Examinando por Autor "Campo, M."

Mostrando 1 - 4 de 4

4D-Printed Resins and Nanocomposites Thermally Stimulated by Conventional Heating and IR-Radiation
(ACS, 2021) Cortés, A.; Aguilar, Jose L.; Cosola, A.; Fernández Sanchez-Romate, Xoan Xosé; Jiménez-Suárez, A.; Sangermano, M.; Campo, M.; Prolongo, Silvia G.
The shape memory (SM) capabilities of nanocomposites based on two photocurable acrylated/methacrylated resins, doped with carbon nanotubes (CNTs), and manufactured by digital light processing 3D printing were investigated. The mechanical properties and glass transition temperature (Tg) can be tailored in a broad range by varying the weight ratio of the two resins (Tg ranging from 15 to 190 °C; Young’s modulus from 1.5 to 2500 MPa). Shape fixity (SF) and recovery (SR) ratios are strongly influenced by the temperature being significantly higher at temperatures close to the Tg. The results confirm that the SF strongly depends on the stiffness of chain segments between cross-linking points, whereas the SR mainly depends on the cross-link density of the network. CNT addition barely affects the SF and SR in the conventional oven, whereas the recovery speed using IR heating is significantly increased for the doped nanocomposites due to their higher IR absorbance.
Enhancing efficiency and sustainability of digital light processing 3D-Printing by novel two-stage processing of carbon nanotube reinforced nanocomposites
(Elsevier, 2024-03) Cortés, A.; Bañón-Veracruz, M.; Jiménez-Suárez, A.; Campo, M.; Prolongo, M.G.; Prolongo, S.G.
3D printing has gained a spot within the industry during the last decade due to the advantages it presents regarding conventional manufacturing technologies. Nevertheless, the high processing time and the material waste due to the use of printing supports are still some of the main challenges that have to be addressed. In this research work, a simple strategy to minimize the processing time and the material waste is carried out through a two-stage processing method. Here, a flat specimen is obtained using a vat photopolymerization 3D printer, presenting a low curing degree. Then, the specimen is bent and subsequent post-curing treatments are performed to increase the cross-link density, thus fixing the desired shape. Furthermore, carbon nanotubes were used as nanoreinforcement for increasing the mechanical properties and exploiting their Joule heating capabilities for the thermal post-curing treatment, being way less energy-consuming (around 1W) than using a conventional oven (around 750 W). The results obtained with a proof-of-concept evinced the suitability of the proposed two-stage processing method to enhance the efficiency and sustainability of the 3D printing process. The printing time and the material waste were reduced by 94.3 % and 16.7 % on average, respectively, with regard to printing the part directly on its final desired shape, as well as showing a shape fixity ratio of around 98 %. Furthermore, an enhancement of the mechanical properties was obtained due to the reorientation of the printed layers during the two-stage processing
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
Sequential and selective shape memory by remote electrical control
(Elsevier, 2021) Cortés, A.; Pérez-Chao, N.; Jiménez-Suárez, A.; Campo, M.; Prolongo, S.G.
Shape memory (SM) materials have been widely investigated for several years. Most polymers present SM behaviour based on their thermo-mechanical properties. However, they are usually stimulated by an external heating source, hindering their industrial application. The addition of carbon nanotubes (CNT) allows turning conventional SM polymers into electro-active actuators. In this regard, the resistive heating by the Joule effect is considerably fast with a low energy cost. The most used epoxy resins cured at high temperature are based on diglycidyl ether of bisphenol A (DGEBA) cured with aromatic amine hardeners, such as diaminodiohenylsulfone (DDS) and 4,4′diamine-diphenylmetane (DDM). In this work, they were synthesised with modification of the epoxy/amine ratio to vary the crosslinking density of networks so as to build up different viscoelastic properties in order to tailor their SM behaviour. Electrically conductive nanocomposites were manufactured by adding a CNT percentage above the percolation threshold. A comparison of SM behaviour stimulated by traditional convection and resistive heating was carried out, confirming the higher recovery ratio, speed, and applicability of the electrical stimuli. In addition, the configuration of electrodes allows the design of self-deployable materials with remote control. In this way, the most common dual-shape SM polymers (one permanent shape and one temporary shape) can easily develop several stable temporary shapes. Moreover, the electrical remote control provides sequential and selective actuators, enhancing their performance for developing smart structures with shape memory capability.