Poly(p‐phenylene sulfide) nonisothermal cold‐crystallization

Abstract

AbstractThe poly(p‐phenylene sulfide) (PPS) nonisothermal cold‐crystallization behavior was investigated in a wide heating rate range. The techniques employed were the usual Differential Scanning Calorimetry (DSC), and the less conventional FT‐IR spectroscopy and Energy Dispersive X‐ray Diffraction (EDXD). The low heating rates (Φ) explored by EDXD (0.1 K min−1) and FT‐IR (0.5–10 K min−1) are contiguous and complementary to the DSC ones (5–30 K min−1). The crystallization temperature changes from 95 °C at Φ = 0.05 K min−1 to 130 °C at Φ = 30 K min−1. In such a wide temperature range the Kissinger model failed. The model is based on an Arrhenius temperature dependence of the crystallization rate and is widely employed to evaluate the activation energy of the crystallization process. The experimental results were satisfactorily fit by replacing in the Kissinger model the Arrhenius equation with the Vogel–Fulcher–Tamann function and fixing U* = 6.28 k J mol−1, the activation energy needed for the chains movements, according to Hoffmann. The temperature at which the polymer chains are motionless (T∞ = 42 °C) was found by fitting the experimental data. It appears to be reasonable in the light of our previously reported isothermal crystallization results, which indicated T∞ = 48 °C. Moreover, at the lower heating rate, mostly explored by FT‐IR, a secondary stepwise crystallization process was well evidenced. In first approximation, it contributes to about 17% of the crystallinity reached by the sample. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2725–2736, 2005