Crystallization behavior of biobased poly(butylene furandicarboxylate) (PBF): Influence of amorphous chain mobility, diffusion and nucleation on thermodynamic and kinetic control

Abstract

Isothermal and nonisothermal crystallization behavior of biobased poly(butylene 2,5-furandicarboxylate) (PBF) was studied by means of DSC, TMDSC and advanced kinetic analysis. Despite its significance for sustainable materials, several key aspects of its crystallization behavior remain poorly understood. Therefore, changes in the slope of the effective activation energy (E_α) dependencies occurring during the crystallization process are highlighted. The first change appears at the initial stage of crystallization for both heating and cooling, while the second change happens at the end of crystallization. These transitions suggest a shift in the rate-limiting step of crystallization, influenced by thermodynamic or kinetic factors. At the end of the process, the crystallization rate generally decelerates due to the reduced mobility of polymer chains, causing deviations from the Hoffman-Lauritzen (HL) theory's predictions. The present study identifies temperature-specific breaks in the effective activation energy dependencies, correlating with changes in crystallization rates at 145 °C, 137 °C, and 125 °C during cooling, and 83 °C, 87 °C, and 95 °C during heating. The rigid amorphous fraction (RAF) was found to decrease to zero around 85 °C, leading to increased polymer chain mobility and reactivation of crystallization at higher temperatures. Thus, the deviations in E_α between 83 and 86 °C align with RAF devitrification temperatures. This agreement proves that the isoconversional kinetic analysis can lead to the prediction of the temperature range of the RAF vitrification. The combination of advanced isoconversional analysis and HL rate equation accurately predicts the maximum growth rate temperature (T_max ∼117 °C), in perfect agreement with experimental data, confirming the nonisothermal model's validity and reliability. Interpretations of the variations of E_α in terms of thermodynamic and kinetic control of the overall crystallization rate are given. 16 meaningful kinetic parameters have been optimized with success.