Property investigation of polypropylene/multiwall carbon nanotube nanocomposites prepared via in situ polymerization

In this study, polypropylene/carbon nanotube nanocomposites were prepared via in situ polymerization using a bi‐supported Ziegler ? Natta catalytic system. In this system, magnesium ethoxide and multiwall carbon nanotubes (MWCNTs) are jointly used as catalyst supports. SEM images reveal the distribution and quite good dispersion of MWCNTs throughout the polypropylene (PP) matrix. The thermal properties of the samples were examined using DSC and TGA tests. The results show that the crystallization temperature of the nanocomposites significantly increases while the melting point is not markedly affected. In addition, the thermal stability is improved. The melt rheological properties of PP/MWCNT nanocomposites in the linear and nonlinear viscoelastic response regions were studied. An increment of the complex viscosity (η^*), storage modulus (G′) and loss modulus (G′′) and a decrement of the loss factor (tan δ) compared with neat PP are observed. Steady shear flow experiments show an increase in shear viscosity with increasing the MWCNT content. © 2013 Society of Chemical Industry     

Mechanical and thermal properties of polyphenylene sulfide/multiwalled carbon nanotube composites

Polyphenylene sulfide (PPS)/multiwalled carbon nanotube (MWCNT) composites were prepared using a melt‐blending procedure combining twin‐screw extrusion with centrifugal premixing. A homogeneous dispersion of MWCNTs throughout the matrix was revealed by scanning electron microscopy for the nanocomposites with MWCNT contents ranging from 0.5 to 8.0 wt %. The mechanical properties of PPS were markedly enhanced by the incorporation of MWCNTs. Halpin‐Tsai equations, modified with an efficiency factor, were used to model the elastic properties of the nanocomposites. The calculated modulus showed good agreement with the experimental data. The presence of the MWCNTs exhibited both promotion and retardation effects on the crystallization of PPS. The competition between these two effects results in an unusual change of the degree of crystallinity with increasing MWCNT content. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Morphology,crystallization, and mechanical properties of poly(ethylene terephthalate)/multiwall carbon nanotube nanocomposites via in situ polymerization with very low content of multiwall carbon nanotubes

So far, the reported content of multiwall carbon nanotubes (MWNTs) in polymer/MWNTs nanocomposites is usually above 0.1 wt %. In this article, we will report our work on the study of the morphology, crystallization, and mechanical properties of poly(ethylene terephthalate) (PET)/MWNTs nanocomposites prepared by in situ polymerization with very low content of MWNTs (from 0.01 to 0.2 wt %). Well‐dispersed MWNTs with a big network throughout PET matrix were observed by SEM. The very small amount of MWNTs displayed a great nucleating effect on the PET crystallization. The crystallization temperature was improved for 6.4°C by using only 0.01 wt % MWNTs. The decreased chain mobility of PET by adding MWNTs was evident by the formation of imperfect or smaller/thinner crystallites with low melting temperature. An increased storage modulus was also achieved for the nanohybirds with MWNT content less than 0.05 wt %. Our result indicates that using very low content MWNTs (less than 0.1 wt %) is a simple way to achieve good dispersion, yet with remarkable enhancement for polymer/MWNTs modification. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3695–3701, 2007     

Improving tensile strength and toughness of melt processed polyamide 6/multiwalled carbon nanotube composites by in situ polymerization and filler surface functionalization

The effect of processing method and condition on the dispersion status of multiwalled carbon nanotubes (MWCNTs), and mechanical properties of the MWCNT/polyamide 6 (PA6) composites are investigated. Different melt processing conditions are used to dilute the master batch produced by melt process or in situ polymerization. Both MWCNTs and carboxyl group functionalized MWCNTs (MWCNTs‐COOH) are compounded with PA6 at different loadings (0.1, 0.25, 0.5, and 0.75 wt %) to study the effect of chemical modification of MWCNTs on the mechanical properties of the final composites. It is demonstrated that chemical modification of MWCNTs has a positive effect on the strength of the composites as an increase of 5–10 MPa was observed. More importantly, a near 5 MPa increase in strength and more importantly, a maximum of 138% increase in strain at break were observed for the composites produced by in situ polymerization, indicating a toughening and strengthening effect of CNT on the composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

