Comparison of glass transition measurements between carrimed rheometer and differential scanning calorimetry using methylacrylate-vinylidene chloride copolymer

The potential of the Carrimed CSL 500 rheometer for the thermal analysis of methylacrylate-vinylidene chloride (MA-VDC) random copolymer was evaluated by comparing the glass transition temperature (T_g) of the copolymers with the value obtained from the differential scanning calorimeter. The major relaxation phenomenon in amorphous polymers, namely the glass transition temperature, could be identified clearly using the Carrimed rheometer. Samples of varius contents of methylacrylate in methylacrylate-vinylidene chloride copolymer were prepared as solvent cast films. Small amplitude oscillatory measurements showed as a function of temperature, that methylacrylate-vinylidene chloride copolymer between 12% and 70% methylacrylate (MA) content showed glass transition temperatures between 48°C and 63°C. For the methylacrylate content ranging from 4% to 70%, the saran copolymers had glass transition temperatures between 12°C and 56°C. Both techniques showed the T_g of the methylacrylate-vinylidene chloride copolymer first increased and then decreased with increasing methylacrylate content. Both methods show a peak in the T_g vs. percent methylacrylate content of the copolymer at around 50% methylacrylate content. Small angle amplitude measurements also showed that it is very sensitive to the frequency. The T_g obtained using the Carrimed CSL 500 rheometer is very reproducible and is comparable with that obtained using the standard DSC.