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

Autor:	R. D. Sedgwick, C. E. Forbes, Shaul M. Aharoni, F. Mares, Willis B. Hammond, K. P. O'Brien, D. M. Hindenlang
Rok vydání:	1986
Předmět:	chemistry.chemical_classification Reaction mechanism Ethylene Polymers and Plastics Intrinsic viscosity Organic Chemistry Chemical modification Polyester End-group chemistry.chemical_compound chemistry Chain (algebraic topology) Polymer chemistry Materials Chemistry Alkyl
Zdroj:	Journal of Polymer Science Part A: Polymer Chemistry. 24:1281-1296
ISSN:	1099-0518 0887-624X
DOI:	10.1002/pola.1986.080240614
Popis:	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.
Databáze:	OpenAIRE
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