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Epoxy network structure effect on physical aging behavior
Author(s) -
Lin Y. G.,
Sautereau H.,
Pascault J. P.
Publication year - 1986
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.1986.070320424
Subject(s) - epoxy , enthalpy , differential scanning calorimetry , materials science , isothermal process , relaxation (psychology) , arrhenius equation , curing (chemistry) , thermodynamics , annealing (glass) , composite material , glass transition , calorimetry , activation energy , chemistry , polymer , physics , psychology , social psychology
Using dicyandiamide as curing agent, several epoxy networks are formed with different formulations and curing cycles. Both sub‐ T g isothermal enthalpy relaxation and dynamic enthalpy relaxation in transition zone have been studied using differential scanning calorimetry (DSC). The isothermal enthalpy relaxation rates of all epoxy networks are quite similar and in good agreement with Arrhenius' law. Nevertheless, dynamic relaxation behaviors in the transition zone are very different. These observations are discussed in connection with relaxation mechanism and chemical structure of the networks. Evolutions of mechanical properties during sub‐ T g annealing are monitored by means of three‐points bending tests. The ductility of unprecured epoxy networks decreases with time; otherwise, the precured and/or filled networks present a stability with regards to mechanical properties. Explanations for these phenomena take into account a possible competition between the relaxation of residual stresses and the network structural relaxation.