Polymerization kinetics of acrylate monomers under UV/EB radiation: from labscale monitoring to the modelling of industrial curing

Electron beam curing (EBC) is foreseen as a promising technology for the fabrication of carbon fiber reinforced aeronautic and space structures. Epoxy acrylate resins and adhesives have been developed for this purpose. These new applications require high mechanical performances over a broad range of service temperature. A model was developed to predict the polymerization of acrylate resins in order to limit time and cost of development. This paper presents the different investigations conducted to examine the effects of dose and dose rate distribution, the evaluation of the temperature map during irradiation and finally the evolution of degree of curing in correlation with Tg. The radiation-induced polymerization of an epoxy acrylate formulation has been investigated with laboratory samples and equipments to set the bases of a model for the curing kinetics. The conversion versus dose profiles were monitored with a very high resolution by means of FTIR spectroscopy in various curing conditions (dose rates and temperatures). The resulting data were analyzed and correlated to the progress of vitrification measured by thermomechanical analysis. A model including the WLF relation for combining the two contributions was proposed and describes satisfactorily the observed conversion—dose profiles. The mode! was adapted for describing the actual thermal and conversion profiles seen by acrylate matrix under industrial curing conditions with the 10 MeV - 20 kW Unipolis facility. This model allows to predict the thermal history and the final thermomechanical Tg of the matrix in a given volume element treated with a specific dose-time profile.