Reactively compatibilised polymer blends: a case study on PA6/EVA blend system

Abstract

Reactive compatibilisation of immiscible polymers is becoming increasingly important and a representative study with PA6/EVA system is the focus of this paper. Morphological studies and crystallization behaviour of uncompatibilised and compatibilised blends of PA6/EVA were studied as functions of dispersed phase concentration (EVA or EVA-g-MA) and maleic anhydride (MA) content. Impact properties of the compatibilised PA6/EVA blends were studied as a function of MA content at fixed dispersed phase concentration. SEM studies of cryogenically fractured surfaces showed an increase in average domain size with increase in EVA level. On contrary, the average domain size and the domain size distributions reduced significantly in the presence of EVA-g-MA. This observation is found consistent with increase in EVA-g-MA concentration at a fixed MA level and also at a fixed concentration of dispersed phase with different level of MA in binary and ternary compositions. Morphological observations also revealed that the phenomenon of coalescence is slower in the presence of EVA-g-MA indicating the formation of in situ graft co-polymer at the interface. Impact strength of the compatibilised PA6/EVA blends increased significantly as compared to uncompatibilised PA6/EVA blends. Crystallization studies indicate that PA6 and EVA (or EVA-g-MA) crystallize separately at their bulk crystallization temperature. The degree of crystallinity is reduced marginally with increase in EVA level, whereas, the decrease in crystallinity is more in the presence of EVA-g-MA. SAXS studies indicate the superposition of PA6 and EVA lamellar scattering and the possible mode of insertion is random in nature. In case of reactive systems, SAXS studies also revealed the hindered crystal growth of PA6 and EVA due to the interfacial reaction.