Multi-walled Carbon Nanotubes Loading Research Articles

Morphological and electrical characterization of conductive polylactic acid based nanocomposite before and after FDM 3D printing

ABSTRACTThree dimensional (3D) printing holds strong potential for the formation of a new class of multifunctional nanocomposites. Therefore, both the nanocomposites and 3D printing communities need to make more collaborations and innovations for developing and processing of new polymers and composites to get benefit of functionalities of 3D printed nanocomposites. The contribution of this paper is the creation of 3D printable filaments from conductive polymer nanocomposites using a melt mixing process. Multi‐walled carbon nanotubes (MWNTs) and high‐structured carbon black (Ketjenblack) (KB) were incorporated into polylactic acid. The percolation threshold of MWNT composites is 0.54 wt % and of KB composites is 1.7 wt % by four‐point resistance measurement method. In the similar melt mixing process, there was no dependence of diameter of produced 3D printer filaments on the MWNT loading, instead the diameter was dependent on the KB loading and increased with increasing the filler amount. The conductivity of extruded filaments from 3D printer in low filler contents decreases with increasing extruder temperature, yet in higher filler contents there is no effect of extruder temperature on conductivity. Finally, the resistance decreases exponentially with the increase of cross‐sectional area of 3D printed tracks. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47040.

Comparing the performance of electrospun and cast nanocomposite film of polyamide-6 reinforced with multi-wall carbon nanotubes

This study aims at fabrication and characterization of two different structures of electrically conductive polyamide 6/multi-wall carbon nanotube nanocomposite films at different multi-wall carbon nanotube concentrations including electrospun nanofibrous and cast films. Morphology, embedded multi-wall carbon nanotubes into nanofiber, thermal behavior, electrical conductivity and wettability of films were characterized. Scanning electron microscopy images depicted that the nanofiber diameter decreased with increased nanofillers. Enhancement of crystallinity, electrical and tensile properties, and simultaneously achieving a low percolation threshold confirmed good nanotube dispersion by employing a polymeric emulsifier, polyvinylpyrrolidone. The electrospun film crystalline content increased 18.5% and the cast ones increased 46.8% at 7 wt.% multi-wall carbon nanotubes loading. The electrospun and cast membrane electrical conductivity increased by 10 and 12 orders of magnitude. These results demonstrated higher values compared to previously reported data for polyamide 6/multi-wall carbon nanotube nanocomposites. The electrospun film Young’s modulus increased 93% and that of casted one increased 267%, due to the increased crystallinity after adding carbon nanotubes into the films.

Nanocomposite Ultrafiltration Membranes Incorporated with Zeolite and Carbon Nanotubes for Enhanced Water Separation

The objective of this work is to develop a new class of nanocomposite ultrafiltration (UF) membranes with excellent solute rejection rate and superior water flux using zeolitic imidazolate framework-8 (ZIF-8) and multi-walled carbon nanotubes (MWCNTs). The effect of ZIF-8 and MWCNTs loadings on the properties of polyvinyldifluoride (PVDF)-based membrane were investigated by introducing respective nanomaterial into the polymer dope solution. Prior to filtration tests, all the membranes were characterized using several important analytical instruments, i.e., SEM-EDX and contact angle analyzer. The addition of the nanoparticles into the membrane matrix has found to increase the membrane pore size and improve its hydrophilicity compared to the pristine membrane. The separation performance of membranes was determined with respect to pure water flux and rejections against bovine serum albumin (BSA) and humic acid (HA).The experimental findings indicated that the nanocomposite membranes in general demonstrated higher permeation flux and solute rejection compared to the pristine membrane and the use of ZIF-8 was reported to be better than that of MWCNTs in preparing nanocomposite UF membranes owing to its better flux and high percentage of solute rejection.

High Strength Conductive Polyamide 6 Nanocomposites Reinforced by Prebuilt Three-Dimensional Carbon Nanotube Networks.

