Crosslinked carboxylated SBR composites reinforced with chitin nanocrystals

This study aims to develop and characterize the nanocomposites using sulfur cross-linked carboxylated styrene-butadiene rubbers (S-xSBR) as the matrix and chitin nanocrystals (CNCs) as nanofillers. The composites’ morphology and properties were examined by light transmittances, fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), dynamic mechanical analysis (DMA), thermo gravimetric analyzer (TGA), and tensile properties determination. The addition of CNCs has slight effect on transparency of the composite films. FTIR data confirm the interfacial interactions between CNCs and S-xSBR via hydrogen bonds. CNCs are uniformly dispersed in the matrix from SEM result. The addition of CNCs can significantly improve the tensile strength and modulus both in static and dynamic states. The tensile modulus and tensile strength of S-xSBR/CNCs composites with the 4 wt.% CNCs is 62.5 % and 97.6 % higher than that of pure S-xSBR. The storage modulus, glass transition temperature, and the thermal stability of the composites are higher than those of the neat S-xSBR. The mechanical properties of the composite films are water-responsive, as the swollen samples exhibit obviously decreased strength and modulus. The greatest mechanical contrast is shown in the S-xSBR/CNCs composites with 2 wt.% CNCs loading whose tensile modulus decrease from 60.4 to 6.1 MPa after swelling equilibrium. The significant reinforcement effect of CNCs on S-xSBR is attributed to the unique structure of CNCs and the interfacial interactions in the composite.     

Effects of water on drawability,structure, and mechanical properties of poly(vinyl alcohol) melt‐spun fibers

Poly(vinyl alcohol) (PVA) melt‐spun fibers with circular cross‐section and uniform structure, which could support high stretching, were prepared by using water as plasticizer. The effects of water content on drawability, crystallization structure, and mechanical properties of the fibers were studied. The results showed that the maximum draw ratio of PVA fibers decreased with the increase of water content due to the intensive evaporation of excessive water in PVA fibers at high drawing temperature. Hot drying could remove partially the water content in PVA as‐spun fibers, thus reducing the defects caused by the rapid evaporation of water and enhancing the drawability of PVA fibers at high drawing temperature. The decreased water content also improved the orientation and crystallization structure of PVA, thus producing a corresponding enhancement in the mechanical properties of the fibers. When PVA as‐spun fibers with 5 wt % water were drawn at 180 °C, the maximum draw ratio of 11 was obtained and the corresponding tensile strength and modulus reached ～0.9 GPa and 24 GPa, respectively. Further drawing these fibers at 215 °C and thermal treating them at 220 °C for 1.5 min, drawing ratio of 16 times, tensile strength of 1.9 GPa, and modulus of 39.5 GPa were achieved. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45436.     

A commercial production route to prepare polymer‐based nanocomposites by unmodified multilayer graphene

In this study, we report our progress toward an effective method to prepare polyamide 6 (PA6)/multilayer graphene (MLG) nanocomposites via in situ polymerization. The thermal and mechanical properties of PA6 nanocomposites were investigated with low unmodified MLG content of 0.01–0.5 wt %. The dispersion of MLG sheets in the host matrix was studied in extensive detail while the properties of the resultant nanocomposites were systematically measured. Results indicate that the mechanical properties of the nanocomposites were significantly enhanced; the flexural modulus, flexural strength and impact strength increased by ～97%, ～69%, and ～76% relative to pristine PA6. Furthermore, the thermal stability of nanocomposites was enhanced and the weight loss temperature of PA6 was increased ～15°C at 0.5 wt % content of MLG. Moreover, incorporation of low loading of MLG can increase the crystallization speed of PA6 composites and promote the formation of the γ‐crystalline phase while also improving the crystallization temperature. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42742.     

Cellulose Nanocrystals/ZnO as a Bifunctional Reinforcing Nanocomposite for Poly(vinyl alcohol)/Chitosan Blend Films: Fabrication,Characterization and Properties

