High‐temperature reactions of hydroxyl and carboxyl PET chain end groups in the presence of aromatic phosphite

Abstract

When melt‐extruded in the presence of triphenylphosphite (TPP), the molecular weight of polyesters such as poly(ethylene terephthalate) (PET) increases with time. Analysis of the PET chain end groups and model studies of high‐temperature reactions indicate that, most likely, the process leading to chain extension of PET in the presence of TPP takes place in two steps. In the first step, TPP rapidly reacts with the hydroxyl end groups by displacing one phenoxy group from the TPP. In the second step, a slow reaction takes place between the alkyldiphenyl phosphite and carboxylic chain end groups, forming an ester bond between the carboxyl and alkyl groups, and producing diphenylphosphite (DPP) as a reaction by‐product. The DPP tautomerizes to its pentacovalently bonded stabler form of diphenylphosphate, the form in which the DPP was usually detected in our analyses. The ester formation results in the extension of the PET chains. Model studies are presented which support the proposed mechanism.

Toughening of recycled poly(ethylene terephthalate) with a maleic anhydride grafted SEBS triblock copolymer

“…Some popular chain extenders are dianhydrides, bis(oxazolines), bis(dihydrooxazines), carbodiimides, diepoxides, and diisocyanates. Thus, Aharoni et al 24 studied the chain extension reaction of PET with 0.5-2.5 wt % of triphenylphosphite (TPP). Although TPP greatly increased the molecular weight of PET, one drawback was that this reaction also produced diphenylphosphite as byproduct.…”

Reactive extrusion of recycled poly(ethylene terephthalate) with polycarbonate by addition of chain extender

“…Some popular chain extenders are dianhydrides, bis(oxazolines), bis(dihydrooxazine), carbodiimides, diepoxides, and diisocyanates. Aharoni et al 24 studied the chain extension reaction of PET with 0.5-2.5 wt % of triphenylphosphite (TPP). Although TPP greatly increased the molecular weight of PET, one drawback was that this reaction also produced diphenylphosphite as byproduct.…”

Reactive extrusion of poly(L‐lactic acid) with glycidol

“…Solid state postcondensation technology is employed to increase the molecular weight of polycondensates. [7][8][9][10][11] Chain extension of PLLA in reactors has been reported using various chain extenders such as diisocyanates, oxazolines and hydroxyl-functionalized epoxides. [12][13][14][15][16] Block copolymers of poly(glycidol) and PLLA have also been reported.…”