Artículos
Silvia González Prolongo
1. Electromagnetic Interference Shielding of a Sequential Dual-Curing Thiol-Epoxy System Reinforced with GNPs with High Shape Memory
Autores:
Collado, I., Vázquez-López, A., Heredia, S., De la Vega, J., Jiménez-Suárez, A., Maestre, D., & González Prolongo, S.
Medio / Año de publicación / Quartile:
Revista ACS Applied Materials & Interfaces / 2025 / Q1
Abstracto:
Modern electronics face several challenges during operation, such as interference of disruptive electromagnetic signals and high temperatures within a limited space. Both electromagnetic interference (EMI) and thermal management could be tackled simultaneously by employing smart efficient materials with high thermal and electrical conductivity. A dual-curing epoxy system, a new subset of adaptable materials, could potentially solve those challenges, with the proper selection of the reinforcement. Moreover, its manufacturing and synthesis process, which involves a sequential curing stage, constitute an attractive, selective, and fast methodology. The thiol–epoxy chemistry allows the synthesis of an epoxy system with high shape-memory capabilities while retaining optimal mechanical properties. Herein, dual-curing epoxy systems reinforced with graphene nanoplatelets (GNPs) are manufactured. The influence of the GNPs content is evaluated, which greatly increases upon loading while retaining a high shape-memory fixation and recovery rates (near 99%). A maximum EMI shielding efficiency of 24 dB is achieved for the higher GNPs content, which is endowed by the high electrical conductivity of the system. Moreover, a modelization of the near-field and far-field EMI shielding is reported, which agrees with experimental observation. This report shows the potential and multifunctional nature of dual-curing epoxy composites for EMI shielding and shape-memory-related application.
2. A comparative approach for self-healing of carbon nanotube epoxy/polycaprolactone composites: Joule, Infrared, and oven heating
Autores:
Calderón‐Villajos, R., Vázquez‐López, A., Jiménez‐Suárez, A., Sánchez‐Romate, X. X. F. & González Prolongo, S.
Medio / Año de publicación / Quartile:
Revista Polymer Composites / 2025 / Q1
Abstracto:
The self-healing process in PCL (polycaprolactone)/epoxy blends is studied in order to optimize the healing process and understand its underlying mechanism. For this purpose, PCL/epoxy blends are prepared with and without multiwall carbon nanotubes (MWCNTs) addition. Three different self-healing heat-inducement techniques are used (an oven, Joule effect, and infrared (IR) lamp) as a function of healing time (2, 5, 10, and 15 min) and PCL concentration (5, 10, and 15 wt%). The results obtained demonstrate that the addition of MWCNTs to the polymer matrix in PCL/epoxy blends accelerates the self-healing process, attributed to an improved heat diffusion in MWCNTs/PCL/epoxy blends. The best self-healing results were obtained with the highest self-healing time and concentration of PCL, caused by the higher probability of the crack formation over a PCL reservoir. The most efficient techniques to induce the self-healing process in PCL/epoxy blends with and without MWCNTs are the conventional oven and the Joule Effect, respectively, being faster the latter method, as it induces a homogeneous internal heating of the material. Moreover, Joule effect can be controlled remotely, while IR radiation is a noncontact technique, which can be applied in situ. The three heating methods are evaluated considering these factors alongside their energy efficiency, establishing a method to choose a specific heating source for similar systems.
3. Analysis of bio-based epoxy resins: Impact of amine hardeners on thermal, thermomechanical, optical and electrical properties of epoxidized resveratrol with high Tg
Autores:
Isarn, I., Collado, I., Jiménez-Suárez, A., & González Prolongo, S.
Medio / Año de publicación / Quartile:
Revista Reactive And Functional Polymers / 2024 / Q1
Abstracto:
Epoxidized resveratrol (RES) has been cured with different amines in order to compare their possibilities to obtain high-temperature resistance of bio-based epoxy resins. Materials obtained from the bio-based monomer present glass transition temperatures (Tg) among the highest ever reported for an epoxy-amine curing system, with extremely high char residue, making them excellent candidates for extremely high-temperature applications. Particularly, epoxidized RES stoichiometrically cured with 4,4′-sulfonyldianiline (DDS) reached 297 °C, measured as the tan δ peak by DMTA, and two other materials, using 4,4′-methylenedianiline (DDM) and 4,4′-diaminodicyclohexylmethane (CAA) as curing agents, exceeded 300 °C. In fact, the material begins to degrade before the chains are fully relaxed, so they are thermosetting that never go completely into the rubbery state. Additionally, this resin improves the direct current (DC) insulating character (∼1015 Ωcm) while decreasing the optical band gap (∼2 eV) when compared to other epoxy resins available, which is of great interest for photovoltaic applications. Moreover, some of the materials presented a very high char residue proportion when heated (>40 wt% at 800 °C under nitrogen atmosphere), presenting good fire-retardant properties.
