Grafting of Isobutylene–Isoprene Rubber with Glycidyl Methacrylate and Its Reactive Compatibilization Effect on Isobutylene–Isoprene Rubber/Polyamides 12 Blends

Isobutylene–isoprene rubber (IIR)/polyamides 12 (PA12) blends are well known for their high gas barrier property and thus find applications in refrigeration hoses, tire inner liners, and so on. Nevertheless, the design and preparation of a good compatibilizer for the IIR/PA12 blend is required because of the poor compatibility between PA12 and the IIR phases. In this study, an efficient reactive compatibilizer, glycidyl methacrylate (GMA)-grafted IIR (IIR-g-GMA) copolymer, and GMA/styrene (St)-grafted IIR (IIR-g-St-GMA) copolymer were produced through the free-radical melt grafting reaction, which were initiated by dicumyl peroxide (DCP). Compared with IIR-g-GMA, IIR-g-St-GMA shows a significantly higher grafting degree because the fast generated, more stable St-grafted IIR macroradicals can act as a "bridge" to connect GMA molecules on IIR macroradicals. The results indicate that reactive compatibilization occurs by the introduction of the copolymer, and the extent of the interfacial reaction and compatibilization effect increases with increasing the copolymer content and the grafting degree of GMA. Nanomechanical mapping images of atomic force microscopy show that the average interfacial thickness of the blend largely increases from approximately 55 to 120 nm after compatibilization with 30 phr IIR-g-St-GMA. Meanwhile, the size of the IIR dispersed phase domains largely decreases from 3 to 5 μm to approximately 0.7 μm after compatibilization with this copolymer. The compatibilization mechanism of the copolymers on IIR/PA12 blends is discussed.