Thermoplastic xylan derivatives and related blends

Abstract

The relationship between substituent chemistry and melt behavior for xylan derivatives was investigated by differential scanning calorimetry and parallel-plate dynamic viscometric measurements. Xylan esters exhibit characteristic Tg values which decrease with increasing size of substituent. However, these materials do not flow at temperatures well above Tg • The ether derivative hydroxypropyl xylan was found to flow at substitution levels higher than 0.5 degree of substitution, with melt viscosity decreasing as the degree of sUbstitution increased. The influence of viscosity ratio and composition on the texture of melt-blends of hydroxypropyl cellulose and polystyrene was studied for viscosity ratios of O. 08 to 0.55. Blends were examined by SEM and TEM. It was found that composition was the determining factor in texture, and not viscosity ratio over the range tested. Extrusion problems limited the range of compositions tested to 40% biopolymer or less. Phase inversion was not observed, although inversion was expected for some samples based on predictive models in the literature.