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Magnesium dichloride (MgCl2)-supported titanium catalyst with diisobutyl phthalate (DIBP) and 3,5-di-isopropyl 1,2-phenylene diethyl dicarbonate (CD1, non-phthalate) internal donor was synthesized using magnesium alkoxide precursor. Additionally, a catalyst without the internal donor was prepared for comparative analysis. The synthesized catalysts were characterized and compared with respect to composition, surface area, particle size and morphology. The effect of CD1-based magnesium dichloride-supported Z–N catalyst was investigated for propylene polymerization and compared with DIBP-based and without internal donor Z–N catalyst system. The catalyst system with the CD1 internal donor demonstrated a higher MFI in the resultant polypropylene, suggesting a superior hydrogen response during propylene polymerization compared to both the DIBP-based and the donor-free catalyst systems. The molecular weight of the polymer was studied through gel permeable chromatography and compared for all catalyst system. The scanning electron microscope image of the polymer resin indicates spherical morphology and exact replication of catalyst. Catalyst systems exhibiting such elevated hydrogen responses hold significant industrial relevance, especially demand of high MFI PP grades in the automotive industry. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide(MoS2) has a special structure and excellent mechanical properties, making it a promising reinforcing filler for polymers. Carbon dots (CDs) have good antioxidant properties, and the addition of CDs during the synthesis of MoS2 can affect its morphology and size. In this work, a new one-step hydrothermal synthesis process was employed to prepare CDs/MoS2 hybrid particles. Thiourea, sodium molybdate, and glucose were employed as sources of sulfur, molybdenum, and carbon, respectively. The structure and morphology of MoS2 and CDs/MoS2 were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), mapping surface scanning (SEM–EDS), and Fourier transform infrared spectroscopy (FTIR). The results show that the prepared 2H-MoS2 is stacked into flower-like spheres with size around 2–10 μm; with the formation of CDs, the size of MoS2 rapidly decreases to less than 1 μm and the CDs are evenly distributed on its surface with mass ratio of 40.2% (CDs in CDs/MoS2). Subsequently, the CDs/MoS2 were used as reinforcing fillers for natural rubber (NR) latex. The results of mechanical properties show that tear strength, tensile strength, modulus, and elongation at break are increased by the addition of CDs/MoS2 in a very lower loading, and the maximum increment ratio is 45.6% and 12.1% when compared to NR-0; the dynamic mechanical analysis and cross-link density results indicated that the CDs/MoS2 can simultaneously improve rigidity and elasticity of NR. The thermal stability results suggest that the CDs/MoS2 shows positive effects on thermal stability of NR. [ABSTRACT FROM AUTHOR]

In this paper, the silicone rubber (SR)/thermoplastic polyurethane (TPU) composites and its compatibilizers were studied by molecule dynamics simulation and experiment. Three compatibilizers, fluorosilicone rubber (FSR), dendritic hydroxyl-terminated silicone oil (DHSO), and fluorinated modified tetraethyl orthosilicate grafted silicone rubber (FTEOS-g-SR) were introduced into the SR/TPU composites. The simulation results showed that the cohesion density of pure SR was 3.072 × 108 J/m3, the solubility parameter was 17.504 (J/cm3)0.5, the Young's modulus was 4.0139 GPa, the shear modulus was 1.4493 GPa, and the bulk modulus was 5.8061 GPa. Moreover, the cohesion density of SR/TPU/FSR and SR/TPU/DHSO increased to 4.693 × 108 and 3.459 × 108 J/m3, solubility parameter increased to 21.662 and 18.597 (J/cm3)0.5, the Young's modulus increased to 6.6399 and 6.0020 GPa, shear modulus increased to 2.4377 and 2.2060 GPa, and bulk modulus increased to 8.0148 and 7.1653 GPa, respectively. However, the cohesion density, solubility, and young's modulus of SR/TPU/FTEOS-g-SR decreased to 2.617 × 108 J/m3, 16.174 (J/cm3)0.5, 3.872 GPa, 1.7510 Gpa, and 1.6365 GPa. These results demonstrated that both FSR and DHSO can improve the mechanical properties of the SR/TPU composites, while the FTEOS-g-SR reduced their mechanical properties. The compatibility and mechanical properties of SR/TPU composites modified by FSR and DHSO were verified and compared. The factors such as blending temperature, blending ratio, and TPU types of SR/TPU composites were considered. Compared to composites cured at 185 °C, those cured at 175 °C exhibited better mechanical properties. The dynamically vulcanized SR/TPU (3:7, mass ratio) materials showed superior tensile strength and elongation at break when compared to the SR/TPU (5:5, mass ratio) composites. Moreover, the polyether type of TPU was found to be more favorable than the polyester type for obtaining a blended composite with good tensile properties. The experimental results demonstrated that both compatibilizers contributed to improving the mechanical properties of the composites to a certain extent. The scanning electron microscope (SEM) test revealed that FSR enhanced the dispersion of SR in the TPU matrix. Additionally, charge distribution simulation analysis indicated the presence of abundant intermolecular hydrogen bonds between FSR and TPU, which played a significant role in the excellent compatibility and mechanical properties observed in this blend system. [ABSTRACT FROM AUTHOR]

