Compatibilizing effect of a maleic anhydride functionalized SEBS triblock elastomer through a reaction induced phase formation in the blends of polyamide 6 and polycarbonate: 1. Morphology and interfacial situation

Abstract

The result of a study on the effect of poly[styrene-b-(methylene-co-butylene)-b-styrene] triblock copolymer functionalized by maleic anhydride (SEBS-gMA) on the morphology and interface of the incompatible polymer blends of polyamide 6 (PA6) and polycarbonate (PC) is presented. The electron spectroscopic imaging with transmission electron microscopy was introduced to investigate the morphological features and interfacial situation of these blends. It has been found that the functionalized SEBS is dispersed in PA6 phase at about 50 nm in diameter and also exists on the domain boundary of PA6 and PC to envelope the PC domains in the blends with a matrix of PA6, while the unmodified SEBS attaches to PC particles but does not surround the domains. This means that the in situ reaction between PA6 and SEBS-gMA during mixing induces the envelop formation of SEBS on PC domains. The formation of SEBS-gMA phase on the interface works as a coupling agent to improve interfacial adhesion between PA6 and PC, which leads to the disappearance of voids on the domain boundary generated due to the different volume shrinkage between PA6 and PC in fast cooling in a mould. In the PC rich blends, SEBS-gMA is occluded in PA6 domains and exists on the interface between PA6 and PC, while with unmodified SEBS the dispersed SEBS and PA6 phases form separate dispersed phase in PC matrix. Dynamic mechanical analysis has revealed that the glass transition temperatures (Tgs) of PA6 and PC phases in the blends are slightly lower than the respective pure polymers and that the incorporation of SEBS-gMA does not affect the Tgs of each phase. This indicates that chemical reactions between PA6 and PC during melt mixing, which produce low molecular weight species of PC occurred regardless of the incorporation of SEBS-gMA and that SEBS-gMA on the domain boundary is not miscible enough to reside within the PC domains.