The plasticizer effect on preparation and properties of etherified corn starchs films

The effects of different concentrations of glycerol, sorbitol, and poly(vinyl alcohol) plasticizers in etherified starch films are investigated. Water vapor and gases (CO2, N-2 and O-2) permeability and on mechanical, thermal, morphological properties were evaluated. The SEM micrographs showed dense and homogeneous films with irregularities according to the plasticizer used. Mechanical properties of the films were influenced by the plasticizer type. Films with glycerol showed lower values of tensile strength at break, and higher deformation, when compared to the other films considered. No permeability to CO2, N-2 and O-2 was observed at pressures ranging from 1 to 3 bar. Contact angle was also determined to characterize the films hydrophilicity, and the etherified corn starch films with PVA plasticizer showed lower contact angle, therefore higher wettability. The humidity of the films as a function of the water activity was determined, according to several models found in literature. Films with glycerol plasticizer showed higher water vapor permeability due to their hydrophilic character. (C) 2015 Elsevier B.V. All rights reserved.