Stability of POSS crosslinks and aggregates in tetrafluoroethylene-propylene elastomers/OVPOSS composites exposed to hydrochloric acid solution

Tetrafluoroethylene-propylene elastomer (TFE/P) and octavinyl-polyhedral oligomeric silsesquioxane (OVPOSS) composites were prepared by milling at room temperature and heat vulcanization at 170 °C. Subsequently, the composites were immersed and aged in a 10 wt% hydrochloric acid solution for 2, 4, and 6 days at 140 °C, and their aging behaviors were investigated. The results show that as the aging time increases, the tensile strength and crosslink density gradually decrease, while the mass- and volume-change rates accordingly increase. The aging samples along with the unexposed sample were characterized by means of wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), 29Si nuclear magnetic resonance (NMR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) analyses. The results reveal that in an aging environment, the crystalline structure of the OVPOSS aggregates and the cage structure of the OVPOSS were partly damaged. Meanwhile, the crosslinks between the OVPOSS and TFE/P chains were also damaged and the OVPOSS cage transformed into smaller compounds containing Si-OH groups.