Preparation of highly conductive reduced graphite oxide/poly(styrene-co-butyl acrylate) composites via miniemulsion polymerization

Polymer/reduced graphite oxide (rGO) composite nanoparticles with a high electrical conductivity were synthesized using the miniemulsion polymerization technique. The rGO was modified with a reactive surfactant, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), to facilitate monomer intercalation into the rGO nanogalleries. The AMPS-modified rGO was emulsified in the presence of styrene (St) and butyl acrylate (BA) monomers, and the stable miniemulsion was polymerized to form poly(St-co-BA)/rGO composite latex nanoparticles. The transition in the composite nanoparticles from an electrical insulator to an electrical conductor occurred at an rGO content of 10 wt% (relative to the monolayer content), yielding an electrical conductivity of 0.49 S/cm. The electrical conductivity of the composite nanoparticles reached 2.22 S/cm at 20 wt% rGO, yielding a much better conductivity than other polymer composites prepared using a GO filler. Importantly, the miniemulsion polymerization method for fabricating poly(St-co-BA)/rGO composite nanoparticles is easy, green, low-cost, and scalable, providing a universal route to the rational design and engineering of highly conductive polymer composites.     

GO表面原位生长CNTs改善聚丙烯导热复合材料分散与界面形态

二维结构氧化石墨烯(GO)纳米片在高分子导热复合材料领域有良好应用前景,但常受限于片层间相互作用过大导致的局部团聚,不利于力学性能和导热性能的提高。借助GO纳米片表面和边缘提供的大量活性位点以吸附铁基催化剂,进而通过微波辅助合成方法在GO表面原位生长碳纳米管(CNTs)的策略,在数分钟内合成具有三维多层次结构的纳米杂化体(GO-CNT)。通过常规熔融共混方法,可获得GO-CNT在聚丙烯(PP)基体中良好剥离与均匀分散形态,明显不同于GO/PP复合体系中严重的局部团聚现象。均匀分散的GO-CNT对PP复合材料的力学性能和导热性能提升效果显著：在3%(质量分数)含量下,复合材料的屈服强度和热导率分别达到了38.0 MPa和0.76 W/(m·K),较纯PP增幅分别为20%和230%,明显优于传统GO改性复合材料。本研究为解决纳米片状填料在导热复合材料中的应用瓶颈提供了可行的结构设计策略和复合材料制备方法。     

High-Performance and Biobased Polyamide/Functionalized Graphene Oxide Nanocomposites through In Situ Polymerization for Engineering Applications

In this study, biobased polyamide/functionalized graphene oxide (PA-FGO) nanocomposite is developed using sustainable resources. Renewable PA is synthesized via polycondensation of hexamethylenediamine (HMDA) and biobased tetradecanedioic acid. Furthermore, GO is functionalized with HMDA to improve its compatibility with biobased PA and in situ polymerization is employed to obtain homogeneous PA-FGO nanocomposites. Compatibility improvement provides simultaneous increases in the tensile strength, storage modulus, and conductivity of PA by adding only 2 wt% FGO (PA-FGO2). The tensile strength and storage modulus of PA-FGO2 nanocomposite are enhanced dramatically by ≈50% and 30%, respectively, and the electrical conductivity reached 3.80 × 10^–3 S m⁻¹. In addition, rheology testing confirms a shear-thinning trend for all samples as well as a significant enhancement in the storage modulus upon increasing the FGO content due to a rigid network formation and strong polymer-filler interactions. All these improvements strongly support the excellent compatibility and enhanced interfacial interactions between organic–inorganic phases resulting from GO surface functionalization. It is expected that the biobased PA-FGO nanocomposites with remarkable thermomechanical properties developed here can be used to design high-performance structures for demanded engineering applications.     

