Changes on surface morphology of corn starch blend films.

Abstract

This study aims at evaluating the influence of enzymatic degradation solution on the surface morphology and thermal properties of a poly(ethylene-vinyl alcohol) copolymer-corn starch thermoplastic blend (SEVA-C), as a function of immersion time. To perform this study, three different batches were assessed using SEVA-C samples of different thicknesses and a fixed weight of 1.6 g, immersed in alpha-amylase (50 u/L) up to 90 days at 37 degrees C. TGA, contact angle measurements, scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques were used. Three degradation mechanisms are considered in these systems: namely, mass loss due to plasticizer leaching (glycerol), starch enzymatic cleavage, and synthetic polymer fractions degradation. Enzymatic hydrolysis of the starch fraction and subsequent leaching from the internal bulk structure led to an increase in surface porosity, pore size, roughness, and to the development of small pits throughout the surface, as observed by SEM and AFM.