Polycarboate is a plastic, which is very good at resisting impacts without puncturing or shattering. If thick enough it is bullet proof. It has a specific gravity of about 1100 Kg m cubed compared to steel of 7600 Kg m cubed so just under 7 times lighter than steel for a given volume and so is very popular as additional armour for Robot Wars.
Ultra Violet Light
Unfotunatly Polycarbonate degrade in ultra violet light where it becomes weak and brittle, so don't leave it in bright sun light for long periods, test any you are give by either hitting it with a hammer or try bending it. If it shatters throw it away.
If you want to paint polycarbonate use the paints designed for polycarbonate, as most react with the polycarbonate and make it soft. We did some tests by painting some samples and then trying to bending them. The painted samples where very easy to bend. For Miss Struts we used two layers of ploycarbnate, a very thin one we painted and a thick one on the outside as the armour.
We also found painting polycarbonate very difficult, the paint will not stick to it, so we roughed up the surface using an electric sander.
The best advise is don't paint it.
Polycarbonate is quite esay to cut, and so is not good armour against cutting weapons.
We cut polycarbonate using an electric jigsaw