Summary: As proposed earlier (Macromol. Rapid Commun., 2004, 25, 733) the Kg and U* parameters of the Hoffman‐Lauritzen theory can be derived from isoconversional analysis of DSC data on melt crystallization. In this study, the analysis is extended to include both melt and glass crystallization data. The analysis of DSC data on non‐isothermal crystallization of poly(ethylene terephthalate) (PET) and poly(ethylene 2,6‐naphthalate) (PEN) demonstrates that for each of these polymers the combined melt and glass crystallization data can be described by single set of the Kg and U* values. The respective values for PET are 3.6 × 105 K2 and 7.5 kJ · mol−1 and for PEN 2.2 × 105 K2 and 6.6 kJ · mol−1. The use of combined data sets helps to improve the precision of computations.

Thermogravimetry and differential scanning calorimetry (DSC) have been used to study the thermal and thermo-oxidative degradation of polystyrene (PS) and PS−clay nanocomposite. An advanced isoconversional method has been applied for kinetic analysis. Introduction of the clay phase increases the activation energy and affects the total heat of degradation that suggests a change in the reaction mechanism. The obtained kinetic data permit comparative assessment of fire resistance of the studied materials. Relaxation kinetics have been measured by DSC and dynamic mechanical analysis. As compared to virgin PS, the clay nanocomposite shows the glass transition at a higher temperature and demonstrates markedly larger activation energy. This suggests that the clay phase lowers the molecular mobility of PS which is another factor contributing to the increased thermal stability of the nanocomposite.

Differential scanning calorimetry has been used to study the α-relaxation (glass transition) as well as β-relaxation (sub-T g relaxation) in both virgin polystyrene (PS) and PS−clay nanocomposite. The β-relaxations have been measured as a small endothermic peak that appears on heating of the samples previously annealed at temperatures from 30 to 80 °C. The relaxations have been characterized by determining the effective activation energies (E) and evaluating the sizes of cooperatively rearranging regions at the glass transition (V g). The values of V g have been determined from the heat capacity data. The β-relaxation in both systems shows comparable values of E that increase with annealing temperature from ∼90 to 170 kJ mol-1. In the PS−clay system the increase occurs slower, suggesting that this process is more decoupled from the α-relaxation than in virgin PS. The α-relaxation demonstrates markedly larger values of E (∼340 vs ∼270 kJ mol-1) for the PS−clay system than for virgin PS. The PS−clay system has also been found to have a significantly larger value of V g, 36.7 nm3 as compared to 20.9 nm3 for PS. The increase in E and V g reflects an increase in molecular cooperativity that is introduced by the mutually dependent motion of the polymer chains anchored to the surface of clay sheets.

The alpha- and beta-relaxation processes in amorphous indomethacin have been studied by using differential scanning calorimetry. The beta-process has been detected as a small endothermic peak that emerges before the glass transition step when reheating samples previously annealed in the temperature region -20 to +5 degrees C. The activation energy of the beta-process is approximately 57 kJ mol(-1), and shows an increase with increasing temperature as it approaches the glass transition region. In the glass transition region, the effective activation energy of relaxation decreases with increasing temperature from 320 to 160 kJ mol(-1). Heat capacity measurements have allowed for the evaluation of the cooperatively rearranging region in terms of the linear size (3.4 nm) and the number of molecules (90). The beta-relaxation fades below -30 degrees C, which provides a practical estimate for the lower temperature limit of physical instability in indomethacin. It is demonstrated experimentally that nucleation of indomethacin takes place in the temperature region of the beta-relaxation.