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This study aims to develop sustainable, renewable and biodegradable biocomposite films from environmentally friendly materials. For this purpose, completely biodegradable polymer composites were prepared by mixing polylactic acid (PLA) with a new source, quince peel (QP), by solvent casting method, and their structural, mechanical and thermal properties were examined. The tensile strengths of the composites prepared using QP in proportions varying between 5% (P5Q) and 30% (P30Q) by weight vary between 21.13 ± 0.80 and 12.01 ± 0.10 MPa, and their elongations at break vary between 11.33 ± 0.38 and 4.08 ± 1.06 %. As the QP contribution increased, the tensile strength and breaking elongation of these composites generally decreased, while the elastic modulus also increased. Among these composites, whose elastic modulus varies between 1040.00 ± 140.01 and 811.33 ± 13.31 MPa, it was determined that the elastic modulus (1040.00 ± 140.01 MPa) of the 20% QP added composite (P20Q) was higher than the others. When the thermal analysis of PLA/QP films were examined, it was observed that the glass transition temperatures (Tg) were between 58.54 and 51.45°C and the melting temperatures (Tm) were between 167.71 and 164.28°C, and these temperatures generally decreased with increasing QP doping. When the T50 values, which represent the temperature at which 50% of the composite materials decompose, were examined, it was found that the QP-added ones were higher than the pure composites. While this value was 317.96°C in pure PLA composite, T50 values varied between 327.92 and 340.80°C depending on the varying QP ratios. According to the XRD results performed to evaluate the crystalline properties of PLA composites containing quince bark, the crystallinity of pure PLA was determined as 19.5% and the crystallinity of composites containing 5, 10, 20 and 30 wt % QP additives was determined as 19.3, 18.3, 16.4 and 14.6%, respectively. [ABSTRACT FROM AUTHOR]

The metal cross-linking fluorinated polyacrylate colloid has a high cross-linking density, high transparency, high heat resistance and hydrophobicity. In this paper, the metal cross-linking fluorinated polyacrylate colloid is synthesized via the semi-continuous seeded emulsion polymerization technology, which uses the self-made magnesium acrylate, calcium acrylate and zinc acrylate as metal crosslinker and dodecafluoroheptyl methacrylate as a fluorine monomer. In this study, the ablation effect of the metal ions is weakened by the increased amount of environmentally friendly and polymerizable anion emulsifier DNS-86. The demulsification phenomenon of emulsion is successfully overcome through destroying the double layer structure of micelles or colloid particles by polyvalent metal ions. The colloidal particle size is smaller and the particle size distribution of the colloid is more uniform. Colloidal film has a good hydrophobicity and the glass transition temperature and the thermal decomposition temperature are high. [ABSTRACT FROM AUTHOR]

This work evaluates the effect of plasma treatment on the wettability, dynamic mechanical and thermal properties of compression-molded composite panels produced from wood fiber (WF) and polypropylene (PP). Initially, WF was treated with different plasma durations (60, 120, and 180 s radiation). Afterward, the contact angle, moisture uptake, storage modulus, loss modulus, damping loss, and weight loss of the specimens prepared from untreated and plasma-treated were evaluated. Results revealed that the plasma treatment facilitates the interactions between WF and PP, and increases the adhesion properties. Compared with the lowest contact angle of 74.8° for the untreated specimens, the highest contact angle was found in the treated specimens around 79.06°, 81.29°, and 82.7°, using 60 and 15 using 180 s plasma radiations. Furthermore, the water absorption of the specimens reduced as a result of plasma treatment. The plasma-treated specimens demonstrated better molecular restriction and larger dynamic modulus than the unmodified ones. The tan δ peak signifying the glass transition temperature of composites shifted to a higher temperature, in the presence of plasma treatment. It was noted that the thermal stability of the composite panels produced from plasma-treated wood was remarkably improved. [ABSTRACT FROM AUTHOR]

The structural, optical, morphological and thermal properties of poly (methyl methacrylate) (PMMA)/boehmite nanocomposite films were studied by Fourier transform infrared spectroscopy (FT-IR), UV-Vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) studies. The FT-IR spectra of composites showed the characteristic band of boehmite nanoparticles at 518 cm−1 indicating an effective interaction between PMMA and boehmite. The UV-visible measurements showed that the optical energy gaps for the direct permitted transitions decreased as boehmite content increased. The orientation of nanoparticles observed from XRD revealed that the addition of boehmite increases the crystallinity of PMMA. The SEM analysis showed the uniform distribution of boehmite in the PMMA matrix. The shift in glass transition and melting temperatures to higher temperature domains were revealed by DSC analysis. From the TGA studies, the reinforcement of PMMA with boehmite nanoparticles increases thermal stability. The electrical conductivity was measured using the impedance technique, and it was studied as a function of nanoparticles loading, applied frequency ranging from 100 to 106 Hz and at different temperatures. The AC conductivity of the composite increases with frequency and temperature. The activation energy was also measured for all samples at various applied frequencies, and it was observed that it decreased with increasing nanoparticle loading. The dielectric constant of PMMA increases with nanoparticle concentration up to 7 wt%. The modulus, tensile strength, hardness, and impact properties of the PMMA/boehmite nanocomposite films were significantly enhanced by the reinforcement of nanoparticles into the polymer matrix. The excellent optical properties, mechanical strength and electrical properties obtained for 7 wt% loaded nanocomposite films enable them to be used in the construction of electromagnetic induction shielding materials, conducting adhesives, and flame-resistant flexible optoelectronic devices. [ABSTRACT FROM AUTHOR]