In this study, cellulose nanocrystals/zinc oxide (CNCs/ZnO) nanocomposites were dispersed as bifunctional nano-sized fillers into poly(vinyl alcohol) (PVA) and chitosan (Cs) blend by a solvent casting method to prepare PVA/Cs/CNCs/ZnO bio-nanocomposites films. The morphology, thermal, mechanical and UV-vis absorption properties, as well antimicrobial effects of the bio-nanocomposite films were investigated. It demonstrated that CNCs/ZnO were compatible with PVA/Cs and dispersed homogeneously in the polymer blend matrix. CNCs/ZnO improved tensile strength and modulus of PVA/Cs significantly. Tensile strength and modulus of bio-nanocomposite films increased from 55.0 to 153.2 MPa and from 395 to 932 MPa, respectively with increasing nano-sized filler amount from 0 to 5.0 wt %. The thermal stability of PVA/Cs was also enhanced at 1.0 wt % CNCs/ZnO loading. UV light can be efficiently absorbed by incorporating ZnO nanoparticles into a PVA/Cs matrix, signifying that these bio-nanocomposite films show good UV-shielding effects. Moreover, the biocomposites films showed antibacterial activity toward the bacterial species Salmonella choleraesuis and Staphylococcus aureus. The improved physical properties obtained by incorporating CNCs/ZnO can be useful in variety uses.     

Preparation and characterization of poly(glycerol sebacate)/cellulose nanocrystals elastomeric composites

Poly(glycerol sebacate) (PGS) is one of the new elastomers used for soft tissue engineering, while improving its limited mechanical strength is the biggest challenge. In this work, a novel biodegradable elastomer composite PGS/cellulose nanocrystals (CNCs) was prepared by solution‐casting method and the mechanical properties, sol–gel contents, crosslink density, and hydrophilic performance were characterized. The thermal and degradation properties of composites were also investigated. Results show that the addition of CNCs into PGS resulted a significant improvement in tensile strength and modulus, as well as the crosslink density and the hydrophilicity of PGS. When the CNCs loading reached 4 wt %, the tensile strength and modulus of the composite reached 1.5 MPa and 1.9 MPa, respectively, resulting 204% and 158% increase compared to the pure PGS. Prolonging the curing time also improved the strength of both the neat PGS and PGS/CNCs composites according to the association and shift of hydroxy peaks around 3480 cm^?1. DSC results indicate that the addition of CNCs improved both the crystallization capacity and moving capability of PGS molecular chain. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42196.     

Mechanical and thermal properties of poly(butylene succinate)/plant fiber biodegradable composite

Biodegradable polymeric composites were fabricated from poly(butylene succinate) (PBS) and kenaf fiber (KF) by melt mixing technique. The mechanical and dynamic mechanical properties, morphology and crystallization behavior were investigated for PBS/KF composites with different KF contents (0, 10, 20, and 30 wt %). The tensile modulus, storage modulus and the crystallization rate of PBS in the composites were all efficiently enhanced. With the incorporation of 30% KF, the tensile modulus and storage modulus (at 40°C) of the PBS/KF composite were increased by 53 and 154%, respectively, the crystallization temperature in cooling process at 10°C/min from the melt was increased from 76.3 to 87.7°C, and the half‐time of PBS/KF composite in isothermal crystallization at 96 and 100°C were reduced to 10.8% and 14.3% of that of the neat PBS, respectively. SEM analysis indicates that the adhesion between PBS and KF needs further improvement. These results signify that KF is efficient in improving the tensile modulus, storage modulus and the crystallization rate of PBS. Hence, this study provides a good option for preparing economical biodegradable composite. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of crosslinking methods toward poly(vinyl alcohol) properties: Microwave irradiation and conventional heating

In this study, crosslinking of poly(vinyl alcohol) (PVA) with tartaric acid, as crosslinker, is performed using microwave irradiation. A comparison between the properties of PVA crosslinked using microwave irradiation and conventional heating methods is also discussed. While the water absorption, tensile and thermal properties of PVA crosslinked by either of the methods are comparable, microwave irradiation took only one‐eighth (14 min) of the time compared to conventional heating. In comparison with PVA (42 MPa), the strength of PVA crosslinked with 35% TA increased to 145 and 153 MPa for conventional heating and microwave irradiation, respectively. Water absorption of crosslinked PVA film is successively reduced to less than 30% in comparison with PVA (～200%). Moreover, the crosslinked films are stable at higher temperatures in comparison with PVA. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46125.     

Thermoplastic polyvinyl alcohol/multiwalled carbon nanotube composites: Preparation,mechanical properties,thermal properties,and electromagnetic shielding effectiveness

This study uses the solution mixing method to combine plasticized polyvinyl alcohol (PVA) as a matrix, and multiwalled carbon nanotubes (MWCNTs) as reinforcement to form PVA/MWCNTs films. The films are then laminated and hot pressed to create PVA/MWCNTs composites. The control group of PVA/MWCNTs composites is made by incorporating the melt compounding method. Diverse properties of PVA/MWCNTs composites are then evaluated. For the experimental group, the incorporation of MWCNTs improves the glass transition temperature (T_g), crystallization temperature, T_c), and thermal stability of the composites. In addition, the test results indicate that composites containing 1.5 wt % of MWCNTs have the maximum tensile strength of 51.1 MPa, whereas composites containing 2 wt % MWCNTs have the optimal electrical conductivity of 2.4 S/cm, and electromagnetic shielding effectiveness (EMI SE) of ?31.41 dB. This study proves that the solution mixing method outperforms the melt compounding method in terms of mechanical properties, dispersion, melting and crystallization behaviors, thermal stability, and EMI SE. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43474.     

