Structure and physical properties of starch/poly vinyl alcohol/laponite RD nanocomposite films.

Nanocomposites of starch, poly vinyl alcohol (PVOH), and laponite RD (LRD) were produced by solution mixing and cast into films. In general, an increase in LRD content (0-20%) enhanced tensile strength and decreased water vapor permeability, irrespective of the relative humidity (50% and 75% RH). Tensile strength (TS) of starch/PVOH/LRD films ranged from 6.51 to 13.3 MPa. At 75% RH, TS was up to 65% higher as compared to films with sodium montmorillonite as filler. The most striking results were obtained with respect to elongation at break (E%), which ranged from 144% to 312%. Contrary to other polymer/clay nanocomposites, E% increased on addition of 5-20% LRD and was up to 175% higher than the control without clay. Nanocomposite structure and interactions were investigated using X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. Results indicated that LRD was a compatibilizer and cross-linking agent between polymers, and has the potential for use in biodegradable packaging films with good mechanical performance even in high humidity conditions.