Investigation of thermal and viscoelastic properties of polymers relevant to hot melt extrusion, III: polymethacrylates and polymethacrylic acid based polymers
Polymers serve as major constituents of drug products prepared by hot melt extrusion (HME) and hence it is necessary to understand their behavior under heat and mechanical stress for the development of successful HME processes. The aim of this work was to generate a database of physicochemical properties for polymethacrylates and polymethacrylic acid based polymers relevant to HME. Only neat polymers were used and no drug or plasticizers were added. All six polymers used were amorphous and had < 2% moisture. In differential scanning calorimetric (DSC) studies, the three homo block copolymers, Eudragit® E PO, Eudragit® RL PO and Eudragit® RS PO, had glass transition temperatures (Tg) of 57 °C, 63 °C and 64 °C respectively, and in thermogravimetric analysis (TGA) they showed weight loss due to thermal degradation at 250 °C, 166 °C and 170 °C, respectively. Thermomechanical analysis was conducted to investigate rheological properties of the polymers, which predicted their melt extrusion ranges to be 127-150 °C, 165-170 °C, and 142-167 °C respectively. In contrast, the hetero block copolymers: Eudragit® L 100, Eudragit® S 100 and Eudragit® L 100-55 had Tg of 195 °C, 173 °C, and 111 °C, respectively, and onsets of their degradation, as measured by TGA, were in the range of 173-176 °C. The predicted HME processing temperatures of Eudragit® L 100, Eudragit® S 100 and Eudragit® L 100-55 were greater than 200 °C and hence these polymers should not be processed as it is.