The addition effects of zinc (Zn), cobalt (Co), and magnesium (Mg) based metallic stearates into poly (lactic acid) (PLA) matrix were investigated through torque rheometry, thermogravimetry (TG) and in the Differential Scanning Calorimetry (DSC). PLA compounds/metallic stearates were processed using an internal laboratory mixer with 0.25 wt% Zn, Co, and Mg. Torque rheometry results indicated that PLA/stearate compounds showed higher thermomechanical degradation during processing related to PLA. PLA viscosity is reduced upon stearates addition, especially in the compound with Zn. This behavior suggested PLA chain scission in the presence of metallic stearates during processing, corroborating the decrease in the torque plots. PLA/Zn started to lose weight at lower temperatures than the other compounds, indicating higher pro-oxidant potential. It was observed that Co and Zn significantly reduced the glass transition temperature (Tg), as well as PLA's crystalline parameters, which suggests PLA's molecular scission during processing, heading to greater flexibility and reducing Tg. Zn stearate was the most aggressive to PLA's thermomechanical degradation, suggesting a stronger pro-degradant effect. [ABSTRACT FROM AUTHOR]

Properties of cyclized natural rubbers (NR) with various degrees of cyclization (∼4-22%) were investigated in this study. Prior to compounding with rubber additives, the cyclized rubbers were initially prepared by dropping various concentrations of acid (5-30 wt%) to the NR latex, followed by coagulation and drying. The results revealed that the degree of cyclization increased with acid concentration. Increased ring structure formation in the modified NR tended to increase the torque difference during crosslinking, as the cyclic ring structures acted as steric hindrances. The crosslink density was found to decrease with increasing cyclization level due to the loss of active sites for crosslink formation, increasing swelling capability of the cyclized rubbers. The 100% and 300% moduli, tensile strength and extensibility of the NR reduced with increasing degree of cyclization due to a reduction of crosslink density. As a result of cyclic structure formation and a reduction of unsaturated double bonds in the NR, the stability of cyclized NR at elevated temperatures was improved over the pure NR, in a manner dependent on the level of cyclization. Single glass transition temperature was seen in the NR while two glass transition temperatures were noticed in the cyclized NR. The thermal stability of 22% cyclized NR was 50°C higher than that of the pure NR and the aging properties of the cyclized NRs were also greater mainly due to a reduction of unsaturated double bonds. This suggests that cyclized NR may find applications in products requiring thermal resistance. [ABSTRACT FROM AUTHOR]

The increased demand for the discovery of new conducting materials encourages the researchers for the development of advanced electronic technologies. In the present study, nanocomposites of poly (anthranilic acid- co -indole) / (PANA- C o -PIN) and magnetite nanoparticles (Fe3O4) were prepared via a one-step polymerization method and evaluated by various analytical techniques. The Fourier transform infrared spectroscopy (FT-IR) spectra proved the presence of Fe3O4 nanofillers in the copolymer at 507 cm−1. Optical characterization (UV-Vis) shows a clear blueshift indicating strong interactions between Fe3O4 and PANA- C o -PIN. The X-Ray diffraction (XRD) patterns revealed an increase in crystallinity due to the well dispersed nanoparticles. FESEM images evidenced the morphological changes caused by the uniform dispersion of nanoparticles in the copolymer matrix. The nano-dispersion of magnetite nanoparticles in the copolymer was confirmed by High-resolution transmission electron microscopy analysis. Magnetic properties of nanocomposites obtained from a vibrating sample magnetometer (VSM) showed an increase in the saturation of magnetism with the addition of nanoparticles and the composite exhibited superparamagnetic behaviour. The thermal stability and glass transition temperature of the nanocomposites were greatly enhanced with the addition of nanoparticles and were determined with the help of Thermogravimetric Analysis (TGA) and Differential scanning calorimetry (DSC) respectively. Filler-dependent electrical properties showed a linearly increased DC conductivity with the addition of nanoparticles. The impedance analysis showed that the AC conductivity and dielectric properties of the nanocomposites were higher than the copolymer and the maximum electrical properties were observed for 15 wt.% of composites. The ammonia gas sensing performance of copolymer composite indicates the easy access of gas molecules to the sensor surface through the metal oxide nanoparticles. The synthesized copolymer nanocomposites showed high sensitivity and fast response to ammonia gas. The prepared composite with good thermal properties, dielectric constant, ammonia gas sensing and magnetoelectric properties is a promising candidate for use in nanoelectronics devices. [ABSTRACT FROM AUTHOR]

