structure is independently included.

Hypothesis: Sand production from oil reservoirs is marked by many problems, such as well productivity reduction, operating equipment corrosion, and an increase in production costs; therefore, sand control in unconsolidated reservoirs is crucial for operating companies. Chemical injection into the production vessel, in order to strengthen and reduce sand formation, would be one of the most important methods of sand control.Methods: In this study the effectiveness of a Co[AM-AMPS-AAC]/PEI-MBA(CO) hydrogel nanocomposite in sand control was investigated. The acrylamide-based nanocomposite is strengthened structurally and thermally by the addition of double crosslinkers and nanoparticles. Structural, morphological, thermal, rheological, compressive strength and flooding tests were carried out to define and assess its efficacy.Findings: According to X-ray diffraction test findings, nanoparticles are evenly distributed throughout the structure. Morphological tests demonstrated the production of a dense, homogenous, and porous structure and validated the presence of nanoparticles in the structure. According to the thermal gravimetric test, adding nanoparticles increased the starting temperature of degradation from 80 to 195°C. The strain and frequency sweep rheological tests investigated the behavior of the material under different strains and stresses; they confirmed the preservation of the strong structure and linear viscoelastic behavior at a temperature of 90°C, strains between 0.1 and 20%, and frequencies between 0.1 and 10 Hz. The injection of 0.5 PV (pore volume) of 1% (by wt) nanocomposite to the sand pack resulted in a 730% increase in the axial strength of the sand pack according to the compressive strength test and 90% reduction in sand production measured by the chemical flooding test. Considering the stability and proper efficiency in the reservoir's harsh conditions, having linear viscoelastic properties, increasing compressive strength, and reducing sand production, the hydrogel nanocomposite designed in this research is proposed as a new and optimal product to control sand production and migration.

Hypothesis: Due to the special properties of nanomaterials, the production of nanoparticles has received much attention in recent years and various methods have been used to produce these materials. One of the methods is to use polymer structures to control nanostructures. Therefore, it is possible to produce cobalt chromate nanoparticles with certain dimensions using a polymer network with controllable pore size.Method: Polyacrylamide gel was used as a template to trap metal ions to form nanoparticles in this polymer template, and the polymer network was removed with the aid of heat treatment to produce the final nanoparticles. Therefore, cobalt chromate nanoparticles were fabricated by polyacrylamide gel method. The synthetic parameters like the temperature of polymer network formation and calcination temperature on the products were investigated. The manufactured product was characterized by different methods of analysis.Findings: The results showed that the gel formation rate becomes faster with increasing temperature. X-Ray diffraction results showed that although the initial product is amorphous, a cobalt chromate crystalline spinel was produced after heat treatment at 800°C. Scanning electron microscope images showed the formation of particles with dimensions in the range of 50 to 150 nm. The thermal analysis results revealed that the polymer gel formation is destroyed after heat treatment up to 650°C. Electron microscope images showed that most of the particles have dimensions between 50 and 150 nm. The produced samples were used as photocatalysts for the degradation of methylene blue dye. The degradation results showed that the nanoparticles produced by this method effectively degrade the dye as a water pollutant. Also, the effect of the amount of photocatalyst on photodegradation yield was investigated and the results showed that by increasing the powder to maximum 3 mg, the degradation efficiency increases.

Hypothesis: Incorporating different types of nanoparticles, especially metal oxide nanoparticles, into the polymeric nanofiber substrate improves different properties of the web. In this research, citric acid is used as an environmentally friendly cross-linking agent to reduce the hydrophilic property of chitosan-polyvinyl alcohol web. Cerium oxide nanoparticles (nanoceria) as an antioxidant and antibacterial agent are used to increase the biological capabilities of the web for healing applications.Methods: Chitosan (CS)/poly(vinyl alcohol) (PVA)/citric acid (CA) nanofibers with the mass ratios of 1:1:0.5 and 2:3:1 (CS:PVA:CA) were prepared and electrospun. Nanoceria was loaded into the optimal blend prepared for electrospinning. In continuation, the physical-morphological properties, cell compatibility, non-cytotoxicity, and antibacterial activity of the resulting webs were investigated.Findings: Physical-morphological investigations show that the CS:PVA:CA (2:3:1) nanofiber which was electrospun under 15 kV and 18 cm is the optimal nanofiber with an average diameter of 175±29 nm. The contact angle is about 42 degrees, indicating a suitable decrease in hydrophilicity and maintaining the physical integrity of the web. The SEM images show a bead-less morphology with an average diameter of 274±38 nm for nanofibrous web containing 1.5% (by wt) CeO2. The presence of nanoceria and interactions of the functional groups in the components were evident in their EDS and FTIR spectra, respectively. The results of the cell-culturing demonstrate the proper growth and proliferation of fibroblast cells on both with and without-nanoceria webs. The result of the MTT test confirms the non-toxicity of both scaffolds. The antibacterial investigations show improvements in antibacterial activities of the nanofibers containing cerium-oxide against both gram-positive and gram-negative bacteria. In general, the results determined that the presence of nanoceria in chitosan-polyvinyl-alcohol-citric acid electrospun nanofibers has clearly improved the biological properties, especially the antibacterial behavior of the obtained web, so it can be used as a suitable dressing for wound healing application.

