Modification with tertiary amine catalysts improves vermiculite dispersion in polyurethane via in situ intercalative polymerization

Abstract

In situ intercalative polymerization is an environmentally-friendly process to produce polymer-clay nanocomposites with good clay dispersion. In this work, quaternary ammonium salts with tertiary amine groups were synthesized to modify clay as catalytically active modifiers for polyurethanes. Polyol dispersions with the catalyst-modified vermiculites were prepared by ultrasonication and examined by X-ray scattering and rheology. In the polyurethane elastomers synthesized from the above dispersions in a solvent-free process, X-ray scattering showed that the clay was highly intercalated/exfoliated without noticeable peaks for d < 9 nm, and TEM images revealed that the local dispersion of clay sheets was affected by the structure of the modifier. Addition of the modified clay to the polyurethane elastomers had only a small effect on the phase separation between hard and soft segments as deduced from DSC, FT-IR and DMA results. Thermo-mechanical and barrier properties of the composites were evaluated, and with one modifier, the nanocomposites showed a 390% increase in tensile modulus at 25 °C and a 40% reduction in CO2 permeability at a loading of 5.3 wt% of catalyst-modified clay.