New Screw Concept Maximizes Melting, 1998 Polymers, Laminations & Coatings Conference Proceedings

Grooved feed throats have been in use in blown film extrusion of high density polyethylene with single screw extruders for many years. There have been severe wear problems with them due to the very high pressures that are generated at the end of the feed section. The author believes that this is because present screw designs are melting limited. The thrust of this paper is to report on our study of a new very high melting rate screw concept to eliminate this problem and provide higher rates per revolution of the screw at very low melt temperatures. Although the most recent experiments were conducted at Phillips Petroleum’s research lab in Bartlesville, Ok on a Kautex blow molding machine, hereafter refered to as the blow molder, using this new screw design, the data is indicative of rates and melt temperatures that cold be achieved in blown film. The goal was to confirm the theory that grooved fed extruders can produce much greater rates and the high pressures encountered with traditional screws are due to the restriction of low melting capability of these screw designs which would be applicable to blown film extrusion as well.