A relationship between the glass transition temperature (Tg) and fractional conversion for thermosetting systems

✍ Scribed by R. A. Venditti; J. K. Gillham

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 317 KB
• Volume: 64
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(19970404)64:1<3::aid-app1>3.0.co;2-s

✦ Synopsis

An equation, based on thermodynamic considerations to relate the glass transition temperature, T g , to compositional variation of a polymer system, is adapted in this article for modeling the T g vs. fractional conversion ( x) relationship of reactive thermosetting systems. Agreement between the adapted equation and experimental T g vs. x data is found for several thermosetting crosslinking systems (i.e., epoxies and cyanate ester/polycyanurate) as well as for reactive thermosetting linear polymer systems (i.e., polyamic acid and esters to polyimides). The equation models the experimentally obtained T g vs. x behavior of thermosetting systems which include competing reactions. Agreement for widely varying molecular structures demonstrates the generality of the equation. The entire T g vs. x relationship can be predicted for a thermosetting material by using the T g vs. x equation and the values of the initial glass transition temperature, T g 0 , the fully reacted system glass transition temperature, T gϱ , and the ratio of the change in specific heat from the liquid or rubbery state to the glassy state (Dc p ) at T g0 and T gϱ , Dc pϱ /Dc p 0 . The values of T g 0 , T gϱ , and Dc pϱ /Dc p 0 can be measured generally from two differential scanning calorimetric experiments.