Self-Cross-linking Acrylate Copolymer/Organoclay Nanocomposite Emulsion Coating: Nanoindentation and Nanoscratch Behavior

Self-cross-linking poly(methyl methacrylate-co-butyl acrylate-co-hydroxy ethylmethacrylate) P(MMA-co-BA-co-HEMA) latex particles and its composites with organically modified montmorillonites (OMMTs) were prepared via emulsion polymerization. The condensation of hydroxyl groups (OH) in the copolymer structure especially at higher curing temperatures, 80 and 150 degrees C, resulted in emulsion coatings with high gel contents and stiffness. The chemical structure and nanostructure of resulting self-cross-linked composite coats were studied using Fourier-transform infrared (FTIR) and small angle X-ray scattering (SAXS), respectively. The effect of curing temperature and OMMT (organoclay) type and level on the nanoscratch resistance and nanoindentation behavior of the self-cross-linking acrylate copolymer was investigated. The nanoscratch test results showed that the incorporation of Closite15A inside the copolymer network considerably decreased the maximum grooving depth and increased the friction and scratch coefficient of the copolymer when compared with other OMMTs used. Furthermore, the introduction of 3 wt.% Closite15A further increased the surface hardness of the copolymer coating at curing temperature of 80 degrees C.