oa South African Journal of Chemical Engineering - Evaluation of commercial plastics purging compounds on a laboratory film blower
Application of purge compounds allows rapid colour and material changes in plasics converting machines. They have both a cleaning and a purging action. In this paper we postulate that slip flow patterns can contribute to a purging action. This implies that the cleaning and purging functions can have conflicting requirements with respect to the wall shear stress. Commercial purge products function according to additional methods including filler abrasion, solvent dissolution and the dislodging of deposits with the aid of surfactants. Six different commercial purge compounds were tested for their colour change efficiency using polyethylene and switching from blue to clear in a laboratory film blower. The products based on a scuffing mechanism in combination with surfactants clearly outperformed the other types.
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