Hypothesis: Methyl orange is a dye used in various industries such as printing and dyeing. Since methyl orange is not affected by conventional biological treatment and is not easily decomposed, the release of effluents containing this toxic compound into environment has adverse effects on human life and the aquatic ecosystem. Therefore, it is necessary to remove this dye from various wastewaters Among the common methods of water purification, the method of adsorption by bioadsorbents is considered as a simple, efficient and inexpensive method. In the present study, walnut shell modified with polyaniline nanofibers (PANI/WNS) has been used for removal of methyl orange dye. This modified adsorbent is a good candidate since it has favorable characteristics including suitable morphology and positively charged functional groups for removal of anionic dyes.Methods: PANI/WNS was prepared through aniline polymerization reaction on the surface of walnut shell particles and characterized using FTIR, FESEM, EDX, BET and XRD techniques. The effect of various physical and chemical parameters such as initial pH, contact time, adsorbent dose and initial dye concentration on the removal rate of methyl orange was studied and optimized. Also, thermodynamic parameters such as ΔH, ΔS and ΔG were investigated.Findings: The adsorbent is able to remove methyl orange dye in acidic environment. Optimization of the effective parameters on the adsorption process showed that the maximum methyl orange removal was obtained under conditions of pH 3, contact time of 140 min, adsorbent dosage of 0.35 g/L and dye initial concentration of 50 mg/L. Evaluation of laboratory data by different isotherm models showed that the highest correlation coefficient is related to Langmuir isotherm model and is equal to 0.9975, which indicates that the dye adsorption process is limited to a monolayer Also, the maximum adsorption capacity for methyl orange dye was obtained as 243.9 mg/g at 25°C, which is a significant amount compared to similar adsorbents reported in the literature and indicates the high ability of the studied modified bioadsorbent for removal of anionic dyes such as methyl orange. In addition, based on the results of the kinetic studies, the pseudo-second order model showed a better description of the laboratory data. Thermodynamic studies showed that the adsorption of the dye is a favorable, spontaneous and endothermic process.

Hypothesis: Among the types of bioplastics, poly(lactic acid) (PLA) has the ability to compete with petroleum-based polymers due to its favorable properties such as high tensile strength and high modulus of elasticity. Brittleness is the main disadvantage of PLA which limits its practical applications in some industrial fields like packaging and textile. Blending of PLA with other flexible bioplastics like polycaprolactone (PCL) and adding nanoparticles like graphene into PLA are among the techniques that can be used to balance the stiffness and toughness of PLA.Methods: Nanocomposites based on PLA/PCL/graphene (G) were prepared by melt mixing using an internal mixer with direct feeding method. In all samples the weight ratio of PCL dispersed phase to PLA matrix phase was 30:70, and three different weight percentages of nanographene (0.5, 1 and 2) were used. A rheometric mechanical spectrometer (RMS), X-ray diffractometer (XRD), and a scanning electron microscopy (SEM), as well as tensile and differential scanning calorimetry (DSC) measurements were used to study the microstructure, morphology, mechanical and thermal properties, respectively.Findings: The results of XRD showed that graphene nanoparticles are well dispersed in the polymer matrix. The SEM results demonstrated that incorporation of graphene nanoparticles into the PLA/PCL sample led to a decrease in the PCL droplet size. The melt linear viscoelastic measurements showed that incorporation of 2% (by wt) of nanographene into PLA/PCL sample enhanced the storage modulus and complex viscosity by about 200 and 400% due to well-dispersion of nanoparticles in the matrix that led to the formation of a 3D network between nanographene and/or nanographene-polymer chains. The tensile test results showed that the elastic modulus tensile strength, and elongation-at-break increased by 126.63%, 80.48%, and 97.36% respectively, by adding 2% graphene nanoparticles to the PLA/PCL sample. The results of the thermal tests also showed that the addition of nanographene and PCL to the PLA polymer causes the nucleation effect and the creation of active nucleation centers, and the crystallinity percentage of the PLA phase increases, but the effect of PCL in this research was more evident than that of nanographene.

