Coated Nano-Sized CaCO ₃ Reinforced Semi-Crystalline EPDM

Nano-sized calcium carbonate (CaCO ₃ ) was used to reinforce a semi-crystalline ethylene-propylene-diene monomer rubber (EPDM). For comparison, micron-sized CaCO ₃ was also studied. It was found that both nano-sized CaCO ₃ and micron-sized CaCO ₃ improved the mechanical properties of the EPDM vulcanizates, and nano-sized CaCO ₃ exhibited better reinforcement effect than micron-sized CaCO ₃ . The difference in reinforcement effects of nano-sized CaCO ₃ and micron-sized CaCO ₃ was explained in terms of the filler particle size and the crosslink density of the vulcanizates. The nano-sized CaCO ₃ was also modified by titanate, borate, and aluminate-titanate complex coupling agents and used to reinforce EPDM vulcanizates. The results showed that titanate coupling agent coated nano-sized CaCO ₃ exhibited the best reinforcement ability. FE-SEM micrographs showed that stearic acid, titanate, and aluminate-titanate complex coupling agents could improve the dispersion of the CaCO ₃ in the rubber matrix remarkably, whereas borate coupling agent could not. The effect of modified nano-sized CaCO ₃ on the dynamical mechanical properties was also studied. Incorporation of CaCO ₃ reduced the glass transition temperature (Tg) of the vulcanizates. In comparison with nano-sized CaCO ₃ , micron-sized CaCO ₃ depressed the Tg more remarkably.