ABSTRACT:The application of rubber seed oil (RSO) and epoxidized RSO (ERSO) as a plasticizer in acrylonitrile butadiene rubber (NBR) was studied using RSO and ERSO with different levels of epoxidation. The results indicated that ERSO could be used as a less leachable and low volatility plasticizer for NBR. The use of ERSO in NBR gave better abrasion resistance whereas the tensile strength and tear strength were comparable to those vulcanizates that contained dioctyl phthalate as a plasticizer.
SYNOPSISThe melt rheology of blends of natural rubber ( N R ) and ethylene-vinyl acetate copolymer (EVA) has been studied with reference to the effects of blend ratio, cross-linking systems, shear stress, and temperature. When EVA formed the dispersed phase, the viscosity of the blends was found to be a nonadditive function of the viscosities of the component polymers at lower shear region, i.e., a positive deviation was observed. This behavior has been explained based on structural buildup of dispersed EVA domains in the continuous NR matrix. The effect of the addition of silica filler on the flow characteristics of the blends has been investigated. The melt elasticity parameters such as die swell, principal normal stress difference, recoverable shear strain, and elastic shear modulus of NR-EVA blends were also evaluated. 0 1993 John Wiley & Sons, Inc. I NTRO DU CTI 0 NIn recent years, blending of two or more polymers to produce the required combination of properties for specific end uses is gaining industrial importance. Knowledge of flow behavior of polymer blends is of paramount importance to optimize processing operations. In polymer blends, the viscosity of individual components plays a critical role in the flow and forming of compounds. Several investigations have been made to understand the complicated rheological behavior of polymers in view of its relevance to processing.'-4 The melt flow behavior of polymer blends and that of polymers containing cross-linked particles have been studied by different research group^.^-" Danesi and Porter l 1 studied the rheological behavior of polypropylene and ethylene propylene rubber. They explained how the state of dispersion is affected by conditions of blend preparation and extrusion. Utracki and Samut l 2 studied the flow properties of various polyethylene blends. Kuriakose and De13 and Thomas et al.14 studied the * To whom all correspondence should be addressed. Recently, Varughese l5 studied the rheological behavior of poly (vinyl chloride) /epoxidized natural rubber (PVC/ENR) blends. All these studies indicated that the dispersed phase in an immiscible blend is deformable and may give rise to wide range of sizes and shapes during processing. This, in turn, determines the morphology of the system. The melt rheology is particularly sensitive to morphology. Blends of ethylene-vinyl acetate copolymer (EVA) and natural rubber ( NR) are now being used in many applications such as in cables and footwear. These materials combine the superior mechanical properties of NR and the excellent aging properties of EVA. Recently, we have examined the miscibility, morphology, mechanical properties, and aging characteristics of these However, the rheological behavior of these blends has not been studied. This paper examines the rheological characteristics of NR-EVA blends by capillary rheometry. The effects of blend ratio, cross-linking system, and silica on the viscosity of the blends have been studied. In addition, the morphology of extrudate has been examined to understand the...
To obtain good reinforcement by silica filler in nonpolar rubbers, it is almost essential to use coupling agents, such as bis(triethoxy silyl propyl) tetrasulfane (TESPT). Chemicals that can interact with the silanol groups on the silica particles and reduce their network formation are also expected to enhance reinforcement. We made a comparative evaluation of TESPT, epoxidized rubber seed oil (ERSO), and their combination as a coupling agent and a plasticizer in silica-filled natural rubber compounds. The results indicate that compounds containing ERSO showed physical and mechanical properties between that of TESPT and naphthenic oil. The action of ERSO in the improvement of the properties was expected to be bifunctional and similar to that of TESPT; that is, it caused the hydrophobation of silica, which increased its degree of dispersion and the formation of chemical bonds with the rubber, thereby ensuring strong polymer-filler interactions.
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.
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