Graphene/poly(styrene‐b‐isoprene‐b‐styrene) nanocomposite optical actuators

This article presents an optomechanical actuator, which is driven by infra red (IR) radiation. The actuator is a nanocomposite‐containing graphene platelets embedded in poly(styrene‐b‐isoprene‐b‐styrene) (SIS) matrix. 0.1 mm thick free‐standing nanocomposite films are fabricated by a simple process of solvent casting. We demonstrate that graphene/SIS nanocomposite contracts on irradiation with IR radiation under strained conditions, whereas expansion behavior was exhibited by them when no prestrain is applied. A maximum photomechanical stress of 28.34 kPa and strain upto 3.1% was obtained for these nanocomposite actuators. We have also studied the mechanical characteristics and thermal degradation of these nanocomposite actuators. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3902–3908, 2013     

Functionalization of carbon nanotubes with (3‐glycidyloxypropyl)‐trimethoxysilane: Effect of wrapping on epoxy matrix nanocomposites

In this work, multiwalled carbon nanotubes (MWCNT), after previous oxidation, are functionalized with excess (3‐glycidyloxypropyl)trimethoxysilane (GLYMO) and used as reinforcement in epoxy matrix nanocomposites. Infrared, Raman, and energy‐dispersive X‐ray spectroscopies confirm the silanization of the MWCNT, while transmission electron microscopy images show that oxidized nanotubes presented less entanglement than pristine and silanized MWCNT. Thickening of the nanotubes is also observed after silanization, suggesting that the MWCNT are wrapped by siloxane chains. Field‐emission scanning electron microscopy reveals that oxidized nanotubes are better dispersed in the matrix, providing nanocomposites with better mechanical properties than those reinforced with pristine and silanized MWCNT. On the other hand, the glass transition temperature of the nanocomposite with 0.05 wt % MWCNT‐GLYMO increased by 14 °C compared to the neat epoxy resin, suggesting a strong matrix–nanotube adhesion. The functionalization of nanotubes using an excess amount of silane can thus favor the formation of an organosiloxane coating on the MWCNT, preventing its dispersion and contributing to poor mechanical properties of epoxy nanocomposites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44245.     

Preparation and characterization of epoxy nanocomposites containing surface‐modified graphene oxide

A three‐step grafting procedure has been used to graft the epoxy monomers (DER332) and the curing agents (diamino diphenyl methane (DDM), onto graphene oxide (GO) surface. The surface modification of GO has been performed by grafting of Jeffamine D‐2000, followed with subsequent grafting of DER332 and DDM, respectively. Fourier transform spectroscopy and thermogravimetric analysis indicate successful surface modification. The resulting modified GO, that is, (DED)‐GO, can be well dispersed in the epoxy monomers. The epoxy nanocomposites containing different GO contents can then be prepared through curing processes. The dispersion of GO in the nanocomposites is characterized by transmission electron microscopy. It is found that the tensile strength and elongation at break of epoxy nanocomposite with only 0.2 wt % DED‐GO are increased by 30 and 16% as compared with the neat epoxy resin, respectively. Dynamic mechanical analysis results show that 62% increase in storage modulus and 26°C enhancement in the glass transition temperature of the nanocomposite have been achieved with the incorporation of only 0.2 wt % of DED‐GO into the epoxy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40236.     

Conducting epoxy networks modified with non‐covalently functionalized multi‐walled carbon nanotube with imidazolium‐based ionic liquid

Multi‐walled carbon nanotube (MWCNT) was non‐covalently functionalized with room‐temperature ionic liquid (IL), 1‐butyl‐3‐methyl‐imidazolium tetrafluoroborate and blended with epoxy pre‐polymer (ER) with the assistance of ultrasonication in the presence of acetone as a diluting medium. The ability of IL in improving the dispersion of MWCNT in epoxy pre‐polymer was evidenced by transmission optical microscopy. The corresponding epoxy/MWCNT networks cured with anhydride displayed an increase of the electrical conductivity of around three orders of magnitude with the addition of IL in a proportion of MWCNT/IL = 1:5 mass ratio. The effect of IL on dynamic mechanical properties and thermal conductivity was also evaluated. The improved thermal and electrical properties was attributed to the better dispersion of MWCNT within the epoxy matrix by IL, evidenced by transmission electron microscopy of the ER/MWCNT networks cured with anhydride. Raman spectroscopy was also used to confirm the interaction between MWCNT and IL. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43976.     