Oriented polylactic acid (PLA)/graphene oxide (GO) nanosheets tapes were prepared via uniaxial solid state drawing. The effect of various drawing conditions, including drawing ratio (DR), temperature (DT), and speed (DS) on mechanical, thermal, structural, and barrier properties were studied. Structural studies showed oriented structure for the drawn tapes with aligned polymer chains and GO nanosheets. Differential scanning calorimetry revealed improved glass transition temperature (Tg) and crystallinity (Xc) after drawing. In addition, Tg and Xc were increased more by increasing DR and DT. The highest Tg and Xc were achieved for 3/70/50 tape with values of 73°C and %22, respectively. Higher thermal stabilities and enhanced barrier properties were achieved after drawing, especially at the higher DR. Finally, tensile testing revealed simultaneous improvement in stiffness and toughness due to strain hardening for all the drawn tapes. The strength and elastic modulus were increased after increasing DR, DS, and DT and reached the highest values of 149 MPa and 3.6 GPa for 3/70/50. Overall, the properties were controllable by the processing conditions. [ABSTRACT FROM AUTHOR]

This work focused on the preparation of biopolymer blend nanocomposites from chitin (CT) and cashew tree gum (CTG) with different contents of copper sulphide nanoparticles (CuS) by solution casting method. The formation of nanocomposites have been characterized by FT infrared (FTIR), UV spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), thermogravimetry (TGA), differential scanning calorimetry (DSC) and impedance analysis. The characteristic absorption of nanoparticles in the FTIR spectra and shift in UV spectra of blend composites revealed the strong interaction between CuS nanoparticles and the polar segments of CT/CTG blend. With the increase in dosage of nanoparticles, a decrease in amorphous domains has been noted in the XRD scans. The uniform distribution of nanoparticles in CT/CTG network has been confirmed by the SEM analysis. HRTEM of the blend composites reveals the formation of hemispherical nanoparticles with a diameter of 15–30 nm. The glass transition temperature of blend composites increased with the addition of nano-CuS in the polymer matrix. Compared to the pure CT/CTG blend, the prepared nanocomposite showed higher thermal stability. Mechanical properties such as tensile strength and hardness of the blend nanocomposites were greatly enhanced by the reinforcement of CuS into the CT/CTG matrix. The AC conductivity and dielectric properties of the nanocomposites increased with the concentration of fillers and the magnitude of these properties was higher than the pure polymer blend. [ABSTRACT FROM AUTHOR]

Polycarbonate (PC) /graphene nanocomposite was prepared using multilayer graphene (MLG) with loadings of 0.5, 1, and 3 wt% via melt mixing process. Morphological, structural, and thermal properties of the PC/MLG nanocomposites are investigated to look into the influence of MLG on the nanocomposite. A significant increase (∼6.4°C) in glass transition temperature is observed upon the addition of 3 wt% of MLG into the polycarbonate matrix. This increase in glass transition temperature may be due to the interaction between the MLG and polycarbonate polymer matrix. The specific heat capacity of pure PC and PC/MLG nanocomposites varies linearly with temperature below their glass transition. Upon the addition of MLGs, the overall thermal stability of PC/MLG nanocomposites increases with MLG loadings. A maximum increase about 29.23°C in T onset of thermal decomposition is observed in PC/MLG nanocomposite having 3 wt% of MLG loading. The activation energy (Ea) of thermal decomposition is also calculated by kinetic analysis of thermal decomposition of the PC/MLG nanocomposites using Horowitz–Metzger and Broido's methods. [ABSTRACT FROM AUTHOR]

Polymer foams offer high sustainable performance in terms of their lightweight potential, insulation and high specific mechanical properties. The foaming of polymers depends on the properties of gas-laden solids or liquids. For foaming in the solid state, the foaming temperature must be higher than the glass transition temperature of the saturated polymer system. Moreover, the knowledge of sorption conditions and thermal properties is crucial for foam formation. In this study, the correlation between the glass transition temperature and the sorption conditions was investigated. This comparison was made by determining the sorption behavior for different pressure levels and the corresponding glass transition temperature using a high-pressure differential scanning calorimetry. The time, pressure and CO2 content were varied. For the first time, the Chow model could be verified for PLA with a coordination number of 3. [ABSTRACT FROM AUTHOR]

This study focuses on a new fabrication of nanocomposite based on Polyurethane Copolymer (PUC) intercalated with organo-modified montmorillonite nanoparticles (OMMT), via an efficient combination of solution mixing and melt blending processes. The combination of solution mixing and melt interaction processes produced PUC/OMMT nanocomposites with enhanced properties. The OMMT filled PUC was characterised by TEM and tensile test. The effect of thermal treatment process was also studied due to subsequent microphase separation of PUC resulting from microdomain miscibility. TEM observation recognised a decent dispersion state of OMMT within PUC, owing to their exfoliated and intercalated structure. This morphology was greatly influenced by induced thermal treatment. The dynamic mechanical thermal analysis (DMTA) revealed that storage modulus and glass transition temperature of the nanocomposites increased with OMMT incorporation. The tensile modulus and tensile strength of nanocomposites showed an improvement with the addition of OMMT. [ABSTRACT FROM AUTHOR]

