GEL-PERMEATION CHROMATOGRAPHY (GPC) OF REPEATEDLY EXTRUDED POLYETHYLENE TEREPHTHALATE (PET)

The paper deals with gel permeation chromatography (GPC) monitoring of the behaviour of PET (polyethylene terephthalate) after repeated extr usions. Virgin PET was submitted to three successive extrusion/drying cycles and then the samples were swelled with hexafluoroisopropanol an d treated with chloroform. GPC analysis was carried out at room temper ature on a B.C.S. Serial LC 2000 GPC system equipped with a series of four GPC columns with UV detection at 254 nm and chloroform as eluent. GPC results showed that after each extrusion step the molecular weigh t distribution of the PET was different and Mw, Mn and Mz decreased. T hese findings suggest that during each extrusion degradation occurs an d that repented extrusions, as in the case of the recycling PET, may c ause an alteration of the molecular weight distribution of the origina l PET.