Microfluidics and rheology of carbon black suspensions for In-Mold Coating applications: some insights into the slip flow phenomena

Abstract

Microfluidics and rheology are critical to modeling material processes such as In-Mold Coating (IMC). In the IMC process, a carbon black suspension is injected onto the surface of the molded part while the part is still in the mold. Due to the microscopic length scale of the IMC flow (10–25 μm), a study of the slip flow and rheological properties at high shear rates of the coating liquid becomes significant. A customized microslit rheometer was developed and used to measure the viscosity of a coating material being considered for IMC in the channel gaps between 25 and 100 μm (C. Aramphongphun Ph.D. Dissertation, The Ohio State University, 2006). The results were interpreted assuming true slip at the wall. In this paper, we present further insights into the slip flow phenomena. It is assumed that there is a fluid layer of lower viscosity near the wall, which accounts for the appearance of slip. The previously obtained data is interpreted using this assumption.