Determination of ultra-low glass transition temperature via differential scanning calorimetry

A novel method was developed to determine the ultra-low glass transition temperature ( T g ) of materials through physical blending via differential scanning calorimetry . According to the Fox equation for polymer blends , a blend of two fully compatible polymers has only one T g . The single T g is a function of the T g s of the two simple polymers. Thus, the ultra-low T g of one material can be obtained from the T g s of another polymer and their blends. The error of T g measurements depends on the measurement error of the T g s for the blends and another polymer. The method was successfully applied to determine the T g s of acetyl tributyl citrate (ATBC), tributyl citrate (TBC) and poly(ethylene glycol)s (PEG)s with different molecular weights . The T g s for ATBC, TBC, PEG-4000 and PEG-800 were −57.0 °C, −62.7 °C, −76.6 °C and −83.1 °C, respectively. For all the samples, the standard deviation of measurements was less than 3.3 °C, and the absolute error of measurements was theoretically not more than 5.3 °C. These results indicate that this method has acceptable precision and accuracy.