Study On Chain-extension Of PET During Reactive Extrusion

Test the raw material by some methods and the results show that there is no any otherpolymer in the flakes but PET. The average intrinsic viscosity([η]) of the flakes is 0.65dL/g.The change of [η] and the extruded situation of PET were studied with variousextruders, including single screw extruder, twin-screw extruder, grafting reactive extruder andpolycondensation reactive extruder. Experiment results showed that PET product of higher[η]and good toughness were obtained from recycled PET flake of drink bottle withpolycondensation reactive extruder designed by ourselves. It is the best machine reactorsuitable to increase [η]of PET of all.The influence of chain extender kind, content and reactive processing conditions on [η]of extruate was studied carefully using the chain extenders of 2,2'-Bis(2-oxazoline) (BOZ),Pyromellitic dianhydride (PMDA) and the mixture of the both with polycondensation reactiveextruder during reactive extrusion processing. Experiments showed that when the amount ofextender was 0.2wt%, [η] of recycled PET was increased 0.09dL/g based on BOZ;Combining BOZ with PMDA as chain extenders [η] of PET had a certain extentimprovement; Meanwhile PET was increased to 0.85dL/g when the amount of PMDA wasonly 0.25wt%. The optimal reactive conditions were as follows: reactive zone temperature of260℃, screw rotation speed of 45rpm, vacuum degree of 0.1MPaDSC and WAXD analysis results showed that the reactive extruded recycled PET and thepure industrial PET had the same thermal properties and crystal lattice, which proved that thereactive extruded recycled PET was suited to process PET bottle.The industrial reactive extruder was designed according to the experiments and was putin practice to process the recycled PET flakes. The results were better. In addition, somefactors which influenced the [η] of chain-extended PET products were studied.Furthermore, the change of [η] and CV of extruates was studied carefully based on thePET chips with the polycondensation reactive extruder during reactive extrusion processing.Experiments showed that [η] of PET products could be increased on some extent whenPMDA and BOZ were used separately. A higher [η] (0.90dL/g) and lower CV(25 eq/10~6g) ofPET could be obtained at the reactive conditions as follows: reactive zone temperature of 260℃, screw rotation speed of 45rpm, vacuum degree of 0.1MPa, both 0.2wt% PMDA and 0.2%BOZ as the chain extender.