4. Bio-based epoxy vitrimer with inherent excellent flame retardance and recyclability via molecular design
Autores:
Zhou MH, Ao X., Islam M, Liu YY., González Prolongo S., Wang DY.
Medio / Año de publicación / Quartile:
Revista International Journal of Biological Macromolecules / 2024 / Q1
Abstracto:
The development of biobased fire-safe thermosets with recyclability heralds the switch for a transition towards a circular economy. In this framework, we introduced a novel high-performance bio-epoxy vitrimer (named GVD), which was fabricated by forming a crosslinking network between bio-epoxy glycerol triglycidyl ether (Gte), varying amounts of reactive flame-retardant agent 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) (0–7 wt%) and a vanillin-based hardener (VA) with imine bonds. For instance, the epoxy vitrimer GVD5, featuring a DOPO content of 5 wt%, achieved a V-0 rating in the vertical burning test (UL-94) and obtained a limiting oxygen index (LOI) value of 31 %, surpassing the performance of pristine epoxy. Furthermore, the peak heat release rate and total heat release of GVD5 were reduced by 38.2 % and 26.3 %, respectively, compared to pristine epoxy. The GVD vitrimers further demonstrated exceptional reprocessability and recyclability, attributed to the presence of dynamic imine bonds within the topological crosslinking network. Remarkably, the epoxy vitrimers maintained the mechanical properties of the parent epoxy. Therefore, this work provides a facile strategy for fabricating high-performance and multi-functional bio-epoxy thermosets.
5. Characterization of conductive particle dispersion in textile coatings through Joule's effect monitoring analysis
Autores:
Ruiz-Calleja T, Jiménez-Suárez A, Calderón-Villajos R, González Prolongo S.
Medio / Año de publicación / Quartile:
Revista Textile Research Journal / 2024 / Q2
Abstracto:
Achieving proper dispersion of pigments, dyes, or other additives, such as microcapsules or nanoparticles, within printing pastes or textile coatings is crucial for obtaining a homogeneous result. In certain specialized applications, such as coloration technology, it is possible to use colorimetry tools, visual examination, and even artificial vision to identify defects. However, none of these techniques comprehensively map the specific additive distribution. This paper proposes a novel approach: monitoring the distribution of conductive particles (graphene nanoplatelets, referred to as GNPs) within an acrylic coating paste using the Joule's effect. Four different dispersion systems (ultrasound mixer, blender, toroidal agitation, and three-roll mill) are employed. Thermographic images provide an accurate view of how conductive particles are distributed. This complements data from numerical values, such as the maximum and average temperatures recorded for each sample. In certain cases, relying solely on numerical values can be inadequate or insufficient, hence the novelty of this article emphasizing the significance of using the Joule's effect to assess the distribution of conductive particles. Concerning the mixing systems, optimal dispersion of GNPs in distilled water is most effectively achieved using an ultrasound mixer, with enhanced uniformity as dispersion time increases. For mixing the components of the coating paste, the toroidal agitation method yields the best result. Employing the three-roll mill is discouraged for this application due to its propensity to induce phase separation.
6. Combining de-icing and self-healing for wind blades through an innovative multilayer coating approach
Autores:
Cortés, A., Esperanza, A., Gómez‐Sánchez, J., Sanchez‐Romate, X. F., González Prolongo, S., & Jiménez‐Suárez, A.
