Super toughened renewable poly(lactic acid) based ternary blends system: effect of degree of hydrolysis of ethylene vinyl acetate on impact and thermal properties

Abstract

Poly(lactic acid) (PLA) is one of the most promising biopolymers due to its biodegradable nature and good tensile strength. In spite of these advantages, the low impact strength and slow crystallization rate exhibited by PLA limit their end use applications. In order to overcome these drawbacks, an attempt has been made in the present study to prepare binary and ternary blends of PLA with Ethylene Vinyl Acetate (EVA) and ethylene vinyl alcohol (EVOH). The effect of degree of hydrolysis of EVA on the thermal and mechanical properties of PLA is investigated. Fourier transform infrared spectroscopy analysis elucidated the fact that the hydrolysis process is effective with respect to the increase in hydrolysis reaction time. Differential scanning calorimetry results disclose the prominent decrement in cold crystallization temperature and display a distinct melt crystallization peak in comparison with neat PLA. This is a clear indication that EVOH acted as a nucleating agent to increase the crystallization rate of PLA. The decrement in terms of tensile properties clearly indicated the reduction in stiffness after addition of EVOH in the PLA matrix. For the ternary blends of PLA, four fold increment in terms of elongation at break (%) and impact strength properties are observed as compared to neat PLA. Morphological studies revealed the presence of good adhesion between the PLA matrix and EVOH.