Accounting for Spatial Variations during Photopolymerization of
1,6-hexane-diol Diacrylate in the Presence of Oxygen
Abstract
A dynamic model is proposed for photopolymerization of 1,6-hexane-diol
diacrylate (HDDA) with bifunctional initiator bis-acylphosphine oxide
(BAPO) in the presence of oxygen. This partial-differential-equation
(PDE) model predicts time- and spatially-varying vinyl-group conversion
as well as concentrations of monomer, initiator, oxygen, and seven types
of radicals. Experiments to obtain diffusivities of oxygen, BAPO and
HDDA are reported. Oxygen-related parameters are estimated using
real-time Fourier-transform infrared (FTIR) conversion data. FTIR
experiments were conducted using a range of film thicknesses (8-17 μm),
BAPO levels (1-4 wt%) and light intensities (200-6000 W/m^2). The
model predicts qualitative trends. Conversion predictions for runs with
high intensities (≥5000 W/m^2) and high BAPO (4 wt%) are accurate
with a root-mean-squared error (RMSE) of 0.04. Larger RMSE (0.13) for
runs with lower intensities and BAPO indicates that improved parameter
estimates are required. Parameter estimates will be updated using in
future using a model that accounts for shrinkage during polymerization.