Preparation of silica coated with polyethylene by in situ polymerization with metallocene catalyst

Abstract

Nowadays , natural rubber is used as a raw material to produce several products due to its high strength. However, it has limit to be used because of low mechanical property. So, it needs to be improved by adding some filler, which is silica. Nevertheless, silica needs altering to be more hydrophobic as the rubber matrix. Thus it could be used to improve the silica surface by in situ polymerization. In this study, the in situ polymerization of ethylene over metallocene catalyst with three types of silica obtained from rice husk, commercial and synthesized silica. The modified methylaluminoxanes (MMAO) is used as cocatalyst. There were three parts of this study. The first part was studied the characteristics of silica before and after immobilization with MMAO, prepared by ex situ immobilization method by by XRF, N2 physisorption, SEM-EDX , XRD, XPS, and TGA-DSC. The second part studied the catalytic activities of silica at different temperatures (60oC and 70oC) and immobilization method (ex situ and in situ). The in situ immobilization expressed higher catalytic activity than the ex situ method. The activity of polymerization via ex situ immobilization of SiO2-Com was the highest at 70oC and SiO2-Syn was the highest catalytic activity at 60oC. However, the morphologies of polymer with ex situ immobilization, which was spheroidal were better than in situ immobilization which was irregular shape. All obtained polymers were characterized in the third part by SEM-EDX , XRD, and TGA-DSC. It can be concluded that the SiO2-Com coated with polyethylene by in situ polymerization with metallocene catalyst at 70oC via ex situ immobilization expressed the highest catalytic activity. SiO2-RH coated with polyethylene by in situ polymerization with metallocene catalyst at 70oC via ex situ immobilization expressed the lowest catalytic activity.