Crosslinked poly(vinyl alcohol) and starch composite films. II. Physicomechanical,thermal properties and swelling studies

Poly(vinyl alcohol) (PVA) was blended with 10, 20, 30, 40, and 50 wt % of starch with and without crosslinking by solution casting process. The solution‐casted films were dried and tested for physicomechanical properties like tensile strength, tensile elongation, tensile modulus, tear and burst strengths, density, and thermal analysis by differential scanning calorimetry (DSC). These PVA/starch films were further characterized for moisture content; solubility resistance in water, 5% acetic acid, 50% ethanol, and sunflower oil; and swelling characteristics in 50% ethanol and sunflower oil. The crosslinked PVA/starch composite films show significant improvement in tensile strength, tensile modulus, tear and burst strengths, and solubility resistance over the uncrosslinked films. Between the crosslinked and uncrosslinked films, the uncrosslinked films have higher tensile elongation, moisture content, moisture absorption, and swelling over the crosslinked films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 909–916, 2007     

Carrier films behavior during thermoforming process studied using dynamic mechanical thermal analysis (DMTA)

Dynamic mechanical thermal analysis was used to investigate the thermal transitions and modulus/temperature behavior of thermoformable carrier films, and to relate the information obtained to carrier film behavior during the thermoforming process. In this study the glass transition temperatures (T _g) and the temperatures at which crystallization occurred during heating (T _c) of four thermoformable carrier films were measured by using a dynamic mechanical thermal analyzer (DMTA). These films are good candidates for the automotive process, which uses painted carrier films as moldable automotive coatings (MAC). The modulus/temperature behavior of the films was also observed over a wide temperature range, which included thermoforming temperatures. Although films of PETG and PCTG 5445, co-polyesters based on poly(1,4-cyclohexylene dimethylene terephthalate), are thermoformable, their T _g values, 92 and 99 °C, respectively, are not high enough to allow current paint systems (with bake temperature of 100–110 °C) to cure on the films without causing severe film deformation.     

Elaboration of performance of tea dust–polypropylene composites

In this research work, dynamic, mechanical, and thermophysical properties of untreated and 5, 7, and 10 wt % styrene treated tea dust (TD):polypropylene (PP) composites prepared by injection‐molding machine were elaborated. There were distinctive and significant improvement observed in mechanical properties (tensile strength, tensile modulus, and elongation at break), physical analysis (water swelling), dynamic mechanical properties (storage modulus, loss modulus, and tan δ), and thermal behavior and surface morphological properties of styrene treated TD:PP (40:60) composites as compared to that of untreated one. The tensile strength (from 7.00 to 9.95 MPa), tensile modulus (from 350 to 715 MPa), storage modulus (from 8500 to ～10,500 MPa), and loss modulus (from ～150 to ～200 MPa) increased on 10 wt % styrene treatment of TD over the untreated TD:PP (40:60) composites. The styrene treated TD:PP (40:60) composites behaved as more elastic than their pure counterpart. Styrene treated TD:PP (40:60) composites were more thermally more stable (85 °C difference) as compared to virgin PP. Overall, this research also indicates the use of TD waste. An improvement in dispersion of styrene treated TD particles in PP was also observed in the preparation of the PP composites due to good compatibility of styrene with PP. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44750.     

High‐tensile‐strength polyvinyl alcohol films prepared from freeze/thaw cycled gels

The mechanical properties and molecular structure of a poly(vinyl alcohol) (PVA) film, which was obtained by eliminating water from a PVA hydrogel using repeated freeze/thaw cycles, were investigated by tensile tests, thermal analysis, and X‐ray diffraction measurements. The mechanical properties of PVA with 99.9% saponification were measured as a function of the number of freeze/thaw cycles performed. The tensile strength and Young's modulus increased and the elongation at break decreased with increasing freeze/thaw cycles. The tensile strength and Young's modulus of PVA films obtained after seven freeze/thaw cycles were as high as 255 MPa and 13.5 GPa after annealing at 130°C. Thermal analysis and X‐ray diffraction measurements revealed that this is because of a high crystallinity and a large crystallite size. A good relationship between the tensile strength and the glass transition temperature was obtained, regardless of the degree of saponification and annealing conditions. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40578.     

