Vitrification of photo-curing resins by embedded cantilever and Fizeau interferometer

摘要

We present a method for estimating the relative viscosity and vitrification degree of photo-curing polymeric materials. Real-time knowing of solidification transition provides important information for many scientific areas. The technique involves the embedding of one end of a small aluminum cantilever subjected to oscillations of constant amplitude and frequency, into blends made of unfilled dental resins based on bis-GMA-TEGDMA. These resins were activated for visible light polymerization by the addition of camphorquinone (CQ) in combination with dimethylamino ethylmethacrylate (DMAEMA), or ethyl-4-dimethyl aminobenzoate (EDMAB). As the polymerization process progresses, the embedded end of the beam ceases to be free. Thus, changes in the oscillation amplitude at a given point near the lower end measured by a Fizeau fiber optic interferometer can be interpreted as a proportional indicator of solidification in the resin being photocured. Proper measurement of this phenomenon provides a more quantitative support in the early stages of photo-polymerization. Our results show that the resin passes from liquid to gel, and then to a vitreous state, in a short time compared with the total photo-curing evolution. As a consequence, after this transition, polymerization seems to develop mainly by diffusive processes.