Rheological and mechanical behavior of ethyl vinyl acetate/low density polyethylene blends for injection molding

Ethyl vinyl acetate (EVA) is normally injection molded to produce parts with specific properties of flexibility and energy absorption. However, the produced objects often present an excessive flexibility. Furthermore, EVA presents a high viscosity for injection molding technology, and this compels the operator to apply high hydraulic pressures. The addition of PolyEthylene (PE) can provide a higher rigidity to the products, improve the flowability of the melt during processing, and at the same time reduce the cost of the products. In this work, several blends of EVA and low density polyethylene are prepared by melt mixing and injection molded. Rheological, calorimetric, and tensile tests are conducted on the molded specimens with the aim of understanding the performances of the materials also in the view of scrap recycling. On pursuing the mentioned goals, the behavior of the blends in the molten state, during crystallization and in the solid state was analyzed by comparing the experimental data with mixing rules to gather information concerning the morphology of the systems. All the results show that both the melt viscosities of the elastic moduli present significant deviations from the mixing rules, indicating that a phase inversion takes place on increasing the amount of EVA, both in molten and in solid state. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013