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Donostia / San Sebastián, Spain

Altuna F.I.,University of the Sea | Pettarin V.,University of the Sea | Martin L.,Materials Technologies Group | Retegi A.,Materials Technologies Group | And 3 more authors.
Polymer Engineering and Science | Year: 2014

Epoxidized soybean oil (ESO) was proved to be a good alternative to partially replace a synthetic commercial epoxy resin in a formulation to obtain thermosetting polymer, contributing to transform a vegetable oil into a higher added value product. This work focuses on the study of the fracture behavior of copolymers based on anhydride-cured epoxy systems with different contents of ESO as a replacement for the synthetic resin. It was found that fracture toughness was greatly improved when replacing diglycidyl ether of bisphenol A (DGEBA) by ESO, being the critical stress intensity factor (KIC) 1.067 MPa·m1/2 for cured ESO and 0.557 MPa·m1/2 for cured DGEBA. The better performance of ESO networks was ascribed to its higher ability to attain plastic deformation. Moreover, for DGEBA-ESO systems, the morphologies generated during the curing process were also considered to account for the observed results. POLYM. ENG. SCI., 54:569-578, 2014. © 2013 Society of Plastics Engineers. Source


Fernandez R.,Materials Technologies Group | Ramos J.A.,Materials Technologies Group | Esposito L.,Materials Technologies Group | Tercjak A.,Materials Technologies Group | Mondragon I.,Materials Technologies Group
Macromolecules | Year: 2011

Azo-containing polymers are of particular interest in the design of materials for applications in optical recording. The aim of this contribution was the synthesis and characterization of optically active epoxy-based nanostructured thermosets obtained using epoxidized poly(styrene-b-butadiene-b- styrene) (SBS) as templating agent and modified with azobenzene groups. Morphological analysis by means of atomic force microscopy, as well as an investigation about the anisotropic optical properties of the developed materials was carried out. Different types of morphologies from micelles without long-range order to nanostructures with long-range order were achieved depending on the content of epoxidized block copolymer and azobenzene, and on the extent of epoxidation of butadiene blocks. In addition, the study of optical anisotropy showed a clear dependence of the optical storage properties upon the concentration of azo-chromophore in the samples. In particular, a thermoset containing 12.3 wt % of azo-dye and 5 phr of SBS with 46 mol % of butadiene blocks epoxidized revealed a spherical micellar morphology with maximum birefringence in the order of 1.8 × 10 -2 and residual fraction of birefringence of around 0.3 after several weeks of turning off the writing beam. Besides, numerous writing-erasing cycles could also be performed without photodegradation of the materials. Furthermore, comparing parent thermosets and nanostructured systems, similar birefringence values were obtained with the advantage that the latter can also be used as templates for the development of multifunctional advanced thermosetting materials with optical properties. © 2011 American Chemical Society. Source

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