Preparation and properties of polyurethane/multiwalled carbon nanotube nanocomposites by a spray drying process

A spray drying approach has been used to prepare polyurethane/multiwalled carbon nanotube (PU/MWCNT) composites. By using this method, the MWCNTs can be dispersed homogeneously in the PU matrix in an attempt to improve the mechanical properties of the nanocomposites. The morphology of the resulting PU/MWCNT composites was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM and TEM observations illustrate that the MWCNTs are dispersed finely and uniformly in the PU matrix. X‐ray diffraction results indicate that the microphase separation structure of the PU is slightly affected by the presence of the MWCNTs. The mechanical properties such as tensile strength, tensile modulus, elongation at break, and hardness of the nanocomposites were studied. The electrical and the thermal conductivity of the nanocomposites were also evaluated. The results show that both the electrical and the thermal conductivity increase with the increase of MWCNT loading. In addition, the percolation threshold value of the PU composites is significantly reduced to about 5 wt % because of the high aspect ratio of carbon nanotubes and exclusive effect of latex particles of PU emulsion in dispersion. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Investigation of electrical,mechanical, and thermal properties of functionalized multiwalled carbon nanotubes‐reduced graphene Oxide/PMMA hybrid nanocomposites

Electrical, mechanical, and thermal properties of the poly(methyl methacrylate) (PMMA) composites containing functionalized multiwalled carbon nanotubes (f‐MWCNTs) and reduced graphene oxide (rGO) hybrid nanofillers have been investigated. The observed electrical percolation threshold of FHC is 0.8 wt% with maximum conductivity of 1.21 × 10^?3 S/cm at 4 wt% of f‐MWCNTs. The electrical transport mechanism and magneto resistance studied of hybrid composites have also been investigated. Progressive addition of f‐MWCNTs in rGO/PMMA composite results increase in mechanical (tensile strength and Young's modulus) and thermal (thermal stability) properties of f‐MWCNTs‐rGO/PMMA hybrid nanocomposites (FHC). The increased mechanical properties are due to the efficient load transfer from PMMA matrix to f‐MWCNTs and rGO through better chemical interaction. The strong interaction between PMMA and f‐MWCNTs‐rGO in FHC is the main cause for improved thermal stability. POLYM. ENG. SCI., 59:1075–1083, 2019. © 2019 Society of Plastics Engineers     

New piezoelectric damping composites of poly(vinylidene fluoride) blended with clay and multi‐walled carbon nanotubes

Damping materials are used to control mechanical vibrations, and piezoelectric damping composite is a very promising material due to its unique mechanism. In this study, a potential piezoelectric damping composite was developed by simply melt mixing poly(vinylidene fluoride) (PVDF) with small amounts of organic modified montmorillonite (OMMT) and multi‐walled carbon nanotubes (MWCNTs). The piezoelectric, mechanical and electrical properties were investigated using a dynamic mechanical analyser, direct current electrical resistivity measurements, X‐ray diffraction, Fourier transform infrared spectroscopy and the direct quasi‐static d₃₃ piezoelectric coefficient method. It was found that the damping property of PVDF can be greatly improved by adding both MWCNTs and OMMT, and the composite containing 1.9 wt% of MWCNTs and 3 wt% of OMMT showed the best damping property. A model and an approximate calculation were applied to explain the improved damping property. Moreover, similar mechanical properties of PVDF composites were observed in the tensile testing and dynamic mechanical analyser measurements. Copyright © 2012 Society of Chemical Industry     

Improvement in properties of multiwalled carbon nanotube/polypropylene nanocomposites through homogeneous dispersion with the aid of surfactants

The effects of different surfactants on the properties of multiwalled carbon nanotubes/polypropylene (MWCNT/PP) nanocomposites prepared by a melt mixing method have been investigated. Sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (NaDDBS) were used as a means of noncovalent functionalization of MWCNTs to help them to be dispersed uniformly into the PP matrix. The effects of these surfactant‐treated MWCNTs on morphological, rheological, thermal, crystalline, mechanical, and electrical properties of MWCNT/PP composites were studied using field emission scanning electron microscopy, optical microscopy, rheometry, tensile, and electrical conductivity tests. It was found that the surfactant‐treatment and micromixing resulted in a great improvement in the state of dispersion of MWCNTs in the polymer matrix, leading to a significant enhancement of Young's modulus and tensile strength of the composites. For example, with the addition of only 2 wt % of SDS‐treated and NaDDBS‐treated MWCNTs, the Young's modulus of PP increased by 61.1 and 86.1%, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Cellulose acetate/multiwalled carbon nanotube nanocomposites with improved mechanical,thermal, and electrical properties

