Preparation and properties of polyurethane coatings based on acrylic polyols and trimer of isophorone diisocyanate

This paper presents a study on the effect of NCO/OH ratio and an increase in hydroxyl content of acrylic polyols on the properties of polyurethane (PU) coatings. Coating properties studied are gloss, scratch resistance, flexibility and adhesion, mechanical properties include tensile strength, modulus, percent elongation and Shore hardness, while physicochemical properties include chemical resistance and solvent absorption of coated PU samples. A series of acrylic polyols (copolymers) based on butyl acrylate (BA), methyl methacrylate (MMA), styrene and 2-hydroxy ethylacrylate (HEA) were prepared by selecting different percentage of hydroxyl content. Trimer of isophorone diisocyanate (IPDI) was also synthesized in the laboratory. This trimer has trifunctionality. Isocyanurate ring of trimer increases thermal properties of PU. Polyurethanes from these acrylic polyols (containing different percent hydroxyl) and trimer of IPDI were prepared with two different NCO/OH ratios viz, 1.1:1 and 1.2:1. Polyurethanes were coated on substrates for measuring coating properties. Mechanical properties were measured on cast films of the PUs. The experimental results revealed that all polyurethane coatings based on acrylic polyols and IPDI trimer showed good gloss, scratch resistance and excellent adhesion. Thermal stability of these PU samples was found to be better. Physicochemical properties reflected that these PU have excellent chemical and solvent resistance.