A New High-Throughput Screening Tool for the Evaluation of Pigmented UV-A Curable Coatings-A Case Study Using Low Energy Lamps

摘要

Pigmented UV radiation curable coatings have been a challenge to the coatings formulator for a long time.A critical match of pigment and photoinitiator package is crucial for good cure.Another issue facing the coatings chemist is the popularity of low energy lamps,which offer ease of handling,reduced safety efforts,and a significantly lower price tag.Obviously the combination of pigmented coatings and low energy lamps poses a special challenge.Oxygen inhibition of the coatings' surface is a major issue in any low energy light curing application.Efficient through-cure is difficult under high pigment to binder (p/b) ratios,because the low energy radiation can not easily penetrate through the coating.In order to speed up the development cycle,a rapid workflow was needed to screen pigmented formulations for cure under low energy UV-A radiation.For these types of applications a high-throughput screening assay for discovering desirable photoinitiator packages was developed.Fluorescent dye-doped coatings cured under UV-A radiation were extracted with solvent.The relative degree of cure of the film was determined to be inversely related to a combination of the absorbance and fluorescence of the extractant.When this assay is used in conjunction with automated liquid handling and a spectrophotometer with a x-y scanning stage,the coatings formulator can analyze a large variable set in a short period of time.A primary screening of photoinitiator packages using this workflow will be presented.