炭黑/高聚物导电复合材料PTC效应的研究

正温系数 (Positive Temperature Coefficient)导电高分子材料 (PTC材料 )在工业中得到了广泛的应用。本文探讨了炭黑 高聚物导电复合材料 PTC效应产生与衰退的机理 ,综述了其 PTC效应的影响因素。     

In situ polymerization and photophysical properties of poly(p‐phenylene benzobisoxazole)/multiwalled carbon nanotubes composites

Poly(p‐phenylene benzobisoxazole)/multiwalled carbon nanotubes (PBO‐MWCNT) composites with different MWCNT compositions were prepared through in situ polymerization of PBO in the presence of carboxylated MWCNTs. The nanocomposite's structure, thermal and photophysical properties were investigated and compared with their blend counterparts (PBO/MWCNT) using Fourier transform infrared spectra, Raman spectra, Wide‐angle X‐ray diffraction, thermogravimetric analysis, UV‐vis absorption, and photoluminescence. The results showed that MWCNTs had a strong interaction with PBO through covalent bonding. The incorporation of MWCNTs increased the distance between two neighboring PBO chains and also improved the thermal resistance of PBO. The investigation of UV‐vis absorption and fluorescence emission spectra exhibited that in situ PBO‐MWCNT composites had a stronger absorbance and obvious trend of red‐shift compared with blend PBO/MWCNT composites for all compositions. This behavior can be attributed to the efficient energy transfer through forming conjugated bonding interactions in the PBO‐MWCNT composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and properties of poly(methyl methacrylate)/carbon nanotube composites covalently integrated through in situ radical polymerization

Poly(methyl methacrylate) (PMMA)/single‐walled carbon nanotube (SWNT) composites were synthesized by the grafting of PMMA onto the sidewalls of SWNTs via in situ radical polymerization. The free‐radical initiators were covalently attached to the SWNTs by a well‐known esterification method and confirmed by means of thermogravimetric analysis and Fourier transform infrared spectroscopy. Scanning electron microscopy and transmission electron microscopy were used to image the PMMA–SWNT composites; these images showed the presence of polymer layers on the surfaces of debundled, individual nanotubes. The PMMA–SWNT composites exhibited better solubility in chloroform than the solution‐blended composite materials. On the other hand, compared to the neat PMMA, the PMMA–SWNT nanocomposites displayed a glass‐transition temperature up to 6.0°C higher and a maximum thermal decomposition temperature up to 56.6°C higher. The unique properties of the nanocomposites resulted from the strong interactions between the SWNTs and the PMMA chains. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Poly(ethylene oxide)‐multiwall carbon nanotube composites: Effect of dicarboxylic acid salt‐based modifiers

An investigation was carried out to improve the dispersion of multiwall carbon nanotubes (MWCNTs) in the poly(ethylene oxide) (PEO) matrix using a half‐neutralized sodium salt of dicarboxylic acid with various number of carbon atoms. The effects of nature of various modifiers on mechanical properties of PEO were investigated. Among various dicarboxylic acid salts, half neutralized adipic acid (HNAA) is found to be highly effective in achieving the improvement in mechanical and dynamic mechanical properties due to improved dispersion of MWCNT in the PEO matrix. The physical interaction of HNAA with MWCNT (cation–π interaction) has been established using Fourier transform infrared and Raman spectroscopic analyses. Scanning electron microscope and transmission electron microscope (TEM) studies clearly indicate the improvement in the level of dispersion of MWCNT due to the addition of HNAA. Crystallization behavior of the PEO/MWCNT composites made with unmodified and modified MWCNT were studied by differential scanning colorimetry. Our approach is a noncovalent one and does not destroy the π‐electron clouds of MWCNT as opposed to chemical functionalization techniques and particularly attractive because of possibility of preserving the structural integrity of nanotubes as well as improved phase adhesion with polymer matrix. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013     

Preparation and characterization of polymer/multiwall carbon nanotube/nanoparticle nanocomposites and preparation of their metal complexes

