Polyethylene/palygorskite nanocomposites: Preparation by in situ polymerization and their characterization

A naturally occurring clay mineral, palygorskite, which has the microstructure of nano-fibers, was used to support a metallocene compound, Cp₂TiCl₂. After activation by methylaluminoxane, the supported catalyst initiated an in situ ethylene polymerization resulting in the exfoliated dispersion of the nano-fibers into the polyethylene matrix. With no further chemical modification of the palygorskite after thermal treatment, the activity of the supported catalyst was found to be even higher than its solution counterpart under the same polymerization conditions. The addition of the filler in the polymer matrix led to an increase in composite rigidity as reflected by almost doubling the storage modulus at room temperature. Moreover, the filler affects the crystallization process, as observed by DSC and solid-state NMR, reducing the crystallinity up to 28% and the thickness of the rigid phase up to 22% compared with the neat sample.