ISSN:
0025-116X
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Imidization of polyamic acid prepared from pyromellitic dianhydride and 4,4′-methylenedianiline was investigated at 373-493 K. At a certain degree of imidization, depending on the reaction temperature, the reaction is significantly slowed down. For this reason, imidization was divided into two phases, a fast and a slow one, and the rate constants were calculated from the kinetic equation of a first-order reaction. At imidization temperature above 443 K the activation enthalpy of the reaction decreases, probably due to the thermal decomposition of complexes of o-carboxybenzamide groups with residues of the solvent. At higher imidization temperatures also the activation entropy of imidization decreases; this is probably caused by the higher rigidity of the film because of evaporation of the solvent which acts as a plasticizer.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/macp.1990.021911111
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