Investigation of thermal and viscoelastic properties of polymers relevant to hot melt extrusion - II: Cellulosic polymers

Abstract

The purpose of this study was to determine the thermal and viscoelastic properties of cellulosic polymers that may have potential for use in hot melt extrusion (HME). Cellulose ethers of different molecular weight (MW) with varied degrees of substitution and differences in substituted groups were analyzed using modulated differential scanning calorimetry (MDSC), thermogravimetric analysis (TGA) and oscillatory rheometry. The results indicated that the glass transition temperature (Tg) and viscoelastic characteristics of polymers appear to depend on their chain length, molecular weight (MW), and degree and type of substitutions in the main chain. In general, an increase in the chain length or MW increased Tg, as well as, the viscosity (HPMC, MW10000 < MW 25000 < MW 150000 Da). Additionally, substitutions with bulkier groups decreased both the Tg and the viscosity of the polymer. Most of the cellulosic polymers had high viscosity between their Tg and degradation temperature (Td), and could not be extruded by themselves. The thermal properties in combination with polymer viscosity at different temperatures may assist formulating scientists in determining the processability when using HME.