Bismaleimide (BMI) resins are used in carbon fiber reinforced composites for high-temperature applications. Conventional BMI resins require high cure and post-cure processing temperatures, which limit fabrication methods and contribute to residual stress and microcracking. Recently, BMIs with lower cure temperatures have been developed; however, little data on the properties of low-temperature cure carbon/BMI composites are available in the open literature. In this study, processing and properties of a low-temperature cure BMI resin system, referred to here as BMI-2, were evaluated. Along with evaluation of neat resin properties, multi-directional woven carbon fiber reinforced BMI-2 composite laminates were fabricated by an out-of-autoclave, vacuum-bag-only resin infusion method. New data on the mechanical, thermal, and moisture absorption properties are presented. It was found that the resin infusion method produced laminates with fiber volume fraction of approximately 55% and immeasurably low void content. BMI-2 was found to attain a degree of cure of 96% and glass transition temperature of 366°C following a 163°C cure cycle. Cured laminates did not suffer from process-induced cracking at the inter- or intra-laminar levels. Tensile strength and modulus of quasi-isotropic specimens with woven AS4 carbon fiber were 443 MPa and 47.6 GPa, respectively, and failure under quasi-static tension occurred by delamination. Compression strength was stable across a wide temperature range, with quasi-isotropic specimens retaining 60% of their room temperature compression strength at 260°C. Equilibrium moisture content of composite specimens was 1.2% by weight. [ABSTRACT FROM AUTHOR]

This work aims to characterize the influence of hygrothermal conditioning on the mechanical and thermal behavior as well as the fractographic aspects of the interface of poly(ether imide) and glass fiber composite joints welded by electrical resistance using 400 mesh of AISI 304 stainless steel. The composites were mechanically characterized by Lap Shear Strength (LSS) and End Notched Flexure (ENF) testing to investigate maximum shear stress and energy from mode II interlaminar fracture toughness. Fractography was performed by SEM, while the influence on glass transition temperature and working temperature were evaluated by Dynamic-Mechanical Analysis and thermogravimetry. In the conditioned samples, the mechanical properties reduced 23% in the LSS test and 28% in the ENF test, while the fractography studies revealed elements of interlaminar and intralaminar fracture in both conditions. Thermal properties did not change significantly to disqualify this composite when applied to welding. [ABSTRACT FROM AUTHOR]

The research aim was to analyse the changes in the air permeability, waterproofness, surface, mechanical and thermal properties of the polyamide 6.6 fabric with a polyurethane coating before and after 1, 5, and 10 washes in the same conditions using specialized (V1) and universal (V2) laundry detergent. A new approach based on SEM and DSC techniques and assessment of surface free energy combined with standard methods was proposed to explain the nature of observed changes in waterproof and breathable material after washing treatment. SEM analysis indicated that after 10 washes the porosity of the polyurethane coating increased from 8.94% to 14.56% and 18.75% for V1 and V2, respectively. The air permeability increased from 0.747 mm/s for the reference sample to 0.766 mm/s and 0.774 mm/s after 10 washes for V1 and V2, respectively. The waterproofness of the reference sample of 992 mbar decreased with the increasing number of washes to 246 mbar and 122 mbar for V1 and V2, respectively. After 10 washes the surface free energy (γS) decreased by 18.8% and 24.3% for V1 and V2, respectively. The average tensile strength amounted to 833 N and decreased by 13.5% for V1 and by 20% for V2 after 10 washes. The glass transition temperature of the reference fabric was 47.6°C. After 10 washes it increased by 7.2°C and 8.8°C for V1 and V2, respectively. The temperatures of thermal degradation increased by 24.6°C and 22.2°C and the heat of thermal decomposition decreased by 23.6% and 15.8% after 10 washes for V1 and V2, respectively. [ABSTRACT FROM AUTHOR]

Binary and ternary composites were synthesized using a polyester matrix reinforced by two types of carbon inclusions, namely, carbon nanotubes (CNT) and graphite (Gt) (CNT/Gt/Polyester). Thermal analyses were performed, using thermogravimetry and differential scanning calorimetry, which allowed us to observe significant changes in glass transition temperatures and degradation temperatures of the composites. Dielectric measurements were performed in a frequency range from 100 Hz to 1 MHz and temperature from –33 to 107°C. The dielectric permittivity values of the CNT/Gt/Polyester ternary composites, compared to the Gt/Polyester binary composites, indicate that the addition of CNT particles to the Gt/Polyester binary system significantly improved the dielectric permittivity, due to the enhanced interfacial polarization of the host matrix, while the frequency dependence of the electrical modulus spectra revealed a Maxwell–Wagner–Sillars dielectric relaxation process that was found to follow the Cole–Davidson approach. [ABSTRACT FROM AUTHOR]

Polyimide (PI) foams have been developed for decades and widely used as thermal insulation materials. However, the limited mechanical and thermal properties continually being a serious problem that restrict their further applications. In this study, a series of rigid PI foams with excellent mechanical and thermal performance were fabricated by the reaction of benzophenone-3,3',4,4'-tetracarboxylic dianhydride (BTDA) with two diamines of 2–(4-aminophenyl)-5-aminobenzimidazole (BIA) and 4,4'-diaminodiphenyl ether (ODA) with various molar ratios, and the cis-5-norbornene-endo-2,3-dicarbox-ylic acid (NA) was introduced as end-capping and foaming agent. The results demonstrate that the foaming degree decreases with increasing the BIA molar ratio in the polymer chains owing to the elevated melt viscosity of precursor. Furthermore, the prepared rigid PI foams exhibit excellent thermal and mechanical properties. When the BIA contend up to 40 mol%, the glass transition temperature (Tg) and the temperature at 10% of weight loss (Td 10 %) of PI foam increased ∼80°C and ∼35°C in comparison with the pristine PI-0, respectively. In addition, the compressive strength and modulus at 10% strain of PI-4 reached to 5.48 MPa and 23.8 MPa, respectively. For the above-mentioned advantages, the prepared rigid PI foams are promising candidates as thermal insulation and structure support composite materials in the aerospace and aviation industries. [ABSTRACT FROM AUTHOR]

