Tracking lubricants during single screw extrusion of uPVC

Barnard, J. L. ; Robertson, D. D. ; Van Reenen, A. J. (2020-04-02)

CITATION: Barnard, J. L., Robertson, D. D. & Van Reenen, A. J. 2020. Tracking lubricants during single screw extrusion of uPVC. Polymer Testing, 87:106523, doi:10.1016/j.polymertesting.2020.106523.

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Lubrication is one of the most important parameters in unplasticized polyvinyl chloride (uPVC) processing apart from the PVC resin and processing equipment. Lubricants are used in specific ratios to ensure effective fusion of PVC particles. The exact mechanism on how these lubricants interact is not yet fully understood. A widely accepted theory is the interaction mechanism proposed by Rabinovic et al. where lubricants are said to act as surfactants and slip agents. In this study a method for tracking lubricants, by simulating the extrusion process within a single screw extruder, was proposed. A three stage fusion simulation consisted of the feeding zone (stage 1), the compression zone (stage 2) and the metering zone (stage 3). The association interactions between the individual components of a typical uPVC formulation were followed throughout the three stages. External polar and nonpolar lubricants in combination with an internal lubricant was studied. Lubricants were successfully tracked using scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). In conclusion it was found that the use of an internal lubricant promotes dispersion of external lubrication towards PVC. It was also found that there is a competition between the internal lubricant and polar external lubricant.

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