Thermal and scanning electron microscopy/energy‐dispersive spectroscopy analysis of styrene–butadiene rubber–butadiene rubber/silicon dioxide and styrene–butadiene rubber–butadiene rubber/carbon black–silicon dioxide composites

Silica as a reinforcement filler for automotive tires is used to reduce the friction between precured treads and roads. This results in lower fuel consumption and reduced emissions of pollutant gases. In this work, the existing physical interactions between the filler and elastomer were analyzed through the extraction of the sol phase of styrene–butadiene rubber (SBR)–butadiene rubber (BR)/SiO₂ composites. The extraction of the sol phase from samples filled with carbon black was also studied. The activation energy (E_a) was calculated from differential thermogravimetry curves obtained during pyrolysis analysis. For the SBR–BR blend, E_a was 315 kJ/mol. The values obtained for the composites containing 20 and 30 parts of silica per hundred parts of rubber were 231 and 197 kJ/mol, respectively. These results indicated an increasing filler–filler interaction, instead of filler–polymer interactions, with respect to the more charged composite. A microscopic analysis with energy‐dispersive spectroscopy showed silica agglomerates and matched the decreasing E_a values for the SBR–BR/30SiO₂ composite well. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2273–2279, 2005     

Electrically insulating ZnOs/ZnOw/silicone rubber nanocomposites with enhanced thermal conductivity and mechanical properties

In this work, hybrids of surface modified zinc oxide spherical (ZnOs) nanoparticles and tetrapod‐shaped whiskers (ZnOw) were incorporated into the silicon rubber (SR) to prepare the ZnOs/ZnOw/SR nanocomposites. The incorporation of the ZnOs/ZnOw facilitated the formation of three‐dimensional thermally conducting network. It was found that the thermal conductivity of the ZnOs/ZnOw/SR reached up to 1.309 W m^?1 K^?1 when the ZnOs/ZnOw content was 20 vol % (V_m‐ZnOs:V_ZnOw = 7:3), which was nearly 6.5 times that of the pristine SR. The dielectric and resistivity measurements showed that the incorporation of the ZnOs/ZnOw hybrids did not cause much change in the electrical properties. In addition, the results show that the tensile strength of ZnOs/ZnOw/SR nanocomposites is higher than that of pristine SR. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46454.     

Natural rubber/nitrile butadiene rubber/hindered phenol composites with high-damping properties

New natural rubber (NR)/nitrile butadiene rubber (NBR)/hindered phenol (AO-80) composites with high-damping properties were prepared in this study. The morphological, structural, and mechanical properties were characterized by atomic force microscopy (AFM), polarized Fourier transform infrared spectrometer (FTIR), dynamic mechanical thermal analyzer (DMTA), and a tensile tester. Each composite consisted of two phases: the NR phase and the NBR/AO-80 phase. There was partial compatibility between the NR phase and the NBR/AO-80 phase, and the NR/NBR/AO-80 (50/50/20) composite exhibited a co-continuous morphology. Strain-induced crystallization occurred in the NR phase at strains higher than 200%, and strain-induced orientation appeared in the NBR/AO-80 phase with the increase of strain from 100% to 500%. The composites had a special stress–strain behavior and mechanical properties because of the simultaneous strain-induced orientation and strain-induced crystallization. In the working temperature range of a seismic isolation bearing, the composites (especially the NR/NBR/AO-80 (50/50/20) composite) presented a high loss factor, high area of loss peak (TA), and high hysteresis energy. Therefore, the NR/NBR/AO-80 rubber composites are expected to have important application as a high-performance damping material for rubber bearing.     

Aluminum powder filled nitrile rubber composites

Effect of aluminum powder on the properties of nitrile rubber (NBR) composites and the role of bonding agent viz. hexamethylene tetramine‐resorcinol has been investigated. Shore A hardness of the aluminum powder filled composites is lower than that of high abrasion furnace (HAF) and acetylene black (ACB) filled nitrile rubber composites and can be increased by the addition of bonding agent. Equilibrium swelling decreased considerably by the use of hexamethylene tetramine‐resorcinol, suggesting an improved nitrile rubber–aluminum powder adhesion. A marked increase in thermal conductivity is obtained with the incorporation of aluminum powder. Increased thermal conductivity reduced the additional time needed for the vulcanization of thick rubber articles and imparted uniform curing throughout the material. In nitrile rubber, the modulus and tensile strength followed the order HAF > ACB > aluminum powder. Combination of HAF and aluminum powder in NBR gave composites with good thermal conductivity and mechanical properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3156–3161, 2004     