In situ copolymerizations of styrene and methyl methacrylate (MMA) by atom transfer radical random copolymerization in the presence of mesoporous diatomite were performed to synthesize various poly (styrene- co -methyl methacrylate)/diatomite composites. Special characteristics of the mesoporous diatomite were evaluated by X-ray fluorescence, thermal gravimetric analysis (TGA), transmission electron microscope, and nitrogen adsorption/desorption isotherm. Conversion and molecular weight determinations were carried out using gas chromatography and size-exclusion chromatography, respectively. Due to the pendant hydroxyl groups on the surface of the diatomite platelets and polarity change of the reaction medium, addition of 3 wt% mesoporous kieselgur platelets leads to increase of conversion from 69% to 81%. In addition, polydispersity index values of the poly (styrene- co -methyl methacrylate) chains increases from 1.14 to 1.39 by addition of 3 wt% mesoporous diatomite platelets. Increasing the thermal stability of the nanocomposites is demonstrated by TGA. Differential scanning calorimetry shows an increase in glass transition temperature from 66.4°C to 72.5°C by adding 3 wt% of mesoporous diatomite platelets. [ABSTRACT FROM AUTHOR]

In seal applications, thermal characteristics and thermal aging properties of rubber are essential factors in determining the applicable temperature range and lifetime of the seal. In this study, thermal characteristics and thermal aging properties of the acrylonitrile butadiene rubber composite in response to the acrylonitrile (ACN) content were investigated. Thermal stability, glass transition temperature (T g), and dynamic property were determined by thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis, respectively. The results showed that T g, thermal decomposition temperature, and tan δ were increased as the ACN content increased. To investigate the thermal aging properties of the composite, the composite was subjected to an accelerated thermal-oxidative and thermal aging process at 100°C for 168 h. The aged composites were evaluated by investigating the change in cross-link density, mechanical properties, and elastic recovery. The change in the chemical functional group was also studied using attenuated total reflectance Fourier transform infrared spectroscopy. The results indicate that subjecting the composite to thermal-oxidative and thermal aging process decreased the elongation at break and elastic recovery, while the cross-link density, Shore A hardness, and 100% modulus were increased. All of the properties were also dependent on the ACN content as well as the aging conditions. [ABSTRACT FROM AUTHOR]

Polymeric composites absorb moisture by quick surface absorption followed by slow diffusion through the matrix in humid environment. Moisture absorption damages the matrix and interface of fiber reinforced polymer (FRP) composites and consequently, weakens their mechanical and thermal properties. Effects of seawater on mechanical and thermal behavior of base and nanophased carbon fiber reinforced epoxy polymer (CFRP) composites were investigated in this study. It was observed that moisture barrier property of carbon/epoxy composites can be improved by adding a small amount (1 to 3% by weight) of nanoclay as filler. Base and nanophased carbon/epoxy composite panels were fabricated by the vacuum assisted resin transfer molding (VARTM) process and samples were prepared from these panels for mechanical and thermal testing according to ASTM standards. Some of these samples were exposed to seawater for 180 days. Moisture intake by the samples was measured every 10 days for 90 days by which time samples reached a saturated state. Mechanical and thermal behavior of base and nanoclay-infused carbon/epoxy composites with exposure to seawater for 180 days were compared with those with no exposure to seawater for 180 days. Mechanical characterization was performed by compression test. Thermal characterizations were carried out by dynamic mechanical analysis, thermo-gravimetric analysis, and thermo-mechanical analysis tests. Results showed that the 2 wt% nanoclay loading is optimum in terms of moisture barrier capability, compression, and thermal properties. After 90-day exposure to seawater, the 2 wt% nanophased composite absorbed 0.39% moisture compared to 0.67% moisture absorption by the base carbon/epoxy composite. Compressive strength and modulus were decreased by 8.20% and 7.11% respectively, for 2 wt% nanophased composites submerged in seawater for 180 days compared with identical samples with no exposure to seawater. Corresponding data from thermal characterization tests indicate storage modulus and glass transition temperature to be 6.59% and 6.1 °C lower respectively, and the coefficient of thermal expansion to be increased by about 6% for the 2 wt% conditioned sample. SEM study revealed that the nanophased composites exhibited a better bonding between the fiber and matrix compared to the base one even after exposure in the seawater. It is concluded that the excellent barrier capacity, higher surface area, and high aspect ratio of nanoclay are responsible for enhanced durability of the nanophased carbon/epoxy composite in seawater compared to the base one in the same condition. [ABSTRACT FROM AUTHOR]

