Acrylonitrile-butadiene rubber compatibilization

George, J., Joseph, R., Thomas, S., and Varughese, K. T. 1995. High density polyethylene/acrylonitrile butadiene rubber blends Morphology, mechanical properties, and compatibilization. Journal of Applied Polymer Science 57 449-465. 

Although an ethylene vinyl acetate copolymer was immiscible in NR blends, addition of a 6 phr ethylene vinyl acetate block copolymer enabled compatibilization of heterogeneous NR/acrylonitrile butadiene rubber blends. These blends increased the tensile strength, the elongation at break and tear strength due to an increase in the interfacial adhesion between the blended components by increasing the rigidity of the matrix in the presence of the ethylene vinyl acetate copolymers. ... 

Kalf et al. studied the effect of grafting cellulose acetate and methylmethacrylate as compatibilizers on acrylonitrile butadiene rubber (NBR) and styrene-butadiene rubber (SBR) blends. Morphology studies of the samples show an improvement in interfacial adhesion between the NBR and SBR phases in the presence of the prepared compatibilizing agents. The authors also reported the samples with grafted compatibilizers showed superior crosslink density and thermal stability, as compared to the blends without graft copolymers. ... 

Similar to the Nylon/EPR system, the effect of compatibilization on transport properties can be seen in natural rubber/acrylonitrile-butadiene rubber (NR/ NBR) blends compatibilized with poly(ethylene-co-vinyl acetate) (EVAc) [51]. In this case, the penetrant used was benzene. Subsequently, it was noted that the solvent uptake tendency of compatibilized samples was lower, while a greater time lag and minimum values for permeation and diffusion coefficients were exhibited compared to the uncompatibilized blend. The polar CN- end of NBR... 

DV was applied to different systems, e.g., a diene rubber (EPDM, butyl rubber or natural rubber) is associated with a polyolefin (polyethylene or polypropylene) or an acrylonitrile-butadiene rubber (NBR) sample is associated with a polyamide. The high incompatibility between the elastomer and the plastic may be an important obstacle in the preparation of a dynamically vulcanized material, since the properties of the latter depend on the quality of the dispersion. The dispersity of NBR in polyolefins is very low and a polymeric compatibilizer must be added, which often requires grafting and coupling processes. 

Example 5-23) and of ABS-polymers (made from acrylonitrile, butadiene, and styrene), whereby grafting occurs in situ at the beginning of the polymerization process. The formed graft copolymers act in two ways As emulsifiers during the polymerization process and, secondly, in the solid end product as compatibilizer between the thermoplastic hard phase and the rubber-elastic dipersed phase (already in concentrations below 3%). 

Examples of such compatibilized systems that have been studied include EPDM/PMMA blends compatibilized with EPDM- -MMA, polypropylene/polyethylene blends with EPM or EPDM, polystyrene/nylon-6 blends with polystyrene/nylon-6 block copolymer, and poly(styrene-co-acrylonitrile)/poly(styrene-co-butadiene) blends with butadiene rubber/PMMA block copolymer. 

Novel styrenic-based TPEs based on blends of a thermoplastic (polystyrene or styrene acrylonitrile) with a rubber (styrene butadiene or ethylene vinylacetate), with special reference to compatibilization and dynamic vulcanization, were reported by Patel et al. The performance properties were correlated with the interaction parameter and the phase morphology of the blend components [62]. 

The oil resistance and chemical resistance of nitrile rubber is generally superior to that of EPDM rubbers. However, the highly polar nature of acrylonitrile comonomer is responsible for the high incompatibility between nitrile rubber and polypropylene. The dispersability and the stability of nitrile rubber dispersions in the polypropylene matrix are poor. Hence a reactive compatibilization technology was used [Coran and Patel, 1983], It consisted of blending a small amount of a low molecular weight amine-terminated butadiene-acrylonitrile copolymer (ATBN,... 

HDPE-I-butadiene/acrylonitrile rubber was compatibilized by adding maleated HDPE, which reduced domain size, strengthened the interface, and increased tensile and impact strength [61, 62]. 

HDPE -1- butadiene/acrylonitrile rubber was compatibilized by addition of dimethylol phenolic resin, which cured and compatibilized the blend [61, 62]. Cure reactions of diene rubbers with phenolic resins have been observed before [159], and probably formed an interpenetrating polymer network in this study. 

---