The global problem of air pollution and its consequences, as well as the reduction of fossil fuel reserves, have created the need to use alternative energy sources. Therefore, it is necessary to create and develop the required infrastructure of renewable resources in the production of clean energy. In addition, the use of renewable energy sources is essential at all times to replace non-renewable sources continuously The storage of renewable energy, especially on a large scale, is the requirement of this goal. Batteries are one of the most potential technologies for this purpose Currently, lithium ion and flow batteries are the focus of studies for development and commercialization compared to other types of batteries. Flow batteries, especially vanadium type, are more capable of improving components and commercialization for large scale due to the availability of vanadium elements in nature, elimination of the ignition, and cost reduction compared to lithium batteries. One of the main challenges in this type of battery is the development of a high-performance membrane with low cost. Therefore, the description of performance and components of this type of battery, including the role of polymer membrane and characteristics, can create a perspective for its development and commercialization. To this end, in the present paper, the overall structure, performance, and constituent components of this type of battery have been introduced, focusing on the role of polymer membrane and its characteristics as the key component of its technology. Additionally, in each section recent results reported by the researchers have been presented in brief. Finally according to the literature survey, the future perspective, and remaining challenges for the development of this technology are mentioned.

Hypothesis: Nowadays, polymer nanofibers have been extensively used in different industries especially for medical applications. Electrospinning is a simple, versatile and cost-effective technique to prepare nanofibers. For biomedical applications such as tissue engineering poly(lactic acid) (PLA), a biocompatible and biodegradable polymer, has gained great interest. To improve the physical and mechanical properties of electrospun PLA, nanofibers and nanoparticles can be included.Methods: PLA nanofibers were prepared through electrospinning. Silver nitrate was added to increase the conductivity of electrospinning solution, resulting in finer nanofibers. To improve morphology and mechanical properties of the electrospun fibers, silicone rubber nanoparticles (NSR) were added into the electrospinning solution. Scanning and transmission electron microscopies (SEM and TEM) were employed to investigate the morphology of electrospun nanofibers and dispersion of nanoparticles, respectively. To investigate thermal and mechanical properties of the obtained nanofibers, differential scanning calorimetry (DSC) and tensile test were used.Findings: To obtain poly(lactic acid) electrospun nanofibers with fine and defect-free morphology, PLA was dissolved in a mixture of dichloromethane and dimethylformamide (DCM/DMF) solvents with a volumetric ratio of 3/2 Electrospinning solution with 7% poly(lactic acid) containing 0.5% (by wt) silver nitrate led to defect-free nanofibers with a diameter of less than 200 nm. Inclusion of silicone rubber nanoparticles of 1% resulted in finer nanofibers with a diameter of about 123 nm. This was attributed to enhanced elasticity of the solution with addition of elastomeric nanoparticles. Adding silicone rubber nanoparticles increased the cold crystallization temperature and decreased the crystallinity of polylactic acid. Toughness of nanofibers considerably increased in the presence of silicone rubber nanoparticles without sacrificing modulus and strength, indicating high capability of NSR as an impact modifier

Hypothesis: To enhance the crack growth resistance of rubber composites one strategy is to embed mechanisms for viscoelastic dissipation. This can be fulfilled by enlarging the bound rubber content through either increasing the filler-filler or filler-polymer interactions. Improving the filler-polymer interaction through surface modification of silica by silanes is not a favorable route because of the adverse impact of surface modification on lowering the share of filler-filler interaction on the bound rubber content. Modification of the rubber backbone appears to be a proper alternative. The difference in the .performance of these two methods can be observed well in peroxide-cured rubbersMethods: Present contribution performs a comparative study on the impact of modification in rubber or reinforcing silica on the crack growth resistance of peroxide-cured natural rubber (NR). For NR/silica composites, the modifications in rubber and silica are respectively conducted by grafting maleic anhydride or the bi-functional silane of bis(triethoxysilylpropyl)tetrasulfide (TESPT). For the case of maleic anhydride grafting, the influence of initiation by thermal and chemical routes is also comparedFindings: Results revealed that the modification of the rubber with maleic anhydride leads to an increase in the polymer-filler interactions and the bound rubber content. This imparts a favorable balance in mechanical strength and resistance to crack growth of the resulting composite. Tearing resistance of the system containing maleated rubber in the high loading range of silica showed a significant increase of about 150% compared to a neat rubber system filled with unmodified silica. It was suggested that the chemical crosslink density and viscoelastic dissipation are, respectively, the controlling mechanisms of tear resistance in low and high loading range of silica.