The rapidly growing fields of aerospace, energy, and electronic devices raise the demand for materials with ever-increasing mechanical properties and electrical and thermal conductivity. However, the combination of unusual high performance is difficult to attain. In this study, using prebuilt three-dimensional (3D) closely packed interconnected multiwalled carbon nanotube (MWNT) networks as a backbone for assembly of polymer matrix, a novel, green (solvent-free), and energy-saving method to prepare robust, highly electrical, and thermal conductive polyamide nanocomposites is reported. The as-prepared nanocomposites exhibit significant enhancements of 16 orders of magnitude in electrical conductivity and 505% in thermal conductivity, which mainly benefits from the contributions of closely packed 3D networks and conductive pathways of carbon nanotubes. In addition, even at a high MWNT loading of 25 wt %, the as-prepared nanocomposites still possess a high tensile strength of 99.4 MPa and Young's modulus of 5.3 GPa. The performance of the as-prepared nanocomposites exceeds that of most of the composites, which confirms the potential of the prebuilt MWNT network method for fabricating robust and highly conductive nanocomposites and the importance of good interconnectivity of nanofillers-nanofillers and nanofillers-matrix. The special fabrication method could open up a broad range of possibilities for aerospace, conducting elements, and structural nanomaterials, as well as electronic components with the requirements of heat dissipation, mechanical strength, thermal repair, corrosion resistance, and so on.

Experimental and micromechanical modeling of fracture toughness: MWCNT-reinforced polypropylene/glass fiber hybrid composites

In this study, polypropylene-based nano and hybrid composites are prepared with 20 wt% glass fiber and multiwalled carbon nanotubes (MWCNTs) ranging up to 5 wt%. The multiaxial stress fields developed during external loading of composites cause crack propagation by various fracture mechanisms. Among the nanocomposites, it is observed that the critical stress intensity factor (KI) is highest for the one prepared at 3 wt% loading of MWCNTs. The synergistic effect of multiscale fillers in hybrid composite with MWCNT content of 3 wt% results in superior fracture toughness properties as evidenced by 16.6% increase in KI with respect to neat PP. Analytical expressions that take into account the fracture mechanisms like particle debonding and matrix yielding are employed to estimate the composite crack resistance and then compared with experimentally obtained fracture toughness properties. The fracture toughness properties are found to be dependent on composition of fillers, matrix yield strain, and debonding strain of the composites.

Effect of functionalization of carbon nanotubes on vibration and damping characteristics of epoxy nanocomposites

The vibration and damping characteristics of epoxy composites reinforced by pristine and functionalized multi-walled carbon nanotubes (MWCNTs) were investigated experimentally for potential use as integral passive damping elements in structural composite applications. The MWCNTs were introduced into the acetone solvent and then mixed with epoxy resin through a sonication process and mechanical stirring. The solvent was evaporated from the mixture by means of magnetic hot plate and the hardener was added once it was cooled down to room temperature. The MWCMTs/epoxy mixture was then injected into a mold to form the nanocomposite specimens. Nanocomposite specimens were fabricated for six different MWCNT loadings (0.02, 0.041, 0.061, 0.123, 0.25 and 0.37 wt%). Microstructural analysis, tensile and bending tests were carried out to examine the effect of pristine multi-walled carbon nanotubes (p-MWCNTs) and functionalized multi-walled carbon nanotubes (f-MWCNTs). The frequency response functions (FRFs), coherence and phase diagrams of nanocomposites were measured using a forced vibration technique. A periodic up-chirp signal was generated by a shaker to excite the cantilever nanocomposite specimen at the base. The damped natural frequencies and damping ratios were obtained for different loadings of MWCNTs. The experimental results indicated that the damped natural frequencies of p-MWCNTs/epoxy and f-MWCNTs/epoxy composites increased by adding MWCNTs up to 0.12 wt.%, and decreased at higher MWCNTs content. Addition of p-MWCNTs were improved the damping ratio of nanocomposites. While the damping ratios from f-MWCNTs at loadings of 0.02–0.06 wt.% were higher than those from p-MWCNTs, they did not increase at higher CNTs contents for the first mode of vibration.

