Effect of adhesive‐coated glass fiber in natural rubber (NR), acrylonitrile rubber (NBR), and ethylene–propylene–diene rubber (EPDM) formulations. II. Effect of cyclic loading,abrasion, and accelerated aging

Treated glass fibers (RICS, 3 and 6 mm in length) were added at a concentrations of 10, 20, and 30 phr in natural rubber (NR), nitrile rubber (NBR), and ethylene–propylene–diene comonomer (EPDM) formulations, in both plain and carbon black mixes. The compounds were mixed in two‐roll mill and were evaluated for their resistance to hot‐air aging, abrasion, compression set, Goodrich heat buildup, De Mattia fatigue, and for NR mixes, adhesion in the tensile mode. The vulcanizates of the three rubbers showed resistance to hot‐air aging. Abrasion resistance was poor for NR, and it improved with carbon black addition in the presence of treated glass fiber in NBR. In carbon‐black‐added EPDM vulcanizates, the abrasion resistance and fatigue resistance were better. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1124–1135, 2004     

Effects of epoxidized natural rubber (ENR‐50) and processing parameters on the properties of NR/EPDM blends using response surface methodology

The effects of epoxidized natural rubber (ENR‐50) and processing parameters on the properties of natural rubber/ethylene–propylene–diene rubber (NR/EPDM; 70 : 30 phr) blends were studied. The compounds were prepared by melt compounding method. Using response surface methodology of two‐level full factorial, the effects of ENR‐50 contents (?1 : 5 phr; +1 : 10 phr), mixing temperature (?1 : 50°C; +1 : 110°C), rotor speed (?1 : 40 rpm; +1 : 80 rpm), and mixing time (?1 : 5 min; +1 : 9 min) in NR/EPDM blends were evaluated. Cure characteristics and tensile properties were selected as the responses. The significance of factors and its interaction was analyzed using ANOVA and the model's ability to represent the system was confirmed using the constant of determination, R² with values above 0.90. It was found that the presence of ENR‐50 has the predominant role on the properties of NR/EPDM blends. The addition of ENR‐50 significantly improved cure characteristics and tensile strength up to 5.12% and 6.48% compared to neat NR/EPDM blends, respectively. These findings were further supported by swell measurement, differential scanning calorimetry, and scanning electron microscopy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40713.     

NR/EPDM 的共硫化

利用环氧化天然橡胶(ENR)与天然橡胶(NR)和三元乙丙橡胶(EPDM)均有很好相容性的特点，采用硫化促进剂预混工艺对NR／EPDM并用胶实施共硫化。考察了其对NR／EPDM并用胶的硫化特性、硫化胶的物理机械性能和耐热空气老化性能的影响。结果表明：本工艺确实能改善NR／EPDM的共硫化性能，所得硫化胶物理性能较好且操作简单。     

Aging of vulcanizates of formulations for rubber seals

Typical formulations based on NBR (acrylonitrile butadiene rubber), EPDM (ethylene propylene diene monomer rubber), and a NBR–CR (polychloroprene rubber) blend were studied for various properties under accelerated air aging conditions. The trend in tensile properties indicated the propensity of these formulations to oxidative degradation. The derivatives of these properties, such as their retention indices, strain energy, and Mooney–Rivlin constants also showed similar trends. Some of the observations correlate to shelf-aging data, but the time to rupture data derived from ultimate elongation values did not provide tangible conclusions. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 985–994, 1998     

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.     

Study on the milling behavior of chloroprene rubber blends with ethylene–propylene–diene monomer rubber,polybutadiene rubber,and natural rubber

The viscoelastic properties of the blends of chloroprene rubber (CR) with ethylene–propylene–diene monomer rubber (EPDM), polybutadiene rubber (BR), and natural rubber (NR) at different temperature were studied using rubber processing analyzer (RPA). Mooney viscosities of compounds were measured and tight milling and sheeting appearance were observed on a two‐roll mill. The results showed that Mooney viscosities and the elastic modulus of the blends decreased with the increase of the temperature from 60 to 100°C. And the decreasing trends of pure CR, pure NR, and CR/NR blend compounds were more prominent than that of pure EPDM, pure BR, CR/EPDM, and CR/BR blend compounds. For CR/EPDM blend compounds, the decreasing trend became slower with the increase of EPDM ratio in the blend. Compared with pure CR, pure NR and CR/NR blend compounds, pure EPDM, pure BR compounds, and the blend compounds of CR/EPDM and CR/BR showed less sensibility to temperature and they were less sticky to the metal surface of rolls and could be kept in elastic state at higher temperature, easy to be milled up and sheeted. At the same blend ratio and temperature, the property of tight milling of the blends decreased in the sequence of CR/EPDM, CR/BR, and CR/NR. With the increase of EPDM, BR, or NR ratio in CR blends, its property of tight milling was improved. POLYM. COMPOS., 28:667–673, 2007. © 2007 Society of Plastics Engineers     

