Adding Carbon Nanotubes Research Articles

Micro-oxydation of wine in a ceramic vessel with CNT

Wine aging is typically performed using oak barrels. The porosity of the oak wood allows oxygen, which is one of the most important factors in the maturation and ageing of wines, to enter into the barrel in a controlled manner. Even though this is an established method, in has two major drawbacks a) the limited life of the barrels (they can be used up to three times) and b) alcohol evaporation during the ageing process. Our study was inspired by the ancient times when wine was stored in ceramic containers called amphorae. In the present study, ceramic vessels were made of porcelain and investigated as new containers for wine ageing. To create conditions for micro-oxygenation (MOX), the porosity of the porcelain ceramic vessels was modified by adding carbon nanotubes (CNTs) at different concentrations (0.1 to 0.3%). Red wine was stored inside the CNT/ceramic vessels and its total phenols, pH and weight was measured at a period of 5 months. The results showed that there is a potential for creating ageing conditions in porcelain ceramic vessels, as a controlled decrease in total phenols in wine was observed. Specifically, the vessels with a CNTs content of 0.1% showed the least reduction in total phenols, while the vessels with a CNTs content of 0.3% showed the greatest reduction in total phenols. Another advantage is the minimal wine volume reduction observed (0.8–1.8% compared to oak barrels 3–5%).

A review on MWCNTS: the effect of its addition on the polymer matrix

In recent years, it has been realized that nanocomposite materials are candidates for many applications in all fields due to their unique properties. This review aims to study the possibility of modifying some properties of polymers by adding carbon nanotubes to improve their properties by taking advantage of the large surface area of MWCNTs to volume ratio. For this purpose, multi-walled carbon nanotubes were used at different ratios and by different mixing methods. Then the effect of this addition was monitored by the procedure of some mechanical, electrical and thermal measurements of the resulting nanocomposite materials. The results of the tests showed that the quality of the filling depends on the way it is distributed within the polymer matrix, where the homogeneous dispersion of MWCNTs will reflect on the properties of the nanocomposite material thus benefit from the special properties of it. Also, the results showed that the addition of MWCNTs at low ratios achieved uniform distribution and dispersion, so improved the properties of the materials such as tensile strength, elongation at break and young's modulus. The ratio of 0.5 wt % of MWCNTs represented an average value for adding MWCNTs to various types of polymers. These composite nanomaterials can replace other industrial materials in many applications.

Experimental and numerical study of tensile behavior of carbon nanotube reinforced glass-epoxy composite: The multiscale approach

In this paper, a multiscale approach is presented for strength and tensile modulus prediction of carbon nanotube (CNT) reinforced glass-epoxy composite. At the micro-scale, the three-dimensional representative volume element is obtained by randomly orienting the carbon nanotube in the resin according to the weight percentage. The interphase of the nanotube and resin is modeled using a cohesive element method. The behavior of the resin is accounted with a quasi-brittle non-local damage model. At the Mesoscale, the representative volume element is estimated by using the weight percentage of glass fiber and resin generalized with nanotubes. Finite element analyses were conducted to estimate the effective mechanical properties through numerical homogenization. The effect of different percentages of carbon nanotubes on tensile behavior was investigated experimentally and numerically. The results show that adding carbon nanotubes improves the tensile modulus by about 25% and the tensile strength by about 53%. In the numerical study, the strength of the composite is predicted with good accuracy by modeling the damage of resin, glass fibers, and fracture toughness mechanisms of carbon nanotubes such as bridging and pull-out of carbon nanotubes. A good agreement was observed between the simulation results and the experimental results at different percentages of carbon nanotubes.

탄소나노튜브 보강 여부에 따른 자가치료용 마이크로캡슐의 박막 특성 평가

In this study, thin-shell surface observation, storage capability test, and micro-compressive test were performed for self-healing microcapsules using a field emission scanning electron microscope (FE-SEM) and a micro-compressive testing machine. A microcapsule having a melamine-urea-formaldehyde thin-shell and a microcapsule having a melamine-urea-formaldehyde thin-shell reinforced with carbon nanotubes were used. Two carbon nanotube contents were considered: 0.17 wt% and 0.50 wt%. Thin-wall shell state was relatively smooth when microcapsules were not reinforced with carbon nanotubes. It was uneven when microcapsules were reinforced with carbon nanotubes. Prepared microcapsules showed little decreases of weights even when the exposure time was increased regardless of whether they were reinforced with carbon nanotubes. Thus, their storage capability was good. When carbon nanotube content was the same, the fracture load was almost constant without being affected by the diameter of the microcapsule. However, fracture displacement increased with increasing diameter of the microcapsule. When diameters of microcapsules were similar, fracture load and fracture displacement increased when carbon nanotube content increased. It was found that self-healing microcapsules had good storage capability and mechanical properties. Thus, they could be applied to repair damage to composite materials if thin-shell formation mechanism for adding carbon nanotubes is supplemented.