Mechanical,thermal, and transport properties of nitrile rubber–nanocalcium carbonate composites

The article describes the properties of acrylonitrile butadiene copolymer (NBR)–nanocalcium carbonate (NCC) nanocomposites prepared by a two‐step method. The amount of NCC was varied from 2 phr to 10 phr. Cure characteristics, mechanical properties, dynamic mechanical properties, thermal behavior, and transport properties of NBR–NCC composites were evaluated. For preparing NBR nanocomposites, a master batch of NBR and NCC was initially made using internal mixer. Neat NBR and the NBR–NCC masterbatch was compounded with other compounding ingredients on a two roll mill. NCC activated cure reaction upto 5 phr. The tensile strength increased with the nanofiller content, whereas NBR–NCC containing 7.5 phr exhibited the highest modulus. The storage modulus (E′) increased up to 5 phr NCC loading; the reinforcing effect of NCC was seen in the increase of modulus which was more significant at temperatures above T_g. The effect of nanofiller content and temperature on transport properties was evaluated. The solvent uptake decreased with NCC content. The mechanism of diffusion of solvent through the nanocomposites was found to be Fickian. Transport parameters like diffusion, sorption, and permeation constants were determined and found to decrease with nanofiller content, the minimum value being at 7.5 phr. Thermodynamic constants such as enthalpy and activation energy were also evaluated. The dependence of various properties on NCC was supported by morphological analysis using transmission electron microscopy. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Prediction of viscoelastic behavior of interphase in polypropylene‐chopped rice husk composites for β‐relaxation domain

The effect of chopped rice husk (CRH) content on viscoelastic properties and crystallinity of polypropylene (PP) composites was investigated. Composites containing 0, 20, and 40 part per hundred plastics (php) of CRH into PP were prepared by twin‐screw extruder, with maleic anhydride‐grafted PP as the coupling agent. The viscoelastic behavior and the crystallinity of these composites have been studied by dynamic mechanical analysis as well as differential scanning calorimetry, respectively. By the incorporation of CRH into PP, the storage modulus (E′) was found to be increased progressively, whereas the mechanical loss factor (tan δ) decreased in a nonlinear manner. A self‐consistent analysis was proposed for the prediction of viscoelastic response of the interphase between PP matrix and CRH particles. A three‐phase model was applied in a reverse mode, and the viscoelastic behavior of the interphase was extracted and compared with the unfilled matrix. Differential scanning calorimetry results indicated that CRH influences crystallization temperature as well as the degree of crystallinity of the composites. An entrapped polymer within CRH filler and PP matrix was detected by scanning electron microscope, which can be attributed to the interfacial layer with a good adhesion between the main components. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical properties and densification behavior of β‐spodumene/anorthite composites

Although β‐spodumene/anorthite composites are interesting systems, little research work has been done to study their properties. This study aims at investigating the preparation and properties of β‐spodumene/anorthite composites containing β‐spodumene proportions ranging between 10 and 25 mass %. X‐ray diffraction analysis (XRD), Scanning electron microscopy (SEM), and the coefficient of thermal expansion (CTE) were used to characterize the effect of addition of β‐spodumene on the phase relations, microstructure, and thermal expansion behavior of resultant composites. The results show that the presence of β‐spodumene significantly reduces the porosity and reduces the densification temperature. It reduces thermal expansion and enhances the mechanical properties of anorthite‐containing composites.     

Effect of carboxyl on vulcanization and mechanical properties of carboxylated acrylic rubber prepared by 60Co‐γ‐ray‐induced polymerization

Acrylic acid carboxylated acrylic rubber (ACM) and itaconic acid carboxylated acrylic rubber were prepared by ⁶⁰Co‐γ‐ray‐induced emulsion copolymerization. The polymers were characterized using FTIR and ¹³C NMR spectroscopies. The acid value was determined with nonaqueous titration method. The molecular weight and the polydispersity index of the polymers were measured using gel permeation chromatography. The influence of the cure‐site (carboxyl) on the vulcanization and mechanical properties of the ACM was researched by means of rheometric study, gel fraction analysis, mechanical property tests, and dynamic mechanical thermal analysis. The results show that the crosslink density of polymers increases with amounts of the carboxyl cure‐site. The itaconic acid carboxylated ACM has better cure characteristics and mechanical properties than the acrylic acid carboxylated ACM has. In addition, the comparison of ACM prepared by ⁶⁰Co‐γ‐ray‐induced polymerization with ACM prepared by chemical‐initiator‐induced polymerization has been investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5587–5594, 2006     

