Experimental Evaluation of Mechanical Performance, Accelerated-Aging Durability, and Surface Wettability of Elastomeric Waterproofing Membranes

Styrene–acrylic elastomeric waterproofing membranes are widely used in exterior construction because of their flexibility, adhesion, and ease of application; however, their long-term performance depends on resistance to environmental aging and on surface interactions with water. This work presents a comparative experimental assessment of commercially available elastomeric waterproofing membranes, combining tensile/elongation testing before and after hydrolytic, thermal, and QUV accelerated aging with static water contact-angle measurements on selected systems. Four Sika systems (Sika® Elastic Roof, SikaFill®-90 MP, SikaFill®-365 Duralastic Terrace, and SikaFill®) as well as two additional commercially available competitor membranes (Competitor 1 and Competitor 2) were examined. Membrane films were prepared at controlled thickness and curing conditions, and elongation at break and elongation retention were used as primary mechanical durability descriptors. All investigated membranes exhibited pronounced elastomeric behavior in the unaged state, with elongation values exceeding 500% and, for the most flexible formulations, 1000%. Environmental aging progressively reduced deformation capacity, with QUV exposure producing the most severe mechanical degradation. Baseline surface wettability measurements on unaged specimens further differentiated the selected membranes: Competitor 2 revealed the highest mean water contact angle (98.8 ± 3.7°), followed by Sika® Elastic Roof (91.4 ± 2.2°), both indicating hydrophobic behavior; SikaFill® was slightly hydrophilic and close to the 90° transition (87.3 ± 3.3°), while SikaFill®-365 Duralastic Terrace exhibited the lowest contact angle (84.6 ± 3.0°) and hydrophilic behavior. The combined results indicated that initial flexibility alone is insufficient to describe long-term functional performance. Elongation retention provides a direct measure of mechanical durability, whereas contact angle captures differences in baseline surface wettability that are relevant to water–membrane interactions. The observed ranking in wettability highlights the influence of formulation and surface chemistry and provides complementary baseline information alongside the accelerated-aging assessment. These findings support performance-based selection and formulation optimization of elastomeric waterproofing membranes for demanding exterior applications.