Optimization of accelerators on curing characteristics,tensile, and dynamic mechanical properties of (natural rubber)/(recycled ethylene‐propylene‐diene‐monomer) blends

The migration of sulfur from natural rubber (NR) compound to the ground waste ethylene‐propylene‐diene monomer (EPDM) rubber phase may have caused the cure incompatibility between these two rubbers. Optimization of accelerators had been adopted to overcome the cure incompatibility in NR/(R‐EPDM) blends as well as to get increased curative distribution. In this study, blends of NR and R‐EPDM were prepared. The effect of accelerator type on curing characteristics, tensile properties, and dynamic mechanical properties of 70/30/NR/(R‐EPDM) blend was investigated. Four types of commercial accelerators were selected [ie, N‐tert‐butyl‐2‐benzothiazyl‐sulphonamide , N‐cyclohexyl‐benzothiazyl‐sulfenamide (CBS), tetramethylthiuram disulfide, and 2‐mercaptobenzothiazol]. It was found that the tensile strength of the blends cured in the presence of CBS was relatively higher than the other three accelerators. Scanning electron micrographs of CBS‐cured NR/(R‐EPDM) blends exhibited more roughness and cracking path, indicating that higher energy was required toward the fractured surface. The high crosslinking density observed from the swelling method could be verified from the storage modulus (E′) and damping factor (tan δ) where (tetramethylthiuram disulfide)‐cured NR/(R‐EPDM) blends provided a predominant degree of crosslinking followed by N‐tert‐butyl‐2‐benzothiazyl‐sulphonamide , CBS, and 2‐mercaptobenzothiazol, respectively. J. VINYL ADDIT. TECHNOL., 21:79–88, 2015. © 2014 Society of Plastics Engineers     

NR–EPDM covulcanization: A novel approach

Bis(diisopropyl)thiophosphoryl disulfide (DIPDIS) was used successfully as a novel coupling agent cum accelerator to co‐vulcanize the elastomer blend comprising highly unsaturated natural rubber (NR) and ethylene propylene diene rubber (EPDM) of low unsaturation content. The blend vulcanizates produced exhibit improved physical properties that can be further enhanced by implementing a two‐stage vulcanization technique, as well as by judicious selection of the NR‐to‐EPDM ratio. The results indicate coherency and homogeneity in the blend composition of two‐stage vulcanizates. The cure‐rate mismatch problem could thus be solved through the formation of rubber‐bound intermediates with a multifunctional rubber additive (i.e., DIPDIS), thereby restricting the curative migration from lower to highly unsaturated rubber. The blend morphology as revealed by SEM studies accounts for significant improvement in physical properties, particularly in two‐stage vulcanizates. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 800–808, 2001     

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     

Cure characteristics,morphology, and mechanical properties of ethylene–propylene–diene–monomer rubber/acrylonitrile butadiene rubber blends

Blends based on ethylene–propylene–diene monomer rubber (EPDM) and acrylonitrile butadiene rubber (NBR) was prepared. Sulfur was used as the vulcanizing agent. The effects of blend ratio on the cure characteristics and mechanical properties, such as stress–strain behavior, tensile strength, elongation at break, hardness, rebound resilience, and abrasion resistance have been investigated. Tensile and tear strength showed synergism for the blend containing 30% of NBR, which has been explained in terms of morphology of the blends attested by scanning electron micrographs. A relatively cocontinuous morphology was observed for 70 : 30, EPDM/NBR blend system. The experimental results have been compared with the relevant theoretical models. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Recycling of EPDM waste. I. Effect of ground EPDM vulcanizate on properties of EPDM rubber

