The partial replacement of silica or calcium carbonate by halloysite nanotubes as fillers in ethylene propylene diene monomer composites

The effect of partial replacement of silica or calcium carbonate (CaCO3) by halloysite nanotubes (HNTs) on the curing behavior, tensile properties, dynamic mechanical properties, and morphological characteristics of ethylene propylene diene monomer (EPDM) composites was studied. Five different compositions of EPDM/Silica/HNT and EPDM/CaCO₃/HNT compounds (i.e. 100/30/0, 100/ 25/5, 100/15/15, 100/5/25, and 100/0/30 parts per hundred rubber (phr)) were prepared on a two-roll mill. The results indicated that the replacement of CaCO3 by HNTs increased the tensile strength, elongation at break (E_b), and tensile modulus of composites from 0 to 30 phr of HNTs whereas for silica, the maximum tensile strength and E_b occurred at 5 phr loading of HNTs with an enhanced stress at 300% elongation (M300). The curing results show that, with replacement of silica or CaCO3 by HNTs, the cure time (f ₉₀) and cure rate (CRI) were decreased and increased, respectively. Scanning electron microscopy investigation confirmed that co-incorporation, of 5 phr of HNTs with silica would improve the dispersion of silica and enhanced the interactions between fillers and EPDM matrix.