ISSN:
0021-8995
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Using dicyandiamide as curing agent, several epoxy networks are formed with different formulations and curing cycles. Both sub-Tg 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-Tg 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.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1986.070320424
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