Reinforcement effects of nanocarbons on catalyst behaviour and polyethylene properties through in situ polymerization

Abstract

MWCNT (multi-walled carbon nanotube), MWCNT-COOH and xGnP (exfoliated graphene nanoplatelet) were used in the in situ polymerization of ethylene in the presence of a binuclear complex (BNC₄) in which triisobutylaluminum (TiBA) and methylaluminoxane (MAO) were employed as cocatalysts. Functional groups on MWCNT-COOH, MWCNT and xGnP were masked with TiBA. In comparison to BNC₄ (503.3 g PE per mmol Ni per h), not only was the catalytic activity using BNC₄/xGnP (1811.8 g PE per mmol Ni per h) and BNC₄/MWCNT (1025.1 g PE per mmol Ni per h) improved, due to the adsorption of catalyst on the nanocarbon surface, but also the properties of the PE/nanocarbons were markedly affected. A DSC thermogram of PE/xGnP showed a peak together with a shoulder, which was broader than was observed with pure PE, whereas a narrow peak was observed for PE/MWCNT-COOH and for PE/MWCNT. Moreover, nanocarbons with a change in PE morphology were observed through SEM images. The unsaturation content and the extent of branching for polyethylene obtained using BNC₄/Nanocarbons were in the range of 7.6–16.8 and 186–214., respectively. The surface electrical conductivity improved substantially (≈10⁻⁶ S cm⁻¹), relative to pure PE (≈10⁻¹³ S cm⁻¹).