Carbon nanotube‐polymer nanocomposites were synthesized and characterized successfully. In this work, multiwall carbon nanotubes (MWCNT) were opened using HNO₃/H₂SO₄ mixture and filled by metal nanoparticles such as silver nanoparticles through wet‐chemistry method. The oxidized MWCNT were reacted subsequently with thionyl chloride, 1,6‐diaminohexane, producing MWNT‐amine functionalized. Then the MWCNT containing metal nanoparticles were used as a monomer with different weight percentages in melt polymerization with An and CNCl separately. Furthermore, the polyamide and polytriazine modified MWCNT were used for the preparation of metal ion complexes such as Fe⁺² and La⁺³. The structures and properties of nanocomposites were evaluated by TEM, DSC, TGA, and FT‐IR methods. The chelating behavior and sorption capacities of prepared nanocomposites were carried out by using some metal ions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

In situ polymerization of 3‐hexylthiophene with double‐walled carbon nanotubes: Studies on the conductive nanocomposite

Poly(3‐alkylthiophene)s represent a family of conjugated polymers that are soluble and processable, but still retaining the good electrical conductivity of the insoluble parent polymer thiophene ring backbone. Poly(3‐hexylthiophene) (P3HT) is reported to be a best candidate in the family for solar cell applications. In situ polymerization of 3‐hexylthiophene monomer with double‐walled carbon nanotubes (DWCNTs) has been attempted with the aim of addressing two main issues, namely, the interfacial bonding and proper dispersion of the carbon nanotubes in the polymer matrix to get a high‐performing polymer/nanocomposite. Fourier transform infrared spectroscopy, Raman, and X‐ray diffraction studies indicate the physical wrapping of the polymer on the nanotubes in the absence of any ground‐state interaction between them. The ultraviolet–visible measurements also support this view. The photoluminescence quenching indicates the effectiveness of the interface in the formation of the donor–acceptor‐type composite. The impressive conductivity values encourage the utility of the composites as photovoltaic material. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of rigid segment content on the piezoresistive behavior of multiwall carbon nanotube/segmented polyurethane composites

Tensile piezoresistive properties of multiwall carbon nanotube (MWCNT)/segmented polyurethane (SPU) composites comprising 15, 30, and 50 wt % rigid segment (RS) contents and 2, 4, and 6 wt % MWCNT contents are investigated. The physicochemical properties of such composites are used to better understand their mechanical and piezoresistive behavior. Infrared spectra shows that for 15 and 30 wt % RS composites the addition of MWCNTs promotes a more structured RS domain which increases the phase separation, while for 50 wt % RS composites the MWCNTs disrupt the RS domains of the polymer with a high phase separation. Overall, MWCNT content has less effect on the phase separation than RS content. The composites with 6 wt % MWCNT content reached electrical conductivities of the order of ～10^?1 S/m using 15 and 50 wt % RS polymers. Upon deformation, composites with 15 wt % RS and 4 wt % MWCNT achieved changes in electrical resistance of the order of 5000 times their unstrained value, which are outstanding values that can be exploited for applications such as human motion detection. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44448.     

Polyaniline-multiwalled carbon nanotube composites: Characterization by WAXS and TGA

Polyaniline/carboxylated multi-walled carbon nanotube (PAni/c-MWNT) nanocomposites have been synthesized by micellar aided emulsion polymerization with various c-MWNTs compositions, viz., 0.5, 1, 5, and 10 wt %. The microcrystalline parameters such as the nanocrystal size (〈N〉), lattice strain (g), interplanar distance (d_hkl), width of the crystallite size distribution, surface weighted crystal size (D_s), and volume of the ordered regions were calculated from the X-ray data by using two mathematical models, namely the Exponential distribution and Reinhold distribution methods. The effects of heat ageing on the microcrystalline parameters of the PAni/c-MWNT nanocomposites were also studied and the results are correlated. The thermal stability and electrical resistivity of the PAni/c-MWNT nanocomposites were examined with thermogravimetric analysis (TGA) and a conventional two-probe method. The TGA data indicate that the thermal stability of the nanocomposites improved after the incorporation of c-MWNTs. The influence of temperature on the resistivity of the nanocomposites was also measured. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Multiwalled carbon nanotube polymer composites: Synthesis and characterization of thin films

