Chinese regions exhibit a highly uneven distribution of substantial energy re-serves and significant electrical energy loads. The actual situation necessitates the electricity system to depend increasingly significantly on transmission lines, in which composite insulators play a vital role. Historically, conventional fractures have been well treated, but the more recent type of fracture known as decay-like fracture is currently being investigated. In the event of a fracture, mishaps such as transmission line dropping may arise, leading to the termination of power supply and failure to restore it promptly. In order to effectively prevent the occurrence of decay-like fractures, researchers are currently endeavoring to understand the mechanism of this fracture, including its specific initiation point and the process of degradation. Drawing from prior research, heat has been identified as a reliable indicator of fracture occurrence. The objective of this work is to determine the impact of thermal stress by examining products during the process of thermal aging. Experimental trials are conducted at various temperatures for a duration of 5 h. Following testing, samples and products obtained from studies are subjected to additional observation and analysis using Fourier Transform Infrared spectroscopy (FTIR) and Gas Chromatography Mass Spectrometry (GC-MS). This work quantifies the chemical composition of the related gaseous products and compares the FTIR results of samples before and after trials to determine the changes in functional groups. Analytical findings can serve as the foundation for further investigation of the decay-like fracture mechanism, namely the process of fracture intensification.