Processing, cure characteristics, and mechanical properties of EPDM rubber containing ground EPDM vulcanizate of known composition were studied. Mooney viscosity increases and Mooney scorch time decreases by the addition of the ground vulcanizate. At higher loadings of the ground rubber, the maximum rheometric torque decreases. On addition of ground waste, stress–strain properties and tear resistance increase, whereas heat buildup marginally increases, resilience marginally decreases, low‐strain modulus remains constant, and abrasion resistance decreases. The interplay between the filler effect of the ground EPDM and the crosslink density changes of the EPDM matrix is believed to be the reason for the variation in mechanical properties. It is believed that sulfur migration occurs from the raw EPDM matrix (R‐EPDM) to the ground waste EPDM (W‐EPDM) particle while accelerator migration occurs from W‐EPDM to R‐EPDM. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3293–3303, 2001     

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     

Preparation and characterization of acrylonitrile–styrene–methylmethacrylate terpolymer as a compatibilizer for rubber blends

Acrylonitrile‐co‐styrene‐co‐methylmethacrylate (AN‐S‐MMA) terpolymer was prepared by bulk and emulsifier‐free emulsion polymerization techniques. The bulk and emulsion terpolymers were characterized by means of Fourierr transform infrared spectroscopy, ¹³C nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography, thermal gravimetric analysis, and elemental analysis. The kinetics of the terpolymerization were studied. The terpolymers were then incorporated into butadiene—acrylonitrile rubber (NBR)/ethylene propylene diene monomer rubber (EPDM) blends and into chloroprene rubber (CR)/EPDM blend. The terpolymers were then tested for potential as compatibilizers by using scanning electron microscopy and differential scanning calorimetry. The terpolymers improved the compatibility of CR/EPDM and NBR/EPDM blends. The physicomechanical properties of CR/EPDM and NBR/EPDM blend vulcanizates revealed that the incorporation of terpolymers was advantageous, since they resulted in blend vulcanizates with higher 100% moduli and with more thermally stable mechanical properties than the individual rubbers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3143–3153, 2003     

Use of expanded‐EPDM as protecting layer for moderation of photo‐degradation in wood/NR composite for roofing applications

Changes in tensile properties, sample size, interfacial strength, and thermal conductivity of melt‐laminating layers of wood/ebonite natural rubber (NR) and expanded ethyelene–propylene diene rubber (EPDM) for polymeric roofing applications were monitored under a period of UV aging times for 60 days, the results being compared with single rubber layers of wood/NR and expanded‐EPDM. The experimental results suggested that the tensile modulus of the wood/NR‐EPDM melt‐laminating layer increased with increasing aging time. The tensile strength of the wood/NR layer decreased after prolonged UV aging, and positioned between that of the wood/NR and expanded‐EPDM layers. The sample size reduction of wood/NR layer with expanded‐EPDM top coating layer was lower than that for wood/NR single layer. The peel strength of the wood/NR‐EPDM melt‐laminating layer was found to decrease with increasing UV aging time as a result of delamination of the rubber layers. The thermal conductivity of the wood/NR‐EPDM melt‐laminating layer decreased from 0.085 to 0.070 W/m K with increasing aging times upto 40 days, but tended to increase to 0.080 W/m K at the aging time of 60 days. The experimental results in this work clearly suggested that expanded‐EPDM could be used as protecting layer, not only for moderation of photo‐oxidative degradations of wood/NR layer for roofing application, but also for minimization of dimension changes of the wood/NR‐EPDM melt‐laminating layer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of vulcanization technique on the physical properties of silica‐filled EPDM rubber

The present study aims to enhance EPDM rubber–silica interaction by employing a special technique called Two‐Stage Vulcanization, with the help of a multifunctional rubber additive, bis diisopropyl thiophosphoryl disulfide (DIPDIS). In this process EPDM rubber was heated along with rubber additives up to the time just before the commencement of cure and then filler was incorporated to the preheated rubber to get the final mix. The efficiency of this novel technique is evaluated by the enhancement of physical properties of the silica‐filled vulcanizates. This novel technique is also employed to investigate the effect of a silane‐coupling agent, viz., bis (3‐triethoxy silyl propyl) tetrasulphide (TESPT), in addition to DIPDIS, on the rubber–filler interaction. The positive role of this technique in enhancing the rubber–filler interaction is evidenced by the dynamic mechanical analysis and scanning electron microscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1132–1139, 2006     

