Predicting Blown Film Residual Stress Levels Influences on Properties, 2006 PLACE Conference

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The blown film process extrudes polymer melt from the extruder through an annular die where the bubble is inflated and drawn in the machine and cross directions while being cooled by an air ring system. The extension and cooling play critical roles in this process, directly affecting the residual stress level developed. The residual stress can significantly influence film properties. A new extensional viscosity model was developed to predict the stress developed in the bubble. The bubble cooling effects and crystallization were characterized along the bubble. The results are correlated to changes measured in film properties. How the processing conditions can be modified to provide improved film properties will be discussed.