Characterization of Polymer Flows in Very Thin Gaps

The flow of polymers in micromolding applications is dominated by shear stresses. At high flow velocities and small wall thicknesses, the shear rates can exceed the typical characterization scheme of 10,000 reciprocal seconds. Yet, the effective design of micromolded parts and micromolding processes requires a correct understanding of the flow dynamics. In this paper, analytical models assuming power law fluid behavior are developed and experimentally validated for wall thicknesses of 10, 20, and 100 micro meters. A design of experiments is conducted to consider the effect of wall thickness, channel width, melt temperature, and pressure on flow rate in an isothermal molding process. The results indicate that the power law model is a valid representation for viscous polymer flow in very thin gaps under isothermal conditions, though further work is required to validate the non-isothermal dynamics.