Combined Foaming and Rotomoulding in the Rotofoam Process
July 7th, 2003
Paper to the 19th Annual Meeting of the Polymer Processing Society, Melbourne, Australia, 7th-10th July 2003
S F Bush with O K Ademosu
Abstract
Rotomoulding is an established process for forming relatively large hollow structures by rotating a mould containing polymer powder (typically polyethylene) either about two perpendicular axes or about one axis combined with a rocking back and forth motion along the second, perpendicular axis. Up to now, if such a rotomoulded hollow form needed to be foam-filled, the hollow form has had to be made first in one operation, demoulded, and then, as a comparatively costly second operation, taken to another station where it is filled with polyurethane foam. The UMIST Rotofam process allows the foaming step to proceed at the same time as the moulding step, giving a solid outer skin of one material and a foamed interior made of another. The paper describes experiments on the Rotofoam process at both laboratory scale and full-scale as rotation speeds, feed materials and temperature-time profiles are varied. Large bore steam pipe insulators, damage resisting post covers, cold store doors, harbour fenders and pallets, all made on our industrial collaborators’ plants will illustrate the results obtained in practice from this new industrial proces. A further variant – Rotofil – in which long glass fibre filaments are distributed into the polyethylene skin will also be briefly described.