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

The purpose of the study was to evaluate the thermal and viscoelastic properties of cellulosic polymers commonly used in hot melt extrusion (HME). Cellulose ethers of different molecular weight (MW) with varied degree of substitution and functional groups were analyzed using modulated differential scanning calorimetry (MDSC), thermogravimetric analysis (TGA) and oscillatory rheometry. The results indicate that glass transition temperature (T g ) and viscoelastic characteristics of polymers strongly depend on their chain length, MW, and degree and type of substitutions in the main chain. In general, an increase in chain length or MW was found to increase T g as well as the viscosity (HPMC, MW10000 < MW 25000 < MW 150000). Also, substitutions with bulkier groups decrease the T g and viscosity of the polymer. Most of the cellulosics were found to have high viscosity between their T g and degradation temperature (T d ), and thus cannot be extruded by themselves. The thermal properties in combination with polymer viscosity at different temperature will help formulators determine processability using HME.