SynopsisThe cure behavior of styrene-based thermosets such as orthophthalic polyester, isophthalic polyester, and vinyl ester resins is characterized using both isothermal and dynamic differential scanning calorimetry ( DSC) techniques. In the conventional autocatalyzed kinetic model, it is assumed that the isothermal cure reaction of a thermoset goes to completion, which usually leads to a poor fit with the DSC kinetic data. It appears from the conversion-time profiles that the cure reaction reached a plateau value (a,) less than unity. This is not unexpected, as the molecular mobility of the resin system decreases as the network cures. In this work, we have refined the model to remove this restrictive acsumption by taking the total ultimate conversion (a,) into account in the computation. This improved model permits us a better prediction of the course of the cure reaction of the styrene-based thermosets under isothermal and dynamic conditions. In addition, the cure kinetics of the three thermoset resins are studied and compared on the basis of several kinetic parameters including conversion, cure rate, reaction rate constant, heat of cure reaction, half-life, and Arrhenius parameters. The reactivity of these resins when arranged in ascending order is found to be: vinyl ester < orthophthalic polyester < isoththalic polyester.

A general method for the generation of isobenzofuran intermediates is described. Lithiated aromatic acetals are converted to hydroxyacetals (A) which may be cyclized to isobenzofurans by mild acid treatment through the 1-hydroxyphthalans (B). The isobenzofurans generated insitu are trapped by a variety of dienophiles to provide the expected oxo-bicyclo adducts (C). The mass and 1Hmr spectra of B and C are discussed.

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On p. 354, 1. 7 (main text), 4.18 should read 3-76.

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