Effects of mixing conditions on the reaction of 3‐octanoylthio‐1‐propyltriethoxysilane during mixing with silica filler and natural rubber

The effects of mixing temperature and mixing time on the reaction of 3‐octanoylthio‐1‐propyltriethoxysilane (NXT silane) during mixing with precipitated silica and natural rubber (NR) were investigated. Results showed that the reaction between NXT silane and precipitated silica can proceed at temperatures above 130°C. Because of the blocking group of NXT silane, the silane–NR coupling reactivity is low, so that the reaction of NXT silane with NR occurs only during the curing period. There is no reaction between NXT silane and NR during mixing, which showed that the mixing time of silica‐filled NR compound containing NXT silane must be longer than 10 min at 150°C to obtain the desired silane coupling efficiency. With increasing mill temperature, the coupling efficiency increases. A high mixing temperature promotes improvement of silane–silica coupling efficiency, although the tensile strength, 100% modulus, 300% modulus, and hardness of NR vulcanizates decrease. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2295–2301, 2004     

Mechanical properties and thermal stability of rice husk ash filled epoxy foams

Mechanical properties and thermal stability of epoxy foams filled with white and black rice husk ash were studied. Epoxy foams were prepared from a commercial system and filled with different amounts of both the ashes (0, 6.8, 12.8, 18.0, and 22.7 wt %). The incorporation of both the ashes modified the final morphology of the foam, decreasing the average cell size and increasing the number of cells per volume unit. For all filler percentages used, the specific modulus and strength results showed that the white ash is more effective as reinforcing agent than the black ash. The initial degradation temperature was not affected by the content and type of ash used as the filler. The integral procedure decomposition temperature, weight loss, and char residue results were related to the ash type and atmosphere used in the thermogravimetric analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Influence of talc content on some properties of gamma irradiated composites of polyethylene and recycled rubber wastes

In this study, the synergistic effect of talc content % and gamma irradiation on some mechanical, thermal, electrical resistance, and microstructural properties of the molded waste polyethylene/recycled waste rubber powder (WPE/RWRP) 60/40 was investigated. The ternary composites of talc concentrations, 5, 10, 15, and 20 wt %, were irradiated with doses of 50, 75, 100, and 150 kGy. The composites mechanical properties: tensile strength, elongation at break, and elasticity modulus, and the thermal properties: melting temperature (T_m) and (ΔH) were predicted. Also, scanning electron microscopy, thermogravimetric analysis, and electric conductivity were investigated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mechanical,dielectric, and thermal properties of fluorosilicone rubber composites filled with silica/multiwall carbon nanotube hybrid fillers

In this work, hybrid fillers consist of modified silica (SiO₂) and multiwalled carbon nanotube (MWCNT) were used to improve the mechanical, dielectric, and thermal properties of fluorosilicone (FSR) composites via a direct mechanical mixing method. With the increase of CNT loading in SiO₂/CNT hybrid loading ratio, the tensile properties, dielectric constant, electrical conductivity, and thermal properties all increase without a sharp sacrifice of flexibility. The dielectric constant of FSR-S15/C5 achieved 7,370 @1 kHz, which is about four orders of the FSR-S20, and the dielectric loss remains as low as 0.676 @1 kHz. Therefore, the linkage of SiO₂ and FSR chains not only enhances the interfacial interaction between the fillers and FSR matrix but also decreases the agglomeration of the fillers in matrix. What is more, modified SiO₂ and CNT were designed as the effective hybrid filler to improve the performance of the polymeric matrix through synergic effect.     

