Fully renewable oxygen barrier films of scCO2-processed thermoplastic starch/sugar alcohol blends.

Excellent oxygen barrier films were prepared by blending very small loadings (<1 wt%) of dihydroxyacetone (DHA), erythritol (ET) or xylitol (XT) in thermoplastic starch (TPS), and/or processing with supercritical carbon dioxide (scCO₂) assistance. The minimum oxygen transmission rates (OTR) and all free-volume-hole characteristic (FVH) values of each scCO₂-processed TPS/sugar alcohol film series are somewhat smaller than those of corresponding TPS/sugar alcohol film series without scCO₂-assistance, and decrease with the decrease in sugar alcohol's molecular weight. The minimum OTR values acquired for scCO₂-processed TPS/DHA and TPS/ET blown films are only 3.6 and 4.3 cm³/m²·day·atm, respectively, which meet the demand of high oxygen barrier films having OTR ≦5 cm³/m²·day·atm. The longitudinal or transversal tensile strengths acquired for each scCO₂-processed TPS/sugar alcohol series films are ∼30 % to ∼40 % higher than those of the TPS blown films. Dynamic mechanical relaxations of each TPS/sugar alcohol or scCO₂-processed TPS/sugar alcohol film series reveal that the sugar alcohols are compatible with TPS, as their sugar alcohol contents are ≤ the corresponding compatibility values. The decreased OTR and FVH values acquired for TPS/sugar alcohol or scCO₂-processed TPS/sugar alcohol films are most likely due to them being scCO₂-processed or incorporated with smaller molecular weight of sugar alcohols. [ABSTRACT FROM AUTHOR]