As 2 S 3 is one of the chalcogenide glasses that have attracted increasing interests for compression molding applications. This paper is aimed to evaluate the stress relaxation behavior of As 2 S 3 above its glass transition temperature and calculate its refractive index change during cooling. First of all, creep tests were conducted with cylinder glass specimens at three different temperatures, in order to deduce the shear stress relaxation function by using the relationship with creep compliance function. In addition, the shift factor for thermo-rheological simplicity using Williams-Landel-Ferry equation was obtained. Then, finite element simulation was implemented to verify the calculated shear stress relaxation function. The acquired shear stress relaxation function needs to be modified to compensate the influence of friction on the thickness change in the experiments, so that the simulation results using the modified shear stress relaxation would match the experiments better. Finally, the refractive index changes of As 2 S 3 at different cooling rates were modeled by using the Tool-Narayanaswamy-Moynihan model for structural relaxation behavior. It is confirmed that the slower the cooling rate is, the less the refractive index drop will be. It was also demonstrated that the refractive index drop is strictly dependent on the cooling rate logarithmically by using Tool-Narayanaswamy-Moynihan model. In summary, the results presented in this paper can provide reliable references for viscoelastic characterization of As 2 S 3 glass, crucial for compression molding or similar applications. K E Y W O R D SAs 2 S 3 , chalcogenide glass, compression molding, refractive index drop, stress and structural relaxation, viscoelastic

The development of flow‐induced stresses in extruded sheet made of polypropylene was analyzed. A theoretical model was developed to simulate velocity, temperature, and stress profiles for polymeric materials flowing inside a slit die. The output of this simulation was then used to compute temperature and stress profiles as the extrudate emerged from the die, cooled, and relaxed under no draw conditions. Simulated surface stresses and stress profile across the extruded sheet agreed well with the experimental data for the die temperature effect and the die gap effect at low draw ratios.

Analysis of a plastic sheet extrusion line was carried out using a 2. 5-in. extruder