Thermal birefringence in freely quenched multilayered slabs of amorphous polymers: experiment and simulation

The simulation of the gapwise distribution of the thermally-induced residual birefringence and stresses in freely-quenched PS-PC-PS and PC-PS-PC multi-layered slabs in water was carried out to calculate the gapwise distribution of the transient and residual birefringence. The modeling was based on the linear viscoelastic and photoviscoelastic constitutive equations combined with the first-order rate equation for volume relaxation. The master curves for the Young's relaxation modulus and strain-optical coefficient functions obtained earlier for PS and PC were used in the simulations. The obtained numerical results provided the evolution of the thermally-induced stress and birefringence with time during and after quenching. The predicted gapwise residual birefringence distribution in these slabs was found to be in a fair agreement with the measured results. In addition, the gapwise distribution of the thermally-induced residual birefringence in the multi-layered PS-PMMA-PS, PMMA-PS-PMMA, PMMA-PC-PMMA, and PC-PMMA-PC slabs quenched from different initial temperatures was measured. Explanations were provided for the observed gapwise distribution of the thermal residual birefringence in each layer of these slabs including the effect of the initial temperature.
INTRODUCTION During polymer processing, the polymer undergoes simultaneous mechanical and thermal influences in the fluid, rubbery, and glassy states. These effects introduce orientation, residual stresses, and shrinkage in the products [...]