Theoretical prediction of the pressure gradients in coextrusion of non‐newtonian fluids

Abstract

AbstractIn previous publications we have reported our experimental observations that, when the less viscous component flows outside the more viscous component in sheath‐core coextrusion through a cylindrical die, or in sandwich three layer film coextrusion through a slit die, the pressure gradients in a two‐phase system can be lower than those in the two components flowing individually. The experimental observations suggest that the energy requirement for extrusion can be decreased, and the throughput increased, when one judiciously chooses proper combinations of materials and/or optimal processing conditions. In this paper, we present a theoretical analysis, which shows that the seemingly anomalous behavior of the experimentally observed pressure gradient reduction is indeed possible, depending on the rheological properties of the individual components involved in coextrusion.