Experimental study on the thermal properties of a novel ultra-high performance concrete reinforced with multi-scale fibers at elevated temperatures

The fire resistance of a novel ultra-high performance concrete is critical to its application, while the evolution of its thermal properties with temperature plays a key role in its fire resistance. Therefore, this study presents an experimental investigation of the thermal performance of newly developed ultra-high performance concrete reinforced by cenosphere and multi-scale fibers (MSFUHPC) including carbon nanotubes, calcium sulfate whiskers, carbon fibers, steel fibers, and polyethylene fibers under high temperatures ranging from 25 °C to 800 °C. Meanwhile, scanning electron microscope, thermogravimetry analysis, and mercury intrusion porosimetry tests are also conducted to study the thermal effect on the microstructure. Accordingly, the effect of multi-scale fibers and cenospheres on the thermal conductivity, volumetric specific heat, and thermal expansion of MSFUHPC are discussed. The results show that adding carbon nanotubes, carbon fibers, and hybrid fibers (steel fibers and polyethylene fibers) can increase thermal conductivity, and adding calcium sulfate whiskers and cenospheres exhibits an inverse effect at ambient temperature. In addition, the thermal expansion can be enlarged by incorporating carbon nanotubes or steel fibers and polyethylene fibers and restrained by adding carbon fibers. The influence of calcium sulfate whiskers and cenospheres on thermal expansion depends on their content. At high temperatures, the thermal conductivity shows an overall decreasing trend and the thermal conductivity of MSFUHPC is higher than that of its matrix and traditional UHPC, HPC, and NSC due to the reduction in the generation and propagation of cracks. By contrast, the volumetric specific heat shows an increasing trend with temperature. Besides, the thermal expansion of MSFUHPC is lower than that of UHPC, HPC, and NSC. The formulas of thermal parameters are fitted based on experimental data by considering the multi-scale fibers and temperatures, which can be used as input parameters for the numerical simulation of MSFUHPC structure under fire.

Investigation into the Size Distribution of Al<sub>2</sub>O<sub>3</sub>- ZnO Nanoparticles Dispersed in DI Water and Following the Impact of CNTs on the Stability, Heat Transfer, and Electricity Transfer of Al<sub>2</sub>O<sub>3</sub>- ZnO-CNT Hybrid Nanofluid

The stability of dispersed nanoparticles in the base fluid has always been one of the most important challenges in using nanofluids as a coolant in heat transfer applications in different industries such as modern electronic equipment, heat exchangers, solar technologies, etc. In the present study, the dynamic light scattering (DLS) method is used to obtain the particle size distribution of Al2O3-ZnO dispersed in DI water. After adjusting the optical arrangement and designing the DLS setup, the correlation curves are plotted by analyzing the detected signals of the experiments. Then, a decay rate is derived by fitting an exponential function to the correlation curve to get the particle size distribution by using the Stoke-Einstein equation. In order to investigate the stability of Al2O3-ZnO water-based nanofluid, the particle size distribution profiles are studied several times. In addition, the stability of Al2O3-ZnO-CNT hybrid nanofluid is followed by absorbance measurements using a UV-Vis spectrophotometer. Moreover, the thermal conductivity coefficient and electrical conductivity of the Al2O3-ZnO hybrid nanofluid with and without CNT particles are determined by utilizing KD2 Pro and PCT-407 devices, respectively. The results showed that the peak in the particle size distribution curve for Al2O3-ZnO hybrid nanofluid shifted from 476 nm to 128 nm after 5 days. Furthermore, the inclusion of carbon nanotubes increased the stability of zinc oxide particles in the nanofluid. In addition, by adding carbon nanotubes in a ratio of 1:1:0.5 to Al2O3-ZnO nanofluid and forming 0.05 wt.% hybrid nanofluid, the thermal conductivity coefficient was enhanced by 30% in comparison with deionized water, while a 0.05 wt.% hybrid nanofluid without CNT particles improved the thermal conductivity by 19%. Although the electrical conductivity increased by adding nanoparticles to the base fluid, it didn’t change significantly for nanofluids containing CNTs compared to nanofluids without CNT particles.