Cellulose acetate (CA)‐based nanocomposites with various contents of neat multiwalled carbon nanotube (MWCNT) or acid‐treated one (MWCNT‐COOH) are prepared via melt‐compounding method and investigated their morphology, thermal stability, mechanical, and electrical properties. SEM microphotographs reveal that MWCNT‐COOHs are dispersed uniformly in the CA matrix, compared with neat MWCNTs. FTIR spectra support that there exists a specific interaction between carboxyl groups of MWCNT‐COOHs and ester groups of CA, indicating good interfacial adhesion between MWCNT‐COOHs and CA matrix. Accordingly, thermal stability and dynamic mechanical properties of CA/MWCNT‐COOH nanocomposites were higher than those of CA/MWCNT composites. On the contrary, electrical volume resistivities of CA/MWCNT‐COOH nanocomposites are found to be somewhat higher than those of CA/MWCNT composites, which is because of the deterioration of graphene structures for MWCNT‐COOHs and the good dispersion of MWCNT‐COOHs in the CA matrix. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polyester and multiwalled carbon nanotube composites: characterization,electrical conductivity and antibacterial activity

Poly(butylene terephthalate) (PBT) composites containing multiwalled carbon nanotubes (MWCNTs) were prepared using a melt‐blending process and used to examine the effects on the composite structure and properties of replacing PBT with acrylic acid‐grafted PBT (PBT‐g‐AA). PBT‐g‐AA and multihydroxyl‐functionalized MWCNTs (MWCNTs‐OH) were used to improve the compatibility and dispersibility of the MWCNTs within the PBT matrix. The composites were characterized morphologically using transmission electron microscopy, and chemically using Fourier transform infrared, solid‐state ¹³C NMR and UV‐visible absorption spectroscopy. The antibacterial and electrical conductivity properties of the composites were also evaluated. MWCNTs or MWCNTs‐OH enhanced the antibacterial activity and electrical conductivity of the PBT/MWCNT or PBT‐g‐AA/MWCNTs‐OH composites. The functionalized PBT‐g‐AA/MWCNTs‐OH composites showed markedly enhanced antibacterial properties and electrical conductivity due to the formation of ester bonds from the condensation of the carboxylic acid groups of PBT‐g‐AA with the hydroxyl groups of MWCNTs‐OH. The optimal proportion of MWCNTs‐OH in the composites was 1 wt%; in excess of this amount, the compatibility between the organic and inorganic phases was compromised. Copyright © 2011 Society of Chemical Industry     

Fabrication and characterization of homogeneous composites of polypropylene and multiwalled carbon nanotubes

The polypropylene‐grafted multiwalled carbon nanotubes (PP‐MWCNTs) were produced from the reaction of PP containing the hydroxyl groups and MWCNTs having 2‐bromoisobutyryl groups. The PP‐MWCNTs had a significantly rougher surface than the original MWCNTs. PP‐MWCNTs had PP layers of thickness 10–15 nm on the outer walls of the MWCNTs. PP/PP‐MWCNT composites and PP/MWCNT composites were prepared by solution mixing in o‐xylene. Unlike PP/MWCNT composites, PP‐MWCNTs were homogeneously dispersed in the PP matrix. As a consequence, the thermal stability and conductivity of PP/PP‐MWCNT composites were dramatically improved even if only 1 wt % of PP‐MWNTs was added to the PP matrix. The good miscibility of PP and PP‐MWCNTs plays a critical role in the formation of the homogeneous composites and leads the high thermal stability and conductivity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Polyethylene multiwalled carbon nanotube composites

