Effects of primary and quaternary amine intercalants on the organoclay dispersion in a sulfur-cured EPDM rubber

The effects of primary and quaternary amine modified montmorillonite (MMT) on the nanocomposite formation in an ethylene/propylene/diene rubber (EPDM) were studied. The organoclay was introduced in 10 parts per 100 rubber (phr) amount in the related recipes. X-ray diffraction spectra (XRD) were recorded in various stages of their processing in order to get information about the intercalation process. The curatives found to play a crucial role, as they promote the intercalation/exfoliation phenomena. Incorporation of MMT modified with octadecylamine (MMT-PRIM) in the EPDM and its more polar version (contains maleic anhydride grafted EPDM, EPDM-MA) resulted in intercalated and exfoliated structures, respectively. Deintercalation of the clay (collapse of the layers), generated in both EPDM and EPDM-MA during vulcanization, was attributed to the reactivity of the PRIM and to its ability to participate in complex formation with the curatives (vulcanization intermediates). This explanation was supported by the non-collapse of the MMT layers when the less reactive modifier, viz. octadecyltrimethylamine served as MMT intercalant (MMT-QUAT). In the latter case the corresponding nanocomposite contained mostly intercalated clay layers based on XRD and transmission electron microscopic (TEM) results.