Improvement of properties of silica‐filled styrene–butadiene rubber compounds using acrylonitrile–butadiene rubber

Since silica has strong filler–filler interactions and adsorbs polar materials, a silica‐filled rubber compound has a poor dispersion of the filler and poor cure characteristics. Improvement of the properties of silica‐filled styrene–butadiene rubber (SBR) compounds was studied using acrylonitrile–butadiene rubber (NBR). Viscosities and bound rubber contents of the compounds became lower by adding NBR to the compound. Cure characteristics of the compounds were improved by adding NBR. Physical properties such as modulus, tensile strength, heat buildup, abrasion, and crack resistance were also improved by adding NBR. Both wet traction and rolling resistance of the vulcanizates containing NBR were better than were those of the vulcanizate without NBR. The NBR effects in the silica‐filled SBR compounds were compared with the carbon black‐filled compounds. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1127–1133, 2001     

Effect of low molecular weight polybutadiene as processing aid on properties of silica‐filled styrene–butadiene rubber compounds

Because silica has strong filler–filler interactions, a silica‐filled rubber compound shows a poor filler dispersion compared to a carbon black‐filled one. Improvement of the filler dispersion in silica‐filled styrene–butadiene rubber (SBR) compounds was studied using low molecular weight polybutadiene (liquid PBD) with the high content of 1,2‐unit. By adding the liquid PBD to the silica‐filled SBR compound, the filler dispersion and flow property are improved. The cure time and cure rate become faster as the 1,2‐unit content of the liquid PBD increases for the compounds containing the liquid PBD. The crosslink density increases linearly with increase in the 1,2‐unit content of the liquid PBD. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3135–3140, 2003     

Swelling and mechanical properties of (acrylonitrile‐butadiene rubber)/(hydrogenated acrylonitrile‐butadiene rubber) blends with precipitated silica filled in gasohol fuels

This work studied the effects of hydrogenated acrylonitrile‐butadiene rubber (HNBR) and precipitated silica (PSi) loadings in acrylonitrile‐butadiene rubber (NBR) filled with 60 parts per hundred of rubber (phr) of carbon black (CB) for oil‐resistant seal applications in contact with gasohol fuel. The cure characteristics, mechanical properties, and swelling behavior of HNBR/NBR blends reinforced with PSi before and after immersion in ethanol‐based oils (E10, E20, and E85) were then monitored. This work studied the effects of PSi loading in rubber compounds on the mechanical properties of the rubber blends. The results suggested that the scorch time of CB‐filled NBR/HNBR was not affected by HNBR loading, but the cure time, Mooney viscosity, and torque difference increased with HNBR content. The swelling of the blends in E85 oil were relatively low compared with those in E10 and E20 oils. The recommended NBR/HNBR blend ratio for oil‐resistant applications was 50/50. Tensile strength and elongation at break before and after immersion in gasohol oils increased with HNBR loading, and the opposite effect was found for tensile modulus and hardness. PSi filler had no effect on scorch time, but decreased the cure time of the blends. The swelling level of the blends slightly decreased with increasing PSi content. The recommended silica content for optimum reinforcement for black‐filled NBR/HNBR blend at 50/50 was 30 phr. The results in this work suggested that NBR/HNBR blends reinforced with 60 phr of CB and 30 phr of silica could be potentially used for rubber seals in contact with gasohol fuels. J. VINYL ADDIT. TECHNOL., 22:239–246, 2016. © 2014 Society of Plastics Engineers     

Improvement of properties of silica‐filled natural rubber compounds using polychloroprene

Because silica has strong filler–filler interactions, a silica‐filled rubber compound is characterized by a poor dispersion of the filler. Properties of silica‐filled natural rubber (NR) compounds were improved using polychloroprene (chloroprene rubber [CR]). The bound rubber content of the compound increases and the filler dispersion is also improved by adding CR to the compound. Physical properties such as modulus, tensile strength, abrasion, and crack resistance are improved by adding CR. Elongation at break of the vulcanizates containing CR is longer than that of the vulcanizate without CR, although crosslink density of the former is higher than that of the latter. The improved physical properties are attributed to the good dispersion of silica by adding CR. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2609–2616, 2002     

Influence of the silica content on rheological behaviour and cure characteristics of silica‐filled styrene–butadiene rubber compounds

