Wall slip and spurt flow of polybutadiene

• Published in: Journal of rheology (New York : 1978) Vol. 52; no. 5; pp. 1201 - 1239
• Main Authors: Park, Hee Eon, Lim, Sung Taek, Smillo, Fabricio, Dealy, John M., Robertson, Christopher G.
• Format: Journal Article
• Language: English
• Published: Melville, NY The Society of Rheology 01.09.2008; Society of Rheology
• Subjects: Adhesive slip; Capillary rheometer; Cohesive slip; Cox-Merz rule; Cross-disciplinary physics: materials science; rheology; Deformation; material flow; Effect of pressure; Exact sciences and technology; Maximum stress; Minimum stress; Peeling; Physics; Polybutadiene; Rheology; Rolling; Secondary flow; Sliding plate rheometer; Slip velocity; Spurt; Slip velocity; Maximum stress; Cox–Merz rule; Rolling; Peeling; Cohesive slip; Adhesive slip; Effect of pressure; Sliding plate rheometer; Capillary rheometer; Minimum stress; Polybutadiene; Spurt; Secondary flow; Slip flow; Rheology; Butadiene polymer; Boundary layers; Hydrodynamic instability
• ISSN: 0148-6055; 1520-8516
• DOI: 10.1122/1.2964199

Spurt occurs in the flow of entangled melts in a capillary rheometer in which the driving pressure is controlled. As the driving pressure increases, at a critical value there is a sudden increase in flow rate, often called spurt. This discontinuity is followed by another regime of smoothly increasing flow rate. A phenomenon that may contribute to this instability is a curve of wall shear stress versus slip velocity that has a maximum followed by a minimum, and there are models that predict such behavior. We used a sliding plate rheometer (SPR) to study wall slip for a highly entangled, linear polybutadiene at 1 atm and at 46 MPa . By varying the plate speed, we were able to explore the entire curve of shear stress versus slip velocity. This curve exhibited a maximum and a minimum in the stress, providing support for theories predicting this behavior and an explanation for the spurt effect in capillary rheometry. The spurt flow of the same polymer was also observed, and slip velocities were estimated and compared with those determined using the SPR. The slip velocities obtained using the two instruments were in good agreement.