Bisphenol A polycarbonate has become one of the most important high-tech materials with its high light transmittance, high impact resistance, good temperature resistance and excellent creep resistance.
PC sheets produced with it as raw material currently have great application prospects in aerospace, high-speed trains, automobiles and other fields, but PC sheets have low surface hardness and poor wear resistance, especially poor resistance to UV aging, which leads to a short service life and greatly limits its application.
Due to the poor UV resistance of PC sheet surface, coating technology came into being. Acrylic resin coating, as a coating material that has developed well in recent years, has a series of advantages.
It can bond well to the substrate and has good film-forming properties. The formed coating is transparent, flexible and elastic, and the coating itself has certain aging resistance. The greater advantage is that the adhesion between acrylic resin and PC surface is very good. The bonding performance of the coating and the substrate has a great influence on the surface hardness of the coating.
Of course, the important thing is that UV coating changes many properties of PC board.
Transmittance：
The transmittance and haze of the uncoated PC board are 87% and 0.4% respectively, while the transmittance of the coated PC board is above 87% and slightly higher than that of the uncoated PC board.
This is because the refractive index of the uncoated PC board is 1.586, while the refractive index of the acrylate coating is lower than this value. According to classical optical theory, when the refractive index of the coating is lower than that of the substrate, the coating has an anti-reflection effect on the substrate, so the acrylate UV coating has a certain anti-reflection effect.
Surface hardness：
The hardness of the coated PC board surface is not high, which is equivalent to the hardness of the uncoated PC board, and there is not much improvement, both below 1H. However, the adhesion of the coating is good, reaching 5B. This is determined by the properties of acrylic resin, which has a low hardness and good adhesion to PC, so the adhesion is good. Therefore, considering the flatness and surface hardness of the coating, the content of UV coating cannot exceed 1%.
UV resistance：
Under the same UV radiation, as the UV aging time increases, the transmittance of the uncoated PC board decreases slightly, while the transmittance of the coated PC board hardly changes.
However, the yellow index of the uncoated PC board increases from 0.6 to 11, while the yellow index of the coated PC board is around 1, which is almost unaffected by UV radiation and remains colorless and transparent. This shows that the acrylic UV coating greatly improves the UV resistance of the PC board.
Mechanical properties：
Compared with the uncoated PC board, the tensile strength and elongation at break of the coated PC board are slightly reduced, because the coating destroys the PC surface layer. However, the thickness of the damaged layer is very thin, so the impact is not significant, and the cantilever beam unnotched impact strength shows that the board is not broken and still has the excellent toughness of PC.
In short, the coating does not have much effect on the mechanical properties of the PC board, and it can still maintain the original mechanical properties.
Our company's T-7020 T-7080 is suitable for use in PVC TPU PC and other plastic coil coatings. It has chemical resistance and iodine resistance. We also have other resins to share.