Hypothesis: Carbxylated graghene oxide nanosheets were synthesized and the nanosheets were applied to the surface modification of the polyethersulfonebased nanofiltration membranes for water treatment.Methods: Different concentrations of the synthesized carboxylated graphene oxide nanosheets were used as the surface modifiers to prepare the PES/PEI c-GO nanofiltration membranes. The prepared membranes were analyzed by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), 3D surface images (AFM) and X-ray diffraction (EDX) spectroscopy. The permeability and the separation performance of the constructed membranes were evalueted by the water contact angle, water content, the flow of pure water and the rejection of sodium sulfate salt and heavy metals.Findings: the FTIR analysis showed the formation of favorable bonds in the synthesized carboxylated graphene oxide nanosheets and the fabricated membranes. The membrane surface modification by c-GO nanosheets led to a decrease in membrane roughness and the contact angle decreased from 75° for the neat membrane to 36° for M1 at 0.001 g of carboxylated graphene oxide nanosheets. Moreover, the water content increased and M2 showed the highest water content. The highest pure water flux was obtained at 13.065 L/m2.h for the constructed M2 membrane containing 0.01 g of carboxylated graphene oxide nanosheets. In addition, the highest rejection of sodium sulfate salt (Na2SO4) was observed 67.5 % for the M3 membrane containing 0.1 g of c-GO nanosheets and the highest rejection of copper nitrate (Cu(NO3)2) was obtained 87.21% for the M1 membrane containing 0.001 g of c-GO nanosheets. Furthermore the obtained results indicated the improvement of the anti-fouling properties of the modified membranes containing carboxylated graphene oxide nanosheets compared to the base membrane.

Hypothesis: Among the various pollutants found in natural water, the heavy metal arsenic is more important due to its high toxicity. One of the most efficient methods to remove this pollution from water streams is the surface adsorption method. Zeolite nanocomposites can be considered powerful among arsenic adsorbers. Powder adsorbents are not very effective in industrial systems due to the problems such as clogging of filters, high pressure drop and also the problem of separation from water.Methods: To solve this problem, zeolite nanocomposite powder was transformed into beads using the chitosan gel method in three different types of cross-linking solutions including sodium hydroxide, sodium tripolyphosphate and joint sodium hydroxide/sodium tripolyphosphate. The effect of various parameters such as the type and initial ratio of the materials on the formation of beads was investigated.Findings: The results showed that the beads formed in the sodium hydroxide+sodium tripolyphosphate cross-linking solution and the optimal initial ratio of 1:3 from chitosan to the nanocomposite have a more suitable appearance and strength and better performance in arsenic absorption. In order to confirm and justify the mentioned Findings, SEM, BET and AAS analyses were performed. Operational parameters of initial arsenic concentration and adsorbent dose which are effective on the beads’ adsorption efficiency were investigated and the optimal amount of adsorbent dose was determined as 1 g/L with an efficiency of 92.9%. In order to obtain more information about the method of adsorption and determining the maximum capacity of adsorbents, Langmuir and Freundlich isotherms for granular adsorbents were investigated. The highest adsorption capacity of 7450.7 mg/g was obtained and Freundlich isotherm was in better agreement with the results.

Hypothesis: The use of plasma is widely used as a method to change polymer surfaces. The use of atmospheric cold plasma has more advantages than other plasma, laser and X-ray methods. This method is simple and it uses inexpensive equipment. Considering the many uses of polyethylene in industry, it can be effective to investigate its changes against cold plasma.Methods: A dielectric barrier discharge (DBD) plasma under atmospheric pressure was used to increase the hydrophobicity of low-density polyethylene (LDPE). After studying the optical emission spectrum (OES) of the produced plasma, its effects on surface and depth changes including surface morphology, chemical composition and polymer crystal structure were studied through scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD) and positron lifetime spectroscopy (PALS). Moreover, the contact angle analysis (CA) was used to examine the changes in the hydrophobicity of the polymer. Finding: Based on the data from FTIR and XRD analyses, it was found that plasma irradiation for 180 s affects the depth of a few nanometers of the polyethylene surface and does not cause significant changes in the chemical bonds and crystal structure of the polymer. In other words, plasma radiation can be used for nanometer-scale modification of the surface. On the other hand, the SEM images indicate that the plasma radiation changes the primary flat surface of the polymer into a porous surface. The results of CA analysis, while confirming this issue, show an increase in the hydrophobicity of the polymer after plasma irradiation. The results of PALS spectroscopy also reveal that at micron depth due to the sudden rise in temperature during plasma irradiation, the free volume of the material increases as a result of pore merging.

