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Two different self-healing approaches are studied in this work to analyze the possible contribution of each of the self-healing mechanisms at different temperatures and the possible synergetic effects between them. Thermal and mechanical properties were differently affected by the addition of each of the thermoplastic polymers. This was caused by different phase separations induced during the curing reaction in terms of size and number of the thermoplastic phase domains dispersed within the epoxy matrix and due to the different amounts of thermoplastic polymer that remain solved in the matrix. When using the vitrimeric matrix, phase separation only occurred at the nanometer scale when utilizing poly(bisphenol-A-co-epichlorohydrin) (PBAE) as a thermoplastic agent or higher contents of polycaprolactone (PCL).

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.

Sequential dual-cured epoxy composites, based on off-stoichiometric thiol–epoxy mixtures catalysed by 1-methylimidazole, have been developed by adding carbon nanotubes (CNT). The epoxy curing process initially consists in two thermally activated curing stages: a first thiol–epoxy reaction and later homopolymerization at a higher temperature. This system presents easy shaping/conforming and shape memory properties through thermo-mechanical treatments. Addition of the electrical CNT network into the epoxy matrix allows electrical switching, which increases its performance and in-situ applicability.

A novel nanoreinforced adhesive film has been developed to detect adhesive deformation and crack propagation along the bonding line by means of the electrical response of the material. Adhesive films were doped by spraying an aqueous dispersion of carbon nanotubes (CNTs) over the surface. To determine the sensitivity of bonded joints, single lap shear (SLS) and mode-I fracture energy tests have been carried out while their electrical response has been measured. It has been found that CNT-doped adhesive films are able to detect adhesive deformation and final failure for SLS specimens and crack initiation and propagation along the bonding line for mode-I specimens with a high sensitivity. Sudden increases on electrical resistance are correlated to a rapid growing of the crack length due to instability on crack propagation in a tick-slip case, whereas specimens with a more uniform crack propagation are linked to a steadier increase on electrical resistance, and both of them are properly correlated to the mechanical response. By analyzing more in detail the electrical response and comparing with theoretical approaches, the stick–slip behavior is associated with the presence of porosity and lack of adhesives because of possible manufacturing issues such as adhesive overflowing. These statements are also validated by microstructural analysis. Therefore, the potential and applicability of the proposed adhesive films for evaluating the structural integrity has been demonstrated.

The current tendency in electronics is the reduction of size while continuously increasing the power consumption due to new functionalities and applications. Both aspects generate a heat increment. Consequently, dissipating the heat to the environment is necessary in order to avoid component overheating. [1,2]. The most efficient way to achieve it is to allow the heat to flow from the hot component to a heat sink. In order to improve the efficiency of this process, thermal resistance between both components must be reduced which is usually done by using a thermal interface material (TIM) between both surfaces [3-5]. This material should fill the gaps created due to the microscopic roughness of both surfaces and it must have good thermal conductivity [6]. These air filled gaps result in a very high contact resistance between joined parts, as the air thermal conductivity is very low [7].

The use of carbon nanostructures for epoxy matrices modification has been widely studied, nevertheless there are several alternative methods for manufacturing that try to avoid difficulties related to their tendency to keep entangled. The use of the calendering approach and high shear mixing alternatives is common for dispersing these nanoreinforcements. The present article compares these two methods as well as possible synergies from the use of the two alternatives together. It has been found that the dispersion technique used modifies the final dispersion level reached as well as on the final properties of the different nanocomposites. Nevertheless, this effect depends on the type of nanoreinforcement (structure and functionalization) and the property measured. Results suggest that each carbon nanostructure requires an individual design of the dispersion stage to get the optimum properties. Thus, the optimum technique may be different depending on the final desired properties, and the dispersion cycle should be designed carefully depending of the final material aim and the nanostructure used. Nevertheless, typical dispersion cycles are currently applied for different type of nanoreinforcements.

Abstract: Significant intrusion of geothermal water into fresh groundwater takes place in the Puebla Valley aquifer system, Mexico. The decline in the potentiometric surface due to the overexploitation of the groundwater induces this intrusion. This hydrological system comprises three aquifers located in Plio-Quaternary volcanic sediments and Mesozoic calcareous rocks. The hydraulic balance of the aquifer shows that the annual output exceeds the natural inputs by 12 million m3. Between 1973 and 2002, a drop in the potentiometric surface, with an 80 m cone of depression, was identified in a 5-km-wide area located southwest of the city of Puebla. Chemical analyses performed on water samples since 1990 have shown an increase in total dissolved solids (TDS) of more than 500 mg/L, coinciding with the region showing a cone of depression in the potentiometric surface. A three-dimensional flow and transport model, based on the hydrogeological and geophysical studies, was computed by using the MODFLOW and MT3D software. This model reproduces the evolution of the aquifer system during the last 30 years and predicts for 2010 an additional drawdown in the potentiometric surface of 15 m, and an increase in the geothermal water intrusion.