Three-Layer Sheets Based on Gelatin and Poly(lactic acid), Part 1: Preparation and Properties

Glycerol-plasticized gelatin (Ge-30Gly) and poly(lactic acid) (PLA) films were prepared by heat-compression, molded, and then piled to produce a biodegradable three-layer sheet with PLA as outer layers and Ge-30Gly as the inner layer. Lamination with PLA increased the moisture resistance and reduced the total soluble matter with respect to a single gelatin layer, while keeping transparency. The tensile strength of the multilayer sheet (36.24 +/- 4.27 MPa) increased 16 folds when compared to that of Ge-30Gly. Lamination also exerted beneficial effects on the barrier properties. The WVP of the multilayer sheet (1.2 +/- 0.1 10(-4) kg.m.Pa-1.s(-1).m(-2)) decreased with reference to that of Ge-30Gly, while oxygen permeability (17.1 +/- 2.3 cm(3)(O-2).mm.m(-2).day(-1)) was reduced with respect to that of neat PLA, and the value obtained was comparable to that of Ge-30Gly layer. The presence of plasticized gelatin in the multilayer increased the energy at crack initiation (1.4 +/- 0.3 J.m(-1)) with respect to that of PLA. The improvement attained in all these properties was ascribed to the good compatibility and adhesion of the individual layers featured through hydrogen interactions between the carbonyl group from PLA and the hydrogen from the peptide bonds in gelatin. Compatibility was corroborated by scanning electron microscopy observations at PLA/Ge-30Gly interface and by the absence of additional peaks in the tan delta curve of dynamic-mechanical analysis. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 3102-3110, 2010