Rheological behaviour and cure characteristics of silica‐filled styrene–butadiene rubber (SBR) compounds and SBR compounds filled with both silica and carbon black with different silica contents were investigated. Rheocurves of the time versus the torque of the compounds showed specific trends with the silica content. For the compounds with low silica content (less than 50 phr), the torque decreased immediately after the steep increase at the initial point of the rheocurve and then increased very slowly. For the compounds with high silica content (more than 50 phr), the rheographs showed two minimum torque points; the torque decreased immediately after the steep increase at the start point of the rheocurve and then increased sharply before reaching the second minimum point. This can be explained by the strong filler–filler interaction of silica. The minimum torque of the compound increased slightly with an increase of the silica content up to 50 phr silica content and then increased appreciably. For the silica‐filled compounds, cure times of the t₀₂, t₄₀, and t₉₀ became shorter with an increase of the filler content. For the compounds filled with both silica and carbon black (total filler content of 80 phr), the cure times became longer with an increase of the silica content ratio. © 2001 Society of Chemical Industry     

Improvement of the homogeneity of SBR/NBR blends using polyglycidylmethacrylate‐g‐butadiene rubber

Polyglycidylmethacrylate grafted butadiene rubber (PGMA‐g‐BR) was synthesized by a graft solution copolymerization technique. The PGMA content was determined through titration against HBr. The PGMA‐g‐BR was blended with styrene butadiene rubber/butadiene acrylonitrile rubber (SBR/NBR) blends with different blend ratios. The SBR/NBR (50/50) blend was selected to examine the compatibility of such blends. Compatibility was examined using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and viscosity measurements. The scanning electron micrographs illustrate the change of morphology of the SBR/NBR rubber blend as a result of the incorporation of PGMA‐g‐BR onto that blend. The T_gs of SBR and NBR in the blend get closer upon incorporation of PGMA‐g‐BR 10 phr, which indicates improvement in blend homogeneity. The intrinsic viscosity (η) versus blend ratio graph shows a straight‐line relationship, indicating some degree of compatibility. Thermal stability of the compatibilized and uncompatibilized rubber blend vulcanizates was investigated by determination of the physicomechanical properties before and after accelerated thermal aging. Of all the vulcanizates with different blend ratios under investigation, the SBR/NBR (25/75) compatibilized blend possessed the best thermal stability. However, the SBR/NBR (75/25) compatibilized blend possessed the best swelling performance in brake fluid. The effect of various combinations of inorganic fillers on the physicomechanical properties of that blend, before and after accelerated thermal aging, was studied in the presence and absence of PGMA‐g‐BR. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1559–1567, 2006     

Influences of trans‐polyoctylene rubber on the physical properties and phase morphology of natural rubber/acrylonitrile–butadiene rubber blends

The influence of trans‐polyoctylene rubber (TOR) on the mechanical properties, glass‐transition behavior, and phase morphology of natural rubber (NR)/acrylonitrile–butadiene rubber (NBR) blends was investigated. With an increased TOR level, hardness, tensile modulus, and resilience increased, whereas tensile strength and elongation at break tremendously decreased. According to differential scanning calorimetry and dynamic mechanical analysis, there were two distinct glass‐transition temperatures for a 50/50 NR/NBR blend, indicating the strongly incompatible nature of the blend. When the TOR level was increased, the glass transition of NBR was strongly suppressed. NBR droplets of a few micrometers were uniformly dispersed in the continuous NR phases in the NR/NBR blends. When TOR was added to a 50/50 NR/NBR blend, TOR tended to be located in the NR phase and in some cases was positioned at the interfaces between the NBR and NR phases. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 125–134, 2002     

Fly ash particles and precipitated silica as fillers in rubbers. I. Untreated fillers in natural rubber and styrene–butadiene rubber compounds