Carbon nanotubes and plant diversity reduce greenhouse gas emissions and improve nitrogen removal efficiency of constructed wetlands

Adding carbon nanotubes (CNTs) and manipulating plant diversity are ways to improve the functioning of constructed wetlands (CWs), such as by maintaining the high nitrogen (N) removal efficiency and low emission of gaseous pollutants from CWs used for wastewater treatment. The conversion of biomass improved by diversity to bioenergy can further reduce greenhouse gas emissions. We established 108 microcosms to simulate CWs to explore the effects of adding CNTs to wastewater and assembling plant diversity on ammonia (NH3), nitrous oxide (N2O), and methane (CH4) emissions from CWs. The results showed that (1) plant species mixtures with CNTs lowered NH3 emissions and NH3 emissions per unit N removal (NH3/NR) to 5 and 10%, respectively, compared with monocultures without CNTs; (2) mixtures with CNTs decreased global warming potential integrating N2O and CH4 emissions (GWPnon-CO2) and GWP non-CO2 per unit N removal (GWPnon-CO2/NR) to 28 and 32%, respectively, compared with monocultures without CNTs; (3) CNTs decreased the biomass production in some monocultures, while the mixture with CNTs doubled the biomass production compared with monocultures without CNTs; and (4) the presence of Arundo donax (high mass species) in communities with CNTs decreased GWPnon-CO2/NR to 23% and NH3/NR to 9% of that under monoculture without CNTs. This study suggests that adding CNTs and increasing high species richness or assembling mixtures with high-biomass species are more effective and cleaner for maintaining high N removal and bioenergy production while reducing N2O, CH4, and NH3 emissions in CWs.

Printed Structurally Colored Cellulose Sensors and Displays

AbstractHydroxypropyl cellulose (HPC) is a commercially available and biodegradable cellulose derivative, which is known to self‐assemble into chiral nematic liquid crystal phases in water. These features, including liquid crystal‐induced selective reflections in the visible range, make HPC an ideal biopolymer host material for dynamic structural color‐shifting materials. Herein, HPC is used as a starting matrix material and found that, by adding carbon nanotubes (CNT) to an aqueous dispersion of HPC, the color saturation can be improved without influencing the structural color formation and simultaneously conferring electrical conductivity to the material. Additionally, up to 0.4 wt% of cellulose nanofibrils (CNF) can be added to control and tune the rheological properties of the suspension allowing for 3D printability while also maintaining the structural colors. The HPC‐CNT‐CNF printed composite materials show application for flexible color‐changing devices in the form of a dual readout optical and resistive strain sensor and is used as the active material in a dynamic seven‐segment color display. This multipurpose color‐changing material has the potential to be used in the creation of eco‐friendly visual intelligent devices and biodegradable user interfaces and, as such, contributes to the advancement of the field of sustainable and green electronics.

Utilization of carbon nanotubes and steel fibers to improve the mechanical properties of concrete pavement

BackgroundRigid pavements have become an urgent demand in recent years, as these pavements need less maintenance and renovation than other types. However, traditional rigid pavement faces various challenges and difficulties over its lifetime. It has a much higher initial erection cost than asphalt pavements, a greater sensitivity to dynamic stresses, and a highly susceptible to temperature variations causing cracking. Previous works dealt with these drawbacks by using effective materials as alternatives to cement and/or aggregates in pavements mixtures. In the last few years, much interest has been carried out in nanomaterial applications to improve the mechanical performance of construction materials, which can also be used for rigid pavement constructions. This improvement is due to nanomaterials' role in concrete as nanoreinforcements and nanofillers. On the other hand, various types of fibers have been used to improve the performance of concrete constructions. This study investigates the effect of adding carbon nanotubes (CNTs) and steel fibers (SFs) to concrete mixtures. A series of experiments on concrete mixes with various weight percentages of CNTs (0%, 0.025%, 0.050%, and 0.075%) were added to the mixtures to determine the best cost and amount of CNTs to add to a concrete mix. Compressive, tensile, and flexure strength characteristics are investigated. In the second experimental stage of this work, the effect of adding steel fibers to the mixture was investigated.ResultsAccording to the results, the optimal carbon nanotube content in concrete is 0.05%. Compared to other concrete combinations with varying proportions of CNTs, this quantity offers the maximum compressive, tensile, and flexural strength. Additionally, SFs can improve the mechanical properties of the mix as well as enhance its post-cracking and fatigue behavior. Adding both CNTs with SFs increased compressive, tensile, and flexural strength by 22.7%, 29.3%, and 70.8%, respectively, more than the traditional pavement.ConclusionThis work found that combining SFs with CNTs improves the mechanical properties of the concrete mortar, resulting in a stronger mortar that can withstand more loads than the traditional one.

