A method for polymethymetacrylate coating via self-curable unsaturated polyester primer on metal and glass surfaces

Abstract

A method was developed for protective coating of steel and glass surfaces with poly(methylmethacrylate) (PMMA). In this method, first, a primer coating was formed on the flat surfaces using self-curable polyester, poly(2-hydoxypropyl maleate) (Polymer-1). The polyester was applied onto polished surfaces and heated at 180 °C for 15–120 min to obtain transparent and crosslinked primer layer without using additional crosslinker. Extent of the crosslinking was followed by real time IR methodology, based on decreasing intensity of the maleate double bond vibration at 1640 cm −1. Experiments revealed that the crosslinking (15.4% within 1 h) occurs by addition of hydroxyl groups to the double bonds in the curing process. The top coating with PMMA was performed by crosslinking photo polymerization of methylmethacrylate on the primer in presence of functional polyester (Polymer-2) having methacrylate pendant units. Thus UV irradiation at 350 nm (1.03 × 10 −3 mW cm −2) for 30 min gave crosslinked PMMA coating layer with a Rocker hardness of 4. Real time IR studies revealed that more than 84.6% of the methacrylate groups disappear within 1 h of irradiation. Excellent adhesiveness of the top coating (5B) was ascribed to possible grafting of MMA through the residual maleate double bonds on the primer. Standard coating tests (contact angle, adhesion, hardness, flexibility and acid–base resistance) indicated that the method presented is versatile in coating of metal or glass surfaces with smooth PMMA layer.