In this study, we investigated the effects of untreated precipitated silica (PSi) and fly ash silica (FASi) as fillers on the properties of natural rubber (NR) and styrene–butadiene rubber (SBR) compounds. The cure characteristics and the final properties of the NR and SBR compounds were considered separately and comparatively with regard to the effect of the loading of the fillers, which ranged from 0 to 80 phr. In the NR system, the cure time and minimum and maximum torques of the NR compounds progressively increased at PSi loadings of 30–75 phr. A relatively low cure time and low viscosity of the NR compounds were achieved throughout the FASi loadings used. The vulcanizate properties of the FASi‐filled vulcanizates appeared to be very similar to those of the PSi‐filled vulcanizates at silica contents of 0–30 phr. Above these concentrations, the properties of the PSi‐filled vulcanizates improved, whereas those of the FASi‐filled compounds remained the same. In the SBR system, the changing trends of all of the properties of the filled SBR vulcanizates were very similar to those of the filled NR vulcanizates, except for the tensile and tear strengths. For a given rubber matrix and silica content, the discrepancies in the results between PSi and FASi were associated with filler–filler interactions, filler particle size, and the amount of nonrubber in the vulcanizates. With the effect of the FASi particles on the mechanical properties of the NR and SBR vulcanizates considered, we recommend fly ash particles as a filler in NR at silica concentrations of 0–30 phr but not in SBR systems, except when improvement in the tensile and tear properties is required. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2119–2130, 2004     

Unsaturated polyester as compatibilizer for styrene–butadiene (SBR)/acrylonitrile–butadiene (NBR) rubber blends

The effect of the addition of 5 and 10 phr of unsaturated polyester resin (UPE) on the compatibility and physicomechanical properties of styrene–butadiene (SBR) and acrylonitrile–butadiene (NBR) rubber blends was studied. Differential scanning calorimetry (DSC), scanning electron microscopy (SEM), electrical, and ultrasonic techniques were used to determine the degree of the compatibility (DC). The results obtained revealed that, by the addition of 10 parts per hundred parts of rubber (phr) UPE as a compatibilizer for SBR/NBR blends, the degree of compatibility was greatly enhanced. The rheological and mechanical properties of the blends were also improved. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2314–2321, 2002     

Effect of adding carbon fiber on conductive stability of acrylonitrile‐butadiene rubber composites

In this work, the conductive composites of acrylonitrile‐butadiene rubber (NBR) and conductive carbon black (CCB) were prepared. The volume resistivity of NBR/CCB composites became stable when the addition content of CCB reached 12 wt %. However, when carbon fiber (CF) was added into the composites, the volume resistivity of NBR/CCB/CF composites continued to decrease with the increase of CF addition, which resulted from the formation of the three‐dimensional conductive network in composite matrix. In addition, the effect of acid oxidation of CF surface on the mechanical proprieties and conductive stability of NBR/CCB/CF composites was studied. The results indicated the acid oxidation of CF surface improved the bond structure between NBR and CF, which further decreased the resistance and significantly improved the mechanical properties of the composites. It was demonstrated that the conductive stability of NBR composites after cyclic mechanical and temperature fatigues was remarkably enhanced with the addition of CF. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46668.     

Characterization of barium titanate reinforced acrylonitrile butadiene rubber composites for flexible electronic applications: influences of barium titanate content

The aim of this study was to develop high dielectric constant flexible polymers with a highly efficient and cost‐effective approach using acrylonitrile butadiene rubber (NBR) as the polymer matrix and barium titanate (BT) as the high dielectric constant filler. The BT powder was synthesized with a solid‐state reaction and was characterized using a particle size analyzer, XRD, SEM and Fourier transform infrared spectroscopy. NBR/BT composites were fabricated using an internal mixer with various BT loadings up to 160 phr. The influence of BT loading on the cure characteristics and mechanical, dynamic mechanical, thermal, dielectric and morphological properties was determined. The incorporation of BT in the NBR matrix shortened scorch time and increased delta torque. The mechanical properties, thermal stability and dielectric constant were greatly improved and increased with BT loading. The results suggest that the reinforcement effect was achieved due to strong hydrogen bonding or polar–polar interactions between NBR matrix and BT filler. This is further corroborated by the good dispersion of BT filler in the NBR matrix observed with SEM imaging. These findings can be applied to produce high‐performance dielectric elastomers. © 2020 Society of Industrial Chemistry     

Effect of carbon‐based nanoparticles on the cure characteristics and network structure of styrene–butadiene rubber vulcanizate