Biodegradability of carbon nanotube/polymer nanocomposites under aerobic mixed culture conditions

The properties and commercial viability of biodegradable polymers can be significantly enhanced by the incorporation of carbon nanotubes (CNTs). The environmental impact and persistence of these carbon nanotube/polymer nanocomposites (CNT/PNCs) after disposal will be strongly influenced by their microbial interactions, including their biodegradation rates. At the end of consumer use, CNT/PNCs will encounter diverse communities of microorganisms in landfills, surface waters, and wastewater treatment plants. To explore CNT/PNC biodegradation under realistic environmental conditions, the effect of multi-wall CNT (MWCNT) incorporation on the biodegradation of polyhydroxyalkanoates (PHA) was investigated using a mixed culture of microorganisms from wastewater. Relative to unfilled PHA (0% w/w), the MWCNT loading (0.5–10% w/w) had no statistically significant effect on the rate of PHA matrix biodegradation. Independent of the MWCNT loading, the extent of CNT/PNC mass remaining closely corresponded to the initial mass of CNTs in the matrix suggesting a lack of CNT release. CNT/PNC biodegradation was complete in approximately 20 days and resulted in the formation of a compressed CNT mat that retained the shape of the initial CNT/PNC. This study suggests that although CNTs have been shown to be cytotoxic towards a range of different microorganisms, this does not necessarily impact the biodegradation of the surrounding polymer matrix in mixed culture, particularly in situations where the polymer type and/or microbial population favor rapid polymer biodegradation.

Flexible conductive poly(styrene‐butadiene‐styrene)/carbon nanotubes nanocomposites: Self‐assembly and broadband electrical behavior

ABSTRACTFlexible conductive nanocomposites with the ability of self‐assembly into well‐ordered structures are promising multifunctional materials for energy conversion and storage devices. In this work, flexible nanocomposites based on multi‐walled carbon nanotubes (MWCNTs) and poly(styrene‐butadiene‐styrene) (SBS) were obtained by solution casting, followed by a post‐annealing treatment, during 7 days at 110 °C, to enable the self‐organization of the SBS. The impact of the MWCNTs on the self‐assembly was studied by atomic force microscopy and Small angle X‐rays scattering, and the conductivity of these nanocomposites was analyzed over the broadband frequency range, that is, 10−1–106 Hz. The results revealed that the lower MWCNTs loadings (∼0.2 v %) were the most suitable to achieve a conductive network through the SBS, maintaining self‐assembled domains. These domains include hexagonally packed cylinders and alternating lamellae. Furthermore, at loadings above 1 v %, the impact of further MWCNTs addition on the conductivity was marginal over the whole frequency range and the self‐assembly tendency was progressively reduced. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46650.

Morphology, Nucleation, and Isothermal Crystallization Kinetics of Poly(Butylene Succinate) Mixed with a Polycarbonate/MWCNT Masterbatch.

In this study, nanocomposites were prepared by melt blending poly(butylene succinate) (PBS) with a polycarbonate (PC)/multi-wall carbon nanotubes (MWCNTs) masterbatch, in a twin-screw extruder. The nanocomposites contained 0.5, 1.0, 2.0, and 4.0 wt% MWCNTs. Differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS) results indicate that the blends are partially miscible, hence they form two phases (i.e., PC-rich and PBS-rich phases). The PC-rich phase contained a small amount of PBS chains that acted as a plasticizer and enabled crystallization of the PC component. In the PBS-rich phase, the amount of the PC chains present gave rise to increases in the glass transition temperature of the PBS phase. The presence of two phases was supported by scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis, where most MWCNTs aggregated in the PC-rich phase (especially at the high MWCNTs content of 4 wt%) and a small amount of MWCNTs were able to diffuse to the PBS-rich phase. Standard DSC scans showed that the MWCNTs nucleation effects saturated at 0.5 wt% MWCNT content on the PBS-rich phase, above this content a negative nucleation effect was observed. Isothermal crystallization results indicated that with 0.5 wt% MWCNTs the crystallization rate was accelerated, but further increases in MWCNTs loading (and also in PC content) resulted in progressive decreases in crystallization rate. The results are explained by increased MWCNTs aggregation and reduced diffusion rates of PBS chains, as the masterbatch content in the blends increased.

