Thermal decomposition mechanism of poly(vinyl butyral) with random structure revealed through TG-FTIR-MS, GC-MS, and SVUV PIMS

Understanding thermal decomposition mechanism of polymers with a random structure is essential for both academic research and industrial applications, but remains a complex and less studied area due to its complexity. In this study, we investigated the oxygen-free thermal decomposition behavior of poly(vinyl butyral) (PVB), a polymer with random structure, using a combination of thermogravimetry-Fourier infrared spectroscopy-mass spectrometry (TG-FTIR-MS), gas chromatography-mass spectrometry (GC-MS), and synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV PIMS). Specific structures of dozens of products and some corresponding free radicals during decomposition were successfully identified and distinguished in detail for the first time. According to the temperature dependent evolution behavior, the products can be categorized into several types: "type A product" (n-butanal), "type B products" (lower aldehydes, lower ketones, alkenals, alkenones, etc.), and "type C products" (alkenes, butanoic acid, aromatic and cyclic aliphatic compounds, etc.). Their source reactions leading to the formation of each product type were thoroughly discussed respectively. A comprehensive scheme of the thermal decomposition mechanism of PVB was proposed, which cannot be simply classified into any of the three major thermal decomposition categories. Our work provides valuable insights into the thermal decomposition mechanism of PVB and offers a valuable approach for studying the thermal decomposition behavior of other polymers with random structures.