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Thermomechanical and large deformation behaviors of antiplasticized epoxy resins: Effect of material formulation and network architecture
Author(s) -
Pandini Stefano,
Bignotti Fabio,
Baldi Francesco,
Sartore Luciana,
Consolati Giovanni,
Panzarasa Guido
Publication year - 2017
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.24555
Subject(s) - materials science , epoxy , glass transition , composite material , ultimate tensile strength , macromolecule , deformation (meteorology) , dynamic mechanical analysis , stoichiometry , polymer , organic chemistry , chemistry , biochemistry
A series of amine‐hardened epoxies were prepared by systematically varying the stoichiometric ratio and the relative amounts of diepoxide and monoepoxide resin to chemically control the material composition and macromolecular architecture (chain segments flexibility; crosslink density; amounts of dangling groups). Positron Annihilation Lifetime Spectroscopy was used to investigate the free volume associated to the various epoxy formulations, while dynamic‐mechanical analysis was employed to investigate their network density and their primary and secondary mechanical relaxations. The mechanical behavior at small and large strain was studied by means of tensile and compression tests. The results pointed out that deviations from the ideal stoichiometric composition and the addition of monoepoxide resins lead to significant room temperature stiffening, together with a reduction of the crosslink density and glass transition temperature. This behavior, phenomenologically associated to antiplasticization, was interpreted according to the specific macromolecular architecture and ascribed to chain mobility hindrance, as revealed by secondary transitions, whereas no significant contribution from the free volume could be evidenced. Furthermore, it was shown that depending on the strain scale and on the corresponding deformational mechanisms, the mechanical response may be differently influenced either by the presence of dangling groups or by the network density. POLYM. ENG. SCI., 57:553–565, 2017. © 2017 Society of Plastics Engineers