Polyurethanes, mainly synthesized by addition reactions of polyols with diisocyanates, have been considered as the most widely used polymers in various industries due to the variety of raw materials, synthetic methods and properties. The high demand, the significant share of the world market and the abundant use of this category of polymers have involved the major consumption of petroleum-based polyols and diisocyanates. Nonetheless, environmental challenges and the crude oil crisis have led to greater interest in renewable resources and systems based on green chemistry. Today, with the synthesis of waterborne polyurethanes) WPUs) and the use of water as a safe solvent, the release of volatile organic compounds and the production of solvent-based systems have been prevented to a considerable extent. The non-toxicity, non-flammability, environmentally friendly, and the wide applications of WPUs in plastics, paints, adhesives, printing ink and biomaterials are among the reasons for further development of these water-based systems. Because there are only a few commercially available diisocyanates in the synthesis of WPUs, it is the choice of polyol which may determine the WPUs properties. The most convenient renewable raw materials are natural oils, polysaccharides, wood and proteins, and vegetable oils which are the most beneficial options and have been widely studied. Today bio-polyols obtained from different vegetable oils have become vital in the synthesis of WPUs. However, castor oil has attracted special attention, as an excellent substitute for petroleum-based polyols and has been used in polyurethane compounds due to its availability, biodegradability and inherent hydroxyl groups. Considering the importance of bio-polyols and their role in the development of vegetable oil-based WPUs, in this article, while briefly introducing WPUs and their synthetic methods, the properties of WPUs based on castor oil, as the only natural polyol, are reviewed. Some green approaches to acquire a clear picture of the current and potential future applications of WPUs based bio-polyols in various fields are introduced.

Hypothesis: The modification of aromatic polymers, such as poly(ether ether ketone) (PEEK), by sulfonation modification, can result in fabricating polyelectrolyte membranes (PEMs) as the alternatives to Nafion for direct methanol fuel cell (DMFC) applications. Due to the effective role of nanomaterials in reducing the permeability in nanocomposites, the addition of natural or organically modified montmorillonite (OMMT) nanofillers to the sulfonated matrix, with the optimum degree of sulfonation, can reduce the methanol permeability and increase the efficiency of the fuel cell.Methods: PEEK was sulfonated at various degrees in solution state. Based on the selectivity parameter, the optimal degree of sulfonation (DS) was introduced. In order to prepare the nanocomposite membranes, using an ultrasonic agitator, different amounts of MMT and OMMT (Cloisite 15A or chitosan-modified MMT (CMMT)) nanofillers were added to the sulfonated polymer with optimal DS, and the resulting mixtures were cast. In this study, the ion exchange capacities (IEC) of the membranes were measured. The selectivity parameter (as ratio of proton conductivity to methanol permeability) at 25°C, as well as DMFC performance at 25°C and 1M feed of methanol for different membranes were determined and the results were compared with those of Nafion 117.Findings: The optimum DS for sulfonated poly(ether ether ketone) (SPEEK) was 62%. X-ray diffraction (XRD) patterns proved that nanoclays were exfoliated in the structure of nanocomposites at small loading weight of 1% (by wt). The proton conductivity and methanol permeability, as well as the performance test, showed that SPEEK/CMMT-based nanocomposite membranes have the highest maximum power generation density compared to other nanocomposite membranes or Nafion 117. Accordingly, SPEEK/CMMT polymer electrolyte membranes are promising candidates for direct methanol fuel cell (DMFC) applications.

Hypothesis: Bismaleimide resin, due to its favorable mechanical and thermal properties, can improve the properties of epoxy resin. 4,4'- Bis(maleimido)diphenylmethane resin (BMI) is one of bismaleimide resins that can be cured simultaneously with epoxy resin by amine curing agents and both resins can be cured with the same curing cycle. This improves the physical-mechanical properties of epoxy-based composites.Methods: BMI resin was synthesized using the reaction between maleic anhydride and 4,4'-diaminodiphenyl methane in acetone to form an intermediate of amic acid. The dehydration of the amic acid was carried out to form an imide using acetic anhydride, triethylamine and sodium acetate. The product was characterized by FTIR and 1H NMR spectroscopy techniques. The synthesized resin was blended with DGEBA epoxy resins in different amounts of 10, 20, 30 and 40 phr. Next, the blends were cured by 4,4'-diaminodiphenyl methane as a curing agent, and the composites were prepared from the blends and glass fibers. The interlaminar shear strength (ILSS) of the prepared composites was measured as a key parameter of composites. The curing behavior of epoxy/bismaleimide blend was investigated using isothermal differential scanning calorimetry (DSC) and FTIR spectroscopy.Findings: 4,4'-Bis(maleimido)diphenylmethane resin was used to improve ILSS properties of the composite prepared based on DGEBA epoxy resin and glass fibers. The value of 52.50 MPa was obtained as the optimum value of ILSS at 78°C for the mixture with 30 phr of bismaleimide. DGEBA and BMI resins have the ability to simultaneously cure by 73% and 78% using MDA curing agent at 160°C. Full curing of the epoxy and bismaleimide mixture requires a temperature higher than 160°C, such as 220°C.

