Search

Based on a novel phenylacetylene capped polyimide (PI) with unique high-temperature resistance, its curing kinetics and thermal decomposition behavior were investigated. The curing mechanism and kinetics were studied by differential scanning calorimetry (DSC), and the activation energy (Ea) and pre-exponential factor (A) of the curing reaction were calculated based on the Kissinger equation, Ozawa equation, and Crane equation. According to the curve of conversion rate changing with temperature, the relationship between the dynamic reaction Ea and conversion rate (α) was calculated by the Friedman equation, Starink equation, and Ozawa–Flynn–Wall (O-F-W) equation, and the reaction Ea in different stages was compared with the results of molecular dynamics. Thermogravimetric analysis (TGA) and a scanning electron microscope (SEM) were used to analyze the thermal decomposition behavior of PI resins before and after curing. Temperatures at 5% and 20% mass loss (T5%, T20%), peak decomposition temperature (Tmax), residual carbon rate (RW), and integral process decomposition temperature (IPDT) were used to compare the thermal stability of PI resins and cured PI resins. The results display that the cured PI has excellent thermal stability. The Ea of the thermal decomposition reaction was calculated by the Coats–Redfern method, and the thermal decomposition behavior was analyzed. The thermal decomposition reaction of PI resins at different temperatures was simulated by molecular dynamics, the initial thermal decomposition reaction was studied, and the pyrolysis mechanism was analyzed more comprehensively and intuitively. [ABSTRACT FROM AUTHOR]

The aim of this research is to investigate basalt as a natural mineral-based fibre together with a vitrimeric resin as a sustainable alternative to standard composite materials. Vitrimers combine the properties of thermoset and thermoplastic polymers, enabling the repair of specimens and hence prolonging the lifetime of the composite material. The micro-mechanical characteristics between the basalt fibres and the vitrimer resin are reported and shown to match those of a standard Skyflex K51 epoxy resin. Discontinuous (4 mm) basalt fibres were employed to produce aligned discontinuous fibre-reinforced composites (ADFRCs) using the high-performance discontinuous fibre (HiPerDiF) technology. The mechanical characteristics of the laminates were investigated through tensile testing and the fracture zones were analysed under a scanning electron microscope. By normalising the results by their respective fibre volume fraction, it was discovered that the vitrimer–basalt ADFRCs exhibited, on average, a 4% higher strength and a 25% higher stiffness compared to their basalt epoxy counterparts. The repair potential of the vitrimer ADFRC specimens was explored during low-temperature compression repair. Two approaches were tested using double-sided local- and full-patch repair. Both successfully recovered a significant amount of their prime strength. In conclusion, the potential of the sustainable vitrimer–basalt composite is shown by its competitive mechanical performance. Combining this with the manufacturing flexibility, repair potential, and recyclability of the material, the vitrimer–basalt composite seems to be a competitive alternative to standard glass epoxies. [ABSTRACT FROM AUTHOR]

Polymers generally form incompatible mixtures that make the process of recycling difficult, especially the mechanical recycling of mixed plastic waste. One of the most commonly used films in the packaging industry is multilayer films, mainly composed of polyethylene (PE) and polyamide (PA). Recycling these materials with such different molecular structures requires the use of compatibilizers to minimize phase separation and obtain more useful recycled materials. In this work, commercial polyisoprene–graft–maleic anhydride (PI-g-MA) was tested as a compatibilizer for a blend of PE and PA derived from the mechanical recycling of PE/PA multilayer films. Different amounts of PI-g-MA were tested, and the films made with 1.5% PI-g-MA showed the best results in terms of mechanical properties and dart impact. The films were also characterized thermally via thermogravimetric analysis (TG) and differential scanning calorimetry (DSC), using Fourier-transform infrared spectroscopy (FTIR), and morphologically using a scanning electron microscope (SEM). Other parameters, such as tearing and perforation, were analyzed. [ABSTRACT FROM AUTHOR]

The crystal morphology and conformational changes during crystallization of a polypropylene random copolymer (PPR) are the basis for understanding its crystallization process. In this work, novel rare-earth β-nucleating agent WBN-28 was directly added into PPR to induce β-crystallization. The results of differential scanning calorimetry (DSC) showed that it has an excellent β-crystal-induced effect. The β-crystal content could surpass 85%, calculated from wide-angle X-ray diffraction (WAXD) data. The morphology of the β-crystal and α-crystal was intuitively observed via a polarizing optical microscope (POM). The β-crystallites were interconnected to naturally develop plate-like crystalline regions possessing a certain size, and the α-crystallites with sufficient thicknesses possessed a cross-hatched phenomenon. The bundle-like supramolecular structure of the β-crystal induced by WBN-28 was further observed via a scanning electron microscope (SEM). The conformational changes in the crystallization process of PPR were resolved via high-resolution infrared spectroscopy to understand its β-crystallization in depth. The conformational changes during the crystallization of PPR were found to be different from those of the isotactic polypropylene homopolymer (PPH); they had their own characteristics. This will provide guidance for understanding the β-crystallization of PPR in depth. [ABSTRACT FROM AUTHOR]

In this study, the traditional mini split Hopkinson tension bar (SHTB) was enhanced for the dynamic mechanical performance testing of single fiber/resin interface of composites. Single Aramid III fibers were modified using a polyamine modification treatment. Quasi-static and dynamic tensile tests of modified single Aramid III fibers were conducted using an electronic tensile testing machine and mini SHTB. The test results indicated that the surface modification employing the Catechol-Tetraethylenepentamine (Cat-TEPA) approach had a negligible effect on the tensile mechanical properties of single Aramid III fibers. The microdroplet method was introduced to measure the dynamic interfacial shear strength (IFSS) of Aramid III fiber/waterborne polyurethane resin using a mini SHTB. The dynamic shear test results revealed an increase in the dynamic shear strength of the modified Aramid III fiber/resin interface from 36.16 MPa to 41.51 MPa. Furthermore, the Scanning Electron Microscope (SEM) photography of the modified single Aramid III fiber after debonding exhibited regular grid structures on the debonding area, which can prevent debonding between the single fiber and the microdroplet, thereby enhancing interfacial shear performance. [ABSTRACT FROM AUTHOR]

Mycelium-based bio-composites (MBCs) represent a sustainable and innovative material with high potential for contemporary applications, particularly in the field of modern interior design. This research investigates the fabrication of MBCs for modern interior materials using agro-industrial wastes (bamboo sawdust and corn pericarp) and different fungal species. The study focuses on determining physical properties, including moisture content, shrinkage, density, water absorption, volumetric swelling, thermal degradation, and mechanical properties (bending, compression, impact, and tensile strength). The results indicate variations in moisture content and shrinkage based on fungal species and substrate types, with bamboo sawdust exhibiting lower shrinkage. The obtained density values range from 212.31 to 282.09 kg/m3, comparable to traditional materials, suggesting MBCs potential in diverse fields, especially as modern interior elements. Water absorption and volumetric swelling demonstrate the influence of substrate and fungal species, although they do not significantly impact the characteristics of interior decoration materials. Thermal degradation analysis aligns with established patterns, showcasing the suitability of MBCs for various applications. Scanning electron microscope observations reveal the morphological features of MBCs, emphasizing the role of fungal mycelia in binding substrate particles. Mechanical properties exhibit variations in bending, compression, impact, and tensile strength, with MBCs demonstrating compatibility with traditional materials used in interior elements. Those produced from L. sajor-caju and G. fornicatum show especially promising characteristics in this context. Particularly noteworthy are their superior compression and impact strength, surpassing values observed in certain synthetic foams multiple times. Moreover, this study reveals the biodegradability of MBCs, reaching standards for environmentally friendly materials. A comprehensive comparison with traditional materials further supports the potential of MBCs in sustainable material. Challenges in standardization, production scalability, and market adoption are identified, emphasizing the need for ongoing research, material engineering advancements, and biotechnological innovations. These efforts aim to enhance MBC properties, promoting sustainability in modern interior applications, while also facilitating their expansion into mass production within the innovative construction materials market. [ABSTRACT FROM AUTHOR]

The effect of polyamide 11 (PA11) on the thermal stability and light transmittance properties of silicone-based thermoplastic vulcanizates (TPVs) has been investigated. The blends were prepared through a dynamic vulcanization process by adding 15, 30, and 45 wt% PA11 to the silicon-based TPVs, respectively. The effect of PA11 on the dispersion of silicone rubber in the TPVs after dynamic vulcanization was characterized by a scanning electron microscope (SEM), the thermal stability of the compounds was evaluated through the changes in mechanical performance in the thermo-oxidative aging process, and the light transmittance of TPVs was measured by a haze meter. The results showed that adding PA11 to silicone-based TPVs caused a decrease in the size of the silicone rubber particles after dynamic vulcanization, resulting in improved dispersion. Due to this, by increasing the compatibility between the segments through silicone's effective dispersion, the amount of light absorption was reduced, and the amount of light transmittance was increased. Finally, according to the results of the thermal aging test, it was found that TPVs with 30 and 45 wt% PA11, respectively, showed outstanding thermal resistance after aging at 160 °C and 168 h and did not melt down. [ABSTRACT FROM AUTHOR]

