The objective of this work was to develop precise quantitative methods of analysis for determining repeat units of polyesters. These methods have In common an alkaline hydrolysis of polyesters followed by gas chromatographic determination of the glycols and acids produced from the hydrolyses. In order to obtain rapid chromatographic analyses, trimethylsllyl derivatives of the glycols and acids were formed by a reaction with /V,0-bis(trlmethylsllyl)trifluoracetamlde. The relative standard deviation varies from 0.8 % for the determination of 1,4-butanedlol to approximately 2% for 1,4-cyclohexanedlmethanol. For the determination of different concentrations of Isophthalic acid, the standard deviation varies from 0.7 to 2.4%. These methods provide rapid and precise determinations for selected acids and glycols In polyesters.Several methods have been described for determining the diethylene glycol content of poly(ethylene terephthalate) (PET) (1-3). These methods have in common the decomposition of the polyester through alkaline hydrolysis or hydrazinolysis followed by the determination of the diethylene glycol content by titration or gas chromatographic methods (4-8). However, none of these methods describe the quantitative determination of other glycol or acid content of polyesters. The objective of this work was to develop a precise, accurate method to determine the glycols and methyl ester end groups in PET and to develop a method for general use in determining glycols and acids in polyesters.
Notes stereochemistry of the heterocyclic derivatives at C-2 to be the same as the corresponding ketone, the hydrazines could have isomerized the methyl moiety during the condensation reaction. Use of semicarbazone or thiosemicarbazone resulted also in pyrazoles. All of the pyrazoles IIIa,c,d,f and VI exhibited uv maxima at 225-227 µ, which shifted to 231-235 µ in acidified alcohol. The phenylpyrazoles IIIb,e had a maximum at 253 µ, which was not affected by acidification. No attempt was made to ascertain the exact location of the phenyl ring.The pyrimidines IV were best prepared by melting an intimate mixture of the 1,3-diketones and guanidine carbonate or thiourea. Use of the standard baseor acid-catalyzed condensation conditions resulted only in the destruction or the recovery of diketone. The aminopyrimidines had double maxima of 230 and 303 µ, which could be shifted by acid to 226 and 312 µ, respectively. Thiourea product IVb had peaks at 233 and 286 µ.
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