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Molar mass of poly(ethylene terephthalate) (PET) during ultimate uniaxial drawing

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Author: Göschel, U. · Cools, P.J.C.H.
Type:article
Date:2000
Institution: Centraal Instituut voor Voedingsonderzoek TNO
Source:Polymer Engineering and Science, 7, 40, 1596-1605
Identifier: 88908
Keywords: Nutrition · Concentration (process) · Crazing · Crystallization · Drawing (forming) · Esterification · Light scattering · Mechanical properties · Molecular dynamics · Organic solvents · Polycondensation · Size exclusion chromatography · Viscosity measurement · Molar mass · Molecular mobility · Transesterification · Ultimate uniaxial drawing · Polyethylene terephthalates

Abstract

The changes of the average molar mass Mw, Mn, Mz, and molar mass distributions during multistep uniaxial drawing of poly(ethylene terephthalate) (PET) to achieve ultimate mechanical properties have been studied in detail by means of size exclusion chromatography (SEC) with triple detection: concentration, viscosimetry, and light scattering, using HFIP as solvent. An increase in molar mass of PET due to post-polycondensation and/or transesterification during drawing at a high temperature of 160 to 230°C was found. Moreover, drawing leads to crystallization and large orientation in the amorphous phase, which results in lower molecular mobility and prevents a further growth in chain length. Crazing under extreme drawing conditions occurs and affects a decrease in molar mass.