Polyethylene (PE) multiwalled carbon nanotubes (MWCNTs) with weight fractions ranging from 0.1 to 10 wt% were prepared by melt blending using a mini-twin screw extruder. The morphology and degree of dispersion of the MWCNTs in the PE matrix at different length scales was investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and wide-angle X-ray diffraction (WAXD). Both individual and agglomerations of MWCNTs were evident. An up-shift of 17 cm⁻¹ for the G band and the evolution of a shoulder to this peak were obtained in the Raman spectra of the nanocomposites, probably due to compressive forces exerted on the MWCNTs by PE chains and indicating intercalation of PE into the MWCNT bundles. The electrical conductivity and linear viscoelastic behaviour of these nanocomposites were investigated. A percolation threshold of about 7.5 wt% was obtained and the electrical conductivity of PE was increased significantly, by 16 orders of magnitude, from 10⁻²⁰ to 10⁻⁴ S/cm. The storage modulus (G′) versus frequency curves approached a plateau above the percolation threshold with the formation of an interconnected nanotube structure, indicative of ‘pseudo-solid-like’ behaviour. The ultimate tensile strength and elongation at break of the nanocomposites decreased with addition of MWCNTs. The diminution of mechanical properties of the nanocomposites, though concomitant with a significant increase in electrical conductivity, implies the mechanism for mechanical reinforcement for PE/MWCNT composites is filler-matrix interfacial interactions and not filler percolation. The temperature of crystallisation (T_c) and fraction of PE that was crystalline (F_c) were modified by incorporating MWCNTs. The thermal decomposition temperature of PE was enhanced by 20 K on addition of 10 wt% MWCNT.     

Noncovalent functionalization of carbon nanotubes using branched random copolymer for improvement of thermal conductivity and mechanical properties of epoxy thermosets

A branched random copolymer, poly[(hydroxyethyl acrylate)‐r‐(N‐vinylcarbazole)] (BPHNV), was synthesized through a facile one‐pot free radical polymerization with hydroxyethyl acrylate and N‐vinylcarbazole monomers, using 4‐vinylmethylmercaptan as the chain transfer agent. BPHNV was employed to noncovalently modify multiwall carbon nanotubes (MWCNTs) by π–π interaction. The as‐modified MWCNTs were then incorporated into epoxy resin to improve the thermal conductivity and mechanical properties of epoxy thermosets. The results suggest that, due to both the conjugation structure and the epoxy‐philic component, BPHNV could form a polymer layer on the wall of MWCNTs and inhibit entanglement, helping the uniform dispersion of MWCNTs in epoxy matrix. Owing to the unprecedented thermal conductivity of MWCNTs and the enhancement in the interfacial interaction between fillers and matrix, the thermal conductivity of epoxy/MWCNTs/BPHNV composites increases by 78% at extremely low filler loadings, while the electrical resistivity is still maintained on account of the insulating polymer layer. Meanwhile, the mechanical properties and glass transition temperature (T_g) of the thermosets are elevated effectively, with no significant decrease occurring to the modulus. The addition of as little as 0.1 wt% of MWCNTs decorated with 1.0 wt% of BPHNV to an epoxy matrix affords a great increase of 130% in impact strength for the epoxy thermosets, as well as an increase of over 13 °C in T_g. © 2018 Society of Chemical Industry     

Preparation and properties of plasticized starch/multiwalled carbon nanotubes composites

In this work we have studied the utilization of multiwalled carbon nanotubes (MWCNTs) as filler‐reinforcement to improve the performance of plasticized starch (PS). The PS/MWCNTs nanocomposites were successfully prepared by a simple method of solution casting and evaporation. The morphology, thermal behavior, and mechanical properties of the films were investigated by means of scanning electron microscopy, wide‐angle X‐ray diffraction, differential scanning calorimetry, and tensile testing. The results indicated that the MWCNTs dispersed homogeneously in the PS matrix and formed strong hydrogen bonding with PS molecules. Compared with the pure PS, the tensile strength and Young's modulus of the nanocomposites were enhanced significantly from 2.85 to 4.73 MPa and from 20.74 to 39.18 MPa with an increase in MWCNTs content from 0 to 3.0 wt %, respectively. The value of elongation at break of the nanocomposites was higher than that of PS and reached a maximum value as the MWCNTs content was at 1.0 wt %. Besides the improvement of mechanical properties, the incorporation of MWCNTs into the PS matrix also led to a decrease of water sensitivity of the PS‐based materials. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Conductive,mechanical, and chemical resistance properties of polyurushiol/multiwalled carbon nanotube composite coatings

