Dual phase continuity and phase inversion phenomena in natural rubber/ethylene vinyl acetate (EVA) copolymer blends

Abstract

Blending of polymers provide an attractive route to obtain new materials with unique combination of properties. Among the possible blend morphologies are dispersion of droplet, fiber, lamella in continuous phase and cocontinuous morphology. The unique feature of co-continuous is the mutual interpenetration of the phases which exhibits a number of advantageous properties and hence wider range of applications. Therefore, it is important to perform accurate determination of the co-continuous phase morphology and phase inversion phenomena. The rubber co-continuity index (solvent extraction), SEM micrographs and dynamic properties indicated the inversion occurred in the blends with rubber content 40 to 50 wt%. Furthermore, three empirical models (i.e., Ultracki, Steiman et al and Gergen et al models) could predict the phase continuity and phase inversion phenomena but other two (i.e., Paul-Barlow and Metelkin-Blekht models) failed. Therefore, based on rubber co-continuity index, SEM micrographs, dynamic mechanical properties and prediction, the inversion phenomena occurred in the blends with rubber contents in a range of 40-50 wt%. Full co-continuity was found in the blends with the rubber contents of 46 to 60 wt%.