This paper investigates making an injection mouldable conductive plastic formulation that aims for conductivity into the electromagnetic interference (EMI) shielding range, with good mechanical properties (i.e., stiffness, strength, and impact resistance). While conductivity in the range (electrostatic charge dissipation) and EMI shielding have been attained by incorporating conductive fillers such as carbon black, metals powders, and new materials, such as carbon nanotubes (CNTs), this often occurs with a drop in tensile strength, elongation-to-break resistance, and impact resistance. It is most often the case that the incorporation of high modulus fillers leads to an increase in modulus but a drop in strength and impact resistance. In this work, we have used short carbon fibres as the conductive filler and selected a 50/50 PBT/rPET (recycled PET) for the plastic matrix. Carbon fibres are cheaper than CNTs and graphenes. The PBT/rPET has low melt viscosity and crystallises sufficiently fast during injection moulding. To improve impact resistance, a styrene-ethylene-butadiene-styrene (SEBS) rubber toughening agent was added to the plastic. The PBT/rPET had very low-impact resistance and the SEBS provided rubber toughening to it; however, the rubber caused a drop in the tensile modulus and strength. The short carbon fibre restored the modulus and strength, which reached higher value than the PBT/rPET while providing the conductivity. Scanning electron microscope pictures showed quite good bonding of the current filler (CF) to the PBT/rPET. An injection mouldable conductive plastic with high conductivity and raised modulus, strength, and impact resistance could be made. [ABSTRACT FROM AUTHOR]

Polyimide (PI) composite films with enhanced mechanical properties were prepared by incorporating modified fumed silica (FS) particles while preserving their optical and thermal characteristics. The PI matrix was synthesized using a fluorinated diamine, a fluorinated dianhydride, and a rigid biphenyl dianhydride via chemical imidization. Commercially available FS particles, including unmodified FS particles (0-FS) and particles modified with dimethyl (2-FS), trimethyl (3-FS), octyl (8-FS), octamethylcyclotetrasiloxane (D4-FS), and polydimethylsiloxane (PDMS-FS) were used. Scanning electron microscope images and nitrogen adsorption–desorption isotherms revealed well-defined porous structures in the FS particles. The water contact angles on the composite films increased compared to those of the pristine PI films, indicating improved water resistance. The PI/0-FS films exhibited a typical trade-off relationship between tensile modulus and elongation at break, as observed in conventional composites. Owing to the poor compatibility and agglomeration of the PDMS-FS particles, the PI/PDMS-FS composite films exhibited poor mechanical performance and diminished optical characteristics. Although the longer-chained FS particles (8- and D4-FS) improved the tensile modulus of the PI film by up to 12%, a reduction of more than 20% in toughness was observed. The PI composite films containing the methylated FS particles (2- and 3-FS) outperformed 8- and D4-FS in terms of mechanical properties, with PI/3-FS films showing an over 10% increased tensile modulus (from 4.07 to 4.42 GPa) and 15% improved toughness (from 6.97 to 8.04 MJ/m3) at 7 wt. % silica loading. Except for the PI/PDMS-FS composites, all composite film samples exhibited more than 86% transmittance at 550 nm. Regarding thermal properties, the glass transition temperature (Tg) and thermal stability remained stable for most composite films. In addition, PI/3-FS films demonstrated enhanced dimensional stability with lower coefficients of thermal expansion (from 47.3 to 34.5 ppm/°C). Overall, this study highlights the potential of incorporating specific modified FS particles to tailor the mechanical, optical, and thermal properties of PI composite films. [ABSTRACT FROM AUTHOR]

Background: The elaboration of biocompatible nerve guide conduits (NGCs) has been studied in recent years as a treatment for total nerve rupture lesions (axonotmesis). Different natural polymers have been used in these studies, including cellulose associated with soy protein. The purpose of this report was to describe manufacturing NGCs suitable for nerve regeneration using the method of dip coating and evaporation of solvent with cellulose acetate (CA) functionalized with soy protein acid hydrolysate (SPAH). Methods: The manufacturing method and bacterial control precautions for the CA/SPAH NGCs were described. The structure of the NGCs was analyzed under a scanning electron microscope (SEM); porosity was analyzed with a degassing method using a porosimeter. Schwann cell (SCL 4.1/F7) biocompatibility of cell-seeded nerve guide conduits was evaluated with the MTT assay. Results: The method employed allowed an easy elaboration and customization of NGCs, free of bacteria, with pores in the internal surface, and the uniform wall thickness allowed manipulation, which showed flexibility; additionally, the sample was suturable. The NGCs showed initial biocompatibility with Schwann cells, revealing cells adhered to the NGC structure after 5 days. Conclusions: The fabricated CA/SPAH NGCs showed adequate features to be used for peripheral nerve regeneration studies. Future reports are necessary to discuss the ideal concentration of CA and SPAH and the mechanical and physicochemical properties of this biomaterial. [ABSTRACT FROM AUTHOR]

Plant leaves, such as those from Mangifera indica, represent a potential utilization of waste due to their richness in bioactive compounds. Supercritical CO2 allows these compounds to be incorporated into various matrices by impregnation. Combined with its ability to generate polymeric scaffolds, it represents an attractive strategy for the production of biomedical devices. For this purpose, conjugated polymeric scaffolds of biodegradable PLGA (poly(lactic-co-glycolic acid)) and PEDOT:PSS (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)), generated in situ by foaming, were employed for the supercritical impregnation of ethanolic mango leaves extract (MLE) in tissue engineering as a potential application. The extraction of MLE was performed by Enhanced Solvent Extraction. The effects of pressure (120–300 bar), temperature (35–55 °C), and depressurization rate (1–50 bar/min) on the physical/conductive properties and the impregnation of MLE were studied. The scaffolds have been characterized by liquid displacement, scanning electron microscope, resistance to conductivity techniques, measurements of impregnated load, antioxidant capacity and antimicrobial activity. Porosity values ranging 9–46% and conductivity values between 10−4–10−5 S/cm were obtained. High pressures, low temperatures and rapid depressurization favored the impregnation of bioactive compounds. Scaffolds with remarkable antioxidant activity were obtained (75.2–87.3% oxidation inhibition), demonstrating the ability to inhibit S. aureus bacterial growth (60.1 to 71.4%). [ABSTRACT FROM AUTHOR]

Polyetheretherketone (PEEK) is the leading high-performance thermoplastic biomaterial that can be processed through material extrusion (ME) additive manufacturing (AM), also known as three-dimensional (3D) printing, for patient-specific load-bearing implant manufacture. Considering the importance of cyclic loading for load-bearing implant design, this work addresses the high-cycle fatigue behaviour of 3D-printed PEEK. In this work, printed PEEK specimens are cyclically loaded under stress-controlled tension–tension using different stress levels between 75% and 95% of printed PEEK's tensile strength. The experimental results are used to document 3D-printed PEEK's fatigue behaviour using Basquin's power law, which was compared with previous fatigue research on bulk PEEK and other 3D-printing materials. As a pioneering study on its fatigue behaviour, the results from this work show that 3D-printed PEEK exhibits an above-average fatigue strength of 65 MPa, corresponding to about 75% of its tensile strength. Fracture surface analysis suggests that a transition can occur from ductile to brittle fracture with maximum stresses between 85% and 95% of the tensile strength. Evidence of crack propagation features on fracture surfaces under scanning electron microscope (SEM) observation suggests crack initiation in void defects created by printing deposition that propagates longitudinally through line bonding interfaces along layers. Considering this, 3D-printed PEEK's fatigue behaviour can be strongly related to printing conditions. Further research on the fatigue behaviour of 3D-printed PEEK is necessary to support its use in load-bearing implant applications. [ABSTRACT FROM AUTHOR]

The article presents the research results on the influence of variable shock conditions, such as temperature and water, thus reflecting shock atmospheric conditions during freezing and thawing, on the properties of samples produced using 3D printing technology from commonly used materials such as ABS, HIPS, PLA, and ASA. Understanding how different environmental conditions affect the quality, reliability, and durability of 3D prints can help to optimize the printing process and provide valuable information about their application possibilities. Tests related to the strength of the materials, such as static tensile testing, Charpy impact testing, and evaluation of structures, were carried out using a scanning electron microscope (SEM). Changes in chemical properties were measured by performing tests such as FTIR and TGA. Variations in chemical properties were measured by performing tests such as FTIR and TGA. One shock cycle lasting 7 days was sufficient to alter the properties of 3D prints, with the extent of changes depending on the material, as summarized in the test results. [ABSTRACT FROM AUTHOR]

