Study of the Method for the Accurate Determination of Gel Content in Cured Polyaluminocarbosilane Fibers

The curing process is the key process for preparing SiC fibers. Currently, there are fewer reports on the measurement methods related to the curing degree, leading to a lack of effective guidance for controlling the curing degree. The gel content of cured fibers can be measured through Soxhlet extraction to reflect the curing degree, which can be utilized to guide the control of the curing process of fibers. However, there are limited reports on the key influencing factors for accurately determining the gel content through Soxhlet extraction, such as the selection of appropriate extractant, extraction temperature, extraction time, and the selection of wrapping materials for cured fibers with stable mass which require further investigation. In this work, cured polyaluminocarbosilane (PACS) fibers with air oxidation curing are utilized as the research subject, and provide a reference for an accurate method to determine the gel content in cured fibers based on Soxhlet extraction. A wrapping material with lower water absorption and lower cost is preferred, and the effects of key factors such as the extractant, extraction temperature, extraction time, and number of extraction experiments on the accurate determination of gel content are examined to establish the optimal testing conditions. The accuracy and reliability of the method are further verified. This method is anticipated to be expanded to determine the gel content in other types of cured fibers and the cured fibers crosslinked by different processes, providing an effective means of characterizing the control of curing degree in the preparation process of precursor-derived SiC fibers.