Carbon Nanotube Epoxy Research Articles

Piezoresistive performance characterization of strain sensitive multi-walled carbon nanotube-epoxy nanocomposites

Carbon nanotubes polymer nanocomposites have attracted a significant research, which provide interesting aspects for the realization of cost effective, highly sensitive piezoresistive strain sensors. Here, we report on an extensive piezoresistive performance investigation of multi-walled carbon nanotubes (MWCNTs)/epoxy nanocomposite under uniaxial cyclic tensile and compressive loading in low strain range. Dispersion quality of MWCNTs in the epoxy polymer matrix was monitored by scanning electron microscopy. MWCNTs/epoxy nanocomposite was deposited directly on a glass-reinforced epoxy cantilever beam on the same axis with a commercial metallic strain gauge. The strain sensitive nanocomposite presents high-performance properties, including gauge factor up to 78, good stability of ±0.26% for 10h and durability of −0.08% after cyclic loading and unloading. Furthermore, MWCNTs/epoxy nanocomposites show quite small creep up to ±0.26%, fast response and recovery times, low hysteresis under cyclic tensile and compressive loadings and temperature response make the proposed nanocomposites suitable in various potential strain sensor applications including structural health monitoring.

Effective electrical conductivity of carbon nanotube–epoxy nanocomposites

The electrical conductivity of carbon nanotube–epoxy composites is investigated analytically and experimentally. The theoretical predictions of the effective electrical conductivity of carbon nanotube–epoxy composites were performed by the analytical approach based on a micromechanical model of composites. The parametric analysis carried out revealed an influence of geometrical and electrical parameters of the micromechanical model on the effective electrical conductivity of carbon nanotube–epoxy nanocomposite. The nanocomposites made from the DGEBA-based and RTM6 epoxy resins filled with different weight content of Baytubes C150P and N7000 multi-walled carbon nanotubes were prepared. The experimental values of the electrical conductivity of the nanocomposites were compared with those calculated by means of the analytical model.

Study on Carbon Nanotube Dispersion Behavior in Epoxy Resin under Synergistic Effect of Continuous Stretching Flow and Ultrasound Oscillation

In this paper, carbon nanotubes (CNTs) dispersion behavior in epoxy resin under synergistic effect of continuous stretching flow and ultrasound oscillation was studied. A small continuous stretching machine which could provide continuous stretching flow for polymer was designed and manufactured for studying the synergistic effect of continuous stretching flow and ultrasound oscillation on dispersive property. Firstly, the influence of different initial phase angle of dual rotor and mixing time on dispersive property were studied by preparing specimens of CNTs/epoxy resin composite under continuous stretching machine. Then, the synergistic effect of continuous stretching flow and ultrasound oscillation on dispersive property was studied with various ultrasonic power and synergistic time. In this study, the morphology of blends was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that initial phase angle of dual rotor and mixing time had great effect on the dispersion of CNTs in epoxy resin. The degree of CNTs dispersion was best when the initial phase angle of dual rotor was 0°, and increasing mixing time could improve the degree of CNTs dispersion. Increasing ultrasonic power and synergistic time were helpful to disperse CNTs in epoxy resin. It demonstrated that the synergistic effect of continuous stretching flow and ultrasound oscillation had obviously effect on the dispersion of CNTs.

Molecular simulations of the influence of defects and functionalization on the shear strength of carbon nanotube-epoxy polymer interfaces

Unlike earlier studies, which focused on thermoplastics, in this work attention is devoted to carbon nanotube (CNT) reinforced thermoset polymer composites. Specifically, extensive molecular dynamics (MD) simulations were conducted to study the effect of defects and functionalization on the interfacial shear strength (ISS) of carbon nanotube-epoxy composites before and after cross-linking. Three main types of defects (vacancies, adatom, and Stone-Wales (SW)) as well as phenyl functional group were considered in a representative volume element (RVE). The RVE comprised a single-walled CNT embedded in an epoxy matrix, and consistent valence force field (CVFF) was used in all MD simulations. Our results reveal that (i) vacancy defects degrade the ISS, and that the degradation effects depend predominantly on the number of missing atoms and not on the type of vacancy defects, (ii) adatom defects have a marginal effect on the ISS, (iii) SW defects promote greater ISS of cured systems, (iv) phenyl groups dramatically increase the ISS of cured systems, and (v) uncured systems experience lower ISS which is not affected by the number and type of defects and functionalization. The findings of this study will assist in improving our understanding of the operating toughening/weakening mechanisms and the load transfer capability in epoxy-based nanocomposites.

