Investigation of the thermal conversion behavior and reaction kinetics of the pyrolysis of bio-based polyurethane: A reference study

In view of the global objective of carbon neutrality, using natural biomaterials to prepare bio-based polyurethane (BPU) is a significant means of reducing our heavy dependence on fossil fuels. If the utilization of these biomaterials is to increase, appropriate treatment methods after they reach the end of their life cycle are a challenge that must be addressed in advance. In the present study, thermogravimetric (TG) experiments were conducted for bio-based polyurethane (BPU) as a reference case compared to neat polyurethane (NPU) from fossil resources. The resultant generation of pyrolysis products was analyzed using coupled thermogravimetric analysis, Fourier-transformed infrared spectroscopy and gas chromatography mass spectrometry (TG-FTIR-GC/MS). The reaction kinetics were investigated using three model-free methods by Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Starink, in addition to the model-fitting Coats–Redfern (CR) method. The TG analysis indicated that the decomposition of BPU and NPU can be divided into three similar stages with temperature ranges of <200 °C, 220–450/500 °C and above 500 °C. Activation energies (Ea) of BPU and NPU conversion fell in the range of 149.4–221.0 kJ mol−1 and 95.6–162.6 kJ mol−1 respectively when using the model-free methods. The apparent reaction mechanism study revealed that both samples were in accordance with the reaction order models, with orders of 3 for BPU and 2.5 for NPU.