Reactive wetting of polyethylene on ethylene-propylene-diene terpolymer

If wetting is ubiquitous in nature, reactive wetting is up to now mostly described for metallic and ceramic systems. Characterizing wetting between two reactive organic polymers is more challenging due to their similar molecular structure and yet it is crucial to unravel adhesion mechanisms. This is for example the case when combining ethylene-propylene-diene terpolymer (EPDM) with polyolefins like polyethylene (PE). Therefore, in this study, a high temperature contact angle measurement methodology is presented to evidence the occurrence of chemical bonds at the interface. Spreading of PE was found to be restricted on vulcanizing peroxide-based EPDM, while on an already completely vulcanized EPDM, low static advancing contact angles were obtained. This restriction in wetting is ascribed to a co-vulcanization reaction between EPDM and PE. Furthermore, the chemical bonding mechanism is even more pronounced with higher peroxide concentrations in EPDM which also leads to a higher adhesion strength at the interface.