Effects of surface roughness and the chemical structure of materials of construction on wall slip behavior of linear low density polyethylene in capillary flow

Abstract

SYNOPSISThe presence of wall slip during the flow of polymeric melts has significant ramifications on the melts' processability. In this study, the effects of materials of construction and surface roughness on the wall slip behavior of a linear low density polyethylene were investigated, using capillary flow. Capillaries, constructed from copper, stainless steel, aluminum, and glass, were used. The inner surface roughness of the capillaries were characterized by the employment of a profilometer and scanning electron microscopy. The roughness profiles of copper capillaries were also altered by the employment of chemical etching. Using Mooney's analysis, the wall slip velocity values were determined to be in the range of 0.09 to 1.34 mm/s. The wall slip velocity values were the highest for stainless steel and were negligible for aluminum. The relative work of adhesion values of polyethylene were the smallest for stainless steel and copper and the highest for glass. Overall, the wall slip velocity values increased with decreasing surface roughness of the capillaries and with decreasing work of adhesion.

Characterization of thermo-rheological behavior of polymer melts during the micro injection moulding process

“…However, a relative velocity exists at the contact line between the fluid and solid boundary during flow: this is the so called "wall slip" [16]. Slip of polymer melts is explained by flow induced chain detachment/desorption and chain disentanglement.…”

Global Concept for Describing and Investigation of Wall Slip Effects in the Extrusion Process

“…The interactions between the polymer and the metal wall were examined by observing the change in the flow curves when various additives, [2] surface treatments [9][10][11] and solids surfaces [9,12] are used.…”

“…[5,[14][15][16][17] This is confirmed by studies of the flow behavior of plastics in capillaries made of various materials. [9,12,14] The difficulty is to establish suitable descriptive characteristics from this data and to quantify their influence.…”

Analysis on creeping channel flows of compressible fluids subject to wall slip

“…Wall slip of fluids was generally overlooked in many studies but has recently gained an increasing attention in both experimental and theoretical investigations (Uhland 1976;de Gennes 1979;Chen et al 1993;Aral and Kalyon 1994;Denn 2001;Gevgilili and Kalyon 2001;Granick et al 2003;Neto et al 2005;Ballesta et al 2008). Slippage at wall leads to an increase in flow rate in a channel flow, affects flow profiles and the surface smoothness of extrudates emerging from extrusion dies, and plays a role in the development of various flow instabilities Yilmazer and Kalyon 1991;Hatzikiriakos and Dealy 1992a;Hatzikiriakos 1994;Kalyon and Gevgilili 2003).…”