PHOTOINITIATED POLYMERIZATION OF A DIMETHACRYLATE OLIGOMER .1. INFLUENCE OF PHOTOINITIATOR CONCENTRATION, TEMPERATURE AND LIGHT-INTENSITY

The photoinitiated polymerization of dimethacrylate oligomer with 2,2- dimethyl-2-hydroxy acetophenone (Darocur 1173) as radical photoinitiat or was studied by using isothermal photocalorimetry. The effect of tem perature, light intensity and photoinitiator concentration on reaction was investigated. The maximum conversion was obtained at temperature near 90 degrees C. This temperature is above the glass transition temp erature of the resulting material and below the thermal polymerization temperature of the reacting system. Above 90 degrees C, thermal polym erization interferes on photocalorimetric measures. Assuming that glas s transition temperature of the final polymer and conversion are conne cted, we have estimated thermal conversion. A maximum conversion was o btained for a photoinitiator concentration of 1% (w/w) and for the hig hest light intensity studied (2.7 mW cm(-2)). (C) 1997 Elsevier Scienc e Ltd.