Exposure reciprocity law in photopolymerization of multi-functional acrylates and methacrylates

The applicability of the exposure reciprocity law (ERL) to the photopolymerization of acrylates and methacrylates was investigated. It was found that when the oligomer/monomer mass ratio in the systems studied was equal to or greater than 6:4, the ERL applied quite well. The applicability of the ERL to individual (meth)-acrylates was judged by comparing the ratio of I the lowest DC under one of the three I-t combinations to the highest DC under another I-t combination. The ERL is deemed to apply better to a monomer whose ratio is close to unity. It was found that the viscosity and the number of double bonds are two primary attributes. Photopolymerization of those with more than one double bond and with viscosity higher than 100-200 mPa center dot s closely obeys the ERL. This is because the two factors promote the realization of the reaction-diffusion-controlled process, which facilitates monomolecular termination of free radicals.