Aging of Two Coextruded EVOH Geomembranes Exposed to Synthetic MSW Leachate

Coextruded geomembranes (GMs) with an ethylene vinyl alcohol (EVOH) layer (coextruded EVOH GMs) are gaining attention as promising barriers in waste containment facilities due to their excellent resistance to organic contaminants. Laboratory-accelerated aging tests were conducted to evaluate the aging of two 1.5-mm-thick coextruded EVOH GMs: Co-BB, with two black surface layers, and Co-BW, with one black and one white surface layer. Both GMs used the same polyethylene resin in their surface layers but had different additive packages. GM samples were immersed in synthetic municipal solid waste (MSW) leachate at temperatures of 22, 40, 65, 75, and 85°C. Comparative tests were conducted on a 1.5-mm-thick high-density polyethylene (HDPE) GM, which used the same polyethylene resin as the coextruded EVOH GMs but contained a different additive package. The results showed that sealed and unsealed Co-BW GM samples exhibited similar aging behavior, indicating that EVOH’s reaction with water has an insignificant effect on aging of coextruded EVOH GMs. Co-BB GM showed the longest standard oxidative induction time (Std-OIT) depletion times, followed by Co-BW GM and then the HDPE GM. For HP-OIT, the coextruded EVOH GMs had longer depletion times at higher temperatures, while the HDPE GM showed the longest depletion times at lower temperatures. Tensile property degradation in the coextruded EVOH GMs is governed by the surface layers, and the faster OIT depletion and earlier degradation of the HDPE GM at 85°C suggests that, with appropriate surface-layer formulations, coextruded EVOH GMs can serve as promising alternatives to traditional HDPE GMs.