The polyurushiol (PUS)/multiwalled carbon nanotube (MWCNT) composite coatings were prepared by in situ composite method. The fracture morphology of the composite films showed that MWCNTs had been well dispersed in PUS matrix, which significantly decreased the electrical resistivity and the gloss of the composite films. The nonconducting/conducting state transition took place at approximately 3.0 wt% of MWCNTs with the volume electrical resistivity of 10⁴ Ω cm. The results of the mechanical tests revealed that the impact of strength and the storage modulus of the coatings increased with the addition of MWCNTs. Furthermore, the PUS/MWCNTs composite films had good chemical resistance. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Hydrogen bond containing multiwalled carbon nanotubes in polyurethane composites

Introduction of hydrogen bonding sites onto multi‐walled carbon nanotubes (MWCNTs) included carboxylic acid, amide‐amine, and novel amide‐urea MWCNTs for the formation of homogenous polyurethane composites. Acid oxidation and subsequent derivatization introduced hydrogen bonding functionality onto MWCNTs to reveal the effect of surface functionalization on mechanical properties in a 45 wt% hard segment polyurethane matrix. Raman spectroscopy showed an increase in the D/G peak ratio, which indicated successful oxidation, and X‐ray photoelectron spectroscopy also revealed elemental compositions that supported each step of the functionalization strategy. Thermogravimetric analysis supported functionalization with an increase in percent weight loss for each functionalization, and the MWCNT surface functionalization determined pH‐dependent dispersibility. The nonfunctionalized MWCNT composites showed poor dispersion with transmission electron microscopy, and in sharp contrast, the functionalized composites displayed homogenous dispersions. Tensile testing revealed improved stress at break in the functionalized MWCNT composites at low loadings due to homogenous dispersion. POLYM. COMPOS., 37:1425–1434, 2016. © 2014 Society of Plastics Engineers     

Influence of surface modification of carbon nanotube on microstructures and properties of polyamide 66/multiwalled carbon nanotube composites

The melt‐mixing polyamide 66 (PA66) composite samples that incorporated pure, acid‐ and amine‐functionalized multiwalled carbon nanotubes (MWCNTs) were prepared in order to enhance mechanical and frictional properties of PA66 composites. The homogeneous dispersion of amine‐functionalized MWCNTs (D‐MWCNTs) in PA66 matrix was observed from the significantly uniform morphology of tensile fractured surface of the composites. Differential scanning calorimetry measurement indicates that D‐MWCNTs acted as effective nucleation agent for PA66 matrix and the crystallinity of PA66 was increased. The fracture stress and tensile modulus of the composites were significantly improved with the incorporation of D‐MWCNTs, owing to the good dispersion of D‐MWCNTs. Compared with PA66, the PA66 composites with 1.0 wt% D‐MWCNTs were improved considerably in both wear and friction properties owing to the change of the tribological mechanisms. The good dispersion of D‐MWCNTs in PA66 and good interface compatibility between D‐MWCNTs and PA66 favored the formation of a thin layer on the contact surfaces during wear and friction test, which played an important role in reducing wear and friction of the composite and in suppressing the transverse cracks. These results prove the importance of D‐MWCNTs in a positive change of the mechanical and frictional properties of PA66 composites and suggest the applicability prospect of PA66/D‐MWCNTs composites in engineering components.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Plasma treatment‐induced fluorine‐functionalized multi‐walled carbon nanotubes to modify poly(ethylene terephthalate) obtained via in situ polymerization

