AN INVESTIGATION OF THE PARISON SAGGING BEHAVIOR DURING THE EXTRUSION BLOW MOLDING OF COPOLYESTER PETG

The shear and elongational rheological behaviours of a copolyester thermoplastic were determined. The copolyester was then extrusion blow moulded into bottles. The parison extrusion behaviour was studied as the output rate and melt temperature were varied. The inflation behaviour was studied as a function of the inflation pressure. The processing behaviour was correlated to the rheological properties of the polymer melt. A mathematical model of the extrusion blow moulding process developed for polyolefins was tested to verify its application to the copolyester material. From the experimental results it has been shown that the copolyester has suitable rheological behaviour for the extrusion blow moulding process. The process model would require additional parameters to be considered before it could be used for prediction of copolyester melt behaviour in extrusion blow moulding.