Tailored dielectric and mechanical properties of noncovalently functionalized carbon nanotube/poly(styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) nanocomposites

The preparation of high‐dielectric poly(styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) (SEBS) composites containing functionalized single‐walled carbon nanotubes (f‐SWCNTs) noncovalently appended with dibutyltindilaurate are reported herein. Transmission electron microscopy and X‐ray photoelectron and Raman spectroscopy confirmed the noncovalent functionalization of the SWCNTs. The SEBS‐f‐SWCNT composites exhibited enhanced mechanical properties as well as a stable and high dielectric constant of approximately 1000 at 1 Hz with rather low dielectric loss at 2 wt% filler content. The significantly enhanced dielectric property originates from the noncovalent functionalization of the SWCNTs that ensures good dispersion of the f‐SWCNTs in the polymer matrix. The f‐SWCNTs also acted as a reinforcing filler, thereby enhancing the mechanical properties of the composites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Microwave curing of epoxy polymers reinforced with carbon nanotubes

The driver for this study is the observation that heating of carbon nanotubes (CNTs) with electromagnetic field can offer a more efficient and cost‐effective alternative in heat transfer for the production of composites. The idea of this study is twofold; CNT can work as microwave (MW) radiation susceptors and they can act as nanoreinforcements in the final system. To test these assumptions, a household oven was modified to control the curing schedule. Polymers with different CNT concentrations were prepared (0.5 and 1.0 wt %). The dispersion of the CNTs in the epoxy was achieved using shear‐mixing dissolver technique. MW and conventionally cured specimens were also produced in a convection oven for reference. Thermal and mechanical tests were used as control point. A curing schedule investigation was further performed to quantify the energy and time‐saving capabilities using CNT and MWs. The presence of CNTs into epoxy matrix has been proven beneficial for the shortening of the curing time. MW‐cured composites showed the same degree of polymerization with the conventionally cured composites in a shorter time period and this time was reduced as the CNT concentration was increased. A good distribution of the CNT is required to avoid hot spot effects and local degradation. Mechanical performance was, in some cases, favored by the use of CNT. The benefit from the use of MWs and CNT could reach at least 40% in terms of energy needed and time without sacrificing mechanical performance. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Roll‐to‐roll printed carbon nanotubes on textile substrates as a heating layer in fiber‐reinforced epoxy composites

The performance of wind turbines suffers from icing in regions with extreme climate. One approach is to incorporate heating elements into the most susceptible areas of the wind turbine blade as protection against icing and for de‐icing. Cost‐efficient and reproducible fabrication, as well as easy integration is important due to the large area of wind turbine blades. In this work, multi‐walled carbon nanotubes are applied on a 50% poly(ethylene terephthalate) and 50% polyamide non‐woven textile substrate by rotary‐screen printing. The printed layers function as resistive heating elements in a fiber‐reinforced composite. The heating areas are provided with flexographic or screen inline‐printed silver‐electrodes and can be integrated by means of vacuum infusion into a glass fiber‐reinforced epoxy composite laminate. These laminates, which are connected to an intelligent electrical control system, are suitable for melting ice on the surface of components or for preventing the formation of ice. The first promising experiments on heating structures in a rotor blade of a wind turbine at laboratory scale (2 m length) are the basis of studies on intelligent electrical control of heating structures and their behavior at different temperatures. The heating elements were able to melt a 3–4 mm thick ice layer within 25 min in a climate chamber at ?5 °C. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45950.     