Morphological, rheological and electrical properties of composites filled with carbon nanotubes functionalized with 1-pyrenebutyric acid

Abstract Non-covalent functionalization of Multi Wall Carbon Nanotubes (MWCNTs) could provide a solution for preserving their electronic structure facilitating the nanocomposite process preparation. Functionalization of MWCNTs by π-stacking interaction between nanofiller and a pyrene derivative has been explored. The rheological properties of filled epoxy resins highlight very interesting benefits from this kind of functionalization. Besides its peculiar capability for preventing agglomeration in the nanofiller dispersion step, it also efficiently contributes to a decrease in the viscosity of the nanocomposites; hence contrasting one of the most relevant drawback related to the manufacturing processes of the nanocomposites at MWCNTs loading rates beyond the Electrical Percolation Threshold (EPT). Because no damage of MWCNTs occurs, sp2 hybridization of carbon atoms is preserved together with the π-electron delocalization typical of polynuclear aromatic rings. Consequently, no deterioration in the electrical properties are detected; the measured EPT values are typical of nanocomposites containing embedded unfunctionalized MWCNTs (lower than 0.28 wt%), whereas for the electrical conductivity beyond the EPT, an enhancement is observed.

Dielectric and impedance properties of three dimension graphene oxide-carbon nanotube acrylonitrile butadiene styrene hybrid composites

In this work, comparison of dielectric and impedance studies of multi-walled carbon nanotube (MWCNTs), graphene oxide-carbon nanotube (GCNTs) reinforced acrylonitrile–butadiene–styrene (ABS) composites prepared by twin-screw extruder with back flow channel have been carried out. The dielectric relaxation and impedance behavior of these polymer composites have been studied with varying wt. % of MWCNTs and GCNTs reinforced ABS matrix in the frequency range of 102–106 Hz. The results showed that the real part of the impedance of the composites with MWCNTs content of 7 wt % or higher exhibits frequency independent behavior at the low-frequency region, and GCNTs-ABS demonstrates frequency dependent. Also, the relaxation time decreases with increase in wt. % of carbon nanofillers due to the formation of an interconnecting path within the polymer matrix. The Nyquist plots for MWCNTs-ABS composites showed the appearance of a single semicircular arc, whose radius of curvature decreases with increase in MWCNTs loading, suggest the decrease in overall impedance of the composite with high amount of filler loading. The radius of arc in impedance spectra decreases with increasing the percentage of fillers indicating the occurence of conducting behavior. In GCNTs-ABS composites Nyquist plots showed the appearance of a single straight line. The dielectric responses of MWCNTs, GCNTs reinforced ABS composites were investigated. The dielectric constant of MWCNTs-ABS composites gets enhanced significantly with addition 0 to 3 wt % MWCNTs. Room temperature AC conductivity increased with increase in the wt. % of MWCNTs and GCNTs from 10−12 S/cm for the unfilled polymer to 10−5 S/cm for 10 wt % of MWCNTs-ABS and 10−7 S/cm for 10 wt % of GCNTs-ABS composites. The decrease in impedance and enhancement of dielectric properties were due to the interfacial polarization between MWCNTs and ABS. Improved conductivity of MWCNTs-ABS and GCNTs-ABS composites may be useful in electromagnetic interference (EMI) shielding and antistatic materials.

