Photopolymerisable formulations for enhanced properties of pigmented films

Ultraviolet (UV) curing is an important and widely used surface technology for coatings. The curable formulations containing: monomer: epoxydiacrylate, photoinitiating system: 4-methoxy-benzoyldiphenylphosphine oxide/2-hydroxy-2-methyl-1-phenyl-propan-1-one, additive reactive: tertiary amine, and inorganic thermoresistant pigments: white (TiO 2 ) and blue (Al 2 O 3 -Cr 2 O 3 ), were cured like films by UV exposure. A series of experiments was carried out in order to optimise the photoinitiator ratios in photoinitiating system, and pigment content in the photocurable formulation. Films with enhanced mechanical properties (pendulum hardness, scratch resistance), high resistance at solvents and good appearance were developed. In order to provide adequate hiding power of the pigmented formulation, the pigment content has been chosen in the range 5-15%. Up to 15% pigment content may affect the efficiency of photoinitiator. The polymerisation efficiency (conversion and polymerisation rates) of photoinitiating systems in pigmented formulations was performed by differential scanning photocalorimetry (photo DSC) in comparison with the original systems without pigments.