Effects of amino‐functionalized carbon nanotubes on the properties of amine‐terminated butadiene–acrylonitrile rubber‐toughened epoxy resins

Amino‐functionalized multiwalled carbon nanotubes (MWCNT‐NH₂s) as nanofillers were incorporated into diglycidyl ether of bisphenol A (DGEBA) toughened with amine‐terminated butadiene–acrylonitrile (ATBN). The curing kinetics, glass‐transition temperature (T_g), thermal stability, mechanical properties, and morphology of DGEBA/ATBN/MWCNT‐NH₂ nanocomposites were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis, a universal test machine, and scanning electron microscopy. DSC dynamic kinetic studies showed that the addition of MWCNT‐NH₂s accelerated the curing reaction of the ATBN‐toughened epoxy resin. DSC results revealed that the T_g of the rubber‐toughened epoxy nanocomposites decreased nearly 10°C with 2 wt % MWCNT‐NH₂s. The thermogravimetric results show that the addition of MWCNT‐NH₂s enhanced the thermal stability of the ATBN‐toughened epoxy resin. The tensile strength, flexural strength, and flexural modulus of the DGEBA/ATBN/MWCNT‐NH₂ nanocomposites increased increasing MWCNT‐NH₂ contents, whereas the addition of the MWCNT‐NH₂s slightly decreased the elongation at break of the rubber‐toughened epoxy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40472.     

Electrical conductivity and tensile properties of block‐copolymer‐wrapped single‐walled carbon nanotube/poly(methyl methacrylate) composites

Poly(methyl methacrylate) (PMMA) composites containing raw or purified single‐walled carbon nanotubes (SWCNTs) are prepared by in situ polymerization and solution processing. The SWCNTs are purified by centrifugation in a Pluronic surfactant, which consists of polyethyleneoxide and polypropyleneoxide blocks. Both the effects of SWCNT purity and non‐covalent functionalization with Pluronic are evaluated. Electrical conductivity of PMMA increases by 7 orders of magnitude upon the integration of raw or purified SWCNTs. The best electrical properties are measured for composites made of purified SWCNTs and prepared by in situ polymerization. Strains at fracture of the SWCNT/PMMA composites are nearly identical to those of the neat matrix. A certain decrease in the work to fracture is measured, particularly for composites containing purified SWCNTs (?31.6%). Fractography and Raman maps indicate that SWCNT dispersion in the PMMA matrix improves upon the direct addition of Pluronic, while dispersion becomes more difficult in the case of purified SWCNTs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41547.     

Facile covalent surface functionalization of multiwalled carbon nanotubes with poly(2‐hydroxyethyl methacrylate) and interface related studies when incorporated into epoxy composites

Carbon nanotubes (CNTs) have seen increased interest from manufacturers as a nanofiber filler for the enhancement of various physical and mechanical properties. A major drawback for widespread commercial use has been the cost associated with growing, functionalizing, and incorporating CNTs into commercially available polymeric matrices. Accordingly, the main objective of this study was to investigate the effects of adding commercially viable functionalized multiwalled carbon nanotubes (MWCNT) to a commercially available epoxy matrix. The mechanical behavior of the nanocomposites was investigated by mechanical testing in tensile mode and fractures were examined by scanning electron microscopy. The thermal behavior was investigated by differential scanning calorimetry and thermogravimetric analysis. Molecular composition was analyzed by attenuated total reflectance Fourier transform infrared spectroscopy. Mechanical testing of the epoxy/functionalized‐MWCNT indicated that the 0.15 wt % functionalized MWCNT composite possessed the highest engineering stress and toughness out of the systems evaluated without affecting the Young's modulus of the material. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The effect of fluorosilicone modifiers on the carbon nanotube networks in epoxy matrix

