Formation of urethane linkage using copolymers of glycidyl methacrylate, methyl methacrylate, and butyl acrylate

Abstract

Polyurethanes are synthesized from the reaction of diisocyanates and polyols. Isocyanates are quite toxic which creates several complications on exposure. To avoid the usage of isocyanates, different chemistry for the synthesis of polyurethanes is used i.e. cyclic carbonate and amine chemistry. For using this chemistry, the three acrylic monomers, Glycidyl Methacrylate (GMA), Methyl Methacrylate (MMA), and Butyl Acrylate (BA) were copolymerized via solution polymerization technique, in N-methyl pyrrolidinone (NMP) as the reaction medium, and azobisisobutyronitrile (AIBN) as the initiator. The reaction was accompanied by the conversion of epoxy groups to cyclic carbonate groups, by the reaction of the epoxy group of GMA with carbon dioxide in presence of LiBr as a catalyst. The copolymer formed with epoxy and cyclic carbonate groups was cured with monomeric and polymeric diamines. Thin films of 50 µm were applied on steel panels and baked at 130 °C for 40 min. The mechanical optical and chemical resistance properties of the film were studied. The FTIR reports confirmed the polymerization, carbonation, and urethane linkage formation. The cyclic carbonate peak at 1800 cm−1 and urethane linkage at 3380 cm−1 and 1720 cm−1 appeared after carbonation and curing with diamine respectively. Films properties were best observed when cured with the polymeric diamine. This method is not only isocyanate-free but also utilizes carbon dioxide, and hence is sustainable and eco-friendly.