The aim of this article was to elucidate the basic relationships between processing conditions and the mechanical and electrical properties of multiwalled carbon nanotube reinforced polymer composites. In conventional chopped fiber reinforced polymer composites, uniform distributions of fibers throughout the matrix are critical to producing materials with superior physical properties. Previous methods have dispersed carbon nanotubes by aggressive chemical modification of the nanotubes or by the use of a surfactant prior to dispersion. 1 , 2 Here, ultrasonic energy was used to uniformly disperse multiwalled nanotubes (MWNTs) in solutions and to incorporate them into composites without chemical pretreatment. Polystyrene (PS) solutions containing MWNTs were cast and spun to yield thin film MWNT composites. The rheology of PS/MWNT suspensions was modeled using the Carreau equation. MWNTs were found to align at the shear rates generated by the spin casting process. The tensile modulus and strain to failure of samples compared well to classical micromechanical models, increasing with MWNT loading. The composite films showed lower strains at the yield stress than neat PS films. The presence of MWNTs at 2.5 vol % fraction approximately doubles the tensile modulus, and transforms the film from insulating to conductive (surface resistivity, ρ, approaching 10³ Ω/□). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2660–2669, 2002     

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     

Dispersion of multi‐walled carbon nanotubes in poly(aryl ether ketone) obtained by in situ polymerization

BACKGROUND: Recently, much work has focused on the efficient dispersion of carbon nanotubes (CNTs) throughout a polymer matrix for mechanical and/or electrical matrices. However, CNTs used as enhancement inclusions in a high‐performance polymer matrix, especially in poly(aryl ether ketone) (PAEK), have rarely been reported. Therefore, multi‐walled carbon nanotube (MWNT)‐modified PAEK nanocomposites were synthesized by in situ polymerization of monomers of interest in the presence of pre‐treated MWNTs. RESULTS: This process enabled a uniform dispersion of MWNT bundles in the polymer matrix. The resultant MWNT/PAEK nanocomposite films were optically transparent with significant mechanical enhancement at a very low MWNT loading (0.5 wt%). CONCLUSION: These MWNT/polymer nanocomposites are potentially useful in a variety of aerospace and terrestrial applications, due to the combination of excellent properties of MWNTs with PAEK. Copyright © 2009 Society of Chemical Industry     

Electrical and dielectric properties of multiwall carbon nanotube/polyaniline composites

In this paper, electrical and dielectric properties of multiwall carbon nanotubes (MWCNTs)/insulating polyaniline (PANI) composites were studied. A mixture of MWCNTs and insulating polyaniline was dispersed in an ethanol solution by ultrasonic process, subsequently dried, and was hot-pressed at 200 °C under 30 MPa. Electrical and dielectric properties of the composites were measured. The experimental results show that the dc conductivities of the composites exhibit a typical percolation behavior with a low percolation threshold of 5.85 wt.% MWCNTs content. The dielectric constant of the composites increases remarkably with the increasing MWCNTs concentration, when the MWCNTs concentration was close to percolation threshold. This may be attributed to the critical behavior of the dielectric constant near the percolation threshold as well as to the polarization effects between the clusters inside the composites.     

Polymer/carbon nanotube composite emulsion prepared through ultrasonically assisted in situ emulsion polymerization