Structure and properties of polymer compositions based on carbon nanotubes (CNTs) filled epoxy matrix containing fluorosilicone copolymers as additives is discussed. Electrical conductivity and dielectric (microwave) permittivity of the composites can be varied by approximately one order of magnitude without changing the CNT concentration, by careful selection of the additive type and concentration. The mutual solubility of the modifiers and epoxy is a key factor determining both rheological properties of the uncured compositions and electrical properties of cured CNT‐nanocomposites. CNT‐nanocomposites modified with amino‐functional (i.e., epoxy crosslinkable) copolymers demonstrate improved electrical conductivity values at increased additive concentration, connected with the formation of specific segregated microstructure. Fluorosilicone additives added in a specific amount also allow for a decrease of the viscosity of uncured epoxy CNT‐nanocomposites, improving their processability. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46539.     

Nanostructured polymer blends based on polystyrene‐b‐polybutadiene‐b‐poly(methyl methacrylate) triblock copolymers modified with polystyrene and/or poly(methyl methacrylate) homopolymers

Morphologies of polymer blends based on polystyrene‐b‐ polybutadiene‐b ‐poly(methyl methacrylate) (SBM) triblock copolymer were predicted, adopting the phase diagram proposed by Stadler and co‐workers for neat SBM block copolymer, and were experimentally proved using atomic force microscopy. All investigated polymer blends based on SBM triblock copolymer modified with polystyrene (PS) and/or poly(methyl methacrylate) (PMMA) homopolymers showed the expected nanostructures. For polymer blends of symmetric SBM‐1 triblock copolymer with PS homopolymer, the cylinders in cylinders core?shell morphology and the perforated lamellae morphology were obtained. Moreover, modifying the same SBM‐1 triblock copolymer with both PS and PMMA homopolymers the cylinders at cylinders morphology was reached. The predictions for morphologies of blends based on asymmetric SBM‐2 triblock copolymer were also confirmed experimentally, visualizing a spheres over spheres structure. This work presents an easy way of using PS and/or PMMA homopolymers for preparing nanostructured polymer blends based on SBM triblock copolymers with desired morphologies, similar to those of neat SBM block copolymers. © 2017 Society of Chemical Industry     

Tough hyperbranched epoxy/poly(amido‐amine) modified bentonite thermosetting nanocomposites

A tough and highly flexible hyperbranched epoxy and poly(amido‐amine) modified bentonite based thermosetting nanocomposite was demonstrated. The FTIR, XRD, and TGA analyses confirmed the modification of bentonite. The formation of partially exfoliated structure of the nanocomposite with good physicochemical interactions among the hyperbranched epoxy, poly(amido‐amine) hardener and modified clay was investigated by the FTIR, XRD, SEM, and TEM analyses. Significant improvements of 750% toughness, 300% elongation at break, 50% tensile strength, 300% modulus, and 250% adhesive strength of the pristine epoxy were achieved by the formation of nanocomposites with 3 wt % of modified clay. The experimental modulus values of the nanocomposites were compared with three theoretical models to account the interactions between filler and matrix. Thus, the studied epoxy nanocomposite has great potential to be used as an advanced epoxy thermoset. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40327.     

Effectiveness of the preparation of maleic anhydride grafted poly (lactic acid) by reactive processing for poly (lactic acid)/carbon nanotubes nanocomposites

An effective strategy to increase the properties of poly (lactic acid) (PLA) is the addition of carbon nanotubes (CNT). In this work, aiming to improve the surface adhesion of PLA and CNT a new compatibilizer agent was prepared by reactive processing, PLA grafted maleic anhydride (PLA-g-MA) using benzoyl peroxide and maleic anhydride. The effectiveness of the PLA-g-MA as a compatibilizer agent was verified for PLA/PLA-g-MA/CNT nanocomposites. PLA and PLA-g-MA samples were characterized by Fourier transform infrared spectroscopy (FT-IR) to confirm the grafting reaction of maleic anhydride on PLA chains and by rheological analysis to prove the changes in the matrix PLA after the graphitization reaction. Thermal (differential scanning calorimetry and thermogravimetric analysis), mechanical tests (Izod impact strength and tensile test), and morphological characterization were used to verify the effect of the compatibilizer agent. The preparation of PLA-g-MA by reactive extrusion processing proved satisfactory and the nanocomposites presented good thermal and mechanical properties. The addition of the PLA-g-MA also contributed to the greater distribution of CNT and can be used as an alternative for the production of PLA/CNT nanocomposites.     

