Influence of carbon black on uncompatibilised and compatibilised SBR–NBR blends

Abstract

Elastomeric blends based on SBR and NBR have been prepared, giving emphasis to differences in blend composition. It was observed from dynamic mechanical analysis that the SBR–NBR blends can be compatibilised by addition of 5 pphr dichlorocarbene modified styrene/butadiene rubber. The efficiency of carbon black in uncompatibilised and compatibilised blends was evaluated with reference to their processing characteristics and technological properties and the resistance of the vulcanisates towards thermal and oil aging was analysed. The changes in technological properties have been correlated with variations in crosslink density estimated from stress–strain and swelling behaviour. The swelling studies are also extended to evaluate the reinforcing nature of the filler. The results of the study reveal that compatibilised blends show enhanced mechanical properties in the presence of HAF carbon black in comparison with uncompatibilised samples.     

Studies on Epdm/Nr Blends. I. Dielectric and Mechanical Properties

Ethylene-propylene-diene terpolymer rubberlnatural rubber blends (EPDM/NR) in different proportions (100 : 0, 75 : 25, 50 : 50, 25 : 75, and 0 : 100) reinforced with 20 phr semireinforcing furnace carbon black have been studied. The permittivity ?' and dielectric loss ?″ for these samples were determined in the frequency range 10²–10⁷ Hz. Also, their physico-mechanical properties were investigated.

The EPDM/NR blend (75 : 25) possessed the best mechanical properties and stability against aging. Thus, it was chosen to explore the effect of adding carbon black in different quantities up to 50 phr on its electrical and mechanical properties. Three different types of carbon black. namely high-abrasion furnace black, fast-extrusion furnace black, and medium thermal black, were used. At a certain concentration of carbon black, referred to as the threshold percolation concentration, an abrupt increase in ?′ and ?″, which depends on its type, was detected. This could be attributed to some sort of interaction between the blend and the carbon black at higher concentrations.     

Particle size distribution,mixing behavior,and mechanical properties of carbon black (high‐abrasion furnace)–filled powdered styrene butadiene rubber

High‐abrasion furnace black (HAF, grade N330)–filled powdered styrene butadiene rubber [P(SBR/HAF)] was prepared and the particle size distribution, mixing behavior in a laboratory mixer, and mechanical properties of P(SBR/HAF) were studied. A carbon black–rubber latex coagulation method was developed for preparing carbon black–filled free‐flowing, noncontact staining SBR powders, with particle diameter less than 0.9 mm, under the following conditions: carbon black content > 40 phr, emulsifier/carbon black ratio > 0.02, and coating resin content > 2.5 phr. Over the experimental range, the mixing torque τ_α of P(SBR/HAF) was not as sensitive to carbon black content and mixing temperature as that of HAF‐filled bale SBR (SBR/HAF), whereas the temperature build‐up ΔT showed little dependency on carbon black content. Compared with SBR/HAF, P(SBR/HAF) showed a 20–30% mixing energy reduction with high carbon black content (>30 phr), which confers to powdered SBR good prospects for internal mixing. Carbon black and the rubber matrix formed a macroscopic homogenization in P(SBR/HAF), and the incorporation step is not obvious in the internal mixing processing results in these special mixing behaviors of P(SBR/HAF). A novel mixing model of carbon black–filled powdered rubber, during the mixing process in an internal mixer, was proposed based on the special mixing behaviors. P(SBR/HAF) vulcanizate showed better mechanical properties than those of SBR/HAF, dependent primarily on the absence of free carbon black and a fine dispersion of filler on the rubber matrix attributed to the proper preparation conditions of noncontact staining carbon black–filled powdered SBR. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2494–2508, 2004     

Effect of carbon black and thermal aging on the conduction mechanism of natural and styrene butadiene rubbers

Two types of carbon black namely fast extrusion furnace black (FEF) and high abrasion furnace black (HAF) were incorporated with a concentration of 50 phr into styrene butadiene rubber (SBR) and natural rubber (NR). The effect of the time of aging and temperature on the electrical conductivity was studied. It was found that a thermal aging at 95°C leads to the appearance of minimum in conductivity (σ) in both FEF/NR and HAF/NR. This was explained by a competition between two factors: degradation and increase of crosslinking density in the rubber matrix. In case of FEF/SBR and HAF/SBR it seems that these factors have comparable effects on the conductivity after 10 days of aging. From the current-voltage (I-V) characteristics the carrier concentration, trap density, and the drift mobility were calculated. The minimum found in the temperature dependence of σ for FEF/NR is discussed and found to be controlled by the relative dimension of carbon and rubber aggregates.     

