Old Blown Film Dies Never Die - Or Should They? (Guidelines for Refurbishing Versus New), 2001 Polymers Laminations & Coatings Conference Proceedings
Rick Knittel--The blown film process developed from pipe extrusion in the late 1940’s when low density polyethylene first became commercially available. Prior to that time, LDPE film had been made by calendering and by horizontal slot cast extrusion onto a chill roll as an extension of thick sheet extrusion. As the polymer industry developed, technicians playing with the pipe extrusion process allowed inflation air to expand the extrusion to greatly thin the pipe wall to as low as 0.001ly (25-microns) using 2.0 MI LDPE. In the early 1950™s, researchers at fledgling LDPE producer laboratories such as Du Pont, ICI, and Union Carbide and at film producers around the country like Plax and Visking, discovered the blown film process as an extension of the pipe extrusion process. Figures 1 & 2 show several 1940’s and 1950’s patent abstracts on the blown film method assigned to the Plax, Visking and other companies.
Old Blown Film Dies Never Die - Or Should They? (Guidelines for Refurbishing Versus New), 2001 Polym