Preparation and characterization of P(AN‐co‐VA‐co‐DEMA) fibers coated with multiwalled carbon nanotubes by electrostatic interactions

P(AN‐co‐VA‐co‐DEMA) terpolymers were synthesized by aqueous precipitation copolymerization of acrylonitrile (AN), vinyl acetate (VA), and 2‐dimethylamino ethyl methacrylate (DEMA) with an Na₂S₂O₅–NaClO₃ redox initiating system and fibers from these terpolymers were thus prepared by a wet spinning method. Functionalized multiwalled carbon nanotube (F‐MWNT) networks were created on the surface of P(AN‐co‐VA‐co‐DEMA) fibers by a simple dipping method. The morphology and interfacial interactions of the obtained F‐MWNTs‐coated fibers were characterized by scanning electron microscope, Raman spectroscopy, and Fourier transform infrared spectroscopy. The results showed that F‐MWNTs were assembled on the fibers and the density of F‐MWNTs can be controlled by adjusting the F‐MWNTs content in the dipping solution. The assembly process was driven by electrostatic interactions between the negative charges on the nanotube sidewalls and the positive charges of the fibers. The F‐MWNTs‐coated fibers had a good conductivity. The volume resistivity of the fibers coated with 1.18 wt % F‐MWNTs reached 0.27 Ω·cm, while the original mechanical properties were preserved. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42545.     

High thermal conductive m‐xylylenediamine functionalized multiwall carbon nanotubes/epoxy resin composites

In this study, multiwall carbon nanotubes (MWNTs) functionalized by m‐xylylenediamine is used as thermal conductive fillers to improve their dispersibility in epoxy resin and the thermal conductivity of the MWNTs/bisphenol‐A glycidol ether epoxy resin composites. Functionalization with amine groups of MWNTs is achieved after such steps as carboxylation, acylation and amidation. The thermal conductivity, impact strength, flexural strength, and fracture surfaces of MWNTs/epoxy composites are investigated with different MWNTs. The results show that m‐xylylenediamine is successfully grafted onto the surface of the MWNTs and the mass fraction of the organic molecules grafted onto MWNTs is about 20 wt %. The thermal conductivity of MWNTs/epoxy composites is further enhanced to 1.236 W/mK with 2 wt % m‐MWNTs. When the content of m‐MWNTs is 1.5 wt %, the impact strength and flexural strength of the composites are 25.85 KJ/m², 128.1 MPa, respectively. Scanning electron microscope (SEM) results show that the fracture pattern of composites is changed from brittle fracture to ductile fracture. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41255.     

Electrically conductive polycarbonate/ethylene‐propylene copolymer/multi‐walled carbon nanotubes nanocomposites with improved mechanical properties

In this article, the effect of Multi‐walled carbon nanotubes (MWCNTs) on the electrical conductivity and mechanical properties of polycarbonate (PC) toughened with cross‐linked ethylene‐propylene copolymer (EPC) was investigated. The solubility parameters of the PC and EPC were calculated using Hoy methods to clarify the miscibility of the polymer blends. It could be concluded that in the cooled state, the blends form a heterogeneous structure with two separate phases. The tensile, flexural, impact toughness properties of the PC/EPC blend and PC/EPC/MWCNT nanocomposites were carried out to illuminate the optimum concentration of polymer blends and MWCNTs. The 335% increment for the impact strength results appeared with combination of 10% EPC in the PC matrix. The flexural modulus and strength of PC/EPC blend increased by 75.1% and 59.1%, respectively. The Nielsen model was performed to fit the best curve of theoretical simulation to experimental results for elastomeric dispersed in the plastic matrix. Halpin‐Tsai model was applied to estimate the stiffness of nanocomposites blends with different volume fraction and aspect ratio of MWCNTs in the PC/EPC blends. Finally, in the presence of MWCNTs, all nanocomposite samples were semi‐conducting and the percolation threshold of the PC/EPC (10%) blends was between 0.5% and 1.0% MWCNTs. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44661.     