A series of binary composite blends of m -aramid/zinc ionomer (m -Ar/ZnI) with different weight ratio were prepared by the solution blend technique. These composite films were characterized in terms of the structure, crystallinity, morphology, thermal, and mechanical properties. The temperature corresponding to 5% (T 5%) weight loss are in the range of 101–438°C. The composite films showed good storage modulus (in the range of 2.1–3.1 GPa) and high glass transition temperature (T g) (in the range of 254–278°C) and exhibited good tensile strength but it decreased with an increase in the content of ZnI. The strong compatibilizing effect was observed between the m -Ar and ZnI components, where exceptionally self-assembled morphology was formed in the m -Ar/ZnI composite films. The most favorable mechanical and thermal data supported by the finest structure were observed with 3:0.50 weight ratio. This study evaluates the efficiency of ionomer in m -Ar/ZnI composite blends. [ABSTRACT FROM AUTHOR]

This study aimed at producing the biodegradable composite from lignocellulose nanofibers (LCNFs) and Pebax® thermoplastic elastomer. For this purpose, LCNFs at different levels of 0, 1, 3, and 5% were considered. The LCNFs were prepared by benzyl alcohol and then mixed with Pebax®. The liquid phase of the LCNFs and soluble polymer was prepared and then the masterbatches were mixed in an internal mixer (Model 815802, Brabender, Germany). The mixtures from the internal mixer were put into a hot press and test samples were compress-molded. The physical properties results indicated that water absorption and thickness swelling decreased by the addition of more amount of LCNF. By the addition of LCNFs to polymer, the tensile strength and modulus and impact strength were increased compared to samples without LCNF. No regular trend of enthalpy changes was observed as the content of LCNF changed. When the LCNF concentration was increased to 5%, the crystallization temperature was increased. As the LCNF concentration increased to 3%, the glass transition temperature (T g) was decreased, whereas by incorporating more LCNFs, the T g was increased. The result of the Fourier transform infrared spectra showed the peaks at 1740 cm−1 which indicated the presence of polyamide bonds. Also, new peaks were observed in the range of 1400–1500 cm−1 that was probably related to the presence of C−C bonds of glucose at LCNFs chains. [ABSTRACT FROM AUTHOR]

Poly(methyl methacrylate) (PMMA)/poly(ethylene oxide) (PEO) (90/10) nanocomposites containing various amounts of graphene nanoplatelets were fabricated by solution method and then the effects of graphene concentration on morphology, thermal, mechanical, and electrical properties of the nanocomposites were investigated. Characterization by electron microscopy and X-ray diffraction of the nanocomposites showed a relatively good dispersion of graphene sheets in the polymer matrix. The results indicated that thermal stability, glass transition temperature, and mechanical properties of PMME/PEO blend improved by increasing graphene concentration. The electrical properties of polymer nanocomposites revealed a significant improvement with increasing the amount of graphene and the percolation threshold was about 3.33 wt% of graphene. [ABSTRACT FROM AUTHOR]

Novel hybrid blend with the composition of m-aramid and sodium ionomers with different weight ratio percentage were prepared by the solution blending technique. The prepared composite films were characterized by the Fourier-transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The phase structure, compatibility, and morphologies of the composite film were investigated with SEM, DMA, XRD, and transmission electron microscopy (TEM) analysis. The TGA of the composite films shows improvement in the thermal stability. The temperature corresponding to 5% (T 5%) weight losses is in the range of 101–414°C. The storage modulus (in the range of 01.55–3.0 GPa) and glass transition temperature (in the range of 244–276°C) decreased with an increase in the content of sodium ionomers. The tensile strength of the composite films is in the range of 160–185 MPa. This effective approach shows a potential application in the field of m-aramid-based composites. [ABSTRACT FROM AUTHOR]

This research studies the properties of poly (butylene terephthalate) (PBT)-based systems toughened with thermoplastic polyurethane (TPU; 10, 20, and 30 wt%) and reinforced with multiwalled carbon nanotubes (CNTs; 0.1, 0.2, and 0.3 wt%). Different compositions prepared via melt mixing. Morphology studies showed good compatibility between the two polymeric phases in PBT/TPU. The addition of TPU to PBT reduced crystallization rate and melt temperature, while inclusion of CNTs had nucleation effect and increased the degree of crystallinity, crystallization, and melt temperatures. The existence of TPU in PBT caused significant enhancement in notch-impact resistant. The inclusion of CNTs to PBT/TPU blend led to the substantial improvements in tensile and flexural strengths and moduli. Dynamic mechanical thermal analysis revealed that the incorporation of CNTs into PBT/TPU enhanced storage modulus and heightened glass transition temperature. The storage modulus of PBT/TPU/CNT nanocomposite containing 0.5 wt% CNT was comparable with that of pure PBT particularly at high temperatures. [ABSTRACT FROM AUTHOR]