Role of adding carbon nanotubes in the electric and electromagnetic shielding behaviors of three different types of graphene in hybrid nanocomposites

Graphene-related materials (GRM) are promising materials to improve mechanical, electrical, and optical polymer properties. Adding multi-wall carbon nanotubes (MWCNT) on GRM nanocomposites promotes synergistic effects on its electrical properties and electromagnetic interference shielding effectiveness (EMI SE). This study focused on evaluating the addition of MWCNT on three different polycarbonate (PC)/acrylonitrile butadiene styrene (ABS)/GRM nanocomposites. These hybrid nanocomposites were prepared by melt mixing using extrusion and injection-mold processes. The morphologies of the nanocomposites were evaluated by field emission gun scanning electron microscopy (FEG-SEM), and their proprieties were characterized by X-ray diffraction (XRD), oscillatory rheological, dielectric spectroscopy, and EMI SE analyses. The electrical behavior of all hybrid nanocomposites was anisotropic due to the injection-molded preparation process. The lateral size, thickness, and production method of the GRM were indicated to be critical factors for the electrical and EMI SE behaviors of these composites. The nanocomposites with GRM2, which had the smallest lateral size and thickness (graphene nanoplatelets), promoted total attenuation levels around 20 dB with 1.5 wt% of MWCNT, matching the EMI SE required for some commercial applications.

A Multifunctional Light-Driven Swimming Soft Robot for Various Application Scenarios.

The locomotor behavior of creatures in nature can bring a lot of inspiration for the fabrication of soft actuators. In this paper, we fabricated a bionic light-driven swimming soft robot that can perform grasping of tiny objects and achieve the task of object transfer. By adding carbon nanotubes (CNTs), the temperature-sensitive hydrogels can be endowed with light-responsive properties. The fabricated composite hydrogel structure can control the contraction and expansion of volume by light, which is similar to the contraction and diastole behavior of muscles. The oscillation of the fish tail and the grasping action of the normally closed micromanipulator can be achieved by the control of the irradiation of the xenon light source. The bending of the bionic arm can be controlled by the irradiation of a near-infrared (NIR) laser, which transforms the spatial position and posture of the micromanipulator. The proposed scheme is feasible for miniaturized fabrication and application of flexible actuators. This work provides some important insights for the study of light-driven microrobots and light-driven flexible actuators.

A High Conductive Composite Bipolar Plate with Conductive Network Constructed by Chemical Vapor Deposition

In this study, a highly conductive composite bipolar plate with an embedded conductive carbon nanofiber network was prepared by chemical vapor deposition, and a conductive network was constructed inside the composite bipolar plate. The latter network was then compared with a conductive network formed by directly adding carbon nanotubes more evenly distributed. The optimum preparation methods of vapor-grown carbon fibers and the fiber content were analyzed, and the specific surface area and porosity of the bipolar plates were measured and analyzed using a BET test. The results show that the carbon nanofibers prepared under the conditions of 700 °C and a content of 2% exhibited the best effect on improving the performance of the bipolar plates. The conductivity of the prepared bipolar plates could reach 255.2 S/cm, which is 22.1% higher than treatment with multi-walled carbon nanotubes. The bending strength of the prepared bipolar plates was 47.92 MPa, and the interface contact resistance was 6.24 mΩ·cm2. In conclusion, the bipolar plates modified with vapor-grown carbon fibers were a promising kind of material for proton exchange membrane fuel cells.