Production and properties of solvent‐cast poly(ε‐caprolactone) composites with carbon nanostructures

Composites based on carbon nanostructures (CNS) and poly(ε‐caprolactone) (PCL) were produced by solvent casting technique. Single‐walled carbon nanotubes (SWCNTs) and carbon nanofibers (CNFs) were selected, to produce composite films with enhanced properties. The role of CNS type and percentage were investigated in terms of morphological, thermal, mechanical, and dielectrical properties. Composite morphological analysis reveals a good dispersion of CNS, at low and high content. Thermal properties underline the nucleation effect of CNS on PCL polymer matrix. Reinforcing effects in terms of increased tensile modulus were obtained with both nanofillers, but a higher reduction of the ductility was shown in PCL/CNF materials. A higher efficiency to form a conductive network, assessed by AC conductivity, was observed for SWCNTs at concentration lower than 1 wt. % © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Friction properties of graphene reinforced nitrile rubber composites after thermal oxidation aging: Experiment and molecular dynamics simulation

We established friction models for pure NBR, GNS/NBR, and GO/NBR composites through molecular dynamics (MD) simulation. Our study focused on the impact of GNS and GO on the friction properties of nitrile rubber (NBR) composite materials after undergoing thermal oxygen aging. Based on the simulation results, it can be observed that the GNS/NBR and GO/NBR composites' coefficient of friction (COF) decreases by 20.8% and 24.8%, respectively, at 348 K. Additionally, the abrasion rate is reduced by 17.4% and 25.7%, respectively, for the same composites. Adding GNS and GO can effectively improve the friction performance of the NBR composite system, and compared with GNS, GO shows a better enhancement effect. Pure NBR and GO/NBR composite materials were prepared by mechanical blending method, and the friction properties of GO-enhanced NBR composite materials were studied. The experimental results show that the GO/NBR composite material can maintain a low friction and wear coefficient after thermal and oxygen aging. It shows that adding GO can effectively improve the friction properties of NBR composite systems and slow down the weakening effect of aging on the friction properties of NBR composite materials. This is because the GO surface contains wealthy functional groups such as epoxy groups, which enhances the binding strength between the GO and NBR interface so that the GO/NBR composite material exhibits better friction properties and thermal oxygen aging resistance. In addition, the wear surface was characterized by scanning electron microscopy (SEM), revealing the damage mechanism of friction and wear of NBR composite materials.     

Simultaneous enhancement of dielectric and mechanical properties of high‐density polyethylene/nitrile rubber/multiwalled carbon nanotube composites prepared by dynamic vulcanization

Polymer dielectric composites, which possess high dielectric and loss suppression with excellent mechanical properties, are of crucial importance in practical applications. Herein, high‐density polyethylene/nitrile rubber/multiwalled carbon nanotube (HDPE/NBR/MWCNT) composites were fabricated by the dynamic vulcanization (DV) technique. The effect of DV on the structure and properties of HDPE/NBR/MWCNTs was systematically investigated. The results illustrate that the DV technique combines the advantages of the crosslinked phase and melt processability of thermoplastics. With the increase of dicumyl peroxide content, the dielectric permittivity and the mechanical properties clearly increase, due to a better compatibility and dispersibility achieved by DV. More importantly, a continuous decrease of dielectric loss and conductivity are observed with the increase of dicumyl peroxide content. These can probably be assigned to the combination of better dispersion and slower chain mobility of the NBR phase induced by crosslinking. © 2020 Society of Industrial Chemistry     

Effect of γ‐radiation on the thermal and mechanical properties of a commercial poly(butylene adipate‐co‐terephthalate)

BACKGROUND: Poly(butylene adipate‐co‐terephthalate) (PBAT) has attracted wide interest as a biodegradable polymer. However, its use is restricted in certain applications due to its low melting point. RESULTS: PBAT was treated using γ‐radiation. The radiation features were analyzed using Soxhlet extraction, and the ratio of chain scission and crosslinking and gelation dose were determined using the classical Charlesby–Pinner equation. The results showed that PBAT is a radiation‐crosslinkable polymer. The degree of crosslinking increased with increasing radiation dose; the relation between sol fraction and dose followed the Charlesby–Pinner equation. Differential scanning calorimetry analyses showed that the melting temperature (T_m) and the heat of fusion (ΔH_m) of PBAT exhibited almost no change in the first scan. The second scan, however, showed a decrease in T_m and ΔH_m. The glass transition temperature of irradiated PBAT increased with increasing radiation dose. The weight loss of control and irradiated PBAT resulting from thermal degradation was a one‐step process. Moreover, the tensile strength and elongation at break decreased with an increase in radiation dose. However, the Young's modulus and stress at yield were not greatly affected by γ‐radiation. CONCLUSION: PBAT can be crosslinked using γ‐radiation. The crosslinking efficiency is relatively low. The thermal and mechanical properties of PBAT are affected by γ‐radiation. Copyright © 2009 Society of Chemical Industry     