Investigation of non-isothermal crystallization,dynamic mechanical and dielectric properties of poly(ether-ketone) matrix composites

ABSTRACT

Poly(ether-ketone)/hexagonal boron nitride (h-BN) composites reinforced with micrometer-sized h-BN particles were investigated. The composites exhibited glass transition temperature (T_g) and thermal stability over 160°C and 560°C, respectively. The melting point and peak crystallization temperatures of the composites decreased up to 17°C and 12°C, respectively. The linear CTE of the composites decreased both below and above the T_g. The storage modulus increased with increasing h-BN content at all temperatures (50–250°C). The composites possessed excellent dielectric properties with insignificant dispersion with increasing frequency. Thus, resultant composites are promising candidates for the printed circuit boards/electronic substrates.     

Dynamic mechanical and thermal properties of fire-retardant polypropylene

A study of the effect of a series of fire retardants and antimony oxide upon the dynamic mechanical and thermal properties of polypropylene suggests three categories. (1) “Inert Fillers”—These raise the elastis modulus and the heat distortion temperature of polypropylene without shifting its glass transition temperature. The melting point of polypropylene is only depressed by 1–3°C, the heat of fusion and the percentage of crystallinity of polypropylene in these composites is ～10 percent lower at additive concentrations of ～30 percent. Very poor interaction exists between the additive and the thermo-plastic which apparently exist in two separate phases. (2) “Chain Stiffener”—These raise the elastic modulus (～25 percent) and the glass transition (～11°C) for polypropylene; the melting point of polypropylene in the composite is lowered by ～6°C indicative of good interaction between the additive and polypropylene. (3) “Plasticizer”—These lower the room temperature elastic modulus (～20 percent) and the glass transition temperature (～11°C) of polypropylene; the melting point of polypropylene in the composite is depressed by ～10°C indicating good interaction. The efficacy of the “plasticizer” and “chain stiffener” are attributed partially to melting of polypropylene at the processing temperature.     

Thermal property improvement of ethylene‐octene copolymer through the combined introduction of filler and silane crosslink

In many applications, e.g., wire and cable insulation, hot water pipe, high‐temperature properties of polymer are essential. This article presents the use of silane crosslinking together with the addition of particular filler in improving the thermal and mechanical properties of ethylene‐octene copolymer (EOC). The effects of filler surface characteristics on siloxane network structure developed and final properties of the crosslinked products are discussed. The results show an increase in the decomposition temperature of EOC more than 50°C after modification. Only crosslinked composites are able to withstand the high‐temperature environment of aging test which is beyond the melting temperature of the matrix polymer. The crosslinked composites filled with calcium carbonate show superior properties to those with silica, due to a higher crosslink density and tighter network structure formed. The silane coupling mechanism and the presence of bound polymer on silica surfaces cause difficulties for the crosslink formation in the silica filled systems. However, an advantageous influence of both silane coupling and crosslink reaction in the silica filled composites is seen on the enhanced tensile strength and modulus of the materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of UV exposure and thermal history on properties of a preimidized photosensitive polyimide

The structure and properties of a preimidized photosensitive polyimide (Probimide PSPI, a copolyimide of benzophenonetetracarboxylic dianhydride with alkyl groups substituted aromatic diamines) were studied with variations of UV exposure energy and bake temperature by means of wide angle X-ray diffraction, dynamic mechanical thermal analysis, stress-strain analysis, and residual stress analysis. The X-ray diffraction patterns patterns indicate that the PSPI is amorphous in the solid state. The T_g was 378°C ～ 410°C, depending upon the thermal history over the range of 350°C ～ 400°C. At the glass transition region, the dynamic storage modulus E′ was very sensitive to both i-line exposure energy and thermal history. However, the mechanical stress-strain behavior at room temperature was primarily dependent on the thermal history. The mechanical properties were 2.6 GPa ～ 2.9 GPa Young's modulus, 131 MPa ～ 168 MPa tensile strength, 10% ～ 12% yield strain, and 16% ～ 74% elongation at break, depending upon the baking or annealing. These dynamic and static mechanical properties indicate that on the PSPI backbone, crosslinks are formed thermally as well as photochemically. The thermal crosslinks might be formed through thermal liberation of the labile alkyl groups of aromatic diamine moieties and subsequent coupling of the radicals. The thermal degradation was also evidenced in the mechanical properties degraded by baking above 375°C or annealing above 350°C. In addition, during baking and cooling, the residual stress was dynamically measured on Si wafers as a function of temperature. The stress at room temperature was 48 MPa ～ 52 MPa for the PSPI films baked at 350°C or 400°C, regardless of i-line exposure.     