Influence of conductive additives in a nano-impact electrochemistry study of single LiMn2O4 particles

The application of traditional cathode materials for metal-ion batteries in suspensions is recognized as an effective way of enhancing the volumetric energy density of flow batteries. These additives are called solid boosters. We have studied the influence of conducting additives on the rate-limiting steps (i.e. ion or electron transfer) for intercalating LiMn2O4 materials in suspensions. We analyzed the charge distribution and the maximum current resulting from a single particle of LiMn2O4 colliding with an electrode (i.e. nano-impact electrochemistry) and compared the results to studies with added carbon nanotubes in the water to ensure fast mixed ion/electron transfer. LiMn2O4 nanoparticles 76 nm in size were synthesized via a solution combustion method, then mixed with 30 wt% carbon nanotubes as a composite suspension. Electron transfer from the LiMn2O4 particle to the electrode was found to be the critical factor affecting the response during the single-particle collision. With an increase in the potential, the average charge observed for deintercalation from the composite particles increased nonlinearly and reached 47 % deintercalation at 1.1 V vs. Ag/AgCl. At the same time, only 5 % of lithium can be extracted from LiMn2O4 particles when no carbon nanotube additive is present. Therefore, the addition of a conductive component is essential for the effective investigation of intercalation materials in suspensions and in nano-impact electrochemistry studies.

A high anti-impact STF/Ecoflex composite structure with a sensing capacity for wearable design

By encapsulating shear thickening fluid (STF) in Ecoflex-0030, a kind of composite structure with excellent anti-impact and high energy absorption properties was obtained. The drop hammer tests indicated that the increase of STF concentration could improve the anti-impact and energy absorption capacity of STF/Ecoflex. Furthermore, the loss rate of impact energy of STF/Ecoflex was 63.6% and 36.6% higher than that of aluminum alloy and Kevlar materials, respectively. Numerical simulation was used to explore the mechanism. It was found that the shear thickening effect of STF was enhanced with the increase of STF concentration, which could lead to the increase of the stress level of STF and the energy dissipated by friction and viscosity, thereby the anti-impact performance of the composite was improved. Then, the C-STF/Ecoflex was prepared by adding carbon nanotubes (CNTs) to STF, which had excellent impact sensing function and could be combined with Kevlar for multi-functional wearable devices with anti-impact properties.

Effect of carbon nanotubes addition on thermoelectric properties of Ca3Co4O9 ceramics

Increasing the phonon scattering center by adding nanoparticles to thermoelectric materials is an effective method of regulating the thermal conductivity. In this study, a series of Ca3Co4O9/x wt.% CNTs (x = 0, 3, 5, 7, 10) polycrystalline ceramic thermoelectric materials by adding carbon nanotubes (CNTs) were prepared with sol-gel method and cold-pressing sintering technology. The results of x-ray diffraction and field emission scanning electron microscopy show that the materials have a single-phase structure with high orientation and sheet like microstructure. The effect of adding carbon nanotubes to the thermoelectric properties of Ca3Co4O9 was systematically measured. The test results of thermoelectric properties show that the addition of carbon nanotubes reduces the electrical conductivity and Seebeck coefficient of the material. Nevertheless, the thermal conductivity of the samples with carbon nanotubes addition is lower than that of the samples without carbon nanotubes. At 625 K, the thermal conductivity of Ca3Co4O9/10 wt.% CNTs sample is reduced to 0.408 W⋅m−1⋅K−1, which is about 73% lower than that of the original sample. When the three parameters are coupled, the figure of merit of Ca3Co4O9/3 wt.% CNTs sample reaches 0.052, which is 29% higher than that of the original sample. This shows that an appropriate amount of carbon nanotubes addition can reduce the thermal conductivity of Ca3Co4O9 ceramic samples and improve their thermoelectric properties.

Comparative study of electrochromic properties of polyaniline-polyacid layers prepared by spray- coating and drop-casting methods with adding carbon nanotubes

The influence of the coating method (spray-coating or drop-casting onto horizontal substrate) on the electrochromic characteristics of the layers of water-soluble polyaniline-polyacid complex was investigated. It was shown that, in the case of adding single-wall nanotubes, the polyaniline-polyacid layers prepared by the scalable spray-coating technology demonstrate high coloration speed and electrochromic efficiency. Keywords: polyaniline, electrochromism, polyacid, carbon nanotubes.

The Influence of Processing Methods on Corrosion Rates of Magnesium - Carbon Nanotube Nanocomposites: A Short Review

