EXPERIMENTAL-STUDY AND MODELING OF OSCILLATING FLOW OF HIGH-DENSITY POLYETHYLENES

The influence of flow rate and die geometry on the observable flow rat e/pressure relationship of a linear high density polyethylene is inves tigated using a capillary rheometer. The experimental results are appl ied to an adapted version of the relaxation-oscillation model proposed by Molenaar and Koopmans for describing the oscillating flow regime. The current model allows for a quantitative description of the hystere sis cycle in the oscillating flow regime in terms of the main experime ntal variables, such as imposed flow rate, reservoir (barrel) volume, and material compressibility. (C) 1996 Society of Rheology.