Swelling behavior of NR/EPDM rubber blends under compression strain

The effect of different blend compositions of natural rubber (NR)/ethylene–propylene diene monomer rubber (EPDM) on the swelling behavior of that blend in motor oil under compression strain was investigated. The compression recovery of all blend ratios investigated had positive values at low applied compression values (3%). However, at high compression values (18 and 35%), the compression recovery had negative values. The lower weight uptake of motor oil was shown by the EPDM vulcanizate, whereas the 25/75 NR/EPDM blend showed the highest compression recovery. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3052–3057, 2001     

Composites based on CB/CF/Ag filled EPDM/NBR rubber blends with high conductivity

For many applications of conductive rubbers, it is desirable to endow the conductive rubber with high conductivity at low conductive filler loading. In this work, composites based on ethylene‐propylene‐diene monomer (EPDM) rubber and nitrile‐butadiene rubber (NBR) were prepared using carbon blacks, carbon fibers, and silver powders as fillers. As the weight fraction of silver powder increased, the hardness of composites increased gradually while the tensile strength and elongation at break decreased. SEM revealed that the EPDM/NBR blends exhibited a relatively co‐continuous morphology. The differential scanning calorimetry (DSC) curves reported the EPDM/NBR rubber blends were incompatibility. The thermogravimetry (TG) studies showed that adding a small amount of silver powder could improve the thermal stability of composites. These conductive composites exhibited good electrical property. At room temperature, when the total volume fraction of fillers was 15.20%, the volume resistivity of EPDM/NBR blend was only 0.0058 Ω cm. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41357.     

Epoxidized natural rubber as a reinforcement modifier for silica‐filled nitrile rubber

Hydrated silicas impart better physical properties to polar rubbers, compared to those of hydrocarbon rubbers. However, to achieve optimum properties silane coupling agents are crucial in such formulations. Epoxidized natural rubber (ENR) in small proportions is used as a reinforcement modifier for silica‐filled nitrile rubber (NBR). Two systems of cure were used: N‐cyclohexyl‐ 2‐benzthiazyl sulfenamide (CBS) alone and in combination with diphenyl guanidine (DPG). In the CBS accelerated system, incorporation of an optimum concentration of about 15% of ENR on total rubber was found to improve technological properties. Addition of a secondary accelerator further improves these properties. Comparable results are obtained with those containing coupling agent and NBR–ISAF. High bound rubber and volume fraction values indicate a high polymer–filler interaction and gel content resulting from the NBR–ENR interaction. Results of this study reveal that ENR could be used as a reinforcement modifier for the NBR–silica system. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 292–306, 2002     

Nanomodified fillers in chloroprene‐rubber‐compatibilized natural rubber/acrylonitrile–butadiene rubber blends

Because of the structural dissimilarity, natural rubber (NR) and acrylonitrile–butadiene rubber (NBR) are immiscible, and compatibilizers are used during their blending. Neoprene or chloroprene rubber (CR) has a polar chlorine part and a nonpolar hydrocarbon part. Also, it has many advantageous properties, such as oil resistance, toughness, a dynamic flex life, and adhesion capacity. Hence, it is not less scientific to use CR as a compatibilizer in the blending of NBR with NR. Because many fewer studies on the use of neoprene as a compatibilizer in NR–NBR blend preparation are available, efforts were made to prepare 20:80 NR–NBR blends with CR with the aim of studying the effect of poly(ethylene oxide) (PEO)‐coated nano calcium silicate along with nano N‐benzylimine aminothioformamide and stearic acid coated nano zinc oxide in the sulfur vulcanization of the blends. The optimum dosage of the compatibilizer was derived by the determination of the tensile properties, tear resistance, abrasion resistance, compressions set, and swelling values. The tensile strength, tear resistance, and abrasion resistance of the gum vulcanizates of the blend were improved by the compatibilizing action of CR up to 5 parts per hundred parts of rubber (phr). In the case of the filled vulcanizates, the tear resistance, 300% modulus, hardness, and abrasion resistance increased with increasing dosage of nano calcium silicate. The elongation at break percentage decreased as expected when there was an increase in the modulus. Scanning electron microscopy was used to study the phase morphology of the blends. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012