We propose a simple method of measuring polymerization-shrinkage evolution during curing in photopolymer. The real-time spectral fringe analysis of a broadband beam transmitted through a Fabry-Pérot etalon supported by a photopolymer film provides the shrinkage evolution during curing. For the proof-of-principle demonstration a blue-sensitized nanoparticle-polymer composite material is used. It is shown that the measured shrinkage dynamics are well correlated with the photo-calorimetric conversion dynamics of monomer to polymer. We also discuss a discrepancy in steady-state shrinkage between our proposed and holographic Bragg-angle detuning measurements.

We report on the photopolymerization dynamics and the volume holographic recording properties of a thiol-ene based nanoparticle-polymer composite (NPC) doped with a blue-sensitive photoinitiator, Darocur V R TPO, by using a highly coherent blue diode laser operating at a wavelength of 404 nm. Our study indicates that volume gratings recorded in the NPC amount to meeting the material requirements of refractive index modulation and material recording sensitivity for holographic data storage media. It is also found that polymerization shrinkage of recorded NPC gratings is higher than that of the same thiol-ene based NPC with a green (523 nm)-sensitive photoinitiator, Irgacure V R 784/BzO 2 . We attribute such a difference in shrinkage to the photopolymerization dynamics at these recording wavelengths. We show that this shrinkage increase at 404 nm can be mitigated to some extent by controlling the thiol-ene stoichiometry in the NPC. V C 2015 AIP Publishing LLC. [http://dx.

A new monitoring method for the curing process of matrix resin is proposed. In this method, a high-frequency electromagnetic wave transmission line is constructed inside or on the surface of a material and changes in the characteristics of the line during the curing process are measured. The use of a high-frequency electromagnetic wave mainly aims at getting information on the position of the discontinuity or distribution of material properties, making use of its short wavelength. As the first step of the investigations, an experimental setup of a microstrip line and a parallel-wire line was constructed, and changes in the frequency characteristics of reflectance from each of the lines were monitored during the curing of epoxy resin between the pair of conductors of the line. Changes in the characteristics when the resin is partly filled were also investigated to examine the possibility of detecting local distributions or discontinuities. The experimental results are successfully explained by theoretical calculations. Results obtained in this study suggest the potential of the transmission line of a high-frequency electromagnetic wave as a tool for in-situ monitoring of curing and other properties.

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