EPDM Closed Cell Sponge Rubber

A: EPDM closed cell sponge contains internal stress after vulcanization and foaming. Industry data shows typical post-shrinkage of 1.5%–2.5% occurs within 24 hours of die-cutting. For high-precision gaskets, we recommend a pre-compression stabilization treatment (24 hours in a 50°C oven to relieve stress). Standard die-cutting tolerance is ±0.5mm, and precision die-cutting can reach ±0.1mm. Linear shrinkage values of approximately 2% have been reported in industry specifications.

A: This is common for thicknesses >15mm. Heat transfers from the mold surface to the core during vulcanization, resulting in different crosslinking densities throughout the material cross-section. Our solution: For thicknesses >20mm, we use a low-temperature, extended vulcanization process and perform multi-point hardness checks (four corners + center) before shipment, controlling the hardness variation within ±5 Shore C or ±10 Shore OO as referenced in industry datasheets.

A: This is "blooming," caused by migration of vulcanization accelerators or anti-aging agents to the surface. It usually does not affect physical sealing performance, but it may reduce adhesive bonding strength. Our factory strictly controls the formulation and validates every batch with a 70°C/48-hour accelerated aging test (per ASTM D1056 requirements) to ensure no blooming, resulting in a clean surface ready for bonding.

A: Yes. EPDM is inherently UV and ozone resistant due to its saturated polymer backbone. Industry sources confirm "excellent AIR & UV Resistance" for EPDM closed cell foams. However, we recommend confirming the specific hardness grade, as softer foams may be less abrasion resistant in high-traffic outdoor areas.