A. Lawal et Dm. Kalyon, SINGLE-SCREW EXTRUSION OF VISCOPLASTIC FLUIDS SUBJECT TO DIFFERENT SLIP COEFFICIENTS AT SCREW AND BARREL SURFACES, Polymer engineering and science, 34(19), 1994, pp. 1471-1479
Commonly encountered viscoplastic fluids including concentrated suspen
sions of polymeric and ceramic composites, foams, gels, concrete, food
products, and energetic compounds exhibit wall slip during their flow
and processing. For some viscoplastics fluids, especially highly fill
ed suspensions, wall slip may dominate the flow and deformation and he
nce the processing behavior of the suspension The wall slip velocity i
s generally a function of the wall shear stress and temperature. Vario
us factors including the materials of construction i.e., chemical natu
re and the roughness of the wall surface affect the wall slip behavior
of viscoplastic fluids. In this study an analytical model of the extr
usion of viscoplastic fluids under isothermal and fully-developed cond
itions in shallow channels is developed. The model accommodates the us
e of different slip coefficients at barrel and screw surfaces. It thus
permits the investigation of effects of introducing different materia
ls of construction for the barrel and screw surfaces and development o
f design expressions.