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Plate-out in PVC extrusion. II. Lubricant effects on the formation of die plate-out in lead-based rigid PVC formulations



Plate-out is an extrusion phenomenon that causes formulators and processors significant problems when processing poly(vinyl chloride) (PVC). It is an unwanted deposit that forms on the die, calibration, and degassing sections of extrusion equipment that can cause unacceptable streaking and scoring on the final product through continued deposition. In a previous paper, the authors used a range of analytical techniques to identify inorganic and organic components found in samples of industrial plate-out. This paper describes a laboratory methodology to determine the statistically significant properties of polyethylene wax lubricants that contribute to plate-out. A small-scale twin-screw extruder equipped with a plate-out-sensitive die was used to analyze lead-based window profile formulations containing various homopolymer grades of polyethylene wax and oxidized polyethylene or high-density polyethylene lubricants. The influence of these waxes on plate-out is explained in terms of generally accepted lubricant theory, as well as theory proposed by other workers, such as Lippoldt. © 2012 Society of Plastics Engineers.

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