Resin-based friction materials (RBFMs) strengthened by polyether ether ketone (PEEK) fiber were designed and prepared in this study. Specimens incorporating PEEK fiber of 2–8 wt.% were fabricated based on wet granulation, and then the effects of the PEEK fiber content on the mechanical and tribological properties of RBFMs were systematically investigated. The results showed that PEEK fiber can sense the braking temperature and then effectively regulate the comprehensive properties of RBFMs. The specimen incorporating 6 wt.% PEEK fiber obtained the optimal comprehensive performance with a stable friction coefficient (COF), excellent fade resistance and recovery properties, and better wear resistance. The worn surface was inspected using a scanning electron microscope. After the friction–wear test, the specimen with 6 wt.% PEEK fiber presented a number of primary and secondary plateaus and a reduced number of pits with wear debris on the worn surface. The study indicated that PEEK fiber could not only enhance the mechanical and tribological properties of RBFMs at low temperatures because of their high strength and self-lubrication but also adhere to wear debris to reduce abrasive wear at high temperatures; furthermore, the adhered wear debris could form a secondary plateau under normal pressure, which could alleviate abrasion. [ABSTRACT FROM AUTHOR]

The interest in research and development for additive manufacturing (AM) processes has grown significantly over the last years and attracts both industry and academia alike. Among the available AM technologies, stereolithography (SLA) is one of the most discussed, researched, and employed. On the other hand, being based on thermoset resins, all the limitations of this typology of materials still apply, limiting the range of applications of this highly versatile process. To overcome these limitations, especially brittleness, this research analyzes the effects of Tungsten (W) micro-size (average size 1 μm) particles reinforcement on a methacrylate base material. First, the manufacturing process for creating the W-reinforced methacrylate material is presented and investigated to define the effect of pre- and post-processing operations on the quality of the pre-cured solution considering 4% and 10% wt. W particles concentrations. Afterward, tensile, compressive, and impact specimens were manufactured with both concentrations and compared with the experimental results from clear (unfilled) resin-based specimens used as the benchmark. The addition of tungsten particles showed a strong improvement in the impact strength of the methacrylate base material, quantified in 28% for the 4% and 55% for the 10% wt., respectively, although at the expense of a slight reduction in elastic and yield properties on average −12%. Furthermore, using Scanning Electron Microscope (SEM) analyses, the particle–matrix interaction was investigated, showing the interaction between the polymer matrix and the reinforcement and the mechanism by which the impact resistance is enhanced. [ABSTRACT FROM AUTHOR]

The subject of polymer–polymer pair interaction is highly important, bearing in mind that such pairs are used in the construction of machines and equipment, among other uses. Considering that the characteristics of polymer–polymer sliding pairs (e.g., the load limit value and advantageous parameter, PV) differ from those of polymer–metal pairs, the subject is particularly interesting and has been little explored so far. Hence, the present study presents one of the areas of the effects of standstill time (intrinsically characteristic of polymeric materials) on the startup parameters in sliding pairs where the sample and the countersample were made of a polymeric material. Pairs of same-type polymers, POM–POM, PET–PET, and PA6–PA6, were subjected to tests. A test rig dedicated to static friction coefficient determination, whose principle of operation is based on the interdependences between the force characteristics of an inclined plane, was used for this purpose. The sliding pair was successively loaded with 25 N, 50 N, and 75 N, and the standstill time ranged from 0 to 10 min. The determined tribological characteristics were analysed with regard to the standstill time under load, unit pressure, and polymer pair material. An optical profilometer and a scanning electron microscope were used to qualitatively evaluate the effects of standstill time and unit pressure on the surfaces of the interacting elements. Complex interrelationships between the test results and the set experimental parameters were noted. SEM micrographs revealed post-friction changes in the sliding surfaces. [ABSTRACT FROM AUTHOR]

The current treatment for periodontitis is aimed at resolving gingival inflammation, whilst complete periodontal tissue regeneration is not predictable, and it represents a therapeutic challenge. Injectable biomaterials hold tremendous potential in dental tissue regeneration. This study aimed to investigate the ability of an injectable thermosensitive β-tricalcium phosphate (β-TCP) and chitosan-based hydrogel to carry cells and promote periodontal tissue regeneration. In this study, different concentrations of β-TCP-loaded chitosan hydrogels were prepared (0%, 2%, 4%, or 6% β-TCP, 10% β-glycerol phosphate, and 1.5% chitosan). The characteristics of the hydrogels were tested using rheology, a scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), degradation, and biological analyses. The new biomaterial showed a sol–gel transformation ability at body temperature and exhibited excellent chemical and physical characteristics, whilst the existence of β-TCP enhanced the structure and the properties of the hydrogels. The SEM confirmed the three-dimensional networks of the hydrogels, and the typical rheological properties of strong gel were observed. The EDX and XRD validated the successful incorporation of β-TCP, and similar patterns between different groups were found in terms of the FTIR spectra. The stable structure of the hydrogels under 100 °C was confirmed via DSC. Biological tests such as Alamar Blue assay and Live/Dead staining confirmed the remarkable biocompatibility of the hydrogels with pre-osteoblast MC3T3-E1 and human gingival fibroblast (HGF) cells for 14 days, and the results were validated with confocal imaging. This preliminary study shows great promise for the application of the β-TCP-loaded thermosensitive chitosan hydrogels as a scaffold in periodontal bone and soft tissue repair. [ABSTRACT FROM AUTHOR]

Acrylated natural rubber (ANR) with various acrylate contents (0.0–3.5 mol%) was prepared from natural rubber as a raw material and then incorporated with commercial 3D resin to fabricate specimens using digital light processing. As a result, the utilization of ANR with 1.5 mol% acrylate content could provide the maximum improvement in stretchability and impact strength, approximately 155% and 221%, respectively, over using pure 3D resin, without significant deterioration of tensile modulus and mechanical strength. According to evidence from a scanning electron microscope, this might be due to the partial interaction between the dispersed small rubber particles and the resin matrix. Additionally, the glass-transition temperature of the 3D-printed sample shifted to a lower temperature by introducing a higher acrylate content in the ANR. Therefore, this work might offer a practical way to effectively enhance the properties of the fundamental commercial 3D resin and broaden its applications. It also makes it possible to use natural rubber as a bio-based material in light-based 3D printing. [ABSTRACT FROM AUTHOR]

Basalt Fibre Reinforced Polymer (BFRP)-bonded structures are lightweight, high strength, economical, and environmentally friendly, which is very advantageous in the civil sector. The aim of this paper is to provide a comprehensive account of the hygrothermal degradation and failure mechanisms of BFRP-bonded structures by comparing the residual properties of two epoxy adhesive BFRP single-lap joints after ageing for 240 h, 480 h, and 720 h in an extreme hygrothermal environment with pure water at 80 °C. The hydrophilicity and thermal stability of the two adhesives were firstly compared by water absorption and Thermogravimetric Analysis (TGA) tests, and the hygrothermal degradation of the molecular chains and the reduction in Tg were characterised by Fourier Transform Infra-Red (FTIR) spectroscopy and Differential Scanning Calorimetry (DSC) curves. The failure strength and load-displacement curves of the two joints were then compared, and it was found that the strength and stiffness had different trends, while the paired t-test was used to demonstrate the correlation between the failure strength and the adhesive Tg, as well as the difference in the failure mechanisms of the two joints caused by the water absorption rate. The analysis of macrosections and Scanning Electron Microscope (SEM) images summarised the process and reasons for the transition of the failure mode from fibre tearing to hybrid failure, and finally, the changes in elemental concentration and O/C values were analysed by Energy Dispersive X-ray Analysis (EDX), which proved that the degree of hydrolysis could not be used as a judgement of the degradation degree of the joint alone, and provided data support for the application of the BFRP-bonded structure in the humid and hot environment. [ABSTRACT FROM AUTHOR]

