Glass transition temperature versus conversion relationships for thermosetting polymers

✍ Scribed by J. P. Pascault; R. J. J. Williams

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 564 KB
• Volume: 28
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/polb.1990.090280107

✦ Synopsis

Abstract

Owing to enthalpy relaxation, values of the glass transition temperature (T~g~) for partially reacted polymers may depend on the thermal history of samples and the heating rate used for measurements. Use of theoretical relations between T~g~ and the extent of reaction (x) of a thermoset must take this fact into account. The original DiBenedetto equation has been reevaluated as a convenient constitutive equation for expressing T~g~ versus x. An extension of Couchman's approach for the expression of the compositional variation of T~g~ enabled us to derive the same functionality as given by the DiBenedetto equation. Thus, the DiBenedetto equation may be regarded as based on entropic considerations applied to a model of the thermosetting polymer consisting of a random mixture of a fully reacted network with the initial monomers in an amount which depends on the particular conversion level. These two equations have been applied with success to different diepoxy‐diamine copolymers.