Polynorbornene rubbers (PNRs) used in this article were commercial compounds of polynorbornene filled with paraffin oil and fillers. The properties of PNR and ethylenepropylene- diene rubber (EPDM2650) blends with ratios of 100/0, 75/25, 50/50, 25/75, and 0/100 were investigated. Blends were cured by sulfur and accelerator at 150°C and 160°C, respectively. Moving die rheometer, differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), and rubber process analyzer were used to examine the properties of the blends. The PNR exhibited significant reversion that was reduced by blending with EPDM. The thermal cross-linking of PNR occurred during hot air aging. The hot air aging resistance of PNR was improved by blending with EPDM. After 72 h of ozone aging, no obvious cracks were observed on the surface. The DMA results showed that the effective damping temperature range (tanΔ ≥ 0:3) of vulcanized PNR was the broadest at 113°C and then narrowed at higher temperature as the content of EPDM in the blend increased. With an increase in the ratio of EPDM, the glass transition temperature (Tg) of EPDM moved to higher temperatures, as measured by DSC. The tensile strength of neat PNR is the greatest. PNR/EPDM = 75/25 blends showed yield behavior as the Tg of PNR moved to the higher temperature. These effects are attributed to a transfer of the extended oil from the PNR to the EPDM. [ABSTRACT FROM AUTHOR]

The study of mechanical properties of carbon nanotube reinforced polymeric materials under different environmental conditions are very much essential as this material possesses potential for using it in structural parts, automobiles, marine field and so on. This study deals with the effect of moisture absorption on the mechanical and thermal properties of carbon nanotube/epoxy composites by immersing it in sea and distilled water at 30℃ temperature and at 75% Relative Humidity (RH) humidity. Composite specimens containing different wt.% of carbon nanotubes were prepared, tested and subjected to water immersion test. The flexural properties, hardness and glass transition temperature (Tg) of water-immersed specimens were evaluated and compared with unexposed specimens as per the American Society for Testing and Material (ASTM) standard. It is concluded that the water absorption brought certain loss in the mechanical properties and reduction in Tg of the composites. It was also found that moisture uptake affected both sea and distilled water samples in different ways. [ABSTRACT FROM AUTHOR]

Fiber-reinforced composites are a well-recognized option for repair and rehabilitation of the pipelines for the oil and gas industry. Infilled composite sleeve system provides an effective rehabilitation solution, where the sleeve acts as prime reinforcement without any direct contact with steel. However, the long-term performance of the repair is dependent, in part, on the effect of hygrothermal ageing of the composites. In this publication, glass transition temperature and mechanical properties are compared for glass-fiber reinforced vinyl ester composite, both as-manufactured and after hot-wet conditioning at 80℃. The tensile and shear strength reduced substantially during conditioning, whilst the elastic modulus was relatively stable. The average glass transition temperature of the composite dropped from the as-manufactured value of 110℃ to 97℃ and 101℃, after 1000 and 3000 h of conditioning, respectively, indicating that it is stable and that the composite is suitable for use as a pipeline repair material operating at 80℃. The results indicate that a 1000 h conditioning period, specified as a minimum period in ISO/TS 24817 is suitable for representing long-term properties for stiffness-based designs for the composite material and conditioning temperature investigated. [ABSTRACT FROM AUTHOR]

Multiwalled carbon nanotubes (MWCNTs) were modified to covalently attach the carboxylic moiety with their surfaces. Variant concentrations of functionalized multiwalled carbon nanotubes (F-MWCNTs) were introduced into polydimethylsiloxane (PDMS) adopting solution mixing technique. Fourier transform infrared spectroscopy (FTIR) confirms the carboxy functionalization presence on the surface of the nanotubes. X-ray diffraction (XRD) patterns for both MWCNTs and F-MWCNTs illustrate that the crystallinity does not alter with surface modification of the nanotubes. Experimental results simulated that electrical conductivity of the nanocomposites was augmented with increasing filler concentration in the host matrix. Thermal conductivity and thermal impedance of the nanocomposite specimens were evaluated according to developed methodologies and the accumulative data revealed the nanocomposites thermal transport dependence on the F-MWCNTs doping concentration in the host polymer matrix. Thermal stability enhancement with increasing filler incorporation into the polymer matrix was observed in thermogravimetric/differential thermal analyzer (TG/DTA) contours. Crystallization, glass transition, and melting temperatures were examined using differential scanning calorimeter (DSC) and it was observed that phase transition temperatures of the composite specimens can be tuned by varying the nanotubes to matrix ratio. Scanning electron microscopy and energy dispersive x-ray spectroscopy were carried out to analyze the surface morphology/composition of the fabricated nanocomposites and dispersion of functionalized and pristine MWCNTs in the polymer matrix. [ABSTRACT FROM PUBLISHER]

Rice straw (Oryza sativa L.) pulp was treated using a high-pressure homogenizer to make fibril and fibril aggregates. The rice straw fibril and fibril aggregate material was used as reinforcement in a rice straw fibril and fibril aggregates/polyvinyl alcohol nanocomposite that was prepared by casting film under air-dry and freezing–thawing conditions, respectively. The material’s tensile strength was increased by adding the rice straw fibril and fibril aggregates material into the polyvinyl alcohol matrix. The mechanical properties were higher in rice straw fibril and fibril aggregates/polyvinyl alcohol nanocomposites cast under freezing–thawing conditions than those casting under air-drying conditions. Dynamic thermomechanical analysis testing showed that the storage modulus (E′) of the rice straw fibril and fibril aggregates/polyvinyl alcohol nanocomposites was higher than that of polyvinyl alcohol alone when 2% rice straw fibril and fibril aggregates material was added into the polyvinyl alcohol matrix. The glass transition temperature (Tg) rose in neat polyvinyl alcohol and rice straw fibril and fibril aggregates/polyvinyl alcohol nanocomposites cast under freezing–thawing conditions. Differential scanning calorimetry analysis revealed that the melting temperature (Tm), melting enthalpy (ΔHC) and crystallinity (XC) in rice straw fibril and fibril aggregates/polyvinyl alcohol nanocomposites increased to higher values compared to those in neat polyvinyl alcohol when cast under the two conditions. Thermogravimetric analysis showed that the polymer matrixes were stabilized against thermal decomposition by the addition of rice straw fibril and fibril aggregates. The shift of the –OH stretching peak of rice straw fibril and fibril aggregates/polyvinyl alcohol nanocomposites in Fourier transform infrared spectroscopy spectra indicated a good compatibility between rice straw fibril and fibril aggregates and the polyvinyl alcohol matrix in nanocomposites. [ABSTRACT FROM AUTHOR]

