PMMA is a very clear very hard abrasion resistant coating, but it has quite low elongation at break. Plastics also typically have about 10 times the coefficient of expansion as metals and to compound the problem, the coefficient of expansion is higher during the phase change from liquid to solid.
You need something with higher elongation at break. There are impact modified acrylics or copolymers, polycarbonate, polyurethanes and polyesters to consider.
Regards
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