Wall slip of molten high density polyethylene. I. Sliding plate rheometer studies

Abstract

SynopsisExperiments were performed in a sliding plate rheometer with a high density polyethylene to determine the conditions for the onset of slip and the relationship between slip velocity and shear stress. It was found that melt slip occurs at a critical shear stress of approximately 0.09 MPa in both steady and transient shear tests. The effect of the presence of a layer of fluorocarbon at the interface on both the slip velocity and the critical shear stress for the onset of slip, was also studied. Exponential shear was used to study the effect of shear history on slip. Roth steady state and dynamic models for the slip velocity are proposed that are consistent with the experimental observations. Results of oscillatory shear experiments suggest that melt slip is a physicochemical process in which the polymer-wall interface undergoes continuous change during successive cycles.

Rheo-PIV of a shear-banding wormlike micellar solution under large amplitude oscillatory shear

“…It is the appearance and growth of these higher harmonics that lead to the progressive deviation of the shear stress magnitude mea- One interesting aspect of figure 12 (d) is the appearance of a more enhanced even harmonic at ω = 2ω d in the imaginary part of the discrete Fourier transform of the stress response. This suggests that there may be a small amount of wall slip occurring in the system (Hatzikiriakos and Dealy, 1991;Atalik and Keunings, 2004) however the fact that this harmonic is still relatively weak (a factor of 4 weaker than the intensity of the third harmonic at ω = 3ω d ) means that any wall slip that may be occurring is difficult to discern in figures 12 (a) and (b) and does not significantly affect the material response.…”

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

“…The various experimental methods of determining wall slip velocity can be found in an excellent review by Hatzikiriakos [19]. Classic gap-dependence methods, such as Mooney's method [20] and the sliding plate rheometer [17], need a series of capillaries/slits with different diameters or thicknesses. Flow visualization with optical techniques involves additional equipment, such as tracing particles and specially designed monitoring systems.…”

“…Slip of polymer melts is explained by flow induced chain detachment/desorption and chain disentanglement. According to Hatzikiriakos & Dealy's experiments with sliding plate and capillary rheometers [17,18], wall slip occurs when the shear stress exceeds a critical stress, which is around 0.1MPa for Polyethylene. The various experimental methods of determining wall slip velocity can be found in an excellent review by Hatzikiriakos [19].…”

“…Therefore, the relative slip velocity was defined as slip velocity over the maximum slip velocity (u s /u s(max) ) in order to describe the slip behaviour for different thickness slit cavities. Assuming the power law index m=3 [17], the defined relative slip velocity is shown in Fig. 16.…”

Theoretical and experimental research on the friction coefficient of water lubricated bearing with consideration of wall slip effects

“…When the velocity meets the requirement u > u c , we can not say that all the lubricant molecules on the surface occur to slip. Some of the literatures [23,[27][28][29][30] have proposed a simple criterion to distinguish whether wall slip effect has occurred on the solid-liquid interface through theoretical and experimental researches. When the interface tension of the lubricant medium becomes bigger than that of the friction pair material, namely, adhesion fracture occurs before the cohesive fracture of molecular bonds, then the wall slip is very likely to happen.…”