Due to chlorine's ability to kill bacteria and fungi through a chemical reaction, chlorine solutions are commonly used to clean and disinfect numerous public facilities, although these actions are also dependent to the equipment present in those facilities. Accordingly, the interest in studying its effect when in contact with different materials is obvious. This study was carried out through accelerated degradation tests and various analysis methods (optical microscope, scanning electron microscope, and tensile tests). The objective was to observe the wear presented by three polymeric materials, polyvinyl chloride (PVC), high-density polyethylene (HDPE), and polypropylene (PP), when exposed to chlorine's action in swimming pools and drinking water treatment plants. The resulting effect depends on the chlorine content and the type of contact between the chemical agent and the material. The aim was to select the material less likely to be affected by chlorine through tests and analyses, allowing a longer component life. The use of certain more resistant polymeric materials can drastically reduce maintenance, reducing fundamental factors such as costs, the downtime of municipal facilities, and also the risk to public health. It was concluded that PVC has the most stable behaviour overall when in contact with chlorine solutions. [ABSTRACT FROM AUTHOR]

One of the major goals of adhesive dentistry is to improve the interaction of the already-existing adhesives with different substrates by using different application techniques. Thus, the objective of the present in vitro study was to assess the bond performance of four adhesive systems, Prime&Bond Universal (PBU), Clearfil SE Bond (CSE), OptiBond Universal (OBU), and OptiBond FL (OBFL), to dentin using various application modes: passive application (PA), active application (AA), Compo-Vibes modified application (CVM), and Compo-Vibes application (CV). Eighty extracted human molars were allocated into four groups based on the application modalities tested. The micro-tensile bond strength as well as fracture mode were tested in accordance with ISO/TS 11.405 after 24 h and 6 months of aging. Adhesive contact angle (CA) and scanning electron microscope analysis were also performed (n = 3). Statistical tests were performed with α = 0.05. After 24 h, a significant difference with a higher bond strength value was found for PBU in the AA modality and for CSE in the CVM modality (p < 0.05). However, no significant difference was shown between the techniques used among the other adhesives (OBFL and OBU). Moreover, at 24 h, only the PA demonstrated significant differences between the tested materials (p < 0.05). After 6 months, CSE, PBU, and OBU demonstrated significant differences between the techniques (p < 0.05), with a higher bond strength for CSE in AA and CVM modalities, for PBU in AA modality, and for OBU in AA and PA modalities. No significant differences were found between the techniques used among the OBFL (p > 0.05). In addition, only the CVM technique demonstrated significant differences between the tested materials after 6 months. CV and CVM showed a decreased value after aging for CSE and PBU, respectively. However, all the modalities decreased for OBU and OBFL after aging. All the adhesives showed marked resin infiltration into dentinal tubules in AA among all the modalities tested. Both universal adhesive systems (OBU and PBU) demonstrated statistically lower CA when compared to the other systems (CSE and OBFL) (p < 0.05) when applied in the PA mode. Concerning the AA mode, only CSE and OBFL were tested. The AA demonstrated lower CA values compared to the same adhesives in PA (p < 0.05). It could be concluded that the bond strength could be influenced by both materials and application techniques. It seems that the AA technique could be recommended as a gold standard for the application of an adhesive system to dentin. Plus, the CV and CVM modalities after 6 months of aging were considered stable for PBU and CSE, respectively. Consequently, the performance of these adhesive systems might vary when applied to other modalities. Future studies are needed to test this hypothesis. [ABSTRACT FROM AUTHOR]

The growing concern about reducing carbon footprint has led to the progressive replacement of traditional polymeric materials by natural-based biodegradable materials. However, materials from natural sources (i.e., plants) typically possess poorer mechanical properties when compared to conventional plastics. To counterbalance this, they need to be adequately formulated and processed to eventually meet the standards for certain applications. Zein is the major storage protein from corn and can be obtained as a by-product from the corn-oil industry. It is an excellent candidate for producing green materials due to its stability, biodegradability, renewability, and suitable mechanical and technical-functional properties. In the present work, zein was blended with a plasticizer (i.e., glycerol) at three different zein/glycerol ratios (75/25, 70/30, and 65/25) and then injection moulded at three different processing temperatures (120, 150, and 190 °C). The properties of both blends and bioplastics were evaluated using dynamic mechanical analysis (DMA), tensile tests, and water absorption capacity (WUC). The properties–structure interrelation was assessed through a scanning electron microscope. Generally, a higher zein content and processing temperature led to a certain reinforcement of the samples. Moreover, all bioplastics displayed a thermoplastic behaviour finally melting at temperatures around 80 °C. The lack of massive crosslinking enabled this melting, which finally could be used to confirm the ability of zein based materials to be recycled, while maintaining their properties. The recyclability of thermoplastic zein materials widens the scope of their application, especially considering its biodegradability. [ABSTRACT FROM AUTHOR]

Leucaena is a fast-growing tree in the legume family. Its leaf contains a significant amount of protein and is thus widely used as fodder for cattle. To broaden its application in the rubber field, the effects of Leucaena leaf powder and its extracted products on the cure characteristics and mechanical properties of natural rubber were investigated. The extraction of Leucaena leaf was carried out by using a proteolytic enzyme at 60 °C. The digested protein was separated from the residue by centrifugation. Both digested protein and residue were then dried and ground into powder, namely digested protein powder and residual powder, respectively, before being characterized by Fourier transform infrared spectroscopy, scanning electron microscope, thermogravimetric analysis, X-ray diffraction, particle size determination, and protein analysis. After being added to natural rubber at 3 parts per hundred rubber, they significantly reduced both the scorch time and the optimum cure time of the rubber compounds, probably due to the presence of nitrogen-containing substances, without a significant sacrifice of the mechanical properties. For instance, the optimum cure time decreased by approximately 25.5, 35.4, and 54.9% for Leucaena leaf powder, residual powder, and digested protein powder, respectively. Thus, they can be used as green and sustainable fillers with a cure-activation effect in rubber compounding. [ABSTRACT FROM AUTHOR]

Three-dimensional printing has revolutionized drug manufacturing and has provided a solution to the limitations associated with the conventional manufacturing method by designing complex drug delivery systems with customized drug release profiles for personalized therapies. The present investigation aims to design a gastric floating tablet with prolonged gastric floating time and sustained drug release profile. In the present study, a gastro retentive floating device (GRFD) was designed and fabricated using a fused deposition modelling (FDM)-based 3D printing technique. This device acts as a multifunctional dosage form exhibiting prolonged gastric retention time and sustained drug release profile with improved oral bioavailability in the upper gastrointestinal tract. Commercial polyvinyl alcohol (PVA) and polylactic acid (PLA) filaments were used to design GRFD, which was comprised of dual compartments. The outer sealed compartment acts as an air-filled chamber that imparts buoyancy to the device and the inner compartment is filled with a commercial propranolol hydrochloride immediate-release tablet. The device is designed as a round-shaped shell with a central opening of varying size (1 mm, 2 mm, 3 mm, and 4 mm), which acts as a drug release window. Scanning electron microscope (SEM) images were used to determine morphological characterization. The in vitro buoyancy and drug release were evaluated using the USP type II dissolution apparatus. All the designed GRFDs exhibit good floating ability and sustained drug release profiles. GRFDs fabricated using PLA filament show maximum buoyancy (>24 h) and sustained drug release for up to 10 h. The floating ability and drug release from the developed devices were governed by the drug release window opening size and the filament material affinity towards the gastric fluid. The designed GRFDs show great prospects in modifying the drug release characteristics and could be applied to any conventional immediate-release product. [ABSTRACT FROM AUTHOR]

The paper reports a facile synthesis of novel anionic spherical polymer brushes which was based on grafting sodium 2-acrylamido-2-methylpropane-1-sulfonate from the surface of 4,4′-Azobis (4-cyanopentanoyl chloride)-modified carbon spheres. Various characterization methods involving a scanning electron microscope, energy dispersive X-ray spectroscopy, Fourier transform infrared spectrum, and thermo-gravimetric analysis were utilized to analyze the morphology, chemical composition, bonding structure, and thermal stability, respectively. The molecular weight (Mw) and polydispersity (Mw/Mn) of brushes were 616,000 g/mol and 1.72 determined by gel permeation chromatography experiments. Moreover, the dispersibility of ASPB in water and in the presence of aqueous NaCl solutions of different concentrations was investigated. Results show that the dispersibility of carbon spheres has been enhanced owing to grafted polyelectrolyte chains, while the zeta potential of the particle decreases and its brush layer shrinks upon exposure to sodium ions (Na+). [ABSTRACT FROM AUTHOR]

