New Accelerators for Blends of EPDM

Abstract

Through the use of accelerators containing higher alkyl substitution, we have been able to attain improved properties of EPDM diene rubber blends. EPDM/NBR blends vulcanized with sulfur cure systems employing these accelerators compete favorably with CR compounds in heat aging; have essentially the same oil resistance level, and exhibit better low temperature properties. These blends are highly ozone resistant, easy processing, and safe. Because of the versatility of meeting a desired combination of properties by variations both in the ratios of NBR to EPDM and in the selection of the particular grade of each elastomer, these blends will fulfill many sophisticated elastomer applications. These accelerators can also be used to provide non-blooming cure systems for EPDM compounds and safer ultrafast cure systems for diene rubber compounds. We feel that this advance in property improvement in diene rubber EPDM blends through the use of these new accelerators is only the beginning of a whole new compounding technique for blending.

Mercapto-modified copolymers in polymer blends, 1. Functionalization of EPDM with mercapto groups and its use in NBR/EPDM blends

“…In addition, the difference in unsaturation level or in polarity between the elastomers frequently results in a maldistribution of crosslinks in the blend system 1) . Many approaches have been developed to overcome this problem and include, for example, the chemical modification of the accelerators to improve their solubility in both phases 2) , the use of a ternary blend 3) , the graftization of the accelerator onto the elastomer in which the solubility is lower 4) , and the use of interfacial agents containing functional groups which are able to promote a reactive compatibilization 5) . Several authors have used the well-known free-radical addition reaction of thiols to olefinic double bonds to functionalize unsaturated elastomers 6 -8) .…”

Acrylic rubber‐fluorocarbon rubber miscible blends: Effect of curatives and fillers on cure, mechanical, aging, and swelling properties

“…This curing agent may show preferential curing of the blend by crosslinking the FKM through migration into the fluorocarbon rubber rather than the acrylic rubber. Mastomatteo et al20 also have reported on this kind of migration of crosslinking ingredient into one of the phases of ethylene‐propylene‐diene rubber (EPDM)/styrene‐butadiene rubber (SBR) blend because of the difference in polarity. We observed a similar migration of curatives for many other blends 21, 22.…”

A Phase Blending Study on Rubber Blends Based on the Solubility Preference of Curatives

“…Researchers have tried several options: e.g. applying accelerators that have the same solubility towards different phases in the blend; grafting accelerator segments onto EPDM; and changing the polarity of accelerators by alkylation 11–13. In a study of Zhao et al, different formulations were used for blends of SBR and EPDM.…”