ON THE POLYMER EFFECT OBSERVED WITH MACROMOLECULAR PHOTOINITIATORS - A STUDY OF THE VISCOSITY EFFECT ON THE STARTING POLYMERIZATION RATE

Photopolymerizable acrylate compositions including small amounts of po ly(butyl acrylate) were submitted to photocalorimetric measurements in order to investigate the effect of the mixture viscosity at zero conv ersion on the initial polymerization kinetics. No significant change o f the initial polymerization rate profile was observed for starting vi scosities ranging between 4 and 36 mPa.s and for a given concentration of low molecular weight photoinitiating system of the benzophenone-am ine type. This demonstrates that the polymer effect that leads to a hi gher value of the initial polymerization rate (R-p)(0) when using an a nalogous photoinitiating system with the same content in polymeric ben zophenone chromophores cannot be ascribed to the higher viscosity at z ero conversion that results from the presence of the photosensitive ma cromolecules.