Low-temperature exfoliated graphene oxide incorporated with different types of natural rubber latex: Electrical and morphological properties and its capacitance performance

A simple with cost-effective method in the production and fabrication of graphene-based rubber nanocomposites as electrode materials is still remain a global challenge. In this work, we proposed one- and two-step approaches to fabricate an exfoliated graphene oxide (GO) as nanofiller in three different types of rubber latex polymer, namely, low ammonia natural rubber latex (NRL), radiation vulcanized NRL (RVNRL), and epoxy NRL 25 (ENRL 25). The electrical conductivity and capacitive behavior of nanocomposite samples were investigated under a four-point probe and cyclic voltammetry measurements, respectively. Meanwhile, the morphological properties were observed using field emission scanning electron microscopy, energy dispersive X-ray, optical polarization microscope, high-resolution transmission electron microscopy, Fourier-transform infrared spectroscopy, micro-Raman spectroscopy, and X-ray diffraction. The thermal stabilities of the nanocomposites were also investigated by thermogravimetric analysis. Among all, the GO/RVNRL polymer nanocomposite samples performed a better homogeneity with an improved electrical conductivity (~8.6 × 10⁻⁴ Scm⁻¹) as compared with the GO/ENRL 25 (~3.1 × 10⁻⁴ Scm⁻¹) and GO/NRL (~2.6 × 10⁻⁴ Scm⁻¹) polymer nanocomposite samples. In addition, the GO/RVNRL polymer nanocomposite electrodes showed acceptable specific capacitance (5 Fg^-1). The successfully fabricated conductive GO-based rubber nanocomposites are suitable for new supercapacitor electrodes.     

Waterborne acrylic–polyaniline nanocomposite as antistatic coating: preparation and characterization

An antistatic and electrically conductive acrylic–polyaniline nanocomposite coating was successfully synthesized by interfacial polymerization of aniline in the presence of acrylic latex. The acrylic latex was prepared through emulsion polymerization, and aniline was polymerized by in situ interfacial polymerization at the interface of acrylic latex/chloroform phase. Fourier transform infrared spectroscopy (FTIR), UV–Vis spectroscopy and CHNS elemental analysis revealed the existence of 6.24 wt% emeraldine salt of polyaniline (PAni) in the dried film of the nanocomposite. Scanning electron microscopy (SEM) confirmed the presence of colloidal polymer particles in the aqueous phase which was confirmed to have some advantages, including prevention of aggregation of particles, dispersibility improvement and enhancement of the PAni nanofibers aspect ratio in the acrylic polymer matrix. According to SEM results, PAni fibers with the length ranging from 12 to 67 µm and diameters between 0.078 and 1 µm, highly dispersed in the acrylic polymer matrix, were successfully synthesized. Thermal, electrical and mechanical properties of the acrylic copolymer were significantly affected by PAni incorporation. The onset degradation temperature in thermogravimetric analysis revealed that the thermal stability of the nanocomposite was improved compared to that of the pure acrylic copolymer. The nanocomposite film showed electrical conductivity of about 0.025 S/cm at room temperature, along with satisfactory mechanical properties, attractive as an antistatic material in coating applications.     

Latex co‐coagulation approach to fabrication of polyurethane/graphene nanocomposites with improved electrical conductivity,thermal conductivity,and barrier property

This study describes a simple and effective method of synthesis of a polyurethane/graphene nanocomposite. Cationic waterborne polyurethane (CWPU) was used as the polymer matrix, and graphene oxide (GO) as a starting nanofiller. The CWPU/GO nanocomposite was prepared by first mixing a CWPU emulsion with a GO colloidal dispersion. The positively charged CWPU latex particles were assembled on the surfaces of the negatively charged GO nanoplatelets through electrostatic interactions. Then, the CWPU/chemically reduced GO (RGO) was obtained by treating the CWPU/GO with hydrazine hydrate in DMF. The results of X‐ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Raman analysis showed that the RGO nanoplatelets were well dispersed and exfoliated in the CWPU matrix. The electrical conductivity of the CWPU/RGO nanocomposite could reach 0.28 S m^?1, and the thermal conductivity was as high as 1.71 W m^?1 K^?1. The oxygen transmission rate (OTR) of the CWPU/RGO‐coated PET film was significantly decreased to 0.6 cm³ m^?2 day^?1, indicating a high oxygen barrier property. This remarkable improvement in the electrical and thermal conductivity and barrier property of the CWPU/RGO nanocomposite is attributed to the electrostatic interactions and the molecular‐level dispersion of RGO nanoplatelets in the CWPU matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43117.     

