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Time‐temperature–transformation (TTT) diagrams of high T g epoxy systems: Competition between cure and thermal degradation
Author(s) -
Chan L. C.,
Naé H. N.,
Gillham J. K.
Publication year - 1984
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1984.070291109
Subject(s) - epoxy , glass transition , materials science , isothermal process , char , composite material , vitrification , degradation (telecommunications) , polymer chemistry , chemical engineering , polymer , pyrolysis , thermodynamics , medicine , telecommunications , physics , computer science , engineering , andrology
The cure behavior and thermal degradation of high T g epoxy systems have been investigated by comparing their isothermal time‐temperature‐transformation (TTT) diagrams. The formulations were prepared from di‐ and trifunctional epoxy resins, and their mixtures, with stoichiometric amounts of a tetrafunctional aromatic diamine. The maximum glass transition temperatures ( T g ∞ ) were 229°C and > 324°C for the fully cured di‐ and trifunctional epoxy materials, respectively. Increasing functionality of the reactants decreases the times to gelation and to vitrification, and increases the difference between T g after prolonged isothermal cure and the temperature of cure. At high temperatures, there is competition between cure and thermal degradation. The latter was characterized by two main processes which involved devitrification (decrease of modulus and T g ) and revitrification (char formation). The experimentally inaccessible T g ∞ (352°C) for the trifunctional epoxy material was obtained by extrapolation from the values of T g ∞ of the less highly crosslinked systems using a relationship between the glass transition temperature, crosslink density, and chemical structure.