Multiphase polymer processing: Controlled-ingredient-distribution mixing and its effect on some properties of styrene-butadiene (SBR)/butadiene-acrylonitrile copolymer rubber blend compounds

The flex-crack-growth resistance and oil-swelling resistance of a styrene-butadiene (SBR)/butadiene-acrylonitrile co-polymer (NBR) rubber blend are studied as a function of the distribution of ingredients in the individual rubber phases. The blends consist of 70:30 weight ratio of SBR:NBR with incorporation of 82.5 phr carbon black and other ingredients via the controlled-ingredient-distribution mixing procedure. The results show that flex crack growth is affected by the distribution of carbon black. Better flex crack growth resistance could be achieved by adding 10 percent of carbon black to the NBR rubber phase and 90 percent to the SBR phase. The swelling of these rubber blends in ASTM #2 oil is also affected by the location of carbon black and by the mixing history. The blends with more black initially preloaded in the SBR phase have lower swelling, as have blends with shorter cross-mixing time or the mill. A simple equation based on the permeation/moduli of composite materials is proposed to describe the swelling of this rubber blend in terms of the swelling of the constituent rubber phases, the distribution of ingredient in the individual rubber phases, and the blend morphology. One of the key assumptions is to consider the individual black preloaded rubber as a continuum. The quantitative correlation with the observed swelling data is reasonably good.     

DMA analysis of the damping of ethylene–vinyl acetate/acrylonitrile butadiene rubber blends

The mechanical and damping properties of blends of ethylene–vinyl acetate rubber (VA content > 40% wt) (EVM)/acrylonitrile butadiene rubber (NBR), with 1.4 phr BIPB [bis (tert‐butyl peroxy isopropyl) benzene] as curing agent, were investigated by DMA and DSC. The effect of chlorinated polyvinyl chloride (CPVC), silica, carbon black, and phenolic resin (PF) as a substitute curing agent, on the damping and mechanical properties of EVM/NBR blends were studied. The results showed that 10 phr CPVC did not contribute to the damping of EVM700/NBR blends; Silica could dramatically improve the damping of EVM700/NBR blends because of the formation of bound rubber between EVM700/NBR and silica, which appeared as a shoulder tan δ peak between 20 and 70°C proved by DMA and DSC. This shoulder tan δ peak increased as the increase of the content of EVM in EVM/NBR blends. The tensile strength, modulus at 100% and tear strength of the blend with SiO₂ increased while the elongation at break and hardness decreased comparing with the blend with CB. PF, partly replacing BIPB as the curing agent, could significantly improve the damping of EVM700/NBR to have an effective damping temperature range of over 100°C and reasonable mechanical properties. Among EVM600, EVM700, and EVM800/NBR/silica blend system, EVM800/NBR/silica blend had the best damping properties. The EVM700/NBR = 80/10 blend had a better damping property than EVM700/NBR = 70/20. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Curing Characteristics and Mechanical and Morphological Properties of Styrene Butadiene Rubber/Virgin Acrylonitrile-Butadiene Rubber (SBR/vNBR) and Styrene Butadiene Rubber/Recycled Acrylonitrile-Butadiene Rubber (SBR/rNBR) Blends

Curing characteristics and mechanical and morphological properties of styrene butadiene rubber/virgin acrylonitrile-butadiene rubber (SBR/vNBR) and styrene butadiene rubber/recycled acrylonitrile-butadiene rubber (SBR/rNBR) were investigated. Results indicated that the curing characteristics, such as scorch time, t₂, and cure time, t₉₀, of SBR/vNBR and SBR/rNBR blends decreased with increasing vNBR and rNBR content. At similar blend ratios, particularly up to 15 phr, SBR/rNBR blends exhibited higher t₂ and t₉₀ compared with SBR/vNBR blends. Minimum torque (ML) and maximum torque (MH) of SBR/vNBR blends significantly increased with increasing vNBR content. For SBR/rNBR blends, ML increased with increasing rNBR content, but MH exhibited the opposite trend. Tensile strength, elongation at break (E_b), resilience, and fatigue decreased with increasing virgin and recycled NBR content in both blends. Up to 15 phr, the tensile strength, E_b and fatigue life (Kc) of SBR/rNBR blends were higher than in SBR/vNBR blends. The M100 (stress at 100% elongation), hardness, and cross-linking density of both blends also showed an increasing trend with increasing vNBR and rNBR content. The scanning electron microscopy study indicates that rNBR exhibited a weak rNBR-SBR matrix interaction particularly when more than 15 phr of rNBR was used, thus decreasing the mechanical properties of SBR/rNBR blends.     