Medio / Año de publicación / Quartile:
Revista Polymer Composites / 2024 / Q1
Abstracto:
Ice accretion is a huge concern for many wind blades installed in colder regions. The approach of active de-icing systems based on coatings has been recently quite explored. Nevertheless, the concern about an external electrically conductive layer leads to the need to develop multilayer insulating/conductive coatings. For this purpose, a novel multilayer coating consisting of a 3D printed carbon nanotube (CNT) and graphene nanoplatelet (GNP) reinforced nanocomposite is proposed, covered by a top coating consisting of a PCL-based epoxy blend. Here, the CNT/GNP layer presents outstanding Joule heating capabilities due to the enhanced electrical conductivity, which increases significantly when increasing the filler content without drastically affecting the quality of the printed ribbons. More specifically, the temperature reached was about 140°C when applying 30 V for the 4 wt.%CNT and 6 wt.%GNP reinforced specimens. In this regard, this resistive heating can promote the thermal stimulus needed to activate de-icing and self-healing mechanisms on the epoxy/PCL top layer. Healing efficiencies obtained by the Joule effect reached up to 90% efficiency in comparison to convective heating, which showed a 68%, explained by the improved heating transfer from the CNT/GNP layer when applying the resistive heating. Finally, a proof-of-concept test as a de-icing system showed a complete ice removal within 2.9 min when applying the resistive heating in the intermediate CNT/GNP layer, proving the multifunctionality of the proposed multilayer coating for self-heating and self-healing applications.
7. Development of an Electroactive and Thermo-Reversible Diels–Alder Epoxy Nanocomposite Doped with Carbon Nanotubes
Autores:
Lorero I, Rodríguez Á, Campo M, González Prolongo S.
Medio / Año de publicación / Quartile:
Revista Polymers / 2023 / Q1
Abstracto:
The manufacturing of Diels–Alder (D-A) crosslinked epoxy nanocomposites is an emerging field with several challenges to overcome: the synthesis is complex due to side reactions, the mechanical properties are hindered by the brittleness of these bonds, and the content of carbon nanotubes (CNT) added to achieve electroactivity is much higher than the percolation thresholds of other conventional resins. In this work, we develop nanocomposites with different D-A crosslinking ratios (0, 0.6, and 1.0) and CNT contents (0.1, 0.3, 0.5, 0.7, and 0.9 wt.%), achieving a simplified route and avoiding the use of solvents and side reactions by selecting a two-step curing method (100 °C-6 h + 60 °C-12 h) that generates the thermo-reversible resins. These reversible nanocomposites show ohmic behavior and effective Joule heating, reaching the dissociation temperatures of the D-A bonds. The fully reversible nanocomposites (ratio 1.0) present more homogeneous CNT dispersion compared to the partially reversible nanocomposites (ratio 0.6), showing higher electrical conductivity, as well as higher brittleness. For this study, the nanocomposite with a partially reversible matrix (ratio 0.6) doped with 0.7 CNT wt.% was selected to allow us to study its new smart functionalities and performance due to its reversible network by analyzing self-healing and thermoforming.
8. Electromechanical Properties of Smart Vitrimers Reinforced with Carbon Nanotubes for SHM Applications
Autores:
Gómez-Sánchez J, Sánchez-Romate XF, Espadas FJ, González Prolongo S, Jiménez-Suárez A.
Medio / Año de publicación / Quartile:
Revista Sensors / 2024 / Q1
Abstracto:
The Structural Health Monitoring (SHM) capabilities of a well-studied self-healing epoxy resin based on disulfide bonds, through the addition of carbon nanotubes (CNTs), are studied. Since these materials demonstrated, in recent works, a high dependency of the dynamic hardener content on the repair performance, this study aimed to analyze the effect of the vitrimeric chemistry on the electromechanical properties by studying different 2-aminophenyl disulfide (2-AFD) hardener and CNT contents. The electrical conductivity increases with both the CNT and AFD contents, in general. Moreover, an excess of AFD close to the stoichiometric ratio with a low CNT content improved the tensile strength by 45%, while higher AFD contents promoted its detriment by 41% due to a reduced crosslinking density. However, no significant difference in the mechanical properties was observed at a higher CNT content, regardless of the AFD ratio. The developed materials demonstrate a robust electromechanical response at quasi-static conditions. The sensitivity significantly increases at higher AFD ratios, from 0.69 to 2.22 for the 0.2 wt.%. CNT system, which is advantageous due to the enhanced repair performance of these vitrimeric materials with a higher hardener content. These results reveal the potential use of self-healing vitrimers as integrated SHM systems capable of detecting damages and self-repairing autonomously.