Cocontinuous phase morphology for an asymmetric composition of polypropylene/polyamide 6 blend by melt mixing of polypropylene with premelted polyamide 6/organoclay masterbatch

摘要

Cocontinuous morphology was obtained for an asymmetric composition of polypropylene/polyamide 6 (70/30 w/w) blend by controlling melt compounding sequence of PP, PA6, and organoclay. Three different compounding sequences were tested: direct melt mixing of all the components, melt mixing of PP with PA6/organoclay masterbatch, and melt mixing of PP with premelted PA6/organoclay masterbatch. Only the third method promotes cocontinuous morphology. In all three cases, organoclay locates preferentially in the PA6 phase and at the interface, although the level of organoclay dispersion is poorer in the case of direct mixing than in the two-masterbatch approaches. The morphology evolution processes of the three different compounding sequences were investigated and revealed that the main reason for the formation of cocontinuous morphology in the third method is the inhibiting effect of organoclay preincluded in the premelted PA6 phase on phase inversion. The viscosity of PA6 phase and the barrier effect of organoclay were confirmed to be two key factors in promoting cocontinuous structure. Dynamic mechanical analysis shows that the blend having cocontinuous morphology displays higher storage modulus than those having matrix-dispersed morphology at the same organoclay loading.