A Comparison between Cure Systems for EPDM/Montmorillonite Nanocomposites
Two kinds of ethylene-propylene-diene rubber (EPDM)/organic montmorillonite (OMMT) nanocomposites were prepared with two kinds of cure systems: sulfur and peroxide. The experimental results from X-ray diffraction and transmission electron miscroscopy showed that EPDM intercalated the MMT galleries and the MMT was exfoliated and dispersed uniformly in the EPDM composites cured with sulfur. But the MMT was stacked with several layers and existed in an intercalated structure in the EPDM composites cured with peroxide. The EPDM composites cured with sulfur were opaque and had better mechanical properties, while the EPDM composites cured with the peroxide were semi-transparent. Vulcametric curves showed that the MMT retarded the vulcanization reaction of the EPDM composites cured with the sulfur cure system, and furthermore, gave rise to a marked decrease in maximum torque, indicating a lower crosslink density. This was confirmed by swelling measurements. But the corresponding values of the composites cured with the peroxide cure system were virtually unchanged by addition of the OMMT.