Dielectric properties of SBR vulcanizates loaded with HAF carbon black and BaTiO3 ceramics

The influence of HAF carbon black and BaTiO₃ ceramic powder contents in SBR vulcanizates on the dielectric constant (ε′) at different frequencies and at fixed temperature of 303 K is studied well in this article. The temperature dependence of the ac conductivity (σ_ac) was also studied. ε′ appreciably decreases as frequency increased for both filled and unfilled SBR vulcanizates. At each frequency, ε′ gradually decreased with BaTiO₃ loading, but its change at any fixed frequency with BaTiO₃ filler loading is not uniform. For HAF group ε′ (at loading ≥ 40 phr), drops rapidly with frequency. Meanwhile, it increased appreciably beyond a certain HAF filler loading (≈ 20 phr). Experimental values of the dielectric constant of both BaTiO₃ and HAF contents were compared with those calculated by using Tsangaris, Clausius and Bruggman models. Tsangaris model with simple modifications was applied and a fairly good agreement was obtained. The HAF particles or aggregates was found to take the shape of oblate ellipsoids with the minor axes parallel to the applied frequency as detected from the decreasing behavior of the depolarizing factor (Y) with HAF contents. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2227–2234, 2007     

Filling Effect of Silica on Electrical and Mechanical Properties of EPDM/NBR Blends

Filling effect of silica on dielectric and mechanical properties of ethylene propylene diene/acrylonitrile butadiene rubber EPDM/NBR blends with different compositions was studied. To solve the problem of phase separation polyvinyl chloride (PVC) with concentration 10 phr was added. The dielectric data for the investigated systems on the frequency domain 100 Hz to 100 kHz were found to be fitted using Fröhlich function by two absorption regions. These regions ascribe the Maxwell-Wagner effect and the aggregates that are expected to be formed by the addition of different ingredients to rubber. The study led to a conclusion that the blend 75/25 EPDM/NBR possesses the most promising properties. For such reason, this blend was chosen to be loaded with silica in increasing quantities up to 90 phr and then study the various properties. This study indicates that the EPDM/NBR blend loaded with 50–60 phr of silica possess the most suitable electrical and mechanical properties.     

The Effect of Electron Beam (EB) Irradiation in Presence of TMPTA on Cure Characteristics and Mechanical Properties of Styrene Butadiene Rubber/Recycled Acrylonitrile-Butadiene Rubber (SBR/NBRr) Blends

The effect of electron beam (EB) irradiation on the cure characteristics and mechanical properties of unirradiated and irradiated SBR/NBRr blends were investigated. The SBR/NBRr blends were prepared at 95/5, 85/15, 75/25, 65/35, and 50/50 blend ratio with and without the presence of a polyfunctional monomer, trimethylolpropane triacrylate (TMPTA). Results indicated that the scorch time t₂, cure time t₉₀ and minimum torque (M_L) of irradiated SBR/NBRr blend decreased, but the maximum torque (M_H) particularly at 35 and 50 phr of NBRr (recycled NBR) increased with the presence of TMPTA. The stress at 100% elongation (M100), hardness, cross-linking density and tensile strength (particularly after 15 phr of NBRr content) of irradiated SBR/NBRr blends increased after irradiation but the elongation at break (EB) and resilience decreased. The irradiated SBR/NBRr blends showed lower thermal stability than non-irradiated blends. Scanning electron microscopy proved the enhancement in tensile strength when more NBRr were added in SBR matrix where the irradiated surfaces demonstrate more irregularity with increasing crack branching (fracture planes are located at different heights) due to the increased of cross-linked density.     

