Use of functionalized boehmite nanoparticles to improve the hardness and tribological properties of polyurethane films

Plate-like boehmite nanoparticles (BH) produced from aluminum hydroxide by hydrothermal process were functionalized in one step with two different diisocyanates. The amount of free isocyanates that were available for polymerization reaction was determined to be higher in functionalization with the aromatic diisocyanate (diphenylmethane-4,4′-di-isocyanate – MDI). In composite film production MDI functionalized BH (MDI-BH) was used. Polyurethane based nanocomposite films were produced through polymerization of non-functionalized and MDI-BH with two different polyester-polyols that were synthesized by the esterification of 1,4 butanediol with either adipic acid or phthalic anhydride. It was impossible to form films suitable for hardness and tribological tests with non-functionalized BH. Up to 1 wt% MDI-BH additions were effective in increasing the hardness and scratch resistance of films. The increases in abrasion resistance were more significant and followed the increasing trend for MDI-BH additions even up to 5 wt%. The highest increase, which was 400% with respect to the unmodified resin was observed with adipic acid based polyols and this result was obtained at MDI-BH content of 3 wt%.