Synergic effect of temperature and alkalinity on the long‐term durability of pure vinyl ester
Peng Wang, Linyuwen Ke, Haoliang Wu, Christopher K.Y. Leung
Abstract
Abstract This paper presents an experimental approach to investigate the long‐term durability of vinyl ester (VE) used in civil/structural engineering. Various alkaline (pH = 7, 11, 12, and 13) and temperature (23, 40, and 60°C) conditions were considered for accelerated aging over 12 months. The test results reveal only slight changes in water absorption capacity (0.75–1.17%) and mass loss (~1%) for the aged VE, which can be explained by the unchanged glass transition temperature. Furthermore, significant hydrolysis reaction and severe microcracking at an elevated temperature resulted in a higher diffusion coefficient. The VE diffusion coefficient increases from 6.60 × 10 −7 to 1.75 × 10 −6 after 12‐month aging in 23°C water (pH = 7), but becomes 4.00 × 10 −6 mm 2 /s as the water temperature rises to 60°C. Surface microcracks with a depth of ~8.46 and chemical hydrolysis reaction with a 74% increment of OH/CH ratio were observed in the 12‐month aged VE at 60°C. However, the diffusion coefficient was insensitive to alkalinity (pH = 7, 11, 12, and 13) regardless of the exposure time and temperatures, which could be attributed to the similar OH/CH ratio at different alkaline conditions. The results of this study shed light on understanding the VE degradation in harsh environments as applied in fiber‐reinforcement polymer (FRP) composites.