ISSN:
0449-296X
Keywords:
Physics
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The technique of G. Challa was employed for following the reaction of oligomeric poly(ethylene terephthalate) in the presence of antimony trioxide. This technique is based on determining the changes in glycol and bishydroxyethyl terephthalate concentrations with time at a given temperature. The linear trimer of ethylene terephthalate, prepared from terephthaloyl chloride and bishydroxyethyl terephthalate, was employed as starting material. Rate constants were not corrected for catalyst concentrations. The reaction was studied over the temperature range 221-251°C. The equilibrium constant kp/k′ for the polycondensation reaction was found to be 0.36. Observed reaction rates were low but faster than in the uncatalyzed reaction studied by Challa. At 231°C. the values of the rate constants found in the presence of 0.025% by weight antimony trioxide were kp = 0.151.mole-1 hr.-1 and k′ = 0.33 l./mole-hr., and the redistribution rate constant was kR = 0.11 l./mole-hr. From data at four temperatures the estimated activation energies were Ep = 29 kcal. and ER = 24 kcal. The polycondensation rates were low compared with rates calculated from literature data. A mechanism to explain the difference requires that bishydroxyethyl terephthalate endgroups compete successfully with oligomer endgroups for antimony trioxide catalyst and that the bishydroxyethyl terephthalate catalyst product is unreactive in polymerization.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1968.150060417
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