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Physics and kinetics of alkaline hydrolysis of cationic dyeable poly(ethylene terephthalate) (CDPET) and polyethylene glycol (PEG)–modified CDPET polymers: Effects of dimethyl 5-sulfoisophthalate sodium salt/PEG content and the number-average molecular weight of the PEG

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Abstract

This study investigated the physics and kinetics of three cationic dyeable poly(ethylene terephthalate) (CDPET) and four polyethylene glycol (PEG)–modified cationic dyeable PET (PEG-modified CDPET) polymers using differential scanning calorimetry, thermogravimetric analysis, the density gradient method, gel permeation chromatography, a rheometer, and statistical regression analysis. The molar ratios of dimethyl 5-sulfoisophthalate sodium salt (SIPM) for three CDPET polymers were 2, 6, and 10%, respectively. For four PEG-modified CDPET polymers, with molar ratios of SIPM of 2%, the PEG content and the number-average molecular weights (Mn) of PEG were 3/6 (wt %) and 400/2000 (g/mol), respectively. Experimental results revealed that the crystallinities of CDPET and PEG-modified CDPET polymers declined as the SIPM and PEG contents increased. The crystallinity of the PEG400–CDPET polymer exceeded that of the PEG2000–CDPET polymer with the same SIPM and PEG contents. The SIPM and PEG segments did not change the original PET unit cell. The [BOND]SO3Na functional group and the PEG molecules gathered only on the crystal surface and in the amorphous regions. In the kinetic equation of the alkaline hydrolysis of PET, CDPET, and PEG-modified CDPET polymers, β equals 1. Furthermore, the R2 of the kinetic equation for α from 1.09 to 1.25 was better than that of α = 1. The rate constants of alkaline hydrolysis were in the order CDPET-10 > CDPET-6 > PEG2000-6-CDPET-2 > PEG2000-3-CDPET-2 > PEG400-6-CDPET-2 > PEG400-3-CDPET-2 > CDPET-2 > PET. Clearly, the rate constant of the alkaline hydrolysis of CDPET and PEG-modified CDPET polymers increased with SIPM/PEG content and the Mn of the PEG increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 550–556, 2005

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