Enhanced mechanical and electrical properties of polyimide film by graphene sheets via in situ polymerization

In this study, polyimide/graphene nanocomposite films which exhibited significant enhancements in mechanical properties and electrical conductivity were successfully fabricated. Graphene oxide (GO) synthesized by Hummer’s method was chemically modified with ethyl isocyanate to give ethyl isocyanate-treated graphene oxide (iGO), which is readily dispersed in N,N′-dimethylformamide (DMF). The iGO dispersion in DMF was then used as media for synthesis of polyimide/functionalized graphene composites (PI/FGS) by an in situ polymerization approach. It was shown that addition of only 0.38 wt% of FGS, Young’s modulus of the PI/FGS composite film was dramatically increased from 1.8 GPa to 2.3 GPa, which is approximately 30% of improvement compared to that of pure PI film, and the corresponding tensile strength was increased from 122 MPa to 131 MPa. In addition, the electrical conductivity of the PI/FGS with this graphene content was increased by more than eight orders of magnitude to 1.7 × 10⁻⁵ S m⁻¹.     

Exploring interfacial interactions,dielectric, ferroelectric and piezoelectric properties of ultrahigh molecular weight polyethylene/graphene oxide nanocomposites

Graphene oxide (GO) incorporated ultra-high molecular weight polyethylene (UHMWPE) nanocomposites were prepared by encapsulating GO by UHMWPE in an aqueous media via high-shear mixing, which were subsequently dried and compression molded. Morphological characterizations via scanning electron microscopy revealed the intercalation of UHMWPE chains in the graphitic stacks corresponding to GO. Further, dielectric permittivity of UHMWPE/GO nanocomposite of 1 wt% GO showed a drastic increase (~61) as compared to pure UHMWPE (~2) due to an enhanced interfacial polarization. A significantly higher value of remnant polarization (~10 nC/cm²) and coercive field (~3 kV/cm) was observed in UHMWPE/GO nanocomposite of 1 wt% GO, which showed a strong hysteresis loop of polarization versus electric field plot as compared to pure UHMWPE, which displayed a very weak hysteresis loop. The piezoelectric coefficient (d₃₃) of ~9.5 pm/V was estimated in UHMWPE/GO nanocomposite of 1 wt% GO via piezoresponse force microscopy. Nanocomposite sensor devices were also fabricated and piezoelectric output voltage of ~6 V was recorded in UHMWPE/GO nanocomposite of 1 wt% of GO. We report here for the first time the unique ferroelectric and piezoelectric properties displayed by UHMWPE/GO nanocomposites.     

Synthesis and properties of poly(4,4′-oxybis(benzene)disulfide)/graphite nanocomposites via in situ ring-opening polymerization of macrocyclic oligomers

An effective method for the preparation of poly(4,4′-oxybis(benzene)disulfide)/graphite nanosheet composites via in situ ring-opening polymerization of macrocyclic oligomers were reported. Completely exfoliated graphite nanosheets were prepared under the microwave irradiation followed by sonication in solution. The nanocomposites were fabricated via in situ melt ring-opening polymerization of macrocyclic oligomers in the presence of graphite nanosheets. The graphite nanosheets and resulted poly(arylene disulfide)/graphite nanocomposites were characterized with field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), tensile tester and electrical conductivity measurements. Compared with pure polymer, the electrical conductivity of the poly(arylene disulfide)/graphite nanocomposites were dramatically increased and had a value of about 10⁻³ S/cm for the nanocomposite containing 5 wt% graphite. The nanocomposites exhibit as both high performance polymeric material and electrically conductive material. Therefore, they show potential applications as high temperature conducting materials.     

