COMPARATIVE-STUDY OF PHOTOINITIATOR CURING EFFICIENCY USING REGRESSION DATA-ANALYSIS

Regression data analysis was used to compare two alphahydroxy ketone, 1-hydroxycyclohexyl phenyl ketone (HCPK) and 2-hydroxy-2-methyl-1pheny l-propan-1-one (HMPP) and two phosphine oxide, 2,4,6-trimethylbenzoyl diphenyl phosphine oxide (TPO) and bis (2,6-dimethoxybenzoyl) 2,4,4-tr imethyl pentyl phosphine oxide (DMBAPO) photoinitiators in a thin coat ing application. Phosphine oxide is inherently more efficient, especia lly in white pigmented systems than alpha hydroxy ketone because of it s stronger and broader adsorption at longer wavelength. Due to molecul ar weight dilution effect, it is usually required to have a higher TPO concentration in a formulation than HCPK or HMPP to overcome oxygen i nhibition. On the molecular level, however, DMBAPO is the most reactiv e photoinitiator among all of them. Data analysis also suggests that t he number of initiating free radicals generated by DMBAPO is twice of that generated by HCPK or HMPP or TPO. This study also confirms that i n thin coating applications the use of either nitrogen blanket or phot oinitiator blend is a good method for increasing productivity and redu cing formulation cost.