Preparation and characterization of γ‐irradiated crosslinked silicone rubber/organoattapulgite composites

Silicone rubber (SR)/organoattapulgite (OAT) composites were prepared with γ‐irradiation crosslinking at a dose range varied from 30 to 300 kGy. Natural fibrillar silicate attapulgite (AT) was modified by silane coupling agent, and the obtained OAT was used as reinforcing fillers in SR. The effect of irradiation doses on the degree of crosslinking of SR/OAT composites was determined by solvent swelling method. It was found that the molecular weight between crosslinks (M_c) reduced with the increase in irradiation doses. Moreover, the addition of OAT to SR matrix promoted an increase in the crosslinking density of the composites because of the presence of the active crosslinking sites of OAT. The mechanical properties of the SR/OAT composites including tensile strength, elongation at break, and Shore A hardness subjected to various irradiation doses were studied. The experimental results showed that the tensile strength, elongation at break, and Shore A hardness were all improved significantly in the presence of OAT, which indicated that OAT was an alternative reinforcing filler of SR. In addition, the effect of various irradiation doses on the mechanical properties of SR and SR/OAT composites was also investigated. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Thiol‐containing ionic liquid for the modification of styrene–butadiene rubber/silica composites

To introduce thiol–ene chemistry in the modification of composites by ionic liquid (IL), a novel functional IL, 1‐methylimidazolium mercaptopropionate (MimMP), was synthesized and investigated as a modifier for styrene–butadiene rubber/silica composites. MimMP could be hydrogen‐bonded with silica and react with the double bonds of rubber chains via thiol–ene chemistry. The filler networking, curing behavior, filler dispersion, crosslink density, and mechanical performance were fully studied. The filler networking in the uncured rubber compounds was effectively restrained. The vulcanization was largely accelerated by MimMP. The interfacial interaction was quantitatively evaluated and found to consistently increase with increasing MimMP. The mechanical performance and abrasion resistance of the modified vulcanizates improved considerably. The remarkable improvements were mainly ascribed to the improved interfacial structure comprised of MimMP–silica hydrogen bonding and MimMP–rubber covalent bonds via thiol–ene chemistry. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of palm ash loading and maleated natural rubber as a coupling agent on the properties of palm‐ash‐filled natural rubber composites

Natural rubber composites were prepared by the incorporation of palm ash at different loadings into a natural rubber matrix with a laboratory‐size two‐roll mill (160 × 320 mm²) maintained at 70 ± 5°C in accordance with the method described by ASTM D 3184–89. A coupling agent, maleated natural rubber (MANR), was used to improve the mechanical properties of the natural rubber composites. The results indicated that the scorch time and cure time decreased with increasing filler loading, whereas the maximum torque exhibited an increasing trend. Increasing the palm ash loading increased the tensile modulus, but the tensile strength, fatigue life, and elongation at break decreased. The rubber–filler interactions of the composites decreased with increasing filler loading. Scanning electron microscopy of the tensile fracture surfaces of the composites and rubber–filler interaction studies showed that the presence of MANR enhanced the interfacial interaction of the palm ash filler and natural rubber matrix. The presence of MANR also enhanced the tensile properties and fatigue life of palm‐ash‐filled natural rubber composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

氯醚橡胶/丁腈橡胶共混物的结构与性能

研究了不同并用比的氯醚橡胶（ECO）／丁腈橡胶（NBR）共混物的相态结构,力学性能,耐老化性能和耐油性能,透射电镜照片显示：ECO／NBR为70／30（质量份,下同）时共混物呈双连续相：为60／40和40／60时ECO都为分散相,且两相界面清晰。加入NBR降低了ECO的拉伸强度和看断伸长率,以及耐热空气老化性能,随着NBR用量的提高,共混物硫化胶在油中的体积变化率增加,ECO／NBR为70／30时硫化胶在100℃热油中的性能保持率最高,而且体积变化率与ECO的相当。