Multi-walled Carbon Nanotubes In Epoxy Matrix Research Articles

Facile grafting hyperbranched poly(thiol ether‐ester) onto multiwalled carbon nanotubes (MWCNTs) via thiol‐yne click chemistry to enhance the thermal conductivity, mechanical, and thermal properties of MWCNTs/epoxy composites

AbstractIn this study, we report an efficient and rapid technique to achieve the covalent functionalization of multiwalled carbon nanotubes (MWCNTs) by hyperbranched poly(thiol ether‐ester) (HPTEE) via thiol‐yne click chemistry method. The structures of the MWCNTs grafted with HPTEE (MWCNTs‐HPTEE) were characterized and their effects on the epoxy‐based composites were investigated. It was found that the hyperbranched polymers have been successfully grafted onto the MWCNTs surface thorough covalent bonds, which can greatly improve the dispersion of MWCNTs in epoxy matrix and the interfacial interaction between them, contributing to the largely enhanced mechanical and thermal properties. When 0.6 wt% MWCNTs‐HPTEE was added, the composites exhibited the best mechanical properties. An impressive 180% increase in the impact strength and 72.3% increase in flexural strength were observed with respect to the neat epoxy resin. Moreover, at the same filler content, the thermal stability and thermal conductivity of MWCNTs‐HPTEE/epoxy composites outperformed the composites containing the raw MWCNTs. Experimental results demonstrated that the resulted MWCNTs‐HPTEE are more effective on the improvement of properties of epoxy‐based composites as compared with raw MWCNTs.

Enhancement of open hole tensile strength via alignment of carbon nanotubes infused in glass fiber - epoxy - CNT multi-scale composites

Cut-out or holes are unavoidable features in composites for structural assembly and functionality. To enhance the strength of the unidirectional glass fiber reinforced plastic (UD-GFRP) laminates around the cut-outs, multi-walled carbon nanotubes (MW-CNTs) were locally aligned at the periphery of the cut-outs via non-uniform electric field. These multi-scale UD-GFRP composites were fabricated in two configurations based on CNT alignment in parallel and perpendicular directions to the glass fiber orientation. The performance was compared with composites containing randomly oriented MW-CNTs in epoxy matrix and composites without MW-CNTs. The damage evolution was investigated using digital image correlation (DIC) techniques during open hole tensile (OHT) tests. The presence of aligned MW-CNTs around the hole perpendicular to the fiber orientation was able to arrest the pertinent damage modes leading to an increase of the tensile strength by 27% as compared to the control samples fabricated using neat epoxy resin.

Thermo-mechanical and anti-corrosive properties of MWCNT/epoxy nanocomposite fabricated by innovative dispersion technique

Abstract To obtain cluster free homogeneous dispersion of carbon nanotubes in polymer matrix, variety of strategies were applied. In the present work, we report a systematic approach to obtain a superior level of dispersion of multi-walled carbon nanotubes (MWCNTs) in epoxy by applying simultaneously ultrasonic waves and shear force generated by axial flow impeller. The influence of dispersion of MWCNTs on anti-corrosion, mechanical and thermal properties of MWCNT/epoxy nanocomposite was investigated. Field Emission Scanning Electron Microscopy (FESEM) studies confirmed cluster free uniform dispersion of MWCNTs in epoxy matrix, which lead to enhanced tensile strength by 35%, toughness by 53% and storage modulus by 35% on loading of 0.75 wt% of MWCNTs in epoxy. It was found that when mild steel was coated with MWCNT/epoxy nanocomposite (0.75 wt%), the corrosion rate decreased upto 2.5 × 10 −3 MPY and protection efficiency increased upto 99.99%.

Influence of unique structure of glassy carbon on morphology and properties of its epoxy-based binary composites and hybrid composites with carbon nanotubes

The study of interfacial interactions between polymer matrix and particulate fillers is essential for producing composites with enhanced properties. In this work, the influence of the unique glassy carbon (GC) structure on the properties of its binary epoxy composites as well as hybrid nanocomposites with GC and multi-walled carbon nanotubes (MWCNTs) was investigated. The purpose of incorporating MWCNTs into the epoxy matrix (EP) as an addition filler was to obtain nanocomposites with improved properties. The influence of GC particles alone or in combination with MWCNTs on morphological, thermomechanical, and electrical properties of composites was studied in detail. There were found good, homogeneous dispersion of GC and MWCNTs in epoxy matrix as well as strong interfacial interactions between the carbon fillers and epoxy. Mechanical measurements demonstrated that both the tensile and bending properties of the composites, especially the hybrid composites, were greatly improved compared with those of pure epoxy due to the uniform dispersion of fillers in epoxy and significant adhesion between the filler and matrix. The electrical resistivity of hybrid composites, which is directly related to the presence of MWCNTs in addition to the GC, decreased sharply by 9–11 orders of magnitude compared to the insulating matrix. Such composites with enhanced mechanical and electrical properties could be applied in various branches of industry.

