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Investigations were undertaken to find the influence of the initial viscosity of a photocurable system on its photopolymerization kinetics. The model monomers were methacrylic acid (MAA) and bis-GMA. The initial viscosities of the systems were manipulated by adding to the monomers a constant amount (by weight) of poly(oxyethylene)diols of various molecular weights (in the range of 106 — 35000). The ratios of the bimolecular termination rate coefficient to the propagation rate coefficient were determined for each system investigated as a function of the initial system viscosity and of the double bond conversion. It was found that the increase in the initial viscosity can lead either to acceleration or to retardation of the polymerization, depending on monomer structure and its viscosity, but usually decreases the final conversion.