The network structure of styrene–butadiene rubber (SBR) in the presence of carbon black (CB) with two different structures and multi‐walled carbon nanotubes (MWCNTs) was investigated. Swelling behaviour, tensile properties at various strain rates and cure kinetics were characterized. Experimental data were analysed using the Flory–Rehner model as well as the tube model theory. It is found that the network structure of CB‐filled SBR follows a three‐phase composite model including rigid particles, semi‐rigid bound rubber and matrix rubber. This bound rubber is postulated to be critical for the mechanical and deformational properties, development of crosslinking density in matrix rubber and polymer–filler interaction. For MWCNT‐filled SBR, the bound rubber does not show a substantial contribution to the network structure and mechanical performance, and these properties are greatly dominated by the higher aspect ratio and polymer–filler interaction. Additionally it is deduced that the crosslinking density of matrix rubber increases on incorporation of the fillers compared to unfilled matrix rubber. Copyright © 2012 Society of Chemical Industry     

Toughening epoxy resins with solid acrylonitrile–butadiene rubber

The feasibility of using solid acrylonitrile–butadiene rubbers (NBR) with 19 and 33% w/w acrylonitrile to toughen diglycidyl ether of bisphenol A (DGEBA) epoxy resins has been investigated. Thermal analysis experiments revealed a two‐phase morphology of these rubber‐modified epoxies. However, the higher content of acrylonitrile in the rubber caused better compatibility between NBR and the epoxy resin. The rubber with 33% acrylonitrile was found to be an effective toughening agent for DGEBA epoxy resins. Fracture surface studies and also the high tensile strength of crosslinked high molecular weight NBR suggest that the toughening effect should arise from rubber bridging and tearing mechanisms. © 2000 Society of Chemical Industry     

Morphology and mechanical properties of clay/styrene‐butadiene rubber nanocomposites

Based on the character of a clay that could be separated into many 1‐nm thickness monolayers, clay styrene‐butadiene rubber (SBR) nanocomposites were acquired by mixing the SBR latex with a clay/water dispersion and coagulating the mixture. The structure of the dispersion of clay in the SBR was studied through TEM. The mechanical properties of clay/SBR nanocomposites with different filling amounts of clay were studied. The results showed that the main structure of the dispersion of clay in the SBR was a layer bundle whose thickness was 4–10 nm and its aggregation formed by several or many layer bundles. Compared with the other filler, some mechanical properties of clay/SBR nanocomposites exceeded those of carbon black/SBR composites and they were higher than those of clay/SBR composites produced by directly mixing clay with SBR through regular rubber processing means. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1873–1878, 2000     

Effects of trans‐polyoctylene rubber on rheological and green tensile properties of natural rubber/acrylonitrile–butadiene rubber blends

The influence of trans‐polyoctylene rubber (TOR) on the flow property, die swell behaviour and green tensile property of NR (natural rubber)/NBR (acrylonitrile–butadiene rubber) blend compound was investigated as a function of TOR loading level. The pure TOR, NR and NBR compounds were also investigated for comparison with the blend compounds. The shear viscosity of TOR strongly depended on the temperature as well as shear rate. The viscosity of the NR/NBR blend compound was even lower than that of the constituent components at relatively lower shear rates, and the viscosity difference became smaller as the shear rate was increased. The viscosity of the NR/NBR blend compounds was strongly affected by the addition of TOR but the effect became negligible with increasing the shear rate. Both the die‐swell ratio and the surface topology of extrudates were also affected by TOR addition; the dependence on shear rate was much stronger for higher TOR level. The NR/NBR blend compound showed much higher green tensile strength and elongation at break than those of the constituent components. Both the green tensile modulus and strength of the NR/NBR blend compound were greatly enhanced, while the elongation at break was reduced with the addition of TOR. © 2002 Society of Chemical Industry     

Compatibilization of SBR/NBR blends using chemically modified styrene‐co‐butadiene rubber Part 2. Effect of compatibilizer loading

The present work focuses on the compatibization of styrene‐co‐butadiene rubber (SBR)/acrylonitrile‐co‐butadiene rubber (NBR) blends with dichlorocarbene modified styrene‐co‐butadiene rubber (DCSBR) as a function of concentration of compatibilizer and composition of the blend. FTIR studies, differential scanning calorimetry and dynamic mechanical analysis reveal molecular level miscibility in the blends in the presence of compatibilizer. The formation of interfacial bonding is assessed by analysis of swelling behaviour, cure characteristics, stress–strain data and mechanical properties. These studies show that the compatibilizing action of DCSBR becomes more prominent as the proportion of NBR in the blend increases. The resistance of the vulcanizate towards thermal and oil ageing improved with compatibilization. The change in technological properties is correlated with the crosslink density of the blends assessed from swelling and stress–strain data. © 2001 Society of Chemical Industry     

