A modified microscale viscosity model of polymer melts and experimental verification

Abstract

During the micro‐molding of polymer melts, ensuring the viscosity models' accuracy was essential. Existing models had neglected the temperature dependence of microscale factor, rendering them unsuitable for materials with varying temperature sensitivities. This research employed a twin‐bore capillary rheometer and dies of distinct characteristic dimensions as the experimental setup to investigate the viscosity variations across four materials exhibiting diverse temperature sensitivities. A modified MCA viscosity model was established by integrating a microscale factor that accounted for both dimension and temperature dependence into the macroscopic Carreau viscosity model. The traditional MCAc model, which ignored the microscale factor's temperature dependence, offered a comparative reference. These models were subsequently applied to evaluate the influence of coupling effects between viscosity and viscous dissipation on melt temperature, with results compared to experimental data. The results indicated that the MCA model's viscosity forecasts were in closer accord with experimental measurements, maintaining an accuracy within a 16% margin. The models' application to temperature calculations under varying inlet velocities and temperatures confirmed that the MCA model's predictions of the temperature increase along the flow direction were more congruent with experimental outcomes, underscoring the critical importance of incorporating both dimension and temperature dependence when establish microscale viscosity models.