Tuning of microstructure in engineered poly (trimethylene terephthalate) based blends with nano inclusion as multifunctional additive

Immiscible blends and their composites are heterogeneous and have variable morphology due to variation in mesophase regions. Tuning, i.e. controlling the phase dimension is important, thereof we report a “super-combo” effect of multiwalled carbon nanotubes (MWCNTs) in poly (trimethylene terephthalate)/polypropylene (PTT/PP) blend system. MWCNTs act as a good reinforcing agent and compatibilizer in the otherwise immiscible PTT/PP blend. PTT/PP blends (with varying blend ratio and MWCNT loading) were melt mixed and later compression molded. The fabricated sheets were characterized for mechanical and morphological properties. Information regarding morphology was determined using scanning electron microscope (SEM) and transmission electron microscope (TEM). Dispersion of MWCNT in PTT was confirmed by the TEM images. Better understanding is in sighted by carrying out a correlation between mechanical properties with morphology, in-line with theoretical equations and selective dissolution experiments. Mechanical properties of all blend compositions were enhanced with the addition of 1 wt % MWCNTs, in which the blend having higher composition of PTT shows excellent mechanical properties. The addition of different MWCNTs loading in to the 90PTT/10PP composition shows a significant increase in Young's modulus and experimental values showed good alignment with theoretical values especially at lower filler loadings. Key findings from the morphology are in agreement with the mechanical properties and so we propose the super combo effect of MWCNTs as a compatibilizer and reinforcing agent for PTT/PP immiscible blend system. Through performed experiments and theoretical studies, we firmly believe that engineered composites with stabilized morphology will be a promising candidate for engineering materials with diverse applications.

Electromagnetic shielding effectiveness of carbon fabric/epoxy composite with continuous graphene oxide fiber and multiwalled carbon nanotube

Carbon fabric composite is used in technical applications such as aircrafts in which electromagnetic shielding (electromagnetic interference–shielding effectiveness) is required. Traditionally, metallic coatings or metal plates are used for electromagnetic shielding, however, conductive filler-filled composite is also alternative to metal sheets due to its light weight. In the literatures, there are studies about effect carbon nanotube and graphene oxide flakes on electromagnetic interference; however, there are no studies encountered that search the effect of carbon nanotube/graphene oxide fiber and alignment of graphene oxide fiber on electromagnetic interference. Thus, in this study, fabrication of light-weight carbon fabric/epoxy composite filled with graphene oxide fiber, reduced graphene oxide fiber and multiwalled carbon nanotube and alignment of graphene oxide fiber was studied for the first time for both electromagnetic shielding (electromagnetic interference–shielding effectiveness) and electrical conductivity. It was found that reduced graphene oxide with two layers at the same alignment (0–0) leads to increment in the electromagnetic interference–shielding effectiveness value, while reduced graphene oxide with opposite alignment (0–90) leads to decrease in the electromagnetic interference–shielding effectiveness value. Opposite to literatures for graphene oxide flakes, highly rough surface of graphene oxide fiber and reduced graphene oxide fiber causes a deterioration in electromagnetic interference–shielding effectiveness due to disruptive multiple reflections resulted from highly rough surface of graphene oxide fiber, which causes multiple reflection effect. Multiwalled carbon nanotube generally provides higher electromagnetic interference–shielding effectiveness than graphene-based fiber because it has higher conductivity and has no disruptive effect of crimpy surface as graphene oxide fiber. Multiwalled carbon nanotube loading of 15 wt% results to 32 dB electromagnetic interference–shielding effectiveness, which is considered an adequate and moderate level of shielding for many applications.

Sintering and tribomechanical properties of gel-combustion-derived nano-alumina and its composites with carbon nanotubes

Fully pure nano-α-alumina (Al2O3) was prepared following gel-combustion method. Near theoretically dense monolithic Al2O3 and its composites reinforced with multiwalled carbon nanotubes (MWCNTs) were prepared using spark plasma sintering (SPS) at 1500 °C under 40 MPa within 10 min. The shrinkage curves were guided in sequence by the crystallization of the amorphous mass followed by a solid-state sintering. The differential nature of electrical conductivity of both composite phases resulted in enhanced densification through localized joule heating. Formation of ~ 1-μm-sized equiaxed matrix grains with uniform distribution of structurally survived CNTs in it was observed in the sintered composites. Within the investigated loading span, the highest Vickers hardness (HV) values were obtained only at 0.5 wt% MWCNT loading in matrix Al2O3. Improvements in HV values for the composites at 0.2 and 2 kgf indentation loads were found to be ~ 18 and ~ 12%, respectively, in comparison with those obtained for pure matrix phase. Quantitative indentation size effect analyzed through standard mathematical models indicated the role of matrix grain refinement and proper matrix–filler load sharing in changing the true hardness. On the contrary, increased CNT concentration leaded to increased sensitivity toward size effect due to the extreme flexible nature of the filler. Unlubricated linear scratch experiments revealed ~ 30–45% lower specific wear rate (WR) values of the composite specimens compared to SPS-processed monolithic Al2O3. Microstructure and scar profile observations were utilized to describe such enhanced wear resistance of present composites.

