Effect of super critical carbon dioxide and alkali treatment on oxygen barrier properties of thermoplastic starch/poly(vinyl alcohol) films

Sustainable oxygen barrier thermoplastic starch (TPS)/polyvinyl alcohol (PVA) blown films were successfully prepared by blending proper PVA loads during NaOH-treating and supercritical carbon dioxide (scCO(2)) assisted processing. The NaOH-treated TPS or scCO(2)TPS films showed smaller free-volume-cavity characteristics (FVCC) and oxygen transmission rate (OTR) than those of TPS (or scCO(2)TPS) prepared without proper alkali-treatment. Smaller OTR and FVCC values were detected for NaOH-treated scCO(2)TPS films than those of NaOH-treated TPS films prepared without scCO(2)-assistance. All OTR and FVCC values detected for proper alkali-treated scCO(2)TPS( y )PVA( z )films diminished distinctly to a smallest value, when their PVA loads came near a solubility limit value of 27.5 wt%. An essential result is that the OTR of the optimal NaOH-treated scCO(2)TPS( y )PVA( z )film is merely 3.1 cm(3)/m(2) day atm, which meets the requirement of high oxygen barrier plastics. Dynamic molecular relaxations and WAXD patterns detected for proper NaOH-treated scCO(2)TPS( y )PVA( z )films disclosed that PVA was compatible with TPS, as PVA loads were <= the solubility limit value. The distinctly reduced OTR and FVCC detected for optimal NaOH-treated scCO(2)TPS( y )PVA( z )films are partially attributed to the reinforced molecular interactions between hydroxyl groups of TPS and PVA, as they were blended with proper PVA loads during their alkali-treating and scCO(2)-aid processing.

Automated summary

Sustainable oxygen barrier thermoplastic starch (TPS)/polyvinyl alcohol (PVA) blown films were successfully prepared by blending proper PVA loads during NaOH-treating and supercritical carbon dioxide (scCO(2)) assisted processing. The films showed smaller oxygen transmission rate (OTR) and free-volume-cavity characteristics (FVCC) when treated with NaOH and scCO(2) assistance compared to those prepared without treatment. The reduced OTR and FVCC values were attributed to reinforced molecular interactions between TPS and PVA.