[Visible-light cured resin. Selection of reducing agent amine, its appropriate amount and effect on physical...

Studies were done to improve the physical properties, especially degree of conversion of visible-light cured resin (VLCR), and accordingly to lower its water sorption and solubility in water. Trial products of VLCR were prepared using various kinds of amine, reducing agent, and the photoinitiator to be mixed with cyclophosphazene monomer, 4 PN-(TF)1-(EMA)7. As amines ethyl-p-dimethylaminobenzoate (DMAB), methacryloxyethyl-p- dimethylaminobenzoate (DMAB-EMA) and methacryloxyglycidyl-p-dimethylaminobenzoate (DMAB-GMA) were used. Of their set products immersed in water and MeOH, their water sorption, solubility in water, MeOH sorption and solubility in MeOH were examined. The resin with DMAB-EMA used was preferable, showing comparatively small solubility. Next, VLCR, with various amounts of DMAB-EMA mixed, 0.5-5.0 in mol ratio to photosensitizer (CQ + DB), and of their set products water sorption, solubility in water, MeOH sorption, solubility in MeOH, THF sorption and their mechanical properties after immersion in water were examined. Immersion of the resin products in water and MeOH for 30 days, lowered the solubility in water and MeOH to a minimum at the mixing ratio of 3.0 in mol ratio. Solubility in MeOH (HPLC) became minimum at 2.0 in mol ratio, and at less than 2.0, the photosensitizer and monomer were dissolved, while at more than 2.0, the photosensitizer and DMAB-EMA were dissolved. THF sorption decreased in accordance with the increase in the mixed amount of DMAB-EMA, became almost constant at more than 3.0 in mol ratio. The compressive strength of set product after immersion in water for 7 days increased in accordance with the increase of the mixed amount of DMAB-EMA, while the transverse strength also increased up to 2.0 in mol ratio. The optimum reducing agent to be mixed with VLCR was DMAB-EMA, and the mixing ratio should be 2.0-3.0 in mol ratio to photosensitizer.