Dual-cure photochemical/thermal polymerization of acrylates: a photoassisted process at low light intensity

The dual-cure polymerization of an acrylate resin was investigated by combining a conventional technique (temperature measurement at the surface and in the deep zone) with confocal Raman microscopy. Polymerization was first characterized using a thermal initiator alone. Results showed that the thermal system polymerizes slowly and gradually, generating a thermal front that propagates from the bottom of the sample to the surface. Then, a photoinitiator was added to this thermal system. Unexpectedly, at the beginning of the reaction, the addition slows down the thermal polymerization reaction. But quickly, the reaction is accelerated and an almost fully cured material is obtained in a shorter time than the net thermal system. This behaviour highlights a surprising synergistic effect between the photoinitiator and the thermal initiator in the dual-cure polymerization of thick materials.