PE/Clay Nanocomposite with Bimodal Molecular Weight Distribution Produced Via In-Situ Polymerization

Abstract

A Ti-based Ziegler–Natta catalyst supported on the clay was used for producing the polyethylene/clay nanocomposites through in situ polymerization. This catalyst showed high activity in the ethylene polymerization. The two-step polymerization approach, i.e. in the presence and absence of hydrogen, was laid out to broaden the molecular weight distribution of the polyethylene/clay nanocomposite. The molecular weights and molecular weight distribution of the nanocomposites were characterized by the gel permeation chromatography. It was found that the molecular weight distribution was remarkably widened towards bimodal distribution by using the above mentioned approach. The thermal properties of the produced nanocomposites were studied by differential scanning calorimetry and thermal gravimetric analysis. The microstructure of the resulting bimodal polyethylene/clay nanocomposite was investigated by X-ray diffraction and transmission electron microscopy. The thermal gravimetric analysis indicated an improved thermal stability of the produced nanocomposites. In addition, the studies proved the nanocomposite formation with the exfoliated structure of the clay in the polyethylene matrix.