Fabrication and properties of clay-supported carbon nanotube/poly (vinyl alcohol) nanocomposites

Clay-supported carbon nanotubes (Cs-CNTs) were used as novel nanofillers to improve the thermal and mechanical properties of a polymer. Cs-CNT/poly (vinyl alcohol) (PVA) nanocomposite films were successfully fabricated, and their relative properties were investigated by using differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. Experimental results showed that the thermal stability and dynamic mechanical properties of PVA were remarkably enhanced by incorporating the Cs-CNTs into PVA matrix. The largest T_g difference of 14°C was obtained between pure PVA and PVA nanocomposite with 7 wt% Cs-CNTs. Moreover, the storage modulus of PVA was significantly improved by 133% at 50°C, when 7 wt% Cs-CNTs was added to PVA matrix. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Rapid synthesis of high strength cellulose–poly(vinyl alcohol) (PVA) biocompatible composite films via microwave crosslinking

The present study describes microwave (MW)-assisted rapid synthesis of biocompatible poly(vinyl alcohol) (PVA) composite films that demonstrate synergy between reinforcement and crosslinking. Bacterial cellulose (5% w/w) nanowhiskers (reinforcement) and tartaric acid 35% (w/w) (crosslinker) are incorporated in PVA to prepare crosslinked cellulose–PVA composite films. The properties of thus prepared crosslinked cellulose–PVA composite films are compared with samples crosslinked with conventional hot air oven heating (CH). Crosslinking by both of the methods reduces water absorption of PVA by around an order of magnitude and improves its thermal stability. An increase in strength from 42 (PVA) to 172 MPa and 159 MPa for MW and CH crosslinked samples, respectively is also observed. Although composites prepared using MW and CH show similar properties, MW takes only 14 min compared to 2 h in case of CH. Notably, the prepared composites demonstrate hemocompatibility and cytocompatibility, and may also be explored for biomedical applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47393.     

Tensile properties of two-dimensional carbon fiber reinforced silicon carbide composites at temperatures up to 2300 °C

Carbon fiber reinforced silicon carbide (C/SiC) composites are of the few most promising materials for ultra-high-temperature structural applications. However, the existing studies are mainly conducted at room and moderate temperatures. In this work, the tensile properties of a two-dimensional plain-weave C/SiC composite are studied up to 2300 °C in inert atmosphere for the first time. The study shows that C/SiC composite firstly shows linear deformation behavior and then strong nonlinear characteristics at room temperature. The nonlinear deformation behavior rapidly reduces with temperature. The Young’s modulus increases up to 1000 °C and then decreases as temperature increases. The tensile strength increases up to 1000 °C firstly, followed by reduction to 1400 °C, then increases again to 1800 °C, and lastly decreases with increasing temperature. The failure mechanisms being responsible for the mechanical behavior are gained through macro and micro analysis. The results are useful for the applications of C/SiC composites in the thermal structure engineering.     

Thermal and dynamic mechanical properties of organic–inorganic hybrid composites of itaconate‐containing poly(butylene succinate) and methacrylate‐substituted polysilsesquioxane

Itaconate‐unit‐containing poly(butylene succinate) (PBSI) was synthesized by the reaction of 1,4‐butanediol, succinic acid, and itaconic acid in a molar ratio of 2.0 : 1.0 : 1.0, and the obtained PBSI was reacted with methacryl‐group‐substituted polysilsesquioxane (ME‐PSQ) in the presence of benzoyl peroxide (BPO) at 130°C to produce PBSI/ME‐PSQ hybrid composites. The thermal and dynamic mechanical properties of the PBSI/ME‐PSQ hybrid composites were investigated in comparison with those of PBSI cured at 130°C in the presence of BPO. As a result, the hybrid composites showed a much higher thermal degradation temperature and storage modulus in the rubbery state than the cured PBSI (C‐PBSI). The thermal degradation temperature and storage modulus of the hybrid composites increased with increasing ME‐PSQ content. The glass‐transition temperature, measured by dynamic mechanical analysis of the hybrid composites, somewhat increased with increasing ME‐PSQ content. However, the glass‐transition temperatures of all the hybrid composites were lower than that of C‐PBSI. Although the IR absorption peak related to C?C groups was not detected for C‐PBSI, some olefinic absorption peaks remained for all the hybrid composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008