The introduction of carbon nanotubes in a polymer matrix can markedly improve its mechanical properties and electrical conductivity, and much effort has been devoted to achieve homogeneous dispersions of carbon nanotubes in various polymers. Our group previously performed successfully fluorine‐grafted modification on the sidewalls of multi‐walled carbon nanotubes (MWCNTs), using homemade equipment for CF₄ plasma irradiation. As a continuation of our previous work, in the present study CF₄ plasma‐treated MWCNTs (F‐MWCNTs) were used as a nanofiller with poly(ethylene terephthalate) (PET), which is a practical example of the application of such F‐MWCNTs to prepare polyester/MWCNTs nanocomposites with ideal nanoscale structure and excellent properties. As confirmed from scanning electron microscopy observations, the F‐MWCNTs could easily be homogeneously dispersed in the PET matrix during the in situ polymerization preparation process. It was found that a very low content of F‐MWCNTs dramatically altered the crystallization behavior and mechanical properties of the nanocomposites. For example, a 15 °C increase in crystallization temperature was achieved by adding only 0.01 wt% F‐MWCNTs, implying that the well‐dispersed F‐MWCNTs act as highly effective nucleating agents to initiate PET crystallization at high temperature. Meanwhile, an abnormal phenomenon was found in that the melt point of the nanocomposites is lower than that of the pure PET. The mechanism of the tailoring of the properties of PET resin by incorporation of F‐MWCNTs is discussed, based on structure–property relationships. The good dispersion of the F‐MWCNTs and strong interfacial interaction between matrix and nanofiller are responsible for the improvement in mechanical properties and high nucleating efficiency. The abnormal melting behavior is attributed to the recrystallization transition of PET occurring at the early stage of crystal melting being retarded on incorporation of F‐MWCNTs. Copyright © 2009 Society of Chemical Industry     

Filler reaggregation and network formation time scale in extruded high‐density polyethylene/multiwalled carbon nanotube composites

A high‐density polyethylene (HDPE) masterbatch containing 20.2 wt% multiwalled carbon nanotubes (MWNTs) was melt diluted with neat HDPE using two different methods: a twin screw microcompounder and a single‐screw extruder. The electrical properties of these composites were assessed using bulk electrical conductivity measurements, their mechanical properties were evaluated using tensile tests and dynamic mechanical analysis (DMA), and percent crystallinity was determined by wide angle x‐ray diffraction (WAXD) and differential scanning calorimetry (DSC). A percolation threshold (p_c) of 4.5 wt% MWNTs was found in compression‐molded samples. Extruded samples were prepared with nanotube concentrations below and above the compression‐molded percolation threshold (2 and 7 wt% MWNTs) and passed through the extruder twice before entering a low‐shear melt annealing zone. Different melt annealing times were used and their effects on the electrical and mechanical properties of the resulting quench‐cooled composites were evaluated. Results showed that extruded composites were nonconductive, indicating that a conductive nanotube network did not form on the time scale of these experiments. Annealing time also did not affect significantly the mechanical properties of the resulting solid composites. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

In situ polymerization,thermal, damping,and mechanical properties of multiwalled carbon nanotubes/polyisobutylene‐based polyurethane nanocomposites

Despite the development of strong, durable, and cost efficient polyisobutylene‐based polyurethane (PIB‐based PU) materials has yet to be achieved. The well dispersion and maximum interfacial interaction between the nanofiller and the PIB‐based PU at low loading have been scarcely studied. Here, the preparation of PIB‐based PU nanocomposites with Multiwalled carbon nanotubes (MWCNTs) using a simple in situ polymerization method is reported. The thermogravimetric analysis tests show that MWCNTs significantly improved the thermal stability of MWCNTs/PIB‐based PU nanocomposites. Compare to the pure PIB‐based PU the onset temperature of degradation for the nanocomposite was about 20°C higher at 0.7 wt% MWCNTs loading. Efficient load transfer is found between the nanofiller MWCNTs and PIB‐based PU and the mechanical properties of the MWCNTs/PIB‐based PU nanocomposite with well dispersion are improved. A 63% improvement of Young's modulus and slightly increased of tensile strength are achieved by addition of only 0.7 wt% of MWCNTs. The experimentally determined Young's modulus is in well agreement with the theoretical simulation. It is worth noting that the PIB‐based PU and MWCNTs/PIB‐based PU nanocomposites exhibit excellent damping properties (tan δ > 0.3) from −45°C to 8°C. POLYM. COMPOS., 36:198–203, 2015. © 2014 Society of Plastics Engineers     