Covalent functionalization of multiwalled carbon nanotubes with super-hydrophobic property

Abstract Surface covalent functionalization of multiwalled carbon nanotubes (MWCNTs) is carried out by coupling of isocyanate-decorated MWCNTs with hydroxyl-terminated polydimethylsiloxane (HTPS), resulting in the formation of functionalized MWCNTs. Thermogravimetry analysis (TGA) of functionalized MWCNTs-1,2,3 exhibits the similar peaks in the temperature range of 200–500°C, which all correspond to the degradation of chemically grafted polyurethane on the nanotube surface. Field emission scanning electron microscopy (FE-SEM) reveals that as the polyurethane grafted onto the surface of MWCNTs loading ratio increased, the surface roughness of the MWCNTs is reduced. The chemical interaction of HTPS with isocyanate-decorated nanotube surface using the grafting-to strategy in a one-step process is confirmed by Fourier transform infrared spectroscopy (FT-IR). The surface contact angle of MWCNTs-3 with the largest content of polyurethane reached 171°, indicating that the surface covered with low surface energy polyurethane shows a super-hydrophobic property. The good dispersion of polyurethane-functionalized MWCNT-3, particularly at high content in the NR nanocomposites, is evidenced from transmission electron microscopy (TEM).

Raman Microscopy Insights on the Out-of-Plane Electrical Transport of Carbon Nanotube-Doped PEDOT:PSS Electrodes for Solar Cell Applications.

In the present report, we focused on the study of the out-of-plane electrical transport of multiwalled carbon nanotube (MWCNT)-doped poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) composites (PEDOT:PSS-MWCNTs) as electrodes for solar cell applications. The out-of-plane direct current and alternating current electrical transport, rarely studied but not less relevant, was additionally supported with in-plane and out-of-plane confocal Raman microscopy and grazing incidence small-angle X-ray scattering characterizations. The main relevance of our study is the monitoring of the polymer structure all across the polymeric film by using confocal Raman spectroscopy and its correlation with electrical transport. Modifications in the PEDOT benzenoid and quinoid conformations were observed in the vicinities of MWCNTs, and the enrichment of PSS at the indium tin oxide electrode interface was also evidenced. In consequence, the low MWCNT loadings into PEDOT:PSS lead to an increase of the out-of-plane conductivity, but the heavier MWCNT loadings lead to a drastic decrease. The tuning of the doping level of these polymer composites and the understanding of the interface structure are crucial to fabricate electrodes with higher out-of-plane conductivities for organic solar cell applications.

Synthesis and characterization of chiral poly(amide-imide) composite thin films containing functionalized multiwalled carbon nanotubes

The chiral poly(amide-imide) (PAI) was synthesized by the direct polycondensation reaction of imide-dicarboxylic acid, N-trimellitylimido-l-phenylalanine with diamine and 1,5-naphthalenediamine. Multiwalled carbon nanotubes (MWCNTs)/polymer composite films were prepared via dispersing of acid-functionalized MWCNTs (MWCNT-COOH) as reinforcement at MWCNT loadings of 5, 10, and 15 wt%. The PAI/MWCNT composite films were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy (TEM). The TEM results confirmed that the carboxylated MWCNTs were well dispersed in the polymer matrix. The thermogravimetric analysis data showed an improvement of thermal stability of composites containing the MWCNT as compared to the pure polymer. In this research, PAI/MWCNT composite 15 wt% was used as a novel and efficient adsorbent for removal of malachite green dye from aqueous solution.

