Improvement of hardness and compression set properties of EPDM seals with alternating multilayered structure for PEM fuel cells

In Proton Electrolyte Membrane (PEM) fuel cells, seals are used to keep intimate contact between all components as well as to keep the reactant gases and liquid within their respective regions. Suitable seal materials should be chosen and designed to sustain the long term operation. In this paper, EPDM seal materials with soft and hard alternating multilayered structure are fabricated through the multilayered co-extrusion system. The structure and morphology of multilayered and blended EPDM vulcanizates were observed by Scanning electron microscopy (SEM). The results of tensile, hardness, compression set and compression stress relaxation test show that multilayered vulcanizates have lower tensile strength and compression set but higher hardness than blended one. The hardness of multilayered vulcanizates increases with the increase of the layer number, leading to higher sealing force and better dimensional stability. The compression set of multilayered vulcanizates decreases with the increase of the layer number, indicating better sealing capacity and longer working life. The permeability test shows that multilayered materials have nearly same gas permeability property as blended one. The results of aging test reveal that the mechanical properties of EPDM seal materials decrease with time, but multilayered vulcanizates still have lower compression set than blended one after aging.