Ethylene vinyl acetate (EVA)/poly(lactic acid) (PLA) blends and their foams

Thermoplastic elastomer from ethylene vinyl acetate (EVA) was blended with a biodegradable polymer, poly(lactic acid) (PLA), to develop ecofriendly EVA/PLA foams. The thermal and mechanical properties and the morphologies of the blends with various PLA contents between 0 and 40% were investigated. The rheological properties during gel formation were monitored via in-situ through the evolution of torque with curing time. The EVA/PLA blends showed a two-phase morphology made of a continuous EVA matrix and micron or submicron nodules, and also increased the tensile strength and modulus, as well as hardness, with the increase of the added PLA content. This should be attributed to the micronic dispersion of the rigid PLA in the elastic EVA matrix. The foam samples containing below 30% of PLA exhibited a similar cell structure and foaming ratio to the pure EVA; however, the cell size and foaming ratio gradually reduced with the increase of the added PLA content.