A yacht-component customer needed a black, moderately firm EPDM seal for a marine window. Rubbing left a dark mark containing fine black particles. We refined successive molded samples until the mark became lighter and narrower.
Fine particles in the mark directed attention to the molded rubber surface.
The seal was compression-molded in black EPDM for the customer's marine window. It needed a moderately firm feel and a clean contact surface. Rubbing produced a dark trace containing fine black particles from the rubber surface.
The particles showed that the marking problem was surface transfer. We focused the sample refinement on reducing rub-off from the molded seal.
We refined successive molded samples against the customer's requirement for low visible transfer. The later samples left a lighter, finer and narrower trace when rubbed against another surface.
Visible black residue was reduced while the moderately firm seal specification remained the design target.
The mold defines the seal profile, so the manufacturing focus was the rubber surface. Cure time and mold temperature govern vulcanization; press pressure and demolding conditions also influence surface quality. These are the production controls available to reduce loose particles without changing the seal's profile.
Compare the visible mark across successive molded samples, then maintain the selected molding conditions for a consistent surface finish.