The aim of this study was to assess adaptation and bonding to root canal dentin of discontinuous (short) glass fiber-reinforced composite to intra-radicular dentin (DSGFRC). Methods: Seventy virgin human teeth were extracted and then endodontically treated; then samples were randomly divided into 7 groups (n = 10), based on the materials' combinations as follows: Group 1, a two-bottle universal adhesive + DSGFRC; Group 2, a single-component universal adhesive + DSGFRC; Groups 3 and 4, the same materials of Goups 1 and 2 were used but after cleaning of the canal walls with 17% EDTA and final irrigation with 5.25% NaOCl Ultrasound Activated (UA); Group 5, traditional prefabricated fiber posts were luted after being silanized with G-Multi Primer; Groups 6 and 7, like Group 5 but after ultrasonic irrigation (UA). All sample roots were cut 1 mm thick (n = 10) to be evaluated regarding root canal adaptation using a light microscope and scanning electron microscope (SEM) and push-out bond strength. These results were statistically analyzed by Kruskal–Wallis analysis of variance by ranks. The level of significance was set at p < 0.05. Results: Bond strength forces varied between 6.66 and 8.37 MPa and no statistically significant differences were recorded among the groups. By microscopic examination, it was noted that ultrasonic irrigation increased the adaptation of the materials to the dentin surface. Conclusions: Within the limitations of this in vitro study, it may be concluded that when DSGFRC was used for intracanal anchorage in the post-endodontic reconstruction, similar push-out retentive force and strength to those of traditional fiber posts cemented with particulate filler resin composite cements were achieved. [ABSTRACT FROM AUTHOR]

The cross-linked microspheres were prepared and loaded with Favipiravir SARS-CoV-2 antiviral drug, by copolymerization of chitosan (CS) with a polysaccharide extracted from fresh pomegranate peels. Moreover, glutaraldehyde (Glu) has been used as a chemical cross-linker and sodium hexametaphosphate (SHMP) as a physical cross-linker. The extracted polysaccharide was analyzed, and different techniques have been used. The analyses lead to the conclusion that it is pectin. The surface morphology of the prepared microspheres was studied using a scanning electron microscope, where the size and shape factor (S) of the Glu microspheres showed high values (74.27 μm) and (0.852), respectively, meaning their surfaces tend to be rough, whereas the SHMP microspheres showed a smaller size particle (20.47 μm) and a smaller shape factor (0.748), which gives an indication that the SHMP microspheres have smooth surfaces. The swelling studies have shown that Glu microspheres have a higher degree of swelling, which means SHMP microspheres are more compact. The prepared microspheres have shown a higher loading percentage of Favipiravir antiviral drug in SHMP microspheres (37% w/w) in comparison with Glu microspheres (35% w/w), where the electrostatic interaction between the Favipiravir ions and SHMP anions helps for more loading. The microspheres prepared under different types of cross-linking have shown initial burst release of Favipiravir, followed by a step of controlled release for a certain period of time, whose period depends on the pH of the release medium. Both Glu and SHMP cross-linked microspheres have shown high controlled release times in buffered release solutions at pH = 7.4 and for shorter periods at pH = 1.3 and pH = 9.4, which may be related to the type of electrostatic interactions between drug and polymer systems and their reactions with release solution ions. [ABSTRACT FROM AUTHOR]

The European methodology for plastics, as a feature of the EU's circular economy activity plan, ought to support the decrease in plastic waste. The improvement of recycled plastics' economics and quality is one important part of this action plan. Additionally, achieving the requirement that all plastic packaging sold in the EU by 2030 be recyclable or reusable is an important objective. This means that food packaging materials should be recycled in a closed loop at the end. One of the most significant engineering polymers is polyethylene terephthalate (PET), which is widely used. Due to its numerous crucial qualities, it has a wide variety of applications, from packaging to fibers. The thermoplastic polyolefin, primarily polyethylene and polypropylene (PP), is a popular choice utilized globally in a wide range of applications. In the first phase of the current experiment, the materials were obtained by hot pressing with the press machine. The reinforcer is made of Al nanopowder 800 nm and Fe nanopowder 790 nm and the quality of the recycled polymer was examined using Fourier transform infrared spectroscopy (FTIR), a scanning electron microscope (SEM), and differential scanning calorimetry (DSC). From DSC variation curves as a function of temperature, the values from the transformation processes (glass transition, crystallization, and melting) are obtained. SEM measurements revealed that the polymer composites with Al have smooth spherical particles while the ones with Fe have bigger rough spherical particles. [ABSTRACT FROM AUTHOR]

Robust membrane materials with high efficiency have attracted extensive attention in oil/water separation. In this work, carbon particles via candle combustion were firstly adsorbed on the surface of stainless steel meshes (SSMs), which formed a thin hydrophobic coating, and a rough structure was then constructed through chemical vapor deposition and high temperature calcination, with the resultant SSM surface wrapped with uniform silica coating possessing the characteristic of superoleophobicity underwater. Scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray powder diffraction (XRD) were used to characterize the modified SSMs. The prepared SSMs were superhydrophilic in air, and they had superoleophobicity underwater (157.4°). The separation efficiency of five oil/water mixtures was above 98.8%, and the separation flux was 46,300 L·m−2·h−1. After it was immersed in 1 mol/L NaOH, 1 mol/L HCl and 3.5 wt% NaCl for 24 h, respectively, the efficiency was still above 97.3%. Further immersion in the solution of dopamine and octadecylamine resulted in the transformation of superhydrophililc/superoleophobicity-underwater SSMs to superhydrophobic SSMs, and the resultant SSMs with reverse surface wettability was also used for the oil/water separation with good separation efficiency and separation flux. [ABSTRACT FROM AUTHOR]

The addition of nano- and microfillers to carbon-fiber-reinforced polymers (CFRPs) to improve their static mechanical properties is attracting growing research interest because their introduction does not increase the weight of parts made from CFRPs. However, the current understanding of the high strain rate deformation behaviour of CFRPs containing nanofillers/microfillers is limited. The present study investigated the dynamic impact properties of carbon-fiber-reinforced phenolic composites (CFRPCs) modified with microfillers. The CFRPCs were fabricated using 2D woven carbon fibers, two phenolic resole resins (HRJ-15881 and SP-6877), and two microfillers (colloidal silica and silicon carbide (SiC)). The amount of microfillers incorporated into the CFRPCs varied from 0.0 wt.% to 2.0 wt.%. A split-Hopkinson pressure bar (SHPB), operated at momentums of 15 kg m/s and 28 kg m/s, was used to determine the impact properties of the composites. The evolution of damage in the impacted specimens was studied using optical stereomicroscope and scanning electron microscope. It was found that, at an impact momentum of 15 kg m/s, the impact properties of HRJ-15881-based CFRPCs increased with SiC addition up to 1.5 wt.%, while those of SP-6877-based composites increased only up to 0.5 wt.%. At 28 kg m/s, the impact properties of the composites increased up to 0.5 wt.% SiC addition for both SP-6877 and HRJ-15881 based composites. However, the addition of colloidal silica did not improve the dynamic impact properties of composites based on both phenolic resins at both impact momentums. The improvement in the impact properties of composites made with SiC microfiller can be attributed to improvement in crystallinity offered by the α-SiC type microfiller used in this study. No fracture was observed in specimens impacted at an impact momentum of 15 kg m/s. However, at 28 kg m/s, edge chip-off and cracks extending through the surface were observed at lower microfiller addition (≤1 wt.%), which became more pronounced at higher microfiller loading (≥1.5 wt.%). [ABSTRACT FROM AUTHOR]

Treating dentin surfaces with antibacterial agents prior to bonding bioactive restorations might affect their mechanical properties. In this study, we evaluated the effect of silver diamine fluoride (SDF) and chlorhexidine (CHX) on the shear bond strength (SBS) of bioactive restorative materials. Dentin discs were treated with SDF for 60 s or CHX for 20 s and bonded with four restorative materials, namely Activa Bioactive Restorative (AB), Beautifil II (BF), Fuji II LC (FJ), and Surefil One (SO). Control discs were bonded without treatment (n = 10). SBS was determined using a universal testing machine, and a scanning electron microscope (SEM) was used for the evaluation of the failure mode and the cross-sectional examination of adhesive interfaces. The SBS of each material between different treatments and of the different materials within each treatment were compared via a Kruskal–Wallis test. The SBS of AB and BF was significantly higher than that of FJ and SO in the control and CHX groups (p < 0.01). In the latter, SBS was higher in FJ than SO (p < 0.01). SO had a higher value with SDF compared to CHX (p = 0.01). The SBS of SDF-treated FJ was higher than that of the control (p < 0.01). SEM showed a more homogenous and improved interface of FJ and SO with SDF. Neither CHX nor SDF compromised the dentin bonding of bioactive restorative materials. [ABSTRACT FROM AUTHOR]

