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Abstract

Model predictions are presented for the blown film extrusion of low- and linear low-density polyethylenes (LDPE and LLDPE). A modified version of the two-phase Doufas–McHugh model is developed that includes the semi-crystalline rigid rod phase from the beginning at the exit die. This approach removes the artificial switch point built into the previous model version, thereby eliminating the underlying discontinuities and resulting in a more robust model. This improved model is capable of fitting LLDPE and LDPE data over a broader range of blow-up ratio (BUR) and inflation pressure ΔP while using only one set of fitting parameters per material. Model data fits of bubble radius, temperature and crystallinity are shown for each material. The radius and temperature predictions are excellent, while the crystallinity predictions agree favourably with the experimental data.

Keywords

BLOWN FILM EXTRUSION NUMERICAL MODELLING FLOW-ENHANCED CRYSTALLISATION LOW- AND LINEAR LOW-DENSITY POLYETHYLENE

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Microstructure and kinematic aspects of blown film extrusion process: II. Numerical modelling and prediction of LLDPE and LDPE

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