The progress in developing biomaterials for cartilage replacement is still not sufficient, and researchers face the challenge of developing materials that can imitate the physical, chemical, and mechanobiological characteristics of natural cartilage. In this research, the graphene oxide was blended with polyvinyl alcohol/chitosan composite to fabricate composite hydrogels (PVA/Chitosan/GO) using different concentrations of graphene oxide (0, 0.75, 1.5, 2.25, and 3 wt%). The images taken with a scanning electron microscope (SEM) displayed that adding graphene oxide affected the hydrogel structure by reducing the porosity. The composite hydrogel with 3 wt% graphene oxide exhibited the highest compressive strength of 2.15 MPa, and the storage modulus was significantly greater than that of polyvinyl alcohol/chitosan, which satisfied the application requirements. Furthermore, the composite hydrogels displayed excellent antimicrobial activity against Escherichia coli and Staphylococcus aureus bacterial species. They exhibited in vitro cell viability against L929 mouse fibroblasts, which presents the possibility of using composite hydrogel for cartilage regeneration. [ABSTRACT FROM AUTHOR]

Polylactic acid (PLA) is a kind of polyester from biomass. To increase the ductility of PLA, melt blending was used to prepare the polylactic acid/poly(butylene diglycolate) blends in this study. The effect of poly(butylene diglycolate) (PBD) on the thermal, crystallization, tensile, and dynamic mechanical properties of PLA was investigated. The blend containing 30 wt% PBD has a substantially improved elongation at break (79%) due to the lower glass transition temperature of PBD compared to PLA. The results indicated that PLA and PBD exhibited partial compatibility, which was confirmed by dynamic mechanical analysis (DMA) and scanning electron microscope (SEM). Fourier transform infrared spectroscopy (FTIR) analysis showed there is the interaction between PLA and PBD. In summary, the incorporation of PBD resulted in improved mechanical properties, indicating potential for applications requiring enhanced ductility. [ABSTRACT FROM AUTHOR]

There have been continuous efforts to further promote various properties of polymeric materials to meet various industrial demands, especially in the area of thermal, electrical, mechanical and wear properties. This study developed polyvinylidene fluoride (PVDF)-boron nitride (BN) nanocomposites and significantly enhanced their wear and nanomechanical properties by incorporating very low content of carbon nanotubes (CNT). The nanocomposites were developed via simple technique of solution mixing and hot compression. Scanning electron microscope showed that the nanocomposites achieved uniform microstructure with no significant agglomeration of the nanoparticles in the PVDF matrix. The wear rate of PVDF-10wt%BN-0.1wt%CNT was reduced from 5.68 × 10–4 and 5 × 10–3 mm3/Nm for pure PVDF to 1.6 × 10–6 and 8 × 10–6 mm3/Nm at applied loads of 10 N and 20 N, respectively. Also, an increase in hardness and elastic modulus of 225% and 219% for PVDF-10wt%BN-0.1wt%CNT was obtained relative to the pure PVDF at 100-mN applied load. While the nanocomposite showed about 75% and 103% increments compared to PVDF-10wt%BN at 100 mN. This study revealed that the addition of small amount of CNT could further improve the wear and mechanical properties of PVDF-BN as well as any other polymer-ceramic binary systems various advanced engineering applications. [ABSTRACT FROM AUTHOR]

