Quinone-amine polyurethanes: novel corrosion-inhibiting coupling agents for bonding epoxy to steel

A novel series of quinone-amine polyurethanes (QAPs) were synthesized and t ested for their efficiency as corrosion-inhibiting polymeric coupling agent s to enhance the adhesion of epoxy to steel. These polymers were characteri zed using infrared spectroscopy, thermal analysis methods (TGA and DSC), te nsile testing, and gel permeation chromatography. The coupling agent-treate d epoxy-steel torsional joints were tested (dry and after wet environments) in shear, These joints demonstrated a 10-15% dry strength improvement when compared with epoxy-steel control joints. The coupling agent-treated epoxy -steel joints also exhibited excellent hot water (60 degrees C) durability while the epoxy-steel control joints fell apart in 3 days, Epoxy-steel lap shear joints were made with the QAP coupling agents and fractured in shear to study the locus of failure. These joints fail either close to the coupli ng agent-epoxy resin interface or inside the epoxy resin. Steel coupons wer e treated with the QAP coupling agent and top-coated with epoxy resin for t esting in a lab-scale salt-spray chamber. These coupons demonstrated excell ent corrosion resistance when tested for over lj days. The QAPs can serve a s very effective corrosion-inhibiting coupling agents for the epoxy-steel s ystem.