REACTIVE PROCESSING OF RUBBER-PLASTIC BLENDS - ROLE OF CHEMICAL COMPATIBILIZER

The present investigation was aimed at understanding the role of chemical compatibilizers like carboxy-terminated nitrile rubber, amine-terminated nitrile rubber, liquid carboxylated nitrile rubber, etc., in the reactive processing of a dynamically vulcanized 50 : 50 nylon/ HNBR blend. The interfacial parameters for a bilayer specimen of nylon and rubber and structure parameters during the processing were determined. The interfacial thickness (lambda) increased from 48 to 70-80 nm and the interfacial tension (gamma(infinity) decreased from 0.240 to 0.209-0.198 mN /m, depending on the nature and concentration of the compatibilizer. There was, however, an optimum level of the compatibilizer beyond which the thickness did not change significantly. For the ionomeric compatibilizer, lambda decreased after the optimum concentration. The increase in lambda is ascribed to the formation of a graft copolymer of nylon and rubber and the compatibilization reactions. Structure parameters were dependent upon the sequence of mixing of the compatibilizer. If the compatibilizer and the cross-linker were added in the rubber and the mixture was then added to nylon, the mean radius of the dispersed particle was smaller over the range of mixing times. The compatibilizers also reduced the particle size at the early stage of mixing due to reduced interfacial tension. In general, the particle size decreased with mixing time, attained a minimum, and then increased. The volume fraction of the interface was also very large for compatibilized systems. The particles were larger, however, when the compatibilizer was first mixed in nylon. SEM studies indicated that the compatibilizer in the latter case was not acting as a surfactant. (C) 1993 John Wiley and Sons, Inc.