Temperature dependent reinforcement efficiency of carbon nanotube in polymer composite

Abstract The transcendent mechanical properties of carbon nanotube (CNT) hold the promise of delivering contributory reinforcing effect in soft polymeric materials. But, the built-in-risk of the environmental susceptibility of the CNT/polymer interface should be well explored before certifying it for a particular application. Present investigation reports the reinforcement efficiency of CNT in epoxy as a function of environmental temperature. Nanocomposite with 0.2% CNT, which shows maximum strength and modulus at room temperature, exhibits the poorest strength and modulus at 90 °C. Dynamic mechanical thermal analysis (DMTA) has also been carried out to study the variation of thermomechanical properties of nanocomposites with temperature. A decrement in the glass transition temperature (T g ) of the polymer was obtained due to CNT reinforcement upto 0.2%. Post-failure fracture surface analysis was done to underneath the dominating strengthening, toughening and weakening mechanisms.

Investigation on the mechanical and electrical properties of carbon nanotube/epoxy composites produced by resin transfer molding

For industrial application of carbon nanotube/polymer composites, it is critical to produce composites in an efficient way. In this study, large size carbon nanotube buckypaper, which is directly produced by floating catalyst chemical vapor deposition method, was used to reinforce epoxy through conventional resin transfer molding process. The infiltration behavior of resin was analyzed, indicating that efficient carbon nanotube-epoxy interface has been formed near the surface of the composites. With 26.87% weight fraction of carbon nanotubes, the composites show a great enhancement in mechanical properties, that the failure strength and Young’s moduli increase from 45 MPa and 2.5 GPa to 254.39 MPa and 6.69 GPa with a large failure strain over 15%. In addition, the composite film is electrically conductive with a conductivity of 220 S/cm. It also shows linear piezoresistive effect with a gage factor tested to be 2.68, indicating a great potential in multifunctional smart structure applications.

Giant Surface Conductivity Enhancement in a Carbon Nanotube Composite by Ultraviolet Light Exposure.

Carbon nanotube composites are lightweight, multifunctional materials with readily adjustable mechanical and electrical properties-relevant to the aerospace, automotive, and sporting goods industries as high-performance structural materials. Here, we combine well-established and newly developed characterization techniques to demonstrate that ultraviolet (UV) light exposure provides a controllable means to enhance the electrical conductivity of the surface of a commercial carbon nanotube-epoxy composite by over 5 orders of magnitude. Our observations, combined with theory and simulations, reveal that the increase in conductivity is due to the formation of a concentrated layer of nanotubes on the composite surface. Our model implies that contacts between nanotube-rich microdomains dominate the conductivity of this layer at low UV dose, while tube-tube transport dominates at high UV dose. Further, we use this model to predictably pattern conductive traces with a UV laser, providing a facile approach for direct integration of lightweight conductors on nanocomposite surfaces.

Aligned carbon nanotube–epoxy composites: the effect of nanotube organization on strength, stiffness, and toughness

A protocol has been developed for the production of epoxy-based composites containing high-volume fractions of aligned carbon nanotubes. The nanotubes were fabricated as continuous fibres or aligned mats directly from the CVD reactor, in which they were synthesized. The block composites with highly aligned and tightly packed nanotube assemblies were prepared via epoxy resin infiltration, and their volume fraction, distribution, and internal porosity being analysed prior to mechanical testing. The samples were tested in both axial tension and three-point bending. The results show that the strength and stiffness enhancements were close to pro rata with the volume fraction of the carbon nanotubes added. The failure modes were distinctly different from those characteristic of the conventional aligned carbon fibre composites. The fracture surface showed considerable evidence of pull-out of bundles of (~50) nanotubes, but the pull-out appeared to involve the resin matrix which drew out along with the bundles. Subsidiary cracks were bridged by nanotube bundles giving structures reminiscent of crazes in glassy polymers, what constitutes the distinct toughness mechanism and higher resistance to the transverse cracks propagation.

