Polyethylene nanocomposites by gas‐phase polymerization of ethylene in the presence of a nanosilica‐supported zirconocene catalyst system

BACKGROUND: Much of the current research related to the development of in situ nanocomposites of olefins by polymerizing them with metallocenes in the presence of surface‐treated fillers is carried out in the slurry phase. In slurry‐phase methods a large amount of solvent is required and there is always a need of purification of the final product due to the possibility of traces of solvents present in the product. To overcome these drawbacks, to perform solvent‐free metallocene‐catalysed polymerizations with in situ incorporation of inorganic nanoparticles, we have used a gas‐phase polymerization technique as this does not require solvents and also utilizes monomer feed stocks efficiently. RESULTS: The catalyst used for the synthesis of in situ polyethylene nanocomposites by gas‐phase polymerization was nanosilica‐supported zirconocene. The fillers used were Cloisite‐20A, kaolin and nanosilica. Three different in situ polyethylene nanocomposites, i.e. Cloisite‐20A‐filled polyethylene (CFPE), kaolin‐filled polyethylene (KFPE) and nanosilica‐filled polyethylene (SFPE), were prepared by gas‐phase polymerization. The nanocomposites were obtained in the form of fine powder. The polyethylene content in the developed nanocomposites is in the orthorhombic crystalline phase. Using our approach, it is observed that the nanofillers are completely encapsulated by a thin layer of polyethylene. Significantly higher molecular weight polyethylene was formed in the case of KFPE in comparison to CFPE and SFPE. The thermal decomposition temperature, melting temperature and enthalpy are also observed to be higher for KFPE. CONCLUSIONS: The gas‐phase polymerization technique has been successfully carried out for the synthesis of in situ polyethylene nanocomposites. Copyright © 2007 Society of Chemical Industry