Thermosetting polyurethane multiwalled carbon nanotube composites

Thermosetting polyurethane (PU) multi‐walled carbon nanotube (MWCNT) nanocomposites at loadings up to 1 wt % were prepared via an addition polymerization reaction. The morphology of the nanocomposites and degree of dispersion of the MWCNTs was studied using a combination of scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and wide angle X‐ray diffraction (WAXD), and revealed the nanotubes to be highly dispersed in the PU matrix. Addition of just 0.1 wt % MWCNTs resulted in significant enhancements in stiffness, strength and toughness. Increases in Young's modulus, % elongation at break and ultimate tensile strength of 561, 302 and 397% were measured for the nanocomposites compared to the unfilled PU. The effect of the MWCNTs on the modulus of the PU was evaluated using the Rule of Mixtures, Krenchel and Halpin‐Tsai models. Only the Halpin‐Tsai model applied to high aspect ratio nanotubes was in good agreement with the modulus values determined experimentally. Strong interfacial shear stress was found between PU chains and nanotubes, up to 439 MPa, calculated using a modified Kelly‐Tyson model. Evidence for strong interfacial interactions was obtained from the Raman spectra of both the precursor materials and nanocomposites. When the MWCNTs were added to the isophorone diisocyanate an up‐shift of 14 cm^?1 and on average 40 cm^?1 was obtained for the position of the carbon‐hydrogen (C? H) out‐of plane bending (766 cm^?1) and isocyanate symmetric stretch (1420 cm^?1) modes respectively. Moreover, an up‐shift of 24 cm^?1 was recorded for the nanotube tangential mode (G‐band) for the 1.0 wt % nanocomposite because of the compressive forces of the PU matrix acting on the MWCNTs. The dynamic mechanical (DMA) properties of the PU thermoset and the nanocomposites were measured as a function of temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Fabrication of polystyrene/multiwalled carbon nanotube composite films synthesized by in situ microemulsion polymerization

A microemulsion polymerization method was used to achieve better compatibility between polystyrene (PS)/multiwalled carbon nanotubes (MWCNTs) nanocomposites and the host PS matrix to form films with excellent electrical and thermal properties. The films were prepared by embedding the PS/MWCNTs nanocomposite into the PS matrix. The MWCNTs were functionalized with PS nanoparticles to avoid the phase separation problem between the filler and host matrix and to enhance the good dispersibility of MWCNTs in the PS host matrix. The confirmation of the synthesis was analyzed by Fourier transform infrared spectroscopy, nuclear magnetic resonance, and Raman spectroscopy. The variation effect of the PS‐linking density on the MWCNT was revealed by scanning electron microscopy and transmission electron microscopy. An enhancement of the thermal and mechanical properties was revealed by thermal gravimetric analysis, differential scanning colorimetric analysis, and dynamic mechanical analysis. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Mechanical,thermal and electrical properties of multi‐walled carbon nanotube/aluminium nitride/polyetherimide nanocomposites

A series of polyimide‐based nanocomposites containing polyimide‐grafted multi‐walled carbon nanotubes (PI‐g MWCNTs) and silane‐modified ceramic (aluminium nitride (AlN)) were prepared. The mechanical, thermal and electrical properties of hybrid PI‐g MWCNT/AlN/polyetherimide nanocomposites were investigated. After polyimide grafting modification, the PI‐g MWCNTs showed good dispersion and wettability in the polyetherimide matrix and imparted excellent mechanical, electrical and thermal properties. The utilization of the hybrid filler was found to be effective in increasing the thermal conductivity of the composites due to the enhanced connectivity due to the high‐aspect‐ratio MWCNT filler. The use of spherical AlN filler and PI‐g MWCNT filler resulted in composite materials with enhanced thermal conductivity and low coefficient of thermal expansion. Results indicated that the hybrid PI‐g MWCNT and AlN fillers incorporated into the polyetherimide matrix enhanced significantly the thermal stability, thermal conductivity and mechanical properties of the matrix. Copyright © 2012 Society of Chemical Industry     

Functionalization of multiwalled carbon nanotubes with uniform polyurea coatings by molecular layer deposition

In this study, we demonstrate a flexible method for functionalizing multiwalled carbon nanotubes (MWCNTs) with polyurea (PU) coatings using molecular layer deposition (MLD). Uniform and conformal PU films can be deposited on the surface of pristine MWCNTs without any surface treatment. The PU shell thickness and wrapping amount are precisely tunable by changing the number of MLD cycles. The present MLD functionalizing treatment provides better dispersion of the MWCNTs in highly polar solvents such as N,N-dimethylformamide, dimethyl sulfoxide, and 1-methyl-2-pyrrolidinone. Furthermore, the PU layers improve the compatibility between MWCNTs and the polyurethane matrix. Significant increases in tensile strength and modulus are obtained, resulting in greatly enhanced mechanical properties of PU-functionalized MWCNT/polyurethane composites.