Polyamide-based membranes consisting of nanocomposite interlayers for high performance nanofiltration

It is still a task to synthesize polyamide-based membranes with selective layers down to 10–20 nm for high performance desalination. Herein, cellulose nanocrystals (CNC) were used as one-dimensional (1D) nanorods and graphene oxides (GO) as two-dimensional (2D) nanosheets, respectively, to construct nanocomposite interlayers for synthesizing polyamide layers thinner than 15 nm. The 2D nanosheets are homogeneously mixed with the 1D nanorods and effectively reduce the surface roughness of the nanocomposite interlayers with decreasing the mass ratio of CNC/GO. Polyamide layers with a thickness of 10–15 nm have been synthesized at an ultralow monomer concentration of 0.025 wt% on these CNC/GO nanocomposite interlayers. The polyamide-based membranes exhibit extremely high water permeation (45.9 L/m²·h·bar) without losing their salt rejection ability. The nanofiltration performances of these polyamide-based membranes are higher than most of the reported nanofiltration membranes in recent years.     

Multifunctional and environmentally friendly nanocomposites between natural rubber and graphene or graphene oxide

This work describes a green route to multifunctional nanocomposite materials composed of natural rubber (NR) latex and graphene (rGO) or graphene oxide (GO). Aqueous solutions with different concentrations of GO and rGO (prepared with the surfactant cetyltrimethylammonium bromide – CTAB) were mixed with natural rubber latex under magnetic stirring followed by sonication. The slurries obtained after casting were dried in an oven in air at 70 °C for 24 h. The nanocomposites were characterized by TEM and SEM, AFM and KFM. The thermal, electrical and mechanical properties were evaluated using TGA, resistivity measurements (four-point) and DMA. Swelling tests were performed using three solvents with different polarities: xylene, isopropanol and water. The inclusion of filler networks in the polymeric matrices provided significant improvements in the electrical, chemical and mechanical properties, in comparison to the unfilled polymer. In addition, the nanocomposites proved to be biodegradable.     

Fabrication of electrical and thermal conductive thermoplastic polyurethanes-based nanocomposite with azide polyurethane as interfacial compatibilizer

Electrical and thermal conductive polymers have aroused extensive interest in research recently due to their hi-tech applications in the fields of novel electronics. A novel electrical and thermal conductive nanocomposite (MWCNTs@PU/TPU) made with multiwall carbon nanotubes (MWNTs) and thermoplastic polyurethanes (TPU) by using azide polyurethane (PU) as interfacial compatibilizer. The MWNTs could form well-developed electrical and thermal conductive networks in the TPU matrix. The developed nanocomposite inherited advantageous properties from its constituents, namely the high conductivity and diathermancy from MWNTs, and the high mechanical properties from the TPU. Conductivity tests showed that, compared with neat MWCNTs/TPU, the electrical conductivity of MWCNTs@PU/TPU was significantly enhanced (up to 3.4 × 10⁻⁶ S/cm), with incorporating only 3.0 wt% MWCNTs@PU. And most importantly, the thermal conductivity was greatly improved by about 46.4% when the MWCNTs@PU loading was 6.0 wt%.     

水辅混炼挤出聚苯乙烯/氧化石墨烯纳米复合材料的微观结构及流变与热性能

采用自主设计的水辅混炼挤出设备,制备3种氧化石墨烯（GO）含量（0.1 %、0.3 %、0.5 %,质量分数,下同）的聚苯乙烯（PS）/GO纳米复合材料,观察样品的微观结构,测试其流变性能和热性能。结果表明,GO被较好剥离且呈网状较均匀地分散在PS基体中,这主要归因于螺杆混炼流场不断细化PS熔体中的GO悬浮液以及水对熔体的塑化和溶胀效应促进PS分子链插层进入GO片层之间的共同作用;低频区PS/GO样品的储能模量、复数黏度和松弛时间均比纯PS样品的高,这是因为较均匀分散的网状GO片与PS之间形成较强的分子间作用力,降低了PS分子链的活动性;PS/GO样品的热稳定性比纯PS样品的高,这归因于GO片在PS基体中呈网状分布和GO表面存在π键。     

Properties of na‐montmorillonite and cellulