Abstract

This study investigates the chemical resistance of EPDM elastomer composites filled with silica of varying specific surface areas (SSA) when exposed to ammonia. The composites were immersed in 99.5% anhydrous liquid ammonia for 168 h, and changes in crosslinking density, volume, surface and fracture surface morphology, mechanical properties, and dynamic mechanical properties were evaluated before and after immersion. Exposure to ammonia resulted in an increase in crosslinking density, surface roughness, and glass transition temperature (Tg), along with decrease in volume and tanδ. The magnitude of these changes decreased with increasing silica SSA. Overall, EPDM composites containing higher-SSA silica exhibited improved stability in terms of crosslinking density, volume change, mechanical performance, surface characteristics, and dynamic mechanical behavior both before and after ammonia exposure. These findings demonstrate that silica SSA is a critical parameter in the design of EPDM-based seals and gaskets for use in 99.5% anhydrous liquid ammonia environments.

Keywords: 99.5% anhydrous liquid ammonia;chemical resistance;silica-filled EPDM;elastomeric composites