Jute is a ligno-cellulosic natural fiber that ranks second in terms of the volume of cellulosic fibers and is extensively utilized for technical textile applications. The goal of this study is to determine the flame-retardance (FR) properties of pure Jute and Jute-Cotton fabrics treated with Pyrovatex CP New at concentrations of 90% (owf), M:L: 1:7. Both fabrics exhibited a substantial improvement in flame-retardancy. After the ignition period, the recorded flame spread time in both FR treated fabrics was zero seconds; whereas for untreated Jute and Jute-Cotton fabrics, the flame spread time was measured 21 s and 28 s, respectively, to burn their entire length (15 cm). Within these flame-spread times, the length of the char was 2.1 cm and 2.57 cm in the Jute and Jute-Cotton fabrics, respectively. After FR finishing, on both fabrics in the warp and weft directions, the physico-mechanical properties significantly decreased. The deposition of flame-retardant finishes on the fabric surface was determined by Scanning Electron Microscope (SEM) images. According to Fourier Transform Infra-Red Spectroscopy (FTIR) analysis, the flame-retardant chemical had no effect on the inherent properties of the fibers. Thermogravimetric analysis (TGA) analysis revealed that FR treated fabrics had early degradation, resulting in the formation of more char than in the untreated samples. After FR treatment, both fabrics showed a significant improvement in residual mass (more than 50%). Although the formaldehyde content observed in the FR treated samples was significantly greater, it was still within the permitted limit formaldehyde content in textiles intended for outerwear and not worn next to the skin. The results of this investigation demonstrate the potential use of Pyrovatex CP New in jute-based materials. [ABSTRACT FROM AUTHOR]

Composites with natural lignocellulosic fillers are being cited as a viable and sustainable alternative to conventional materials, as they combine lower costs with lower weight. In many tropical countries, such as Brazil, there is a considerable amount of lignocellulosic waste that is improperly discarded, which causes pollution of the environment. The Amazon region has huge deposits of clay silicate materials in the Negro River basin, such as kaolin, which can be used as fillers in polymeric composite materials. This work investigates a new composite material (ETK) made of epoxy resin (ER), powdered tucumã endocarp (PTE), and kaolin (K), without coupling agents, with the aim of producing a composite with lower environmental impact. The ETK samples, totaling 25 different compositions, were prepared by cold molding. Characterizations of the samples were performed using a scanning electron microscope (SEM) and a Fourier-transform infrared spectrometer (FTIR). In addition, the mechanical properties were determined via tensile, compressive, three-point flexural and impact tests. The FTIR and SEM results showed an interaction between ER, PTE, and K, and the incorporation of PTE and K reduced the mechanical properties of the ETK samples. Nonetheless, these composites can be considered potential materials to be used for sustainable engineering applications in which high mechanical strength is not a main requirement of the material. [ABSTRACT FROM AUTHOR]

Nanoparticles of ZnO-Chitosan (Zn-Chit) composite were prepared using precipitation methods. Several analytical techniques, such as scanning electron microscope (SEM), transmitted electron microscope (TEM), powder X-ray diffraction (XRD), infrared spectroscopy (IR), and thermal analysis, were used to characterize the prepared composite. The activity of the modified composite was investigated for nitrite sensing and hydrogen production applications using various electrochemical techniques. A comparative study was performed for pristine ZnO and ZnO loaded on chitosan. The modified Zn-Chit has a linear range of detection 1–150 µM and a limit of detection (LOD) = 0.402 µM (response time ~3 s). The activity of the modified electrode was investigated in a real sample (milk). Furthermore, the anti-interference capability of the surface was utilized in the presence of several inorganic salts and organic additives. Additionally, Zn-Chit composite was employed as an efficient catalyst for hydrogen production in an acidic medium. Thus, the electrode showed long-term stability toward fuel production and enhanced energy security. The electrode reached a current density of 50 mA cm−2 at an overpotential equal to −0.31 and −0.2 V (vs. RHE) for GC/ZnO and GC/Zn-Chit, respectively. Electrode durability was studied for long-time constant potential chronoamperometry for 5 h. The electrodes lost 8% and 9% of the initial current for GC/ZnO and GC/Zn-Chit, respectively. [ABSTRACT FROM AUTHOR]

Articular cartilage is a specialized tissue that provides a smooth surface for joint movement and load transmission. Unfortunately, it has limited regenerative capacity. Tissue engineering, combining different cell types, scaffolds, growth factors, and physical stimulation has become an alternative for repairing and regenerating articular cartilage. Dental Follicle Mesenchymal Stem Cells (DFMSCs) are attractive candidates for cartilage tissue engineering because of their ability to differentiate into chondrocytes, on the other hand, the polymers blend like Polycaprolactone (PCL) and Poly Lactic-co-Glycolic Acid (PLGA) have shown promise given their mechanical properties and biocompatibility. In this work, the physicochemical properties of polymer blends were evaluated by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM) and were positive for both techniques. The DFMSCs demonstrated stemness by flow cytometry. The scaffold showed to be a non-toxic effect when we evaluated it with Alamar blue, and the samples were analyzed using SEM and phalloidin staining to evaluate cell adhesion to the scaffold. The synthesis of glycosaminoglycans was positive on the construct in vitro. Finally, the PCL/PLGA scaffold showed a better repair capacity than two commercial compounds, when tested in a chondral defect rat model. These results suggest that the PCL/PLGA (80:20) scaffold may be suitable for applications in the tissue engineering of articular hyaline cartilage. [ABSTRACT FROM AUTHOR]

This study aims to explore the effects of Thermoplastic Polyurethane (TPU) content on the weld line properties of Polypropylene (PP) and Acrylonitrile Butadiene Styrene (ABS) blends. In PP/TPU blends, increasing the TPU content results in a significant decrease in the PP/TPU composite's ultimate tensile strength (UTS) and elongation values. Blends with 10 wt%, 15 wt%, and 20 wt% TPU and pure PP outperform blends with 10 wt%, 15 wt%, and 20 wt% TPU and recycled PP in terms of UTS value. The blend with 10 wt% TPU and pure PP achieves the highest UTS value of 21.85 MPa. However, the blend's elongation decreases due to the poor bonding in the weld line area. According to Taguchi's analysis, the TPU factor has a more significant overall influence on the mechanical properties of PP/TPU blends than the recycled PP factor. Scanning electron microscope (SEM) results show that the TPU area has a dimple shape on the fracture surface due to its significantly higher elongation value. The 15 wt% TPU sample achieves the highest UTS value of 35.7 MPa in ABS/TPU blends, which is considerably higher than other cases, indicating good compatibility between ABS and TPU. The sample containing 20 wt% TPU has the lowest UTS value of 21.2 MPa. Furthermore, the elongation-changing pattern corresponds to the UTS value. Interestingly, SEM results present that the fracture surface of this blend is flatter than the PP/TPU blend due to a higher compatibility rate. The 30 wt% TPU sample has a higher rate of dimple area than the 10 wt% TPU sample. Moreover, ABS/TPU blends gain a higher UTS value than PP/TPU blends. Increasing the TPU ratio mainly reduces the elastic modulus of both ABS/TPU blends and PP/TPU blends. This study reveals the advantages and disadvantages of mixing TPU with PP or ABS to ensure that it meets the requirements of the intended applications. [ABSTRACT FROM AUTHOR]

This study examines the effects of alkaline treatment on the mechanical and thermal properties of miswak fiber-reinforced polylactic acid. The treatment was performed with three distinct concentrations of sodium hydroxide (NaOH): 1 wt %, 2 wt %, and 3 wt %. The difficulties of interaction between the surface of the fiber and the matrix, which led to this treatment, is caused by miswak fiber's hydrophilic character, which impedes its ability to bind with hydrophobic polylactic acid. FTIR, tensile, TGA, and DMA measurements were used to characterize the composite samples. A scanning electron microscope (SEM) was used to examine the microstructures of many broken samples. The treatment is not yet especially effective in enhancing interfacial bonding, as seen by the uneven tensile strength data. The effect of the treated fiber surface significantly improves the tensile strength of miswak fiber-reinforced PLA composites. Tensile strength improves by 18.01%, 6.48%, and 14.50%, respectively, for 1 wt %, 2 wt %, and 3 wt %. Only 2 wt %-treated fiber exhibits an increase of 0.7% in tensile modulus. The modulus decreases by 4.15 % at 1 wt % and by 19.7% at 3 wt %, respectively. The TGA curve for alkali-treated fiber composites demonstrates a slight increase in thermal stability when compared to untreated fiber composites at high temperatures. For DMA, the composites with surface treatment have higher storage moduli than the composite with untreated miswak fiber, especially for the PLA reinforced with 2 wt % alkali miswak fiber, proving the effectiveness of the treatment. [ABSTRACT FROM AUTHOR]