The objective of this study was to optimize the fermentation parameters by using response surface methodology for increasing pullulan production of Aureobasidium pullulans AZ-6 in synthetic fermentation medium. The optimum conditions were determined as follows: the initial sucrose concentration (X1): 100 g/L; the initial peptone concentration (X2): 11.31 g/L; the initial pH (X3): 6.48; and the temperature (X4): 24.2 °C. In the optimum conditions, the maximum exopolysaccharide (EPS) concentration (Y1), the maximum pullulan concentration (Y2), the specific growth rate (Y3), the maximum specific pullulan formation rate (Y4), and the pullulan yield (Y5) were expected to be obtained as 37.078 and 35.372 g/L, 0.062 h−1, 0.021 [g pullulan/(g mo.h)], and 53.681%, respectively. The observed values of Y1, Y2, Y3, Y4, and Y5 were 36.950 g/L, 35.470 g/L, 0.064 h−1, 0.036 [g pullulan/(g mo.sa)], and 54.480%, respectively, as a result of validation experiments. EPS samples were characterized by Fourier-transform infrared spectroscopy and scanning electron microscope analyses. The optimization process caused more than a 50% increase in EPS and pullulan concentrations. This study showed that the color-variant A. pullulans AZ-6 strain could become a significant industrial strain if it is explored further in the future to produce pullulan on a larger scale. [ABSTRACT FROM AUTHOR]

Phosphoric acid-based geopolymer (PGEO) belongs to acidic material and has many applications in environmental disposal. The curing method has an important impact on the mechanic performance of geopolymers, the existing research concerning PGEO synthesized from fly ash (FA) and phosphoric acid (PA) are performed on the specimens cured at sealed environment, but no related research on the PGEO cured at an open environment is found. Therefore, to investigate the mechanic performance, pH and of PGEO cured in an open environment, the unconfined compressive strength tests were conducted on PGEO specimens cured in an open environment, and its mechanism was investigated using Scanning Electron Microscope, X-Ray diffraction, and Fourier transform infrared reflection (FTIR) tests. Moreover, the thermogravimetric was measured using the thermogravimetric tests. The results showed that in the scope of this study, the compressive strength of the PGEO decreased with the PA concentration and the liquid–solid ratio (L/S) increasing. When the L/S was a fixed value, as the curing time increased, an obvious strength loss was observed for the PGEO with the content of 40 and 50%, but the compressive strength increased first and then, reduced for the PGEO with the content of 40 and 50%, a maximum strength was obtained at 60 days of curing. The open curing for the PGEO is not conducive to the later growth of compressive strength. As the PA concentration and L/S increased, the pH descended. As the curing time lengthened, the pH first raised and then droped, the maximum pH was obtained at 60 days. Furthermore, the compressive strength increased with the pH with a good correlation. The microscopic analysis showed that the crystalline compounds AlSiP3, Ca2P2O7(H2O)2, molecular sieve SAPO-20 (Al0.47Si0.13P0.4)O2, AlPO4-5 (AlPO4), CaHPO4, and AlPO4 in PGEO were detected. Overall, the open curing environment is not conducive to PGEO, and sealed curing should be used in engineering applications. [ABSTRACT FROM AUTHOR]

Solvent-borne polyurethane (PU) is the main product in PU synthetic leather, which has soft handling, breathability, and moisture permeability properties by wet type. The PU film would produce the irregular foam cell by solvent exchanging water. This traditional process would use a lot of dimethylformamide, and it causes much pollution of the environment. Therefore, the water-borne polyurethane system is essential in the textile industry. This study adopted the patented prepolymer process for solvent-free water-borne polyurethane (SFWPU); the foam was formed by a blowing agent and then, coated on the polyester textile with SFWPU foam by coating machine. This research focuses on the polyol composition equivalent ratio of poly(1,4-butylene adipate) glycol (PBA) and poly(tetramethylene ether) glycol from 30:70, 20:80, 10:90, and 0:100. The crystallinity increased on the foam properties with increasing the PBA composition, affecting the foam and tensile properties. Moreover, this research finds that higher crystallinity polyol of PBA contents increased, modulus of SFWPU is increased, and tensile strength is decreased. The scanning electron microscope finds the foam cell would expand by increasing PBA contents, which affects the textile's air permeability and water vapor transmission. The 10% PBA equivalent of ester–ether type SFWPU foam coated on textile, which has windproof and keeps the moisture permeability. [ABSTRACT FROM AUTHOR]

In this study, multiple emulsions stabilized by hydrophobic-hydrophilic cellulose particles from oil palm empty fruit bunch were studied. The responsiveness of the emulsions to pH and the influenced on the release of encapsulated vitamin B9 was studied using high performance liquid chromatography. The cellulose was characterized using Fourier transform infrared spectroscopy, scanning electron microscope, energy-dispersive X-ray spectroscopy, thermogravimetric analysis, differential thermogravimetric and X-ray diffraction. The result showed that crystallinity of native cellulose and modified cellulose were 66.12% and 61.38%, respectively. The emulsions stabilized by hydrophobic-hydrophilic cellulose particles showed unique responsiveness at pH 2, 4 and 7. The droplet size of the emulsion and the release of active constituent (vitamin B9) depends on the pH. The encapsulation efficiency of w/o/w multiple emulsions at pH 4 and 7 was 78.41% and 65.95%, respectively. The result showed that the release of active constituent from w/o/w multiple emulsions can be controlled based on the responsiveness to pH, to develop fascinating new applications for some specific foods, pharmaceuticals, and drug release. [ABSTRACT FROM AUTHOR]