Thermal-air ageing treatment on mechanical, electrical, and electromagnetic interference shielding properties of lightweight carbon nanotube based polymer nanocomposites

Understanding the effect of thermal-air ageing treatment as well as concentration and dispersion of multiwall carbon nanotubes (MWCNT) in chlorinated polyethylene (CPE) system is very crucial for the development of a broad array of technological applications. This present work demonstrates an ultra-sonication assisted solution mixing strategy followed by hot compression for proper distribution of up to 15 wt% MWCNT within CPE matrix. Proper distribution of MWCNTs leads low percolation threshold (∼2.97 wt%) with high electrical conductivity value of 0.0035 S/cm and electromagnetic interference (EMI) shielding efficiency (36 dB) for 15 wt% MWCNT loading in the X-band frequency region (8.2–12.4 GHz). EMI shielding efficiency is discussed based on the nanofiller loading, thickness of material, after thermal-air ageing treatment, and repeated bending test. On account of thorough investigation, the proposed composites explore its emerging potential for making flexible and light weight EMI shields in vast areas from academic to industrial applications.

Hollow microsphere-infused porous poly(vinylidene fluoride)/multiwall carbon nanotube composites with excellent electromagnetic shielding and low thermal transport

Hollow glass microspheres (HGMs) offer advantages such as high chemical stability, light weight, and low cost and were firstly introduced to prepare functional polymer composites of multi-walled carbon nanotubes (MWCNTs) and poly(vinylidene fluoride). When preparing porous composites via hot compaction and selective etching, embedding of HGMs into the polymer matrix promotes the continuity of the conducting pathways in the material system and thus enhances electrical conductivity. Furthermore, HGMs play an important role in multiple scattering and reflecting the incident waves and the synergistic effect between HGMs and the MWCNTs conductive network greatly enhances the electromagnetic interference (EMI) shielding properties of the composites. In this paper, we show that with 10 wt% MWCNT loading, polymer composite samples containing only 2 wt% HGMs exhibit an average EMI shielding effectiveness (SE) of 43.03 dB over the frequency of 8.2–12.4 GHz. This SE value is higher than in samples with no HGMs (25.27 dB). Analysis of the measured scattering parameters reveals that microwave absorption is the primary reason for enhanced EMI SE. The introduction of HGMs also decreases the thermal conductivity of the composites by reducing the active surface area that promotes efficient heat transfer. With the addition of 2 wt% HGMs, the thermal conductivity of the composites reduces by 46.9%, from 0.305 to 0.162 W(mK)−1. This work provides a promising technique to prepare good-quality EMI shielding materials with lower thermal conductivity to meet the requirements of different applications.

Self-sensing performance of MWCNT-low density polyethylene nanocomposites

Carbon nanotubes (CNTs) based polymer nanocomposites offer a range of remarkable properties. Here, we demonstrate self-sensing performance of low density polyethylene (LDPE)-multiwalled carbon nanotubes (MWCNTs) nanocomposites for the first time. The dispersion of the CNTs and the morphology of the nanocomposites was investigated using scanning electron microscopy, x-ray diffraction and Raman spectroscopic techniques. The thermal properties were measured using thermal gravimetric analysis and differential scanning calorimetry and were found to increase with increasing wt% of MWCNTs in LDPE matrix. An overall improvement in ultimate tensile strength, yield strength and Young’s modulus was found to be 59.6%, 48.5% and 129.3%, respectively for 5.0 wt% loading of MWCNTs. The electrical percolation threshold was observed at 1.0 wt% of MWCNTs and the highest electrical conductivity of 2.8 × 10−2 Scm−1 was observed at 5.0 wt% loading of MWCNTs. These piezo-resistive nanocomposites offer tunable self-sensing capabilities with gauge factors in the ranges of 17–52 and 42–530 in linear elastic (strain ∼3%) and inelastic regimes (strain ∼15%) respectively. Our demonstration would provide guidelines for the fabrication of low cost, self-sensing MWCNT-LDPE nanocomposites for potential use as civil water pipelines and landfill membranes.