Dual-Stress aging of UV-CIPP composites: Microbial and mechanical degradation mechanisms in corrosive environments

Ultraviolet cured-in-place pipe (UV-CIPP) has emerged as a prevalent trenchless rehabilitation method, applicable for repairing municipal drainage pipes eroded by sulfuric acid derived from sulfate reducing bacteria (SRB) activity, as well as marine outfall pipes degraded by hydrocarbon-degrading bacteria such as Alcanivorax. To assess UV-CIPP material durability, microbial and bending stress aging tests were conducted in simulated sulfuric acid and seawater environments, and the aging mechanisms and microplastics release were analyzed through comprehensive testing. Results indicated that microbial adhesion to the resin surface enhanced surface wettability and promoted water diffusion, though without significantly altering surface elemental composition, chemical structure, or mechanical properties. Conversely, bending stress propagated resin swelling-induced microcracks into larger fractures, leading to increased roughness and elevated water absorption rates. This process accelerated deterioration at the resin-fiber interface and induced internal glass fiber fractures, ultimately reducing bending strength. After 8640 h of aging, microplastic release reached 106.00-168.06 items/mm², resulting primarily from crack propagation and surface material delamination. Both microorganisms and bending stress increased the relative abundance of larger microplastics by exacerbating surface crack formation.