In this study, multiple emulsions stabilized by hydrophobic-hydrophilic cellulose particles from oil palm empty fruit bunch were studied. The responsiveness of the emulsions to pH and the influenced on the release of encapsulated vitamin B9 was studied using high performance liquid chromatography. The cellulose was characterized using Fourier transform infrared spectroscopy, scanning electron microscope, energy-dispersive X-ray spectroscopy, thermogravimetric analysis, differential thermogravimetric and X-ray diffraction. The result showed that crystallinity of native cellulose and modified cellulose were 66.12% and 61.38%, respectively. The emulsions stabilized by hydrophobic-hydrophilic cellulose particles showed unique responsiveness at pH 2, 4 and 7. The droplet size of the emulsion and the release of active constituent (vitamin B9) depends on the pH. The encapsulation efficiency of w/o/w multiple emulsions at pH 4 and 7 was 78.41% and 65.95%, respectively. The result showed that the release of active constituent from w/o/w multiple emulsions can be controlled based on the responsiveness to pH, to develop fascinating new applications for some specific foods, pharmaceuticals, and drug release. [ABSTRACT FROM AUTHOR]

A pair of polyaniline (PANIs) samples was prepared from HCl or H2SO4 electrolytes containing 0.01 M of aniline, and then subjecting them to electropolymerization. The morphology, structure, and properties of the samples were characterized using scanning electron microscope, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The results demonstrate that the capacitance and morphology of the product depend exclusively on the reactive medium used. The PANI was used as a material electrode in a supercapacitor, and the electrochemical performance of the elaborated electrodes was evaluated using cyclic voltammetry, galvanostatic charge/discharge measurement, and electrochemical impedance spectroscopy. The optimal results for the specific capacitance of the PANI films were achieved under a 5-mVs−1 scan rate, ranging from 410.35 F/g for the FTO/PANI-H2SO4 to 758.72 F/g for the FTO/PANI-HCl. [ABSTRACT FROM AUTHOR]

In the current study, a biocompatible hydrogel sorbent is prepared by chemical conjunction between gum tragacanth polymer chains and polyvinyl alcohol using electron beam irradiation followed by chemical stabilization of tannin on its surface. The synthesized composite hydrogels are analyzed using infrared spectroscopy, scanning electron microscope, X-ray diffraction method and thermogravimetric analysis. Then, the ability of the prepared hydrogel sorbent to remove methyl violet from the aqueous solution is investigated. The sorption data are analyzed via Langmuir, Freundlich and Temkin isotherm models and turned out to be most consistent with the Langmuir isotherm. The maximum Langmuir sorption capacity of gum tragacanth-polyvinyl alcohol/tannin composite hydrogel for the removal of methyl violet was 35.21 mg g−1. The sorption process is found to be endothermic and spontaneous. Experimental data are also analyzed using kinetic equations of pseudo-first-order, pseudo-second-order and Elovich, and are found to be in good agreement with the pseudo-second-order model. [ABSTRACT FROM AUTHOR]

Delamination due to an inferior adhesion between reinforcement material and matrix in carbon fiber-reinforced thermoplastic (CFRTP) composites is a crucial problem to be solved. To this end, this study aims to overcome poor wettability between reinforcing phase, i.e., carbon fiber (CF), and thermoplastic matrix, i.e., polyetherether ketone (PEEK). Herein, CF's surface was tailored by application of different polymeric sizing agents which have different chemical structures. Morphology and topology analyses were performed by Scanning Electron Microscope and 3D laser scanning, respectively. Later, a variety of wettability results were obtained by the sessile drop method used in Contact Angle (CA) measurements for CFs throughout application of each sizing agent applied by dip coating. Sizing materials were designed such that the chemical structure of CF's surface could exhibit compatibility with the matrix itself. Consequently, complete wettability (CA: 0°) was achieved for CFs sized by HPEEK (CF/hydroxylated PEEK (HPEEK)) and the surface free energy (SFE) of CF was enhanced from 5.43 to 72.8 mJ/m2 while the SFE of the PEEK matrix is 40.1 mJ/m2. Moreover, sizing by HPEEK improved the average surface roughness of CF by 32% which enables optimized adhesion. Afterward, repetitive tensile tests were carried out to observe effects of improved interfacial interlocking on the mechanical properties of the final CFRTP composite. Stress–strain curves revealed that the tensile strength of CFRTP improved from 473 to 508 MPa through the sizing of CF by HPEEK whereas pristine PEEK has a much smaller tensile strength (98 MPa) than the aforementioned CF-reinforced composites. The sizing of carbon fiber's surface by HPEEK resulted in an enhanced adhesion with the PEEK matrix. Since the chemical structure and physical properties of sizing agent and matrix are compatible, potential debonding between them was eliminated. Thus, the improved wettability led to a substantial increase in the mechanical strength of the final TP composite. [ABSTRACT FROM AUTHOR]