Recently, hybrid fillers have been found to be more advantageous in energy-harvesting composites. This study investigated the mechanical and electromechanical performances of silicone rubber-based composites made from hybrid fillers containing conductive nanocarbon black (NCB) and molybdenum disulfide (MoS2). A hybrid filler system containing only 3 phr (per hundred grams of rubber) MoS2 and 17 phr NCB provided higher fracture strain, better tensile strength, and excellent toughness values compared to the 20 phr NCB-only-filled and 5 phr MoS2-only-filled rubber composites. The chemical cross-link densities suggest that NCB promoted the formation of cross-links, whereas MoS2 slightly reduced the cross-link density. The higher mechanical properties in the hybrid filler systems suggest that the filler particles were more uniformly distributed, which was confirmed by the scanning electron microscope study. Uniformly distributed filler particles with moderate cross-link density in hybrid filler systems greatly improved the fracture strain and fracture toughness. For example, the hybrid filler with a 17:3 ratio of NCB to MoS2 showed a 184% increment in fracture toughness, and a 93% increment in fracture strain, compared to the 20 phr NCB-only-filled composite. Regarding electromechanical sensing with 2 kPa of applied cyclic pressure, the hybrid filler (17:3 CB to MoS2) performed significantly better (~100%) than the 20 phr NCB-only compound. This may have been due to the excellent distribution of conducting NCB networks and piezoelectric MoS2 that caused symmetric charging–discharging in the toughened hybrid composite. Thus, hybrid composites with excellent fatigue resistance can find dynamic applications, such as in blood pressure measurement. [ABSTRACT FROM AUTHOR]

The effects of alumina particle size and jet pressure on the bond strength of polyetheretherketone (PEEK) were examined to determine the airborne particle abrasion parameters with minimal effects on PEEK and to achieve optimal bond strength, as a reference for future clinical use. An alumina particle with four particle sizes and three jet pressures was used to air-abrade PEEK. Surface roughness (Ra), morphology, chemical structure, and wettability were analyzed using a stylus profilometer, scanning electron microscope, X-ray diffractometer, and contact angle analyzer, respectively. The shear bond strength (SBS) of PEEK and dental resin cement was analyzed using a universal testing machine (n = 10). The failure modes and debonded fracture surfaces were observed using optical microscopy. Airborne particle abrasion increased the Ra and hydrophobicity of PEEK and deposited alumina residues. The SBS generally decreased after thermal cycling. A large particle size damaged the PEEK surface. The effects of different particle sizes and jet pressures on the SBS were only significant in certain groups. Adhesive failure was the main mode for all groups. Within the limitations of this study, 110 μm grain-sized alumina particles combined with a jet pressure of 2 bar prevented damage to PEEK, providing sufficient SBS and bonding durability between PEEK and dental resin cement. [ABSTRACT FROM AUTHOR]

This article investigates the effect of geometrical alternatives for fiber directions on the structural and tribological properties of glass and carbon fibers when molded with epoxy as polymeric composite fabrics for the safety and quality of bushing applications. To confirm the best composite fabric direction, scanning electron microscope and tribological analyses were carried out for the glass and carbon fabrics at horizontal and vertical geometrical alternative orientations. The tribological test was applied using a pin-on-disk tribometer at constant bark velocity of 0.520 m/s against different loads, beginning with 5, 10, 15, and 20 N for the investigated composite samples. The structural measurements demonstrated that the carbon fiber had a high ability to merge with the resin epoxy when compared with the glass fiber. The tribological analysis elucidated that the lower wear volume loss and friction coefficient were obtained when molding the resin epoxy horizontally to the fiber-stacking direction compared with the other vertical direction. Accordingly, the study deduced that the carbon fiber composite material achieves superior wear resistance when molded by resin epoxy horizontally to the direction of tribological wear, which is suitable for several advanced bushing applications. [ABSTRACT FROM AUTHOR]

This paper aimed to experimentally clarify the crushing mechanism and performance of expanded polypropylene foam (EPP) and analyze the influence of density and thickness on its mechanical behavior and energy absorption properties under static crushing loadings. Hence, a series of compression tests were carried out on EPP foams with different densities and thicknesses. For foam with a density of 60 kg/m3, the mean crushing strength, energy absorption (Ea), energy absorption efficiency (Ef), specific energy absorption (SEA), and energy absorption per unit volume (w) increased by 245.3%, 187.2%, 42.3%, 54.3%, and 242.8%, respectively, compared to foam with a density of 20 kg/m3. Meanwhile, compared to foam with a thickness of 30 mm, the mean crushing strength, energy absorption (Ea), energy absorption efficiency (Ef), SEA, and energy absorption per unit volume (w) for foam with a thickness of 75 mm increased by 53.3%, 25.2%, −10.8%, −4.7%, and −10.6%, respectively. The results show that foam density has a significantly greater influence on static compressive performance than foam thickness. The microstructures of the EPP foam before and after static compression were compared by observing with a scanning electron microscope (SEM), and the failure mechanism was analyzed. Results showed that the load and energy as well as the deformation and instability processes of its cells were transferred layer by layer. The influence of density on the degree of destruction of the internal cells was obvious. Due to its larger mass and larger internal damping, thicker foams were less damaged, and less deformation was produced. Additionally, the EPP foam exhibited a considerable ability to recover after compression. [ABSTRACT FROM AUTHOR]

The present study concerns the physico-chemical, structural, mechanical and thermal characterization of Acacia pennata, a natural and almost inexpensive fibre, as a potential reinforcement in polymer composites. The effect of treating the fibre with sodium acetate to increase its qualities has been seen through the use of thermogravimetric analysis, scanning electron microscope (SEM) analysis, X-ray diffraction (XRD), mechanical property tester, and Fourier transform infrared spectroscopy (FTIR). According to XRD analysis, the elimination of lignin and wax-like impurities resulted in an increase in the AP fibre's crystalline index (79.73%). The fibre's thermal stability was also discovered to be 365 °C. Tensile strength (557.58 MPa) and elongation at break both increased by 2.9% after treatment with sodium acetate. The surface nature and quality of AP fibres improved after sodium acetate treatment. It was confirmed by the reduction of chemical compositions (such as hemicellulose, lignin and pectin). Given its density, the fibre can be suggested as a reinforcement in polymer composites for light-weight applications because its lightweight property will be more useful for composite manufacturing. [ABSTRACT FROM AUTHOR]

This work was investigated to prepare a reinforcing composite packaging film composited of soy protein/polyvinyl alcohol (PVA) and nano-TiO2. First, different film compositions were designed by the particle size of nano-TiO2, concentration of nano-TiO2, concentration of polyvinylpyrrolidone (PVP, a dispersing agent for nano-TiO2), and pH of film casting solution. Then, the film composition that yielded the optimal physical properties was identified using orthogonal array design single-factor experiments, considering its physical properties, including tensile strength, elongation, water absorption, water vapor transmission, oxygen permeation, thermal property, and film morphology. The results displayed that the optimal film composition was (1) soy protein/PVA film with 2.5 wt% nano-TiO2, (2) 30 nm nano-TiO2 particle size, (3) 1.5 wt% PVP, and (4) pH 6.0 of film-forming solution. It yielded tensile strength of 6.77 MPa, elongation at break rate of 58.91%, and water absorption of 44.89%. Last, the films were characterized by scanning electron microscope (SEM) and differential scanning calorimetry (DSC). SEM analysis showed that compared with the film without TiO2, the film containing TiO2 has a smoother surface, and DSC determined that adding nano-TiO2 can improve the thermostability of soy protein/PVA film. Therefore, the film prepared in this paper is expected to provide a new theoretical basis for use in the packaging industry. [ABSTRACT FROM AUTHOR]

Rubber products generally need to have high resistance to abrasion, tear, and cutting. Filling short fiber with strong mechanical properties and forming a net in the rubber matrix is a good method to realize the above aims. In this article, ultra-high molecular weight polyethylene (UHMWPE) short fibers with a diameter of 20 μm and a length of 2 cm were filled into natural rubber (NR) to improve the tear strength of the NR. The influence of the short fiber mass fraction and vulcanization conditions on the mechanical properties of the composites were investigated. The results show that the milling process and vulcanization conditions are key factors in enhancing tear resistance performance. Double-roll milling and vulcanization at 143 °C for 40 min result in strong interfacial adhesion between the UHMWPE short fibers and the NR. The addition of 2 phr of UHMWPE fiber increases the tear strength of the composite material by up to 150.2% (from 17.1 kN/m to 42.8 kN/m) while also providing excellent comprehensive performance. Scanning electron microscope (SEM) imaging confirmed that the UHMWPE short fibers are dispersed in the NR matrix homogeneously, and the interface is close and compact. As a control experiment, UHMWPE resin powder was directly filled into the NR, and then the composite was vulcanized using the same process as that used for the NR/UHMWPE short fiber composite. The results show that the mechanical strength of the NR/resin powder composite exhibits minor improvement compared with NR. As there is no complicated surface modification of the UHMWPE fiber, the results reported may be helpful in improving the tear resistance of the industrially prepared rubber conveyor belts. [ABSTRACT FROM AUTHOR]

