Model of UV-curing thickness for new thiol-ene resin for additive manufacturing of energetic materials

A new type of photocurable resin, which can be used for additive manufacturing of energetic materials, was prepared by modified polyether and multifunctional mercaptan. For the curing progress of this resin in a single layer of digital light processing (DLP), we incorporate micro-dynamical mechanism of free-radical photopolymerizations into the thickness-time equation to show how the curing thickness varies with initiator concentration ([I]) and incident light intensity (I₀). We show that the temporal variation of curing thickness depends on two key parameters: the characteristic penetration depth h_a = 1/(ε₁[I]+α₀), where ε₁ is the molar extinction coefficients of initiator and α₀ is the absorption coefficient of oligomer, and critical time T_c = -ln(1-Φ_c)/(kI₀^0.5[I]^0.5), where Φ_c is the gel point of monomer and k is rate constant. Here, we consider the effects of [I] and I₀ to the characteristic penetration depth h_a and the critical time T_c in the early stage of radical polymerization, which means that the concentration of initiator and monomer could be deemed as constants. As predicted by the model, T_c is a linear function of 1/ I₀^0.5 and 1/[I]^0.5. Validation experiments show that the curing thickness predicted by the model is in good agreement with the experimental data. These results can be used for the accurate prediction of parameter setting of 3D printing and the component proportion of resin.