Effect of Fluorination on Thermal and Mechanical Properties of Carbon Nanotube and Graphene Nanoplatelet Reinforced Epoxy Composites

에폭시 수지와의 계면 결합력을 향상시키기 위하여, 탄소나노튜브(CNT)와 그래핀 나노플레이트릿(GNP)을 불소화시켰다. 표면 처리된 CNT와 GNP의 표면화학적 특성은 광전자 분광기를 이용하여 분석되었다. 또한 그 에폭시 복합재의 기계적 성질 및 열안정성을 평가하였다. CNT와 GNP 보강 에폭시 복합재는 CNT 보강 에폭시 복합재와 비교하여 비교적 높은 강도를 보였다. 이러한 결과는 종횡비가 서로 다른 두 강화재 때문에 네트워크 구조가 형성되어 나타나는 크기효과에 기인하였다. 불소화 표면처리된 CNT/GNP 보강 에폭시 복합재의 인장강도, 충격강도 및 열안정성은 미첨가 에폭시와 비교하여 각각 101, 69, 및 130%로 크게 향상되었다. 이 결과는 크기 효과 및 표면 처리에 따른 강화재와 에폭시 수지의 계면 결합력 향상에 의한 시너지 효과에 기인한 것으로 보인다.

Conductivity analysis of epoxy/carbon nanotubes composites by dipole relaxation and hopping models

In this study it was used a numerical technique of successive approximations to estimate parameters of a conductivity model that includes the hopping process and the dipole relaxation for the purpose of describing the behavior of the conductivity measured on nanocomposites with carbon nanotubes in epoxy resin in the range of frequency of 100Hz to 40MHz. Two relaxation bands were detected, one with a response below 10kHz and one above 10MHz. For the first band, it was observed that the nanocomposites become more conductive, and its conductivity less temperature dependent, as the nanotube content increases. The second band is characterized by a large spread in relaxation time. The results show that the percolation threshold is below 0.15vol% and that ‘ac’ hopping is the main transport process above 100kHz, becoming dominant with respect to percolation at higher temperatures (>340K).

Improvement of dispersion of carbon nanotubes in epoxy resin through pyrogallol functionalization

Multiwalled carbon nanotubes (MWNTs) were functionalized with pyrogallol. The functionalized MWNTs were well‐dispersed in the epoxy/curing agent/ethanol solution, as demonstrated by UV‐vis spectra and optical micrographs. Epoxy resin/MWNTs composites were prepared via solution mixing method. The cure behavior was characterized using differential scanning calorimetry. Pyrogallol‐functionalized carbon nanotubes (CNTs) reacted with the epoxy through the mediation reaction of pyrogallol with the curing agent, leading to the interfacial bonding between the functionalized carbon nanotubes (CNTs) and the resin matrix. Due to the excellent dispersion and interfacial bonding, the mechanical strength and electrical conductivity of the epoxy resin/CNTs composites have been improved. POLYM. ENG. SCI. 56:1079–1085, 2016. © 2016 Society of Plastics Engineers

Simultaneous voltammetric detection of ammonium and nitrite from groundwater at silver-electrodecorated carbon nanotube electrode

Ammonium and nitrite are listed by Water Framework Directive as core parameters that should be monitored for the groundwater as drinking water source. This work describes the sensitive protocols for the simultaneous detection of ammonium and nitrite in water at a new silver-electrodecorated carbon nanotubes-epoxy composite electrode (Ag-CNT) using advanced voltammetric technique. A carbon nanotubes-epoxy composite electrode obtained by two-roll mill procedure was decorated electrochemically with silver nanoparticles. This new electrode displays excellent electrocatalytic activity towards the direct oxidation of ammonium and nitrite at well separated less potential values (+0.15 V/SCE for ammonium and +0.7 V/SCE for nitrite). Very good detection sensitivities (0.613 mA mM−1 for ammonium and 0.980 mA mM−1 for nitrite) and the lowest limits of detection (1 μM for ammonium and 0.7 μM for nitrite) were achieved by differential-pulsed voltammetry (DPV) under optimum operating conditions of 0.05 V step potential, 0.2 V modulation amplitude and the scan rate of 0.05 V s−1. This detection protocol was successfully applied to the simultaneous determination of ammonium and nitrite in groundwater samples, and the results were found to be consistent with the values obtained by the standardized spectrophotometry methods.

Processing of Functionalized and Pristine Carbon Nanotube Epoxy Composites with Silane-Treated Glass Fiber

In this work, an attempt has been made to study the bonding between the silane coupling agents and the glass fiber (GF) surface. The mechanical properties of the composites so obtained have been specifically analyzed. It has been experimentally found that epoxy silane (ES)-treated GF mat in a neat epoxy matrix showed considerable improvement compared to amino silane (AS)-treated GF. The effect of heat treatment on GF has also been looked into. Moreover, a new processing technique has been explored, which involves the use of amino functionalized nanotube (ACNT) and pristine nanotube (PCNT), homogeneously and uniformly dispersed in an epoxy matrix. Additionally, the effect of ES- and AS-treated GF in the presence of PCNTs and ACNTs has been studied and it has been found that AS shows strong interfacial adhesion in the ACNT matrix, whereas ES shows improved mechanical behavior in the PCNT matrix. The findings from this study have certainly helped us design improved fiber reinforced nanocomposites with enhanced mechanical properties suitable for marine structures.

Corrosion protection mechanisms of carbon nanotube and zinc-rich epoxy primers on carbon steel in simulated concrete pore solutions in the presence of chloride ions

This study investigates the electrochemical characterization of carbon nanotube and zinc-rich epoxy primers (CNT-ZRPs) on carbon steel in simulated concrete pore (SCP) solutions in the presence of chloride ions. The mechanistic performance of CNT-ZRPs was characterized by adding different zinc content. The electrochemical results indicated a dominant barrier protection effect for the coating with 60wt% Zn while there was a mixed corrosion protection mechanism for the coating with 70wt% Zn and a dominant cathodic protection mechanism for coatings with higher zinc content (80wt% and 90wt% Zn). These barrier and cathodic protection control mechanisms were characterized quantitatively by electrochemical and high-resolution techniques.

Carbon nanotube-epoxy composites: The role of acid treatment in thermal and electrical conductivity

Wet acid oxidation treatment methods have been widely reported as an effective method to purify and oxidize the surface of industrial multi-walled carbon nanotubes. This work examines the use of a concentrated HNO3/H2SO4 mixture in an attempt to optimize the purification procedure of industrial multi-walled carbon nanotubes with diameter distribution statistics. It is shown that acid treatments of several hours are enough to purify the nanotubes. The electrical and thermal conductivities of epoxy composites containing 0.05–0.25 wt% of an acid-treated multi-walled carbon nanotube have been studied. The electrical conductivity of the composites decreases by more than three orders, whereas the thermal conductivity of the same specimen increases very modestly as a function of the filler content.

On the use of dielectric spectroscopy for the real time assessment of the dispersion of carbon nanotubes in epoxy

We report the on line monitoring of the dispersion of carbon nanotubes in a typical aerospace epoxy system via dielectric spectroscopy.

A carbon nanotube–epoxy interface improved damping below the glass transition temperature

Composites made from fibers and epoxy display a low viscous drag and are rarely used as mechanical dampers at room temperature.

Real-time detection of carboplatin using a microfluidic system.

A microfluidic sensor system based on a carbon nanotube-epoxy composite electrode was fabricated to allow detection of the presence of the anti-cancer drug carboplatin in healthy tissue in real time during chemotherapy. Detection of carboplatin was carried out by observing the effects of the drug on the differential pulse voltammetry of free purine bases using a novel carbon nanotube-epoxy composite electrode. In free solution these electrodes performed better than glassy carbon electrodes for oxidation of the free purine bases AMP and GMP, and than DNA-modified carbon nanotube-epoxy composite sensors for detection of carboplatin. On-line carboplatin detection was performed using a computer-controlled microfluidic platform. The methodology for on-line carboplatin detection was optimised in terms of the analysis time and to allow repeated carboplatin measurement using the same electrode. Microdialysis sampling and our microfluidic platform were combined to give a proof-of-concept system for real-time carboplatin detection with a limit of detection of 0.014 μM carboplatin in the sampled media. This paper is dedicated to Craig Lunte's pioneering work in analysis and microdialysis.