Novel soluble carbazole‐based poly(aryl ethers): Preparation,properties, and application for dispersing multiwalled carbon nanotubes

Effectively dispersing of carbon nanotubes (CNTs) is the key to producing high performance CNTs/poly(aryl ethers) (PAEs) composite materials. Here, a series of novel soluble carbazole‐based PAEs with different alkyl side‐chains were synthesized corresponding polymers P1, P2, P3, and P4, and characterized clearly by ¹H NMR and IR. All the polymers exhibited good mechanical properties and thermostabilities (T_g ～ 128–212 °C, T_d5% ～ 450–499 °C) as PAEs. Due to containing lots of large π‐conjugated carbazole derivative units and possess suitable solubility, these non‐conjugated polymers can wrap and disperse MWNTs well (238–416 mg/L) in CHCl₃, and the similar work has been reported rarely. This excellent property makes these polymers become a promising and ideal type solubilizer for CNTs/PAEs composite. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46250.     

In situ fast polymerization of graphene nanosheets‐filled poly(methyl methacrylate) nanocomposites

A series of graphene nanosheets‐filled poly(methyl methacrylate) nanocomposites (GNS/PMMA) is successfully prepared by an in situ fast polymerization method with graphene weight fractions from 0.1 to 2.0 wt %. In situ polymerization is effective in well dispersing of GNS in matrixes and suitable for both low and high content of GNS. The synthesis processes of polymer composites could be simplified and fast by using industrial grade graphene. The GNS fillers are found to disperse homogeneously in the PMMA matrix. The maximum electrical conductivity of the composites achieves 0.57 S m^?1, with an extremely low percolation threshold of 0.3 wt %. The electrical conductivities are further predicted by percolation theory and found to agree well with the experimental results. The results indicate that the microstructures, thermal, electrical, and mechanical properties of PMMA polymer are significantly improved by adding a low amount of graphene nanosheets. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43423.     

Fabrication of polysulfone nanocomposite membranes with silver‐doped carbon nanotubes and their antifouling performance

In this study, polysulfone (PSf)/silver‐doped carbon nanotube (Ag‐CNT) nanocomposite membranes were prepared by a phase‐inversion technique; they were characterized and evaluated for fouling‐resistant applications with bovine serum albumin (BSA) solutions. Carbon nanotubes were doped with silver nanoparticles via a wet‐impregnation technique. The prepared Ag‐CNT nanotubes were characterized with scanning electron microscopy (SEM)/energy‐dispersive X‐ray spectroscopy, X‐ray diffraction, Raman spectroscopy, and thermogravimetric analysis. The fabricated flat‐sheet PSf/Ag‐CNT nanocomposite membranes with different Ag‐CNT loadings were examined for their surface morphology, roughness, hydrophilicity, and mechanical strength with SEM, atomic force microscopy, contact angle measurement, and tensile testing, respectively. The prepared composite membranes displayed a greater rejection of BSA solution (≥90%) and water flux stability during membrane compaction with a 10% reduction in water flux values (up to 0.4% Ag‐CNTs) than the pristine PSf membrane. The PSf nanocomposite membrane with a 0.2% Ag‐CNT loading possessed the highest flux recovery of about 80% and the lowest total membrane resistance of 56% with a reduced irreversible fouling resistance of 21%. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44688.