POLYESTER ADHESION TO CHROMIUM-COATED STEEL FOR POLY(ETHYLENE-TEREPHTHALATE) AND AN ISOPHTHALATE COPOLYMER

The performance of PET [poly(ethylene terephthalate)] and a copolymer of PET has been tested as an adhesive for chromium-coated steel. Crystallinity in the polyesters is found to limit adhesion, probably by restricting chain mobility. Lamination temperatures above the melting point of each polyester give the best adhesion. Degradation of the polyesters at yet higher temperature resulted in both reduced polymer cohesion and adhesion. Optimum bonding to steel was obtained at lamination temperatures between 230 and 275-degrees-C for the copolyester and between 280 and 300-degrees-C for PET. The standard laminate compression time was 15 min at 50 kg/cm2. Adhesion was evaluated by the ASTM T-peel test. Assessments were made by both the peel energy and the peak load for peel.