Polymer-Montmorillonite Nanocomposites: Chemical Grafting of Polyvinyl Acetate onto Cloisite 20A

摘要

This paper is an account of the experiments on grafting polyvinyl acetate onto organophilic montmorillon-ite. Cloisite 20A was reacted with vinyltrichlorosilane to replace the edge hydroxyl groups of the clay with a vinyl moiety. Because the reaction liberates HCI, it was performed in the presence of sodium hydrogencarbon-ate to prevent the exchange of quaternary alkylammo-nium cations with H~+ ions. Only the silanol groups on the edge of the clay react with vinyltrichlorosilane. After the reaction, the product maintained the same basal spacing as the precursor. The radical polymerization of the product with vinyl acetate as a vinyl monomer leads to chemical grafting of polyvinyl acetate onto montmorillonite surface. The homopolymer formed during polymerization was separated from the grafted organoclay by Soxhelt extraction. Chemical grafting of the polymer onto Cloisite 20A was confirmed by infrared spectroscopy. The prepared nano-composite materials and the grafted nano-particles were studied by XRD, SEM, and TEM. Exfoliated nano-composite was obtained for 0.5% clay content. Nanocomposites with 1% and 3% clay contents showed significant intercalation and agglomeration occurred at higher clay loadings. The nanocomposites were studied by thermogravimertic analysis (TGA) and dynamic mechanical analysis (DMTA). Improved thermo-me-chanical properties were observed for nanocomposite with 0.5% clay content.