This article studies the thermal properties of a multi-walled carbon nanotube (MWNT)-reinforced thermoplastic natural rubber (TPNR) nanocomposite. The nanocomposite was prepared using a melt blending method. Various percentages (1, 3, 5, and 7 wt%) of MWNTs were added into TPNR to improve its thermal properties. The laser flash technique was also employed to determine the thermal conductivity, thermal diffusivity, and specific heat capacity of the nanocomposite. The DMA result showed that the glass transition temperature (Tg) increased with the increase in MWNT content. TEM micrographs also demonstrated that a good dispersion of MWNTs was achieved in the TPNR environment. [ABSTRACT FROM AUTHOR]

Melt blending of polylactic acid (PLA) and linear low density polyethylene (LLDPE) was performed to investigate the effects of LLDPE loadings on the morphology, mechanical and thermal properties of PLA/LLDPE blends. LLDPE was blended with PLA from 5-15 wt% and prepared by counterrotating twin-screw extruder followed by injection molding into test samples. The mechanical properties of the blends were assessed through tensile, flexural and impact testings while thermal properties were analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis. Scanning electron microscope was used to study the dispersion and particle size of LLDPE in PLA matrix. The impact strength of PLA improved by 53% with addition of 10wt% LLDPE. However, the tensile modulus and strength, and elongation at break of PLA/LLDPE blends decreased with increasing weight ratio of LLDPE. Similarly, flexural modulus and strength also dropped with addition of LLDPE. DSC results showed that glass transition temperature (Tg) and crystallinity (Xc) of PLA increased with blending of LLDPE. The LLDPE particles size was seen to increase with increasing loadings of LLDPE which explains the unexpected decrease of impact strength after 10 wt%. [ABSTRACT FROM AUTHOR]

This article presents a study on composites exposed to elevated temperatures associated with fire. A thermo-viscoplastic model is proposed for description of the rate-dependent and temperature-dependent behavior of composites at elevated temperatures. AS4/PEEK and E-glass/vinylester composites are chosen to examine the proposed model. Thermo-viscoplastic parameters of the proposed model were determined for each material using experimental data. Off-axis angle tests were performed with various strain rates at various temperatures for E-glass/vinylester woven composite, while experimental data available from literatures were used for AS4iPEEK unidirectional composite. Comparison of the results from the proposed model with experimental data shows good agreement. Also. a few interesting points observed during this study, such as the material behavior near the glass transition temperature, the failure mechanism, and the effect of charring are discussed. [ABSTRACT FROM AUTHOR]

A series of poly(anhydride-esters) based on poly(1,10-bis(o-car- boxyphenoxy)decanoate) (CPD) and poly(1,6-bis(p-carboxyphenoxy)hexane) (p-CPH) were synthesized by melt-condensation polymerization. Poly-(anhydride-esters) that contain CPD hydrolytically degraded into salicylic acid, however, these homopolymers have mechanical and thermal characteristics that limit their use in clinical applications. The synthesis and characterization of copolymers of CPD with p-CPH, a monomer known to generate mechanically stable homopolymers, was investigated. By changing the CPD to p-CPH monomer ratios, the salicylic acid loading and thermal/mechanical properties of the copolymers was a controlling factor; increasing the CPD concentration increased the salicylate loading but decreased the polymer stability; whereas increasing the p-CPH concentration increased the thermal and mechanical stability of the copolymers. Specifically, decreasing the CPD:p-CPH ratio resulted in lower salicylate loading and increased thermal decomposition temperatures. The glass transition temperatures (°C) varied from 27 to 38°C, a desirable range for elastomeric biomedical implants. [ABSTRACT FROM AUTHOR]

The hygroscopic behavior of a woven fabric carbon-epoxy composite and its effect on the viscoelastic properties and glass transition temperature was investigated. The mechanical and thermal properties of the material had been previously fully determined. An experimental study was conducted at full immersion in water and at a specific temperature condition. The moisture absorption process was found to be reversible with a low-saturation moisture uptake. The absorption through-the-thickness was determined to be lower than in the in-plane directions. The coefficients of moisture expansion or hygroelastic coefficients were determined and found to be similar in the warp and fill directions and much lower than through-the-thickness direction. The results were correlated to the behavior of a unidirectional composite with the same fiber and matrix. The viscoelastic properties were not affected during the process but the plasticization was very pronounced. [ABSTRACT FROM AUTHOR]