Predicting photopolymer resin pyrolysis kinetics in ceramic vat photopolymerization additive manufacturing

Abstract

The kinetics of polymers pyrolysis, particularly those containing ethoxylated trimethylolpropane triacrylate ((EtO)₃-TMTPA), is of utmost importance in optimizing the binder removal process that is associated with ceramic vat photopolymerization (CerVPP). Here, we focus on the decomposition kinetics of a simplified resin, which is a photopolymer system that is formulated from (EtO)₃-TMTPA and a photoinitiator (diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide). The thermal behavior of the resin was critically assessed with the use of thermogravimetric analysis (TGA) under atmospheric pressure in a flowing argon gas atmosphere. The Fraser‒Suzuki function was used to deconvolve the TGA peaks in conjunction with nonlinear regression that was based on a finite difference solution of the nonlinear rate equation. From this analysis, pertinent kinetic parameters were obtained. The variation of the kinetic parameters was studied as a function of heating rate. The resulting model allowed for the prediction of thermal decomposition behavior of CerVPP resins for a representative, simulated, yet practical heating rate program. This prediction was compared to TGA measured resin decomposition using the same heating rate program. The model's predictions accurately identified the two primary apparent reaction steps displayed in the differential TGA data.