Preparation and properties of acrylonitrile–butadiene copolymer hybrid nanocomposites with organoclays

Acrylonitrile–butadiene rubber (NBR) hybrid nanocomposites with organoclays were prepared by melt mixing, and their properties were compared with those of conventional rubber compounds filled with carbon black and silica. Based on X‐ray diffraction and transmission electron microscopy, the NBR nanocomposites obtained were found to form generally an intercalated structure, although they formed an exfoliated structure when the organoclay content was low enough, <2 parts per 100 rubber. The NBR nanocomposite showed a simultaneous improvement in ultimate strength and stiffness, which is generally in a trade‐off relation in rubbery materials. A characteristic fracture morphology of ‘laminated board‐type’ was observed for NBR nanocomposites instead of typical ‘cross‐hatched’ morphology in conventional rubber composites. The NBR nanocomposites also showed much higher hysteresis and tension set. Copyright © 2003 Society of Chemical Industry     

Rectorite powder modified by butadiene‐styrene‐vinyl pyridine rubber: Structure and its dispersion in styrene‐butadiene rubber

Rectorite (REC) powders modified by butadiene‐styrene‐vinyl pyridine rubber (VPR) were prepared by spray drying, designated as REC‐VPRs. X‐ray diffraction (XRD), Scanning electron microscope (SEM), and transmission electron microscopy (TEM) analyses showed that in the REC‐VPRs, VPR did not intercalate into the intergallery of layers. However, compared with REC, the layers of REC‐VPRs had more wrinkles and piled loosely. To strengthen the interfacial interaction between VPR and REC, a REC‐VPR was treated by volatilized hydrochloric acid, resulting in the formation of ion bonds between REC and VPR, according to Fourier transform infrared spectra measurements. XRD analyses revealed that the intercalated structure emerged in acid treated REC‐VPR filled styrene‐butadiene rubber (SBR). However, the better dispersion was observed for the SBR composite filled with REC‐VPR without acid treatment, indicating that a proper interfacial interaction between REC and VPR is the key to improve the dispersion of REC layers in SBR. Acid treatment did not improve the tensile and tear strengths of the SBR composite filled with REC‐VPR. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci., 2013     

Silica‐modified SBR/BR blends

The purpose of this article is that the silica‐modified SBR/BR blend replaces natural rubber (NR) in some application fields. The styrene‐butadiene rubber (SBR) and cis‐butadiene rubber (BR) blend was modified, in which silica filler was treated with the r‐Aminopropyltriethoxysilane (KH‐550) as a coupling agent, to improve mechanical and thermal properties, and compatibilities. The optimum formula and cure condition were determined by testing the properties of SBR/BR blend. The properties of NR and the silica‐modified SBR/BR blend were compared. The results show that the optimum formulawas 80/20 SBR/BR, 2.5 phr dicumyl peroxide (DCP), 45 phr silica and 2.5 mL KH‐550. The best cure condition was at 150°C for 25 min under 10 MPa. The mechanical and thermal properties of SBR/BR blend were obviously modified, in which the silica filler treated with KH‐550. The compatibility of SBR/BR blend with DCP was better than those with benzoyl peroxide (BPO) and DCP/BPO. The crosslinking bonds between modified silica and rubbers were proved by Fourier transform infrared analysis, and the compatibility of SBR and BR was proved by polarized light microscopy (PLM) analysis. The silica‐modified SBR/BR blend can substitute for NR in the specific application fields. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Hydrogenation of acrylonitrile–butadiene rubber latexes

The hydrogenation of acrylonitrile–butadiene rubber (NBR) latex was carried out by a system consisting of hydrazine hydrate and hydrogen peroxide, with boric acid as catalyst. Highly saturated hydrogenated NBR (HNBR) latex was obtained through the optimization of the reaction conditions. The dried HNBR was found to be heavily gelled. The cause for the crosslink of dried hydrogenated NBR products was investigated. With the improvement of the hydrogenation system, that is, by adding gel inhibitor to the system, the crosslinking was controlled to a large extent, and dried HNBR with gel content of about 3% was prepared by the improved system. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2072–2078, 2004