ScCO₂-processed thermoplastic starch/chitosan oligosaccharide blown films and their oxygen barrier or antibacterial applications

Abstract Antibacterial and oxygen barrier films were inventively prepared by blending very small loadings (<2 wt%) of chitosan oligosaccharide (COS) or chitosan (CS) in thermoplastic starch (TPS) and/or processing with supercritical carbon dioxide (scCO 2 ). Oxygen transmission rates (OTR) and free-volume-hole (FVH) characteristics of scCO 2- processed TPS/COS and TPS/CS blown films diminish to a minimum, as their COS or CS approach a specific compatibility limit content. The minimum OTR and FVH characteristics of scCO 2 -processed TPS/COS films are somewhat smaller than those of corresponding TPS/COS films without scCO 2 -assistance, and decrease further with decreasing COS molecular weights. The minimum OTR values of scCO 2 -processed TPS/COS blown films with COS’s molecular weight of 200 and 500 are only 4.1 and 4.5 cm 3 /m 2 × day × atm, respectively, and their antibacterial rates of Staphylococcus aureus are ≥97 %, which make them as promising antibacterial and oxygen barrier films having OTR ≦ 5 cm 3 /m 2 × day × atm. Among other things, longitudinal or transversal tensile strengths acquired for the properly scCO 2 -processed TPS/COS or TPS/CS films are ∼30 to ∼50 % higher than those of the TPS films. Dynamic mechanical relaxation results of these scCO 2- processed reveal that chitosan oligosaccharide or chitosan are compatible with TPS, as COS or CS contents are ≤ the compatibility limit value.