Premium
Correlation between viscoelastic behavior and cooling stresses in a cured epoxy resin system
Author(s) -
Nassiet V.,
Habas J. P.,
HassouneRhabbour B.,
Baziard Y.,
Petit J. A.
Publication year - 2005
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.22540
Subject(s) - epoxy , materials science , composite material , differential scanning calorimetry , rheology , viscoelasticity , rheometry , thermosetting polymer , thermodynamics , physics
This work deals with the study of the rheological behavior of an epoxy system subjected to three cooling processes referred to as the normal, air‐, and water‐cooling processes. The system was set up by a difunctional epoxy resin (DGEBA) mixed with a tetrafunctional diamine (mPDA) in stoichiometric proportions. Different samples of (1) neat and cured polymers and (2) alumina—epoxy composites were prepared. The first part of this work was devoted to optimizing the cure cycle of the neat samples using differential scanning calorimetry and rheometry. The best cure cycle is based on a first heat step at 110°C during 10 min followed by a crosslinking stage of 75 min at 180°C. In the second part of the study the influence of the cooling cycle on the thermomechanical behavior of polymer and composite samples was investigated. Measurement of loss modulus, G″, and loss factor, tan δ, versus temperature showed that an intermediate relaxation α′ peak arose between the main and secondary relaxations (resp. α and β). The position and amplitude of the α′ peak increased with the cooling rate. This rheological phenomenon is related to the presence of nonequilibrium stresses frozen in the sample during cooling. The effect of thermal aging on the α′ peak also is reported. Our work also showed the presence of an α′ peak for the composites. However, the amplitude of this peak was more pronounced in the composites because of additional stresses induced by the difference between the resin and the ceramic in thermal expansion coefficients. We showed that a calculation based on a thermoelastic model was useful for qualitative comparison of rheological data on the influence of the cooling process. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 679–690, 2006