Post-crosslinking modification of thermoplastic starch/PVA blend films by using sodium hexametaphosphate.

Thermoplastic starch (TPS)/poly (vinyl alcohol) (PVA) blend films were post-treated by crosslinking through soaking the films in sodium carbonate aqueous solution and sodium hexametaphosphate aqueous solution sequentially and then heating. The effects of the concentrations of the sodium carbonate aqueous solution and the sodium hexametaphosphate aqueous solution, soaking time, heating temperature and time on the properties of the TPS/PVA blend films were investigated. It was found that the crosslinking modification significantly reduced the moisture sensitivity of the TPS/PVA blend films, i.e., lowered the equilibrium moisture content of the blend films, increased the tensile strength and Young's modulus but decreased the elongation at break of the blend films. The described method could be used for post-treating TPS/PVA based products to optimize their properties.