Multiplet relaxation transitions in fluorurethane coating after climate aging

The relaxation transition from a glassy to a highly elastic state (α-transition) of a fluoropolyurethane coating deposited on the surface of VPS-48/778 glass fiber reinforced plastic was studied using the method of dynamic mechanical analysis. It is shown that the relaxation maximum of the dynamic loss modulus in the initial state is a superposition of α1-, α2-, α3-transitions, corresponding, respectively, to transitions from the glassy to highly elastic state of VE-69 enamel and EP-0215 epoxy primer. The transition temperature α1, which is the glass transition temperature of fluoropolyurethane VE-69, after 3 years of exposure decreases in proportion to the average annual air temperature of the region. The transition temperatures α2 and α3 after full-scale exposure due to post-curing increased by 13−15°C and acquired stable values α2 = 99 ± 1°C, α3 = 122.5 ± 0.5°C, regardless of the climatic conditions of the tests.