Improved HPMC films by incorporation of amylose-sodium palmitate
Polymer film blends of hydroxypropyl methylcellulose (HPMC) and amylose-sodium palmitate inclusion complexes (Na-Palm) were produced with no plasticizer, and were observed to have improved physical and gas barrier properties as compared with pure HPMC. The crystalline amylose helices incorporating the hydrophobic sodium palmitate ligand decreased the water vapor permeability of a 50/50% blended film of HPMC/Na-Palm by 40% and decreased oxygen permeability by 96%. The incorporation of 25% Na-Palm into HPMC films resulted in improved elongation, Young’s modulus and toughness. Addition of the amylose-complexes produced relatively smooth, high clarity films which had reduced solubility in neutral and acidic solutions. Increasing concentrations of Na-Palm increased film thermal resilience and increased storage modulus at high temperatures. The heat deflection temperature of the films also increased with increasing concentrations of amylose-complex; HPMC/Na-Palm film blends with >50% Na-Palm displayed almost no material deformation up to 250 °C.
The incorporation of novel amylose-sodium palmitate inclusion complexes into HPMC produced blended films with improved physical and gas barrier properties. The inclusion of the hydrophobic ligand through complexation rather than an emulsion produced a film that was less water permeable and less oxygen permeable due to the crystalline helical complex, without a significant sacrifice of physical properties. Interestingly, the amylose-complexes did not display the typical large deterioration in physical properties, storage modulus, and thermal re- silience which is often observed when starch is utilized in a polymer blend. This suggests that the utilization of amylose-complexes may benefit many bio-based polymer blended products.