Effect of the crystallite size of nano-titania on the characteristics of LLDPE/titania nanocomposites synthesized by in situ polymerization using metallocene catalyst

It is known that the linear low-density polyethylene (LLDPE) can be produced by copolymerization of ethylene and 1-olefins using metallocene catalysts. Metallocene catalyst system can be divided into two systems; homogeneous metallocene catalyst and heterogeneous metallocene catalyst. It was found that homogeneous metallocene catalyst has two major disadvantages; the lack of morphology control of the polymers produced and reactor fouling. Therefore, heterogeneous metallocene catalyst was brought to solve these problems. Polymers filled with inorganic nanoparticles as nanofillers are so-called polymer nanocomposites. It can be produced by the in situ polymerization with the presence of nanofillers added during synthesis by the application of supported metallocene catalysts. In this present study, LLDPE/TiO2 nanocomposites were synthesized by the in situ polymerization with modified methylaluminoxane (MMAO)/zirconocene catalyst. In the first part, the TiO2 nanofillers having different crystallite sizes were employed. The polymerization activities obtained from TiO2 having the highest crystallite size exhibited the highest activity due to its exhibited the weakest interaction. In the second part, the TiO2 nanofillers having different modification with metals were employed. The polymerization activities obtained from unmodified TiO2 exhibited the highest activities due to the unmodified TiO2 had weakest interaction