Interfacial chemistry and morphology of in‐situ compatibilised PA‐6 and PBT based blends

Abstract

AbstractReactive blending is the preferred route for obtaining rubber‐toughened engineering plastics. In this study the chemistry and morphology of in‐situ compatibilised PA‐6/EPM‐g‐MA blends and PBT/E‐MA‐GMA blends are compared. Despite the different chemical structures formed (PA‐6: cyclic imide; PBT: ester), the different side‐reactions that take place (PA‐6: chain scission; PBT: rubber crosslinking) and the different reaction rates (PA‐6: very fast; PBT: rather slow), a general description of reactive blending is proposed. First, a very fast physics‐controlled dispersion of the rubber phase into the polycondensate matrix occurs (from milimeter to micrometer scale). Then the interface, thus generated, is covered via graft‐copolymer formation. This results in a stabilisation against coalescence and in a reduction of the interfacial tension, enabling further dispersion of the rubber phase. In the case of PA‐6/EPM‐g‐MA blends the graft formation occurs so quickly that when the physics‐controlled dispersion is completed, the final dispersion is achieved. In the case of PBT/E‐MA‐GMA blends the graft formation is much slower and the chemistry‐controlled dispersion can hence be considered as a secondary process, yielding the final morphology.