Hypothesis: In the synthesis of vinyl polymers, one of the important parameters that play a significant role in the physical-mechanical properties is the tacticity of monomers within the polymer chain. Polymethyl methacrylate is considered one of the important industrial polymers. The method of its synthesis can have a major effect on this parameter and finally on the final properties. One of the parameters that has a significant effect on the stereoregularity of this polymer is the reaction temperature.Methods: The poly methyl methacrylate was synthesized at three different temperatures of 50, 150, and 250 °C via bulk thermal polymerization method. The most important instrument that can be used to study tacticity order is nuclear magnetic resonance spectroscopy. The tacticity of the polymethyl methacrylate (PMMA) was investigated and studied through alpha-methyl protons splitting and alpha-methyl and carbonyl carbons splitting, respectively, by proton (1HNMR) and carbon (13CNMR) nuclear magnetic resonance spectroscopy in deuterated chloroform (CDCl3) and deuterated tetrahydrofuran (THF-d8). The assignment of all stereosequences at triad level for alpha-methyl proton and pentad level for alpha - methyl carbon and carbonyl carbon were carried out by liquid nuclear magnetic resonance spectroscopy in deuterated chloroform. Bernoullian and first-order Markov statistics models were calculated for the synthesized sample and compared with the experimental results.Findings: The results indicated that probability of meso (Pm) was increased by increasing the methyl methacrylate polymerization temperature. The corresponding probability of meso values determined for synthesized polymethyl methacrylate at 50, 150, and 250°C were 0.203, 0.274, and 0.356, respectively. Finally, the effect of tacticity on glass transition temperature using differential scanning calorimetry (DSC) is discussed. The temperature glassy (Tg) values by DSC results were shown that the synthesized polymethyl methacrylate at 50, 150, and 250°C had 126.0, 125.1 and 102.9 oC, respectively.

Hypothesis: Poly(dimethyl siloxane) block copolymers membranes are a good choice for gas separation application. The mechanical strength and gas separation properties of these polymers can be improved by the preparation of layered membranes. In layered membranes, the coating layer generally controls the flow and selectivity of gas, while the porous substrate plays the role of mechanical strength supplier. The dense layer, at the interface of the substrate and selective layer, can also affect the efficiency of the layered membranes gas separation, and its performance depends on the morphology of the substrate and the gas permeation properties of the substrate and the coating layer. The goal of this research is to prepare and investigate the effect of substrate morphology on the performance of poly(dimethyl siloxane) block copolymers/polyurethane layered membranes.Methods: Polyurethane substrates were prepared through the non-solvent-induced phase separation (NIPS) method. Different substrates with sponge-like and finger-like morphology structures were prepared with the help of changing the concentration of dope solution concentration (10, 20, 25, 30% by weight of polymer) and coagulation bath (molar ratio of water/methanol=100/0, 80/20, 70/30 and 50/50), and used for the preparation of poly(dimethyl siloxane) block copolymer/polyurethane layered membranes.Findings: The polyurethane substrates revealed a finger-like morphology structure when a water coagulation bath was used due to the high exchange rate of solvent/non-solvent. Meanwhile, by adding methanol to the coagulation bath, the morphology of the substrate changed to a sponge-like one. In an overview, the gas separation properties of poly(dimethyl siloxane) block copolymers were improved by using a polyurethane substrate. The results revealed that by changing the morphology of the substrate from finger-like to sponge-like, the CO2 permeability of the membranes improved from 1.58 GPU to 4.53 GPU. While the permselectivity of the layered membranes (CO2/N2) decreased from 21.94 to 12.57.

Gas-liquid membrane contactors are promising alternatives to conventional absorption technologies. However, despite their significant advantages, such systems face the major problem of gradual wetting of the porous polymeric membranes with liquid absorbents. In fact, wetting of porous polymeric membranes by liquid absorbents increases the mass transfer resistance of the membrane phase, which in turn, reduces the gas absorption efficiency. Accordingly, in this paper, the effect of membrane wetting on mass transfer resistance and absorption efficiency has been studied. The influence of effective parameters on membrane wetting phenomenon, such as absorbent and membrane properties, is investigated. In addition, different prevention methods of membrane wetting is discussed in detail. The results show the increase in the rate of wetting at high velocity and pressure of the absorbent. In the case of absorbents-containing organic compounds, their surface tension is decreased rapidly with the increasing concentration of organic compounds, which increased the wetting rate of the membrane. In addition, studies on various polymeric membranes have shown that the structural and chemical changes of the membrane surface, which occur due to long-term contact of the membranes with amine absorbents, strongly increase the wetting of the membranes, and thus, its functionality. Moreover, studies have shown that modifying the surface of membranes is one of the most effective methods to prevent the problem of wetting. By modifying the surface, the free energy of the membrane surface can be reduced and its roughness can be increased, thus increasing the hydrophobicity of the membrane surface. Among these, nanotechnology has been introduced as one of the most important technologies in the production of superhydrophobic membranes to prevent the problem of wetting the porous polymeric membranes.

