A modelling study of the visco-elastic behaviour of polyester-based coil coatings

The time and temperature dependence of the mechanical response of a series of polyester-based hexa(methoxymethyl)melamine cross-linked coil coatings was investigated. Small strain experiments such as dynamic mechanical analysis and stress relaxation are used to determine the parameters required for time-temperature superposition and for the determination of the relaxation spectra of the materials. Tensile tests at a range of temperatures and strain rates are used to show that time-temperature superposition can be successfully extended to cover the ultimate properties of the paints (i.e. those at fracture). Finally, a hybrid visco-elastic/hyper-elastic model is used to capture the tensile stress-strain response of the paints. The success of the visco-elastic component of the model is demonstrated at strains up to 5%, while at larger strains the model behaves best when the experimental behaviour of the material approaches that of rubber, with the fit becoming worse when the mechanical response is that of a ductile plastic.