EFFECT OF COMPACTION TEMPERATURE ON CONSOLIDATION OF AMORPHOUS COPOLYMERS WITH DIFFERENT GLASS-TRANSITION TEMPERATURES

Purpose, The purpose of this study was to relate the combination of gl ass transition temperature (T-g) and temperature of measurement with t he mechanical and compaction properties of some test materials. Method s, Copolymers with different T-g's were synthesised by free radical co polymerisation of methyl methacrylate with lauryl methacrylate. Elasti c moduli were measured by dynamic mechanical analysis at different str ain rates and temperatures. Compaction experiments were performed at d ifferent compaction speeds and temperatures. Results, The difference b etween temperature of measurement and T-g appears to determine both el astic modulus and yield strength completely. They both decrease with d ecreasing difference between temperature of measurement and T-g and in crease with strain rate. At temperatures of measurement higher than th e T-g, the elastic modulus is extremely low because the materials beha ve as rubbers. Consequently, the amount of energy stored during compac tion decreases when the compaction temperature approaches the T-g and increases with strain rate. When the compaction temperature is higher than the T-g, the amount of stored energy is extremely large. The comp action experiments show that the final tablet porosity is completely d etermined by stress relaxation phenomena. Consequently, the final tabl et porosity follows exactly the same relation as that of stored energy . Conclusions, The final tablet porosity is unequivocally determined b y the amount of stored energy. This implies that tablet production at a temperature of about 20 K under the glass transition temperature of the material yields tablets with minimum porosity.