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 bio-materials 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), Kissin-ger-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 tem-perature ranges of < 200 degrees C, 220-450/500 degrees C and above 500 degrees 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.