In this study, ultrasonic irradiation and in situ emulsion polymerization were combined to prepare stable poly(methyl methacrylate‐co‐n‐butyl acrylate) (P(MMA‐BA))/carbon nanotubes (CNTs) composite emulsion, which solves the dispersion problem of CNTs in the latex. Two stages were adopted. In Stage I, ultrasonically initiated in situ emulsion polymerization was conducted to disperse CNTs and prepare the seed emulsion containing polymer coated CNTs. In Stage II, conventional in situ emulsion polymerization was conducted to further enhance the monomer conversion and solid content. The dispersion behavior of MWCNTs in aqueous solution under ultrasonic irradiation was investigated by spectrophotometry. The effects of CNTs content on the emulsion stability and mechanical properties of composite film were studied. The results suggest that in the composite emulsion the long CNTs with a diameter of 20–40 nm are separated and dispersed by the formed polymer latex nanoparticles with a size of 20–40 nm. The spherical polymer latex nanoparticles adhere to the wall of CNTs to form a structure like “grapes on the twig.” The smooth, uniform, and flexible polymer/CNTs composite films were prepared from the composite emulsion. The CNTs can be individually dispersed in P(MMA‐BA)/CNTs composite film. Tensile tests suggest that with the increase in the CNTs content, the Young's modulus and the yield strength of the film increase. Only at 1 wt % CNTs, the Young's modulus increases from 124 to 289 MPa, and the yield strength is improved about ～14%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3123–3130, 2006     

From carbon nanotube coatings to high‐performance polymer nanocomposites

Since their discovery at the beginning of the 1990s, carbon nanotubes (CNTs) have been the focus of considerable research by both academia and industry due to their remarkable and unique electronic and mechanical properties. Among numerous potential applications of CNTs, their use as reinforcing materials for polymers has recently received considerable attention since their exceptional mechanical properties, combined with their low density, offer tremendous opportunities for the development of fundamentally new material systems. However, the key challenge remains to reach a high level of nanoparticle dissociation (i.e. to break down the cohesion of aggregated CNTs) as well as a fine dispersion upon melt blending within the selected matrices. Therefore, this contribution aims at reviewing the exceptional efficiency of CNT coating by a thin layer of polymer as obtained by an in situ polymerization process catalysed directly from the nanofiller surface, known as the ‘polymerization‐filling technique’. This process allows for complete destructuring of the native filler aggregates. Interestingly enough, such surface‐coated carbon nanotubes can be added as ‘masterbatch’ in commercial polymeric matrices leading to the production of polymer nanocomposites displaying much better thermomechanical, flame retardant and electrical conductive properties even at very low filler loading. Copyright © 2007 Society of Chemical Industry     

Preparation and properties of electrically conducting textiles by in situ polymerization of poly(3,4‐ethylenedioxythiophene)

Poly(3,4‐ethylenedioxythiophene) (PEDOT) was in situ polymerized on nylon 6, poly(ethylene terephthalate) (PET), and poly(trimethylene terephthalate) (PTT) fabrics using ferric p‐toluenesulfonic acid (FepTS) and ferric chloride (FeCl₃) as oxidants. The effect of the organic solvents used in the polymerization bath was investigated. Prepared PEDOT/nylon 6 composite fabrics have superior electrical conductivity (0.75 S/cm, in ethanol solvent) compared to those of the other PEDOT composite fabrics. In particular, after five cycles of polymerization, the electrical conductivity of the composite fabric reached about 2 S/cm. However, the nylon 6 fabric was damaged by EDOT radical cations and the strong acidity of FepTS during the polymerization process. It was concluded that PTT fabric, which has excellent elastic recovery and acid resistance, is a suitable substrate for in situ polymerization of PEDOT, because the PEDOT/PTT composite fabric was hardly damaged during the polymerization process and its electrical conductivity is comparatively good (0.36 S/cm, in butanol solvent). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1326–1332, 2005     

Sensing behaviors of polymer/carbon nanotubes composites prepared in reversed microemulsion polymerization

Polystyrene/carbon nanotubes composites were readily prepared by reversed microemulsion polymerization. Compared with the composites prepared by solution mixing, the uniform dispersion of carbon nanotubes in polymer matrix could be obtained more easily and the thermal and electrical properties of the as‐prepared composites were also enhanced. The as‐prepared composites were deposited onto a microelectrode array to fabricate a vapor sensor. The response for different organic vapors was evaluated by monitoring the change in the resistance of the composites upon exposure to various gases. The change in resistance was of the order of about 10³ for the composites prepared by reversed microemulsion polymerization. The chemical sensors based on the composites prepared by reversed microemulsion polymerization presented excellent reproducibility and reversibility in response. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011