Preparation and Characterization of UHMWPE/Graphene Nanocomposites Using Bi-Supported Ziegler-Natta Polymerization

Ultrahigh-molecular-weight polyethylene (UHMWPE)/graphene nanocomposites with molecular weights as high as 3 × 106 g/mol were prepared via in situ polymerization using a bi-supported Ziegler-Natta catalytic system. Effects of [Al]/[Ti] molar ratio, temperature, monomer pressure, and polymerization time on productivity of the catalyst have been investigated. Increasing [Al]/[Ti] molar ratio from 128 to 320, increased productivity from 1667 g PE/mmol Ti.h to maximum value which was 2420 g PE/mmol Ti.h. Further [Al]/[Ti] ratio decreased the productivity. Reaction temperature effect investigation reveals that the optimal activity was obtained at 60°C. the polymerization productivity increases with monomer pressure and decreased with polymerization time. Morphological information was determined by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Obtained results show that graphene layers in these nanocomposites were completely exfoliated and dispersed uniformly in the polyethylene matrix while no nanoparticle cluster has been formed.