Several studies have reported the corrosion rates of magnesium carbon nanotube nanocomposites, but their corrosion behavior is still not well understood. Adding carbon nanotubes (CNTs) to magnesium (Mg) matrices almost always results in an increase in mechanical properties, e.g., increased elastic modulus, hardness, ultimate tensile strength, and yield strength. However, this increase in mechanical properties usually comes at the expense of compromised corrosion resistance. Galvanic interactions between the carbon nanotubes and the magnesium matrix are the usual culprits of nanocomposite corrosion. It is important to study the corrosive behavior of these materials further to create a nanocomposite that is less susceptible to corrosion from the start, i.e., by careful selection of the fabrication method. In the present review, four processing methods (Disintegrated Melt Deposition, Friction Stir Processing, Powder Metallurgy, and Ball Milling), which were used to successfully synthesize magnesium carbon nanotube nanocomposites and test their corrosive properties are discussed. Attempts are made to correlate processing methods to corresponding corrosion rates. It was found that the corrosion rates extracted from each reviewed study may not be readily comparable, and by looking into nanocomposite coatings and carbon nanotube, it was found that volume or weight percent optimization may be the best way to proceed. The findings of this investigation can be used as a starting point for the creation of a magnesium carbon nanotube nanocomposite, which is less inherently susceptible to corrosion as this could take the “potential” out of the many potential applications of these novel materials.

3D bioprinting of an electroactive and self-healing polysaccharide hydrogels.

Polysaccharide hydrogels including alginate, agarose, hyaluronic acid, and chitosan have been widely used as scaffolds in 3D bio-printing field. Konjac glucomannan (KGM) exhibits excellent properties of water solubility, biocompatibility, and biodegradability. Herein composite hydrogels were prepared via Schiff-base reaction between the aldehyde group of oxidized konjac glucomannan (OKGM) and the amino group of branched polyethyleneimine (PEI). The OKGM/PEI composite hydrogel displayed self-healing ability and pH sensitivity and showed shear thinning capability, which is suitable for 3D bio-printing technology. Furthermore, the OKGM/PEI electroactive composite hydrogel was obtained by adding carbon nanotubes (CNTs). Then the rheological behavior and morphology of OKGM/PEI electroactive hydrogels were thoroughly characterized. The conductivities of OKGM/PEI electroactive composite hydrogels increased with increasing the content of CNTs. The rheological behavior and 3D bio-printability of OKGM/PEI electroactive hydrogels were also tested. It was found that CNTs can also improve the bio-printability of OKGM/PEI electroactive hydrogels. Thus, the OKGM/PEI electroactive hydrogels could be employed as scaffolds for muscle and cardiac nerve tissue regeneration.

Simulation of nanofluid-cooled lithium-ion battery during charging: A battery connected to a solar cell

In this study, a lithium-ion battery hybrid cooling system is designed to cool the battery using nanofluid and extended surfaces (microchannels). The battery connected to a solar system is evaluated during charging mode. Initially, according to topology optimization based on the maximum heat transfer and minimum pressure drop, the model with maximum efficiency is proposed. A non-Newtonian hybrid nanofluid containing carbon nanotubes flows inside it. Numerical simulations are performed for this system. The Galerkin finite element algorithm is used to perform the calculations and the simulated results are performed to analyze the flow behavior and heat transfer of non-Newtonian nanofluid around the battery. The results demonstrate that the use of the A-3 model at the Reynolds number of 100 creates the lowest maximum temperature in the battery cell, which is 0.4 °C lower than that in the classic model. Also, at a Reynolds number of 1000, model A-2 has the lowest maximum temperature among different models, which is 0.11 °C lower than the classic model. The use of hybrid nanoparticles in all models reduces initial temperature value and enhances the amount of pressure drop at all Reynolds numbers. Among these, the classic model has the maximum and the A-4 model has the minimum pressure drop among different models at different Reynolds numbers, especially Re = 1000. Finally, it is revealed that adding carbon nanotubes to the base fluid and using the nanofluids in microchannels to cool the battery improves battery performance and enhances battery efficiency.

Electroactive shaping and shape memory of sequential dual-cured off-stoichiometric epoxy/CNT composites

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.The obtained results confirmed that CNTs catalyse the homopolymerization epoxy reaction, hindering the sequential curing process, due to the π–π anchoring of imidazole catalyser over the CNTs surface, enhanced by donor–acceptor interaction.Non-doped off-stoichiometric resins present relatively high thermal strength, with a glass transition temperature in the range of 73–109 °C, and high stiffness, with a storage modulus close to 2–3 GPa. They can be easily conformed at low temperature, 60 °C, before their second curing stage, showing a high shaping efficiency (around 90%) and full fixing efficiency (>98%).Nanocomposites with 0.2% CNT present efficient Joule heating, triggering the shape memory at low voltage, <80 V, with fixing and recovery efficiencies of 60–85%. In addition to its high in-situ applicability, the electrical resistive heating is faster and more efficient than conventional heating in an oven.