Zeolite Activation of Resol Cure of EPDM in Thermoset and Dynamic Vulcanisation

Sulphur vulcanisation and peroxide curing are the main crosslinking technologies for EPDM rubber. Resol curing is the “work horse” for the dynamic vulcanisation of EPDM/PP-based thermoplastic vulcanisates (TPVs), but it is hardly used for thermoset vulcanisation of EPDM, because it is considered to be too slow and suffers from marching cure.

Recently, zeolite was identified as a new co-activator for resol curing, enabling both high cure speed and high curing efficiency. Although emphasis of our studies is on the activation of various resol curing systems for EPDM rubber, it is also shown that this novel way of activation is applicable for resol cure of other types of rubber, including (X)IIR, CR, (h)NBR, BR, SBR and NR. Depending on the particular resol curing system and rubber under investigation, the cure rate is strongly increased (reduction of scorch and vulcanisation times up to 75%) and/or the final degree of crosslinking is enhanced (in some cases almost doubled). Finally, it will be shown that zeolite activation is effective not only for the thermoset vulcanisation of EPDM, but also for the dynamic vulcanisation of EPDM-based TPVs, enabling a reduction of the resol content and, thus, improving the TPV colour characteristics.