Bicomponent nanofibers of cellulose acetate (CA) and polyethylene imine were successfully fabricated by electrospinning technique to capture CO2 gas. The concentration of polyethylene imine was fixed to 25, 50, and 75% compared to the CA concentration. The nanofibers were characterized using FT-IR, X-ray diffraction (XRD) and thermogravimetric analyzer (TGA). The effect of PEI on the morphology of CA nanofibers was studied using scanning electron microscope (SEM). The diameter of electrospun CA/PEI nanofibers becomes larger with the increase of PEI content due to repulsion of electrical force from side polar groups. In addition, PEI diffused on the nanofiber surface was observed at high concentrations of PEI. The CO2 adsorption capacity of electrospun CA/PEI nanofiber membranes was investigated at different temperatures using a BET. The increase of PEI content in nanofibers increased the CO2 adsorption capacity, and the adsorption capacity was larger at lower temperature. The decrease in CO2 adsorption capacity with increasing temperature indicates that CO2 adsorption is more responsible for physisorption. Moreover, the CA/PEI electrospun membrane retains 99% of its initial CO2 adsorption capacity after 5 cycles of the adsorption and desorption process. [ABSTRACT FROM AUTHOR]

Molecularly imprinted polymers (MIPs) have attracted much attention in recent years due to their structure predictability, recognition specificity, and universal application, as well as robustness, simplicity, and cheapness. In this study, firstly, the pre-polymerization process of molecularly imprinted polymer of dipicolinic acid (DPA) was simulated by molecular dynamics. Then, the appropriate functional monomer molecule for printing was selected and its intermolecular bond with the DPA molecule was evaluated. The monomers 2-vinyl pyridine, acrylic acid (AA), and methacrylic acid (MAA) were selected with potential energies of 3.93 kcal/mol, 3.15 kcal/mol, and 2.78 kcal/mol, respectively. Finally, the ability of functional groups to form hydrogen bonds was estimated, and molecularly imprinted polymers (MIPs) and non-imprinted polymers (NIPs) were synthesized by bulk polymerization. MAA and AA were used as functional monomers to identify DPA molecules. The morphology of MIP and NIP was investigated using a scanning electron microscope (SEM). Their performance was evaluated in the absorption of DPA molecules and picolinic acid (PA) molecules and the printing factor of synthesis polymers. The results showed that fabricated MIPs can be used in the structure of sensors, and the synthesis process is a key factor that significantly affects the polymer properties. The MIP based on the AA monomer showed a higher adsorption rate/capacity and maximum printing factor than MAA monomer-based MIP. [ABSTRACT FROM AUTHOR]

Dressing plays important role in wound healing. Hydrogels are three-dimensional structural systems with outstanding properties for wound dressing. However, conventional preformed hydrogels lack versatility in different models and applications. In the present study, two-layer nanofiber-hydrogel nanocomposite was prepared, and their potential application as a dressing was considered. The first layer was made of polyacrylonitrile (PAN) by electrospinning method. Tragacanth hydrogel containing Lavandula angustifolia extract (LAV) and Mupirocin (MUP) was sprayed on the electrospun nanofiber layers as the second layer. Scanning electron microscope (SEM) images of nanofibers showed very fine and continuous fibers with an average diameter 420 nm. Also, SEM images of the cross section of the two-layer dressing confirmed the formation of hydrogel on the nanofibers. The nanofibers showed strong mechanical properties as Young's modulus. The elongation at break was reduced for bilayers containing hydrogel. In vitro cell viability tests showed that two-layer nanofiber-Tragacanth hydrogel composite has no cytotoxicity. Antibacterial properties of the dressing showed a significant effect on inhibiting Staphylococcus aureus. The test results showed that spraying hydrogel on nanofiber layer has dual advantages of electrospun fiber and hydrogel, such as ECM-like fiber structure, high water retention and excellent biocompatibility. [ABSTRACT FROM AUTHOR]