Rheology of electrostatically tethered nanoplatelets and multi-walled carbon nanotubes in epoxy

Multi-walled carbon nanotubes (MWCNTs) dispersed using α-zirconium phosphate (ZrP) nanoplatelets in a glassy epoxy have previously been reported to tremendously improve modulus, strength and ductility in a manner that could not be explained based on continuum-level descriptions of particle-level reinforcement. Several other recent studies have shown similar synergistic improvements in bulk properties for low concentrations of co-dispersed plate-like and rod-like nanoparticles. In this work, we have used rheology as a tool to probe the microstructure and interactions for the ZrP/MWCNT hybrid system in an uncured epoxy pre-polymer fluid. The results are compared to the behavior of model suspensions containing the individually dispersed nanoparticles to more clearly differentiate between particle-level and mesostructural interactions. The linear viscoelastic results show that the ZrP-assisted dispersion approach fully disentangles and stabilizes the MWCNTs in the epoxy fluid. When subjected to large amplitude oscillatory shear or steady shear, the hybrid suspensions show pronounced strain-hardening and shear thickening behaviors, respectively, that were not observed with suspensions containing either individual component. The non-linear behavior is attributed to the direct tethering of the exfoliated ZrP nanoplatelets to the disentangled MWCNTs, which are proposed to serve as mechanically robust junctions. In the solid state, this hybrid network retains sufficient mechanical integrity to delocalize stress concentrations near flaws and cracks in the epoxy matrix, and is responsible for the enormous strengthening behavior observed in this system. The present study provides several potential design considerations for preparation of high-performance nanocomposite systems containing a co-dispersion of interacting nanoparticles.

Epoxy composite dusts with and without carbon nanotubes cause similar pulmonary responses, but differences in liver histology in mice following pulmonary deposition.

BackgroundThe toxicity of dusts from mechanical abrasion of multi-walled carbon nanotube (CNT) epoxy nanocomposites is unknown. We compared the toxic effects of dusts generated by sanding of epoxy composites with and without CNT. The used CNT type was included for comparison.MethodsMice received a single intratracheal instillation of 18, 54 and 162 μg of CNT or 54, 162 and 486 μg of the sanding dust from epoxy composite with and without CNT. DNA damage in lung and liver, lung inflammation and liver histology were evaluated 1, 3 and 28 days after intratracheal instillation. Furthermore, the mRNA expression of interleukin 6 and heme oxygenase 1 was measured in the lungs and serum amyloid A1 in the liver. Printex 90 carbon black was included as a reference particle.ResultsPulmonary exposure to CNT and all dusts obtained by sanding epoxy composite boards resulted in recruitment of inflammatory cells into lung lumen: On day 1 after instillation these cells were primarily neutrophils but on day 3, eosinophils contributed significantly to the cell population. There were still increased numbers of neutrophils 28 days after intratracheal instillation of the highest dose of the epoxy dusts. Both CNT and epoxy dusts induced DNA damage in lung tissue up to 3 days after intratracheal instillation but not in liver tissue. There was no additive effect of adding CNT to epoxy resins for any of the pulmonary endpoints. In livers of mice instilled with CNT and epoxy dust with CNTs inflammatory and necrotic histological changes were observed, however, not in mice instilled with epoxy dust without CNT.ConclusionsPulmonary deposition of epoxy dusts with and without CNT induced inflammation and DNA damage in lung tissue. There was no additive effect of adding CNT to epoxies for any of the pulmonary endpoints. However, hepatic inflammatory and necrotic histopathological changes were seen in mice instilled with sanding dust from CNT-containing epoxy but not in mice instilled with reference epoxy.Electronic supplementary materialThe online version of this article (doi:10.1186/s12989-016-0148-2) contains supplementary material, which is available to authorized users.