Chemical and Biomolecular Engineering Research and Publications

 

Date of this Version

May 1993

Comments

This article was oiginally published in Macromolecules; 1993; 26(23); 6155-6163. Received January 25, 1993; Revised Manuscript Received May 24, 1993. Abstract published in Advance ACS Abstracts, October 15, 1993. Copyright © 1993 American Chemical Society. The American Chemical Society allows the posting of only the title, abstract, tables, and figures from articles appearing in the Macromolecules. This article is published online at the publishers site: http://pubs.acs.org/cgi-bin/archive.cgi/mamobx/1993/26/i23/pdf/ma00075a003.pdf Copyright © 1993 American Chemical Society.

Abstract

A chemical reaction analysis of a thermosetting, urethane resin formulated from a triol and a diisocyanate is reported. Population density distributions of oligomeric molecules, monomer concentration, the cumulative molar concentration of intramolecular bonds, the resin's average molecular weights, and extent of reaction were determined as a function of time. Rate expressions for intermolecular reactions were first order with respect to the concentration of each reactant and were proportional to the functionality of their respective chemical moieties. Rate expressions for intramolecular reactions were first order with respect to the concentration of the reactant and were proportional to the functionality of the limiting chemical moiety on the reactant. The initial ratio of the chemical equivalents and effects of dilution were incorporated into numerical simulations. Stanford and Stepto's experimental data were analyzed. Gel points and the concentration of intramolecular bonds were correlated as a function of conversion. Intramolecular reaction rate expressions derived with the aid of Gaussian chain statistics require the molar concentrations of all chemical isomers of a specified chemical composition. The present reaction rate expression allows chemical isomers to be lumped into a single population density distribution variable, substantially reducing the dimensions of the simulation. Numerical results demonstrate that the simplified rate expression is an excellent.

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