Properties of acrylic-melamine coatings based on high converson prepolymer

摘要

Acrylic copolymers with different amounts of hydroxyl groups were prepared by free-radical solution and suspension polymerisation techniques in presence of benzoyl peroxide (BPO) initiators. Monomers used were hydroxy ethyl methacrylate (HEMA), methyl methacrylate (MMA), butyl acrylate (BA) and styrene. The polymers synthesized were characterized by gel permeation chromatography, IR and ~1H-NMR. The polyols were crosslinked with butoxy methyl melamine in the ratio 85:15 in presence of p-TSA. The practical performance of melamine-cured acrylic coatings was investigated. The free clear coatings were used for dynamic mechanical, thermal, tensile and water vapor permeability study. Supported coatings were used for mechanical property evaluation. The results indicated increased crosslink density and glass transition temperature with the increase of hydroxyl number in the acrylic copolymer. The lower glass transition temperatures of the coatings formulated from polyols synthesized by suspension polymerization method than the coatings formulated from polyols synthesized by solution polymerization method. Coatings formulated from polyols synthesized by suspension polymerization showed more flexible nature as compared to polyols synthesized by solution polymerization method. The thermal stability of the polyols was less than the corresponding crosslinked coatings. The water vapor permeability data showed the anomalous behavior.