Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Plastic profile die design is a complex task because of cross section area and shape changes occurring after die exit. Dimensions of the profile are increased by the extrudate swell phenomenon and decreased by drawdown and shrinkage. An experimental study on the effect of processing conditions on extrudate swell and on the shape of a rectangular profile was done for rigid poly(vinyl chloride), PVC, and high density polyethylene, HDPE, resins. Extrudate swell was found to be a strong decreasing function of residence time in the die and also, for short dies, of entrance geometry. For PVC, equilibrium swell increased with melt temperature. The differences in swelling for the two polymers are explained with the help of creep/recovery data obtained on a stress rheometer. Drawdown, die land length, and melt temperature were shown to have an important effect on the shape of a rectangular profile. Decreasing the die land and increasing the melt temperature had the effect of increasing preferably the thickness while drawdown, by inhibiting the swelling, decreased the thickness.
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