The role of molecular diffusion in the adhesion of EPDM and EPR elastomers

Abstract

AbstractAdhesion of lightly crosslinked sheets of EPDM (ethylene–propylene–diene terpolymer) to themselves and to a Mylar substrate has been investigated over wide ranges of peel rate and test temperature. The effect of incorporating ethylene–propylene copolymer (EPR) before crosslinking, to yield a loose macromolecular network containing dissolved linear EPR macromolecules, was also studied. The self‐adhesion of these materials was found to be much greater than their adhesion to Mylar, over a wide range of effective peel rates. This is attributed to interdiffusion of EPR and EPDM molecular strands. At extremely low peel rates the enhancement of adhesion was smaller, probably because of back‐diffusion, and at high rates, the strength of adhesion became high in all cases. These results are compared to those obtained previously for polyisobutylene‐co‐ isoprene networks containing linear polyisobutylene molecules. The enhancement of self‐adhesion at intermediate rates of peel was considerably greater for the EPDM‐based materials, probably because of a lower degree of crosslinking and a greater tendency to form molecular entanglements.