Examinando por Autor "Lorero, I."

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Mechanical recycling and electro-thermal welding of epoxy vitrimer nanocomposites
(Wiley, 2024-02-03) Lorero, I.; Mujica, A.; Campo M.; Prolongo, S.G.
Vitrimers constitute a new class of recyclable thermosets based on the incorporation of associative dynamic covalent bonds, such as disulfide bonds, into the crosslinked matrix. These reversible bonds usually require excess dynamic bonds to confer proper self-healing and recycling capabilities to the thermoset. In that way, we manufacture epoxy resins cured with 4-aminophenyl disulfide (AFD) in a stoichiometric ratio, and with 10 and 20 wt% of AFD excesses to analyze the effect of composition on resin properties. Beyond the neat vitrimers analysis, we manufacture nanocomposites doped with carbon nanotubes (CNT) to obtain electroactive vitrimers. These epoxy resins and nanocomposites can be mechanically recycled by milling and hot-pressing. The recycled nanocomposites conserve partially CNT integrity and dispersion. Even more, recycled nanocomposites with AFD excesses maintain the mechanical strength of the pristine nanocomposites. Vitrimer nanocomposite samples can be also electrically welded, due to their heating by the Joule effect, through a relatively low voltage application, and therefore with low energy consumption, to obtain a monolithic specimen. In summary, the manufactured epoxy vitrimers and nanocomposites are recyclable and sustainable epoxy materials, which can be processed and reprocessed using technologies easily implementable, fast, and with low energy consumption
Recycling development and shaping of a thermo-reversible epoxy resin with partial contents of Diels-Alder bonds
(Elsevier, 2024-05) Lorero, I.; Rico, B.; Campo, M.; Prolongo, S.G.
Thermo-mechanical recycling and reshaping of dynamic covalent networks is a promising field under development that could help to increase thermoset sustainability. Herein, the reprocessing of a partially reversible epoxy resin with a 0.6 Diels-Alder crosslink ratio, which has a relatively high Tg and a simplified manufacturing route, is studied to determine the optimal conditions for its thermomechanical recycling through milling and hot-pressing, and reshaping. Thus, in this work, we have studied the influence of compaction time, pressure, and temperature on recycled bulk properties. Meanwhile, different heating temperatures and times are also tested to evaluate the cured resin shaping to fix a new geometry and to observe its shape-recovering capability. Their characterization reveals that the recycling method generates dense thermosetting polymers with similar crosslinking structure and behavior, comparable to the virgin resin, inducing light post-curing that increases their glass transition temperature (Tg). The most efficient thermo-mechanical recycling conditions consist of the application of isothermal compaction at 130 °C and 150 bar for 30 min, which leads to resin bulks with comparable properties to the neat resin even after 3 cycles of milling and hot-pressing. On the other hand, the synthesized resin has shown excellent shaping due to the structural relaxation induced by the initiation of retro Diels-Alder reaction, adopting new geometries easily when the samples are heated above their Tg (91 °C) and preserving them after cooling to ambient temperature. Moreover, the samples also show high shape-recovering after heating again up to Tg. This reshaping and recovery have been maintained for several cycles without observing an irreversible lack of shape fixing or shape recovery