Hypothesis: The surface modification of a heterogeneous cation exchange membrane was carried out through a chitosan nanocomposite layer containing copper oxide nanoparticles in an electrodialysis process. The effect of the formed surface layer on the structure and transfer, separation and antibacterial properties of the membranes was investigated. Methods: Double layer membranes were produced by dip-coating method. Scanning electron microscopy (SEM), X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FTIR-ATR), electrical resistance, ionic flux, ability to remove heavy metal ions, water content, water contact angle and antibacterial experiments were employed to examine the membranes.Findings: The EDX and FTIR results confirmed the formation of chitosan-copper oxide nanocomposite layer on the surface of pristine membrane. The SEM images also showed the formation of a uniform layer on the modified membranes. The amount of water content for double-layer membranes showed an increasing trend compared to pristine membranes, although the contact angle results proved an increase in surface roughness for double-layer membranes. The results of ionic properties also showed that the electrical resistances of double-layer membranes decreased to 46% initially by utilizing CuO nanoparticles in the surface layer, whereas the monovalent ionic flux and bivalent flux for heavy metals were enhanced by 50% and >300%, respectively. At high ratios of CuO nanoparticles in the surface layer, the electrical resistance of membranes increased again and the flux showed a decreasing trend. Double-layer nanocomposite membranes showed a high ability to remove copper heavy metal ions and their antibacterial performance was suitable against Escherichia coli. Among the prepared membranes, the double-layer membrane containing 0.001% (by weight) copper oxide nanoparticles showed better performance compared to a pristine and other modified membranes.

Hypothesis: Modifications in chemical formulations of existing commercial polymerization catalysts may deteriorate other catalyst properties, especially stereo- and region-selectivity. Therefore, an absolute necessity for petrochemical polymerization facilities is to find feasible non-chemical routes for tailoring essential parameters, including molecular weight distribution (MWD) width, activity and fragmentation mechanism in order to modify existing catalytic systems. Methods: To this goal, use is made of a recently developed single-particle multipore model (MPM), which describes the reaction-diffusion processes involved in the heterogeneous olefin polymerization to investigate the impacts of initial catalyst porosity, initial catalyst particle size, bulk monomer concentration and pore size arrangement on the above-mentioned parameters. Findings: Modeling a supported Ziegler-Natta catalyst system showed that increasing the initial catalyst porosity or initial particle size or decreasing the bulk monomer concentration decreased the local reaction rate distribution width, resulting in narrower MWDs. Although, the polydispersity index generally changed oppositely due to its dependence on the location of the MWD in addition to its width. The model has elucidated and rationalized two unexplained experimental observations, i.e., increasing initial porosity reduces the catalyst activity in some studies and that polydispersity index generally changes irregularly and unpredictably with bulk monomer concentration. For the physical quantities studied in this work, the reaction rate is directly related to the MWD width, revealing that a trade-off between MWD width and yield should be sought for applications that require higher resistance to melt fracture phenomena, edge waviness and draw resonance. While, the reaction rate, MWD width and polydispersity index did not show any relationship with the participation ratio of the two fragmentation mechanisms. Increasing the initial catalyst porosity or the initial particle radius intensified the more preferred continuous bisection mechanism, thereby dropping the probability in fouling.

Hypothesis: Due to the presence of intra- and inter molecular hydrogen bonding in alginate chemical structure, its electrospinning capability is weak. However, this weakness can be improved through substitution of hydroxyl groups by sulfate groups. This article focuses on the role of degree of substitution of sulfate groups on the physicochemical properties of electrospinning solutions, such as viscosity, electrical conductivity and electrospinning conditions.Methods: Sodium sulfated alginate (SSA) was synthesized through the reaction of sodium alginate and chlorosulfonic acid in formamide as the solvent. The amount of chlorosulfonic acid was varied in order to obtain the SSA samples with different degrees of substitution. The chemical structures of neat alginate and SSA were studied by FTIR and 1H NMR spectroscopy. Degree of sulfation of samples was measured using CHNS elemental analysis, and the electrical conductivity and viscosity of SSA solutions were measured. The SSA nanofibers were fabricated using electrospinning and further crosslinked by a solution of calcium chloride to improve its hydrolytic stability. Finally, the fiber diameter and mechanical properties of the nanofibrous mat were studied by SEM and a tensile mechanical machine.Findings: Both FTIR and 1H NMR analyses have confirmed the formation of sulfate groups in SSA structure. Based on elemental analysis, the degree of substitution (DS) of SSA samples has been measured as 0.9 and 0.5 for SSA1 and SSA0.5, respectively. The electrical conductivity and viscosity of the SSA solutions also increased and decreased by increasing DS, respectively. The SSA1 sample showed better electrospinning capability and higher SSA content in dry electrospun mat compared to those in SSA0.5 sample. Finally, the crosslinked SSA1 mat revealed a lower mechanical strength compared to SSA0.5 mat due to lower crosslink density and higher chain scission of polymeric chains resulted from sulfation reaction.

