Cyclization routes for formation of cyclic oligomers in poly(ethylene terephthalate)

The effect of cyclization routes, alcoholysis, acidolysis and ester-interchange reaction, on the contents of cyclic poly(ethylene terephthalate) (PET) oligomers and their distribution were investigated by regenerating cyclic oligomers from PET (p-PET), carboxyl group end-capped PET (c-PET) and hydroxyl end group blocked PET (b-PET). It was found that the possible cyclization routes in p-PET are alcoholysis, acidolysis and ester-intet change reaction, whereas the routes in c-PET and b-PET are acidolysis and ester-interchange reaction, respectively. By comparing the contents of cyclic oligomers and their possible cyclization routes in the three PETs from one to another, it is concluded that alcoholysis is the most feasi ble route, while acidolysis is more effective than ester-interchange reaction in the cyclic PET formation.