Investigation of electrically conductive acrylonitrile‐butadiene rubber

Electrically conductive acrylonitrile‐butadiene rubbers (NBRs) containing carbon black (CB) as conductive filler were prepared in order to investigate their electrical and mechanical properties. The effects of conductive CB loading, temperature, acrylonitrile content, crosslinking density of vulcanizates, and plasticizer on conductivity were studied. The change in electrical conductivity of NBRs with different amounts of CB showed that there is a certain critical point (percolation threshold) where a significant decrease in electrical resistivity (increase in conductivity) is observed. Mechanical properties such as tensile strength, elongation to break, and surface hardness of vulcanized NBRs were measured. It was found that the percolation threshold was 5 phr of CB for the NBR/CB composites. J. VINYL ADDIT. TECHNOL., 13:71–75, 2007. © 2007 Society of Plastics Engineers.     

Studies on conductivity of nitrile rubber and its blends with NR,EPDM, and PVC

Abstract

Nitrile/butadiene rubber has been made electrically conducting by the incorporation of acetylene black. The change in conductivity and mechanical properties with varying amounts of acetylene black was studied. Nitrile rubber was blended with NR, PVC, and EPDM and their conductivity and mechanical properties were determined after incorporation of acetylene black. On comparison it was found that NBR-NR blends are more conducting than NBR-PVC and NBR-EPDM blends. Blends of NBR-NR containing varying amounts of NR and NBR were prepared with the same amount of acetylene black, and their properties were also studied. A blend of 80:20 NBR/NR was studied in detail by varying the concentration of acetylene black. It was found that electrical conductivity depends on the degree of dispersion of acetylene black in the polymer matrix.     

Electrical and mechanical properties of polyethylene–rubber blends

A systematic electrical and mechanical study was carried out on styrene butadiene rubber (SBR), as a nonpolar rubber, and nitrile rubber (NBR), as a polar one blended with pure and waste polyethylene (PE), low and high density. The compatibility investigations, which were carried out by the dielectric method and confirmed by the calculated heat of mixing, indicate that SBR–PE blends (either low or high density) are compatible, while NBR–PE blends are incompatible. From the electrical and mechanical results, it is found that the addition of waste PE to either polar or nonpolar rubber leads to better electrical and mechanical properties when compared with those for the blends having pure PE. The values of permittivity ε′ are found to increase pronouncely, while the values of dielectric loss ε′ slightly decrease. Shore hardness was also measured for all the investigated systems and found to vary linearly with the permittivity ε′. © 1998 John Wiley & Sons, Inc. J Appl Polm Sci 69: 775–783, 1998     

Electrical Conductivity of Styrene‐Butadiene Rubber/Polyester Short‐Fiber Reinforced with Different Types of Carbon Black

Abstract

Measurements of electrical conductivity for a composite of styrene‐butadiene rubber (SBR) and polyester (PE) short‐fiber reinforced with different types of carbon black [high abrasion furnace (HAF) and fast extruding furnace (FEF) black] in increasing quantities have been carried out at different temperatures (30–60°C). To find out the effect of the type of carbon black, particle size, and the quantity of carbon black, on the electrical conductivity of the SBR/PE short‐fiber composites. It was found that the electrical conductivity increases as the carbon content increases in the composites. Samples loaded with FEF carbon black showed lower conductivity values in comparison with those loaded with HAP carbon black, besides, they possess a reasonable conducting stability as the temperature rises. The results are discussed and interpreted.     

Static deformation of low structure HAF black‐loaded (SBR+NR) rubber blend

The stress‐strain behavior of different concentrations of low‐structure high abrasion furnace black (HAF‐LS, N326)‐loaded rubber blend of styrene butadiene rubber and natural rubber (SBR+NR) of equal parts was measured. Moduli of elasticity and the n‐measure of such blends were calculated using different approaches. An anomaly, of modulus of elasticity, found at 50 phr may be attributed to carbon black reinforcement and to an early crystallization of stretched natural rubber (NR) in the blend. These assumptions are confirmed through the measurement of the swelling factor as a function of time of swelling in kerosene.     

