Physical ageing of coil coatings

摘要

T-bend tests were performed on different coil coated panels at various times after their application. The flexibility of the coatings changed with time. This evolution was attributed to the physical ageing of the coatings because they were not subjected to any other ageing factor. DSC measurements showed that the coatings had different rates of ageing and different magnitudes of ageing explaining that their ranking according to their flexibility was time dependent. A method to predict the ranking of coatings according to their physical ageing at equilibrium is proposed. It consists in measuring the ageing by DSC at a temperature T below the Tg so that the difference (Tg-T) is kept identical for all coatings. A correlation between the T-bend test results and those based on the DSC method was obtained.