Hypothesis: Nowadays, nanotechnology has an important role in the medical industry. Electrospun nanofibers with interconnected structure, high surface-to-volume ratio and good porosity are used in various medical fields. Nanofibers morphology is very effective in their mechanical, thermal, physical and biological properties. The aim of this study is to produce structures with smooth surface and minimized diameter. Methods: Production assessments are made on hybrid nanofibrous structures using combinations of poly(vinyl alcohol)/chitosan (PVA/CS), and gelatin/polycaprolactone (Gel/PCL). The process is done through the electrospinning process of two nozzles facing each other. For this purpose, Gel/PCL has been injected from a nozzle and CS/PVA from another nozzle and the produced nanofibers are collected on a rotating collector. By a Taguchi test design the effect of variable parameters (PVA/CS ratios of 90:10, 80:20, 70:30; gel/PCL ratios of 80:20, 50:50, 20:80; and CS/PVA feed rates of 1, 1.5, 2 mL/h) on morphological properties of the produced scaffold is evaluated.Findings: According to the results, nanofibers with the blend ratios of 75:25 and 80:20 for CS/PVA and gel/PCL, respectively, and flow rate of 1 mL/h for PVA/CS showed an average diameter of about 130 nm and a suitable morphology. A hybrid scaffold made of gel/PCL-PVA/CS can be considered as a very suitable and practical biomaterial in the field of diabetic wound healing, because the presence of gel and CS as natural polymers with excellent biological properties and PCL with high elastic property provide good conditions for imitating natural skin behavior.

Today, the specialists’ attention on polyurethanes is increasing day by day due to easy synthesis, available raw materials, favorable mechanical properties, biocompatibility, and the possibility of providing different products, such as water-based polyurethanes, foams, hydrogels and glues. Chitosan is a natural polymer that is extracted from the deacetylation of chitin and contains glucosamine and N-acetyl glucosamine units. This non-toxic natural polymer has very useful properties such as antimicrobial activity, biocompatibility, biodegradability, and tissue repair and regeneration effects. One of the weaknesses of chitosan is its poor solubility and processability due to its strong intra- and intermolecular hydrogen bonding. Therefore, chitosan has been used mainly in modified form or in combination with other polymers in various applications. The combination of synthetic polymers with natural polymers is of particular importance because natural polymers such as chitosan can show some properties such as biocompatibility, biodegradability, low toxicity, high cell viability, and internal tissue growth; while the synthetic polymers have other characteristics such as favorable processing, mechanical and physical properties, and appropriate chemical and thermal stability. Recently, chitosan has been used in combination with polyurethanes to improve its mechanical properties, thermal stability, biodegradability, antimicrobial properties and biological activity. During these studies, products in various forms such as composite, elastomer, fiber, foam, scaffold, and hydrogel have been prepared for different applications. In this review, polyurethanes containing chitosan and their synthesis methods for various applications are discussed. The products prepared in these studies have been suggested for various applications such as antibacterial coating, wound dressing, tissue engineering scaffold, fabric modification, fibers, hydrogels and foams.

Today, reducing the use of volatile organic compounds is one of the most important issues for environmental protection. Since the 1950s, powder coatings have been widely considered in the surface coating field, especially pipelines, households, and office appliances, due to their environmental friendliness and excellent performance. These types of coatings are solid and they are applied to the surface in the form of powder using different methods such as electrostatic or fluidized bed and then they are cured by heat. In this study, a brief history of the development of powder coatings is described, and it is continued by full report on the types of powder coatings, their production methods and processes, and the research process, emphasizing the type and characteristics of the resins used in this industry. Considering the importance of powder resins in the formulation of powder coatings, the performance of various thermoplastic and thermosetting resins used in these powder coating systems, including polypropylene, polyethylene, poly(vinyl chloride), fluoropolyethylene, nylon, epoxy, polyester, polyurethane, acrylic, cellulose acetate butyrate, and recycled resins are compared. In addition, the method of application and film formation in electrostatic coatings and the factors affecting them are investigated comprehensively. Furthermore, some of the challenges and problems of this giant industry will be introduced in order to improve its quality and curing methods for to expand the applications. Finally, new technical approaches, aiming to save energy and produce more biocompatible powdered products, using infrared curing technology, curing by ultraviolet radiation, or the ability to coat sensitive-temperature surfaces by powder coating are described.