Polyethylene melt interface studies

Since the Navier s slip hypothesis of the last century, most experiments have failed to obtain positive evidence for a slip boundary condition on macroscopic scales in low molar mass liquids. However, Navier s notion of slip turns out to be extremely useful and convenient for the latest description of flow anomalies of highly entangled polymer melts including linear polyethylenes (LPE). The ability of a melt/solid interface to possess two profoundly different states as shown by Fig. 4a,b clearly reveals the potential role of interfacial slip in governing various melt flow phenomena in high pressure extrusion. Before reviewing recent experimental studies that have elucidated the molecular origins of different flow... 

T in Fig. 14.1) and truly amorphous material (middle bar B in Fig. 14.1) - as a model for semicrystalline polyethylene. The goal of studying the interface between crystal and melt also at temperatures different than the melting temperature requires that one imposes certain constraints on the system to keep the interlameUar domain in a metastable state [27]. Crystallization at low temperatures is prevented by keeping the volume constant, while in order to prevent melting at high temperatures the crystal sites are immobile. 

Low density polyethylene (LDPE), high-impact polystyrene (HIPS), acrylonitrile butadiene styrene (ABS), and linear low density polyethylene (LLDPE) resins were used for this study. All resins were manufactured by The Dow Chemical Company. The flow rates for these resins are shown by Table 1. Coefficients of dynamic friction, shear stresses at the interface, and melting fluxes were reported previously for similar resins, but the data were not as comprehensive as those reported here, and most did not extend to high temperatures [1,3,5,9,10-12]. 

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