Improvement of impact-resistant property of glass fiber-reinforced composites by carbon nanotube-modified epoxy and pre-stretched fiber fabrics

Glass fiber-reinforced plastic composites (GFRPs) are often suffered to impact loadings; it is essential to improve its damage-resistant properties and understand the energy absorption mechanisms. In this work, the low-velocity impact behaviors of GFRPs were investigated in consideration of epoxy resins modified with 0, 0.4, and 0.75 % multi-walled carbon nanotubes (MWCNTs) by weight content and pre-stretched fabric at 0, 1.27, and 2.47 kg weight. In comparison with pure GFRPs sample, MWCNT-modified specimens are effective in improving the impact resistance under impact energies at 9, 16, and 22 J in terms of reduced damage factor and enhanced perforation threshold. Microscopic fractographic analysis indicated that the incorporation of MWCNTs in epoxy matrix offered additional mechanisms through breakage, bridging, and pull-out of carbon nanotubes to favor load transfer effect, prevent crack propagation, and thus dissipate more energy. The dynamic thermo-mechanical analysis proved that MWCNTs improved the storage modulus and glass transition temperature of the composites. In addition, the pre-stretched GFRP composites showed more impact resistant than the non-stretched ones through instant load transfer effect.

Improvement in Elastic Modulus of MWCNT/Epoxy Nanocomposites

The effect of multi-walled carbon nanotubes (MWCNT) on the elastic modulus of MWCNT/epoxy nanocomposites was investigated. Carboxylic acid-functionalized MWCNTS (MWCNT-COOH) were obtained by oxidation pristine MWCNTs via sonication in sulfuric-nitric acid. Epoxy-based nanocomposites reinforced with MWCNTs with and without functionalization were prepared. In this work, the elastic modulus of MWCNT reinforced nanocomposite was determined by free vibration test. Experimental results showed that functionalized MWCNTs improved the dispersion of MWCNTs in epoxy matrix leading to the enhancement of elastic modulus compared to those containing MWCNTs without functionalization. Nanocomposites prepared with 1 wt % of MWCNT-COOH exhibited 44 % increase in Young’s modulus.

Synthesis and Characterization of Functionalized Multi-Walled Carbon Nanotubes

Multi-walled carbon nanotubes (MWCNT) were dispersed in a mixture of sulfuric and nitric acid with volume ratio of 3:1. Carboxylic acid-functionalized MWCNTS (MWCNT-COOH) were obtained by oxidation pristine MWCNTs via sonication in sulfuric-nitric acid. Epoxy-based nanocomposites reinforced with MWCNTs with and without functionalization were prepared. Chemical functionalization of MWCNTs by oxidation (MWCNT-COOH) was confirmed by FTIR. The properties of nanocomposites were characterized using scanning emission microscopy (SEM). Experimental results showed that functionalization of MWCNTs improved the dispersion of MWCNTs in epoxy matrix compared to those containing MWCNTs without functionalization.

Fabrication, Morphology and Cure Behavior of Triethylenetetramine-Grafted Multiwalled Carbon Nanotube/Epoxy Nanocomposites

Multiwalled carbon nanotubes (MWCNTs) were first treated by a 3:1 (v/v) mixture of concentrated H2SO4/HNO3, and then triethylenetetramine (TETA) grafting was carried out. X-Ray photoelectron spectroscopy and Raman spectroscopy analyses proved the effectiveness of this kind of chemical functionalization method. The TETA thin layer was formed on the MWCNT surface, which contributes to good dispersion of MWCNTs in epoxy matrix. Cure behaviors of MWCNT/epoxy systems were studied with non-isothermal differential scanning calorimetry. MWCNTs have the retarding effect on the cure reaction owing to their steric hindrance, while TETA functional groups on the MWCNT surface can accelerate the primary amine-epoxide reaction and weaken the inhibition effect on the process of cure. A qualitative analysis of the degree of vitrification in different epoxy systems was performed. The activation energy of the cure reactions was obtained by the Flynn-Wall-Ozawa method.