Electrical and mechanical properties of ethylene propylene diene monomer–chloroprene rubber blend loaded with white and black fillers

The permittivity ε′ and dielectric loss ε" for different ratios of an ethylene propylene diene monomer (EPDM)–chloroprene rubber (CR) blend ranging from 0 to 100 phr were measured over a frequency range from 400 Hz to 60 kHz. The measurements were carried out at room temperature (25°C). The values of ε′ and ε" were found to decrease with increasing EPDM content in the EPDM–CR blend. The sample which possesses the best mechanical and electrical properties was a 50 EPDM–50 CR blend. This sample was chosen to be loaded with 40 phr of some white fillers, namely, calcium carbonate, silica, silitan z, and talc. From the electrical and mechanical investigations, it was found that the use of silica and calcium carbonate in these blends could improve these properties. The electrical and mechanical properties were also studied for the investigated blends loaded with both silica and calcium carbonate with different contents (10–40 phr). It was found that 20 phr is the most promising concentration which can possess better properties. The same trend was obtained by the addition of 20 phr SRF black in addition to the white fillers to the above blends. On the other hand, from the compatibility study between both investigated rubber, it is found that both types are incompatible, in which some improvement may occur by the addition of PVC. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2061–2068, 1998     

A Study of FTIR,Thermal Properties and Natural Weathering Test on NBRVirgin/Recycled with SBR Blends

The effects of styrene butadiene rubber/virgin acrylonitrile butadiene rubber (SBR/NBRv) blends and styrene butadiene rubber/recycled acrylonitrile butadiene rubber (SBR/NBRr) blends on properties such Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) were carried out. Results indicated that, based on intensity of amine peak from FTIR at 85/15 blend ratio (R15) revealed optimum formation of crosslink between SBR and NBR either using virgin or NBRr. TG thermograms of SBR/NBRv blends of all ratios showed better onset thermal stability than SBR/NBRr blends. The change in the horizontal baseline from high to low energy level occurred in virgin NBR blends because the amount of reactive sites available in virgin NBR is higher compared to NBRr. Meanwhile NBRr blends showed T_c because the amount of crosslink occurred in these blends were slightly lower than NBRv blends. Up to 25 phr of NBRr, the tensile strength and elongation at break (E_b) retention of SBR/NBRv blends was better than SBR/NBRr blends after 6 months' weathering test except for M100. The scanning electron microscopy on the surface of both blends after 6 months exposure indicated that the severity of the crack was minimal for SBR/NBRr blends compared to SBR/NBRv particularly at 50/50 blend ratio designated the SBR/NBRr blends that contained more NBRr particles could reduce the degradation towards natural weathering.     

Effect of different coagents on physico‐chemical properties of electron beam cured NBR/HDPE composites reinforced with HAF carbon black

The effect of different coagents on the physico‐chemical properties of NBR/HDPE composites reinforced with 40 phr (part per hundred part of rubber by weight) HAF carbon black and cured with accelerated electrons was investigated. The coagents N,N′‐methylene bisacrylamide (MBAAm) and trimethylol propane trimethacrylate (TMPTMA) were used at a constant content of 10 phr. The physico‐chemical properties such as tensile strength, tensile modulus at 50% elongation (M₅₀), elongation at break (E_b), hardness, soluble fraction (SF), swelling number (SN), electrical conductivity, and thermal properties were studied. The results obtained showed that the TMPTMA as a coagent is more effective than MDA in enhancing the mechanical and physical properties of NBR/HDPE vulcanized composites. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

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     

导电炭黑及与沥青基碳纤维并用对NBR导电、导热性能的影响

研究了导电炭黑(VXC72)用量及与沥青基短切碳纤维(CF)并用对丁腈橡胶(NBR)的力学性能及导电、导热性能的影响;并用扫描电镜(SEM)观察填料的分散状态,同时考察了双辊开炼机对CF长径比的剪切破破坏程度。结果表明,随VXC72用量的增加,NBR/VXC72硫化胶的拉伸强度、撕裂强度和导热系数基本呈线性增加;体积电阻率呈阶梯形下降,逾渗阈值为25 phr。随VXC72/CF并用比的增大,NBR硫化胶的拉伸强度和撕裂强度明显降低,体积电阻率略有减小,而导热系数有一定程度的增加。填充20 phr CF时,NBR的导热系数较填充VXC72时提高了约30%。混炼使CF的长径比L/D剧烈降低,由原来的600降低到10-20,这也许是CF对NBR体积电阻率降低幅度不大的主要原因。