Dynamic mechanical properties and morphology of polyethylene/ethylene vinyl acetate copolymer blends

Dynamic mechanical analysis (DMA) was used to study the miscibility and various transitions (alpha, beta, and gamma) in binary blends of ethylene vinyl acetate copolymer (EVA) with low-density polyethylene (LDPE) and high-density polyethylene (HDPE). Addition of a rubbery phase, such as EVA, reduced all the transition temperatures. A peak broadening of tan 8 was observed with increasing EVA content in the blends. This can be explained by the observed reduction of the crystallinity of the systems. The presence of a single transition peak in the region of glass transition temperature (T-g) has indicated that the blends were miscible. However, morphological investigation by scanning electron microscopy (SEM) revealed the features of a two phase system in which the EVA domains would be dispersed in the polyethylene (PE) phase. The results have demonstrated that DMA is not sensitive enough to study the miscibility of polymeric blends with a similar backbone structures (such as PE and EVA) in view of the small difference in their T-g. For such blends, therefore, the use of direct observations, such as microscopic examinations is necessary. (C) 2004 Wiley Periodicals, Inc.