Orally delivered probiotics must survive transit through harsh environments during gastrointestinal (GI) digestion and be delivered and released into the target site. The aim of this work was to evaluate the survivability and delivery of gel-encapsulated Lactobacillus rhamnosus GG (LGG) to the colon. New hybrid symbiotic beads alginate/prebiotic pullulan/probiotic LGG were obtained by the extrusion method. The average size of the developed beads was 3401 µm (wet), 921 µm (dry) and the bacterial titer was 109 CFU/g. The morphology of the beads was studied by a scanning electron microscope, demonstrating the structure of the bacterial cellulose shell and loading with probiotics. For the first time, we propose adding an enzymatic extract of feces to an artificial colon fluid, which mimics the total hydrolytic activity of the intestinal microbiota. The beads can be digested by fecalase with cellulase activity, indicating intestinal release. The encapsulation of LGG significantly enhanced their viability under simulated GI conditions. However, the beads, in combination with the prebiotic, provided greater protection of bacteria, enhancing their survival and even increasing cell numbers in the capsules. These data suggest the promising prospects of coencapsulation as an innovative delivery method based on the inclusion of probiotic bacteria in a symbiotic matrix. [ABSTRACT FROM AUTHOR]

This in vitro study aimed to compare the microleakage and marginal integrity of methacrylate/ormocer-based bulk-fill composite (BFC) restorations used in cervical marginal relocation with two different layering thicknesses in mesio-occlusal-distal (MOD) cavities exposed to thermo-mechanical loading. Standard MOD cavities were prepared in 60 mandibular molars and assigned into three groups: x-tra fil/AF + x-tra base/XB, Tetric N-Ceram Bulk Fill/TNB + Tetric N-Flow Bulk Fill/TFB, and Admira Fusion x-tra/AFX + Admira Fusion x-base/AFB. Each group was further divided into two subgroups (2 mm and 4 mm) based on the thickness of flowable BFCs (n = 10). The specimens were subjected to thermo-mechanical loading (240,000 cycles) and immersed in 0.2% methylene blue. Following mesiodistal sectioning, the specimens were examined under stereomicroscope (×25) and scored (0–3) for microleakage. Marginal integrity was examined using a scanning electron microscope (SEM). Descriptive statistical methods and the chi-square test were used to evaluate the data (p < 0.05). While there was no statistically significant difference in gingival cement microleakage in the XB and AFB specimens with a 4 mm thickness, microleakage was significantly increased in the TFB specimen (p = 0.604, 0.481, 0.018 respectively). A significantly higher amount of score 0 coronal microleakage was detected in the AFX2 mm + AFB4 mm compared to the TNB2 mm + TFB4 mm (p = 0.039). The SEM examination demonstrated better marginal integrity in groups with 2 mm thick flowable BFCs. Ormocer and methacrylate-based materials can be used in marginal relocation with thin layers. [ABSTRACT FROM AUTHOR]

This study evaluated the apical sealing ability and bioactivity of an experimental gutta-percha containing niobium phosphate bioglass. Thirty-six human premolars were endodontically prepared and divided into three groups: GPC—filling with conventional gutta-percha; GBC—filling with bioceramic gutta-percha (EndoSequence BC); GNB—filling with experimental gutta-percha containing niobophosphate. Teeth were stored in tubes containing 2 mL of simulated body fluid (SBF) solution in an oven for 30 days. Then, the samples were immersed in lanthanum nitrate solution and analyzed for apical nanoleakage (NI) with a scanning electron microscope (SEM/EDS) and transmission electron microscope (TEM). Gutta-percha specimens were immersed for 28 days (SBF) and analyzed in SEM/EDS and X-ray diffraction (XRD) to assess bioactivity. NI data originated from the SEM/EDS were analyzed using the Kruskal–Wallis test (α = 5%). NI data originated from TEM and bioactivity were descriptively reported. Statistical analysis did not detect a significant difference between groups (p = 0.13) for NI. In the bioactivity analysis, an abundant layer of hydroxyapatite was identified only in the surface of the GNB group samples. The gutta-percha containing niobophosphate bioglass promoted an apical sealing similar to EndoSequence BC, in addition to demonstrating bioactivity through the deposition of hydroxyapatite on the surface of the material after immersion in SBF. [ABSTRACT FROM AUTHOR]

Due to the wide scope of applications of additive manufacturing (AM) in making final products, the mechanical strength of AM parts has become very important. Therefore, different tests are being developed to determine the structural integrity of three-dimensional printed components. In this respect, the pin-bearing test is designed to evaluate the response of a fastener, plate, and hole to stress. In this study, two different polymer materials were used to fabricate the samples utilizing the fused deposition modeling technique. Since the specimen width and hole diameter have effects on the pin-bearing strength and structural integrity of the parts, we prepared the specimens with four hole diameters to determine the influence of this ratio. A series of tensile tests were performed, and the stiffness and pin-bearing strength of additively manufactured specimens were determined. The preferred bearing failure mode was observed in several tested specimens. Subsequently, a scanning electron microscope investigation was conducted on the damaged area of the examined specimens to obtain insights into the damage mechanisms and failure behavior of the aforementioned specimens. We used digital image correlation technique to determine the strain field of dumbbell-shaped test coupons. The results of this research can be utilized for new designs of AM parts with a higher mechanical strength. [ABSTRACT FROM AUTHOR]

Delamination, a form of composite failure, is a significant concern in laminated composites. The increasing use of out-of-autoclave manufacturing techniques for automotive applications, such as compression moulding and thermoforming, has led to increased interest in understanding the delamination resistance of carbon-fibre-reinforced thermoplastic (CFRTP) composites compared to traditional carbon-fibre-reinforced thermosetting (CFRTS) composites. This study evaluated the mode I (opening) interlaminar fracture toughness of two non-crimp fabric (NCF) biaxial (0/90°) carbon/thermoplastic composite systems: T700/polyamide 6.6 and T700/polyphenylene sulphide. The mode I delamination resistance was determined using the double cantilever beam (DCB) specimen. The results were analysed and the Mode I interlaminar fracture toughness was compared. Additionally, the fractographic analysis (microstructure characterisation) was conducted using a scanning electron microscope (SEM) to examine the failure surface of the specimens. [ABSTRACT FROM AUTHOR]

The first ever nanofibers produced by the electrospinning of polyvinyl alcohol (PVA) and Spirulina platensis extracts are presented in this article. Spirulina platensis extracts were obtained by ultrasound-assisted extraction (UAE) using two different solvents: a glucose/glycerol-based natural deep eutectic solvent (NADES) and water. Through spectrophotometry analysis, it was possible to determine the pigment yield of the extractions for both extracts: phycocyanin = 3.79 ± 0.05 mg/g of dry biomass (DB); chlorophylls = 0.24 ± 0.05 mg/g DB; carotenoids = 0.13 ± 0.03 mg/g DB for the NADES/Spirulina extracts, and phycocyanin = 0.001 ± 0.0005 mg/g DB; chlorophylls = 0.10 ± 0.05 mg/g DB; carotenoids = 0.20 ± 0.05 mg/g DB for water/Spirulina extracts. Emulsions were formed by mixing the microalgae extracts in PVA (9%, w/v) at different concentrations: 5, 20, 40, and 50% (v/v). Electrospinning was carried out at the following conditions: 13 cm of distance to collector; 80 kV of applied voltage; and 85 rpm of electrode rotation. After the nanofibers were collected, they were checked under a scanning electron microscope (SEM). ImageJ was also used to determine fiber diameter and frequency. SEM results showed the formation of nanofibers for 5 and 20% (v/v) of NADES/Spirulina extract content in the electrospinning emulsions, presenting diameters of 423.52 ± 142.61 nm and 680.54 ± 271.92 nm, respectively. FTIR confirmed the presence of the NADES extracts in the nanofibers produced. Overall, the nanofibers produced showed promising antioxidant activities, with the NADES/Spirulina- and PVA-based nanofibers displaying the highest antioxidant activity (47%). The highest antimicrobial activity (89.26%) was also obtained by the NADES/Spirulina and PVA nanofibers (20%, v/v). Principal Component Analysis (PCA) revealed positive correlations between both the antioxidant and antimicrobial activities of the electrospun nanofibers, and extract content in the emulsions. Moreover, PCA also indicated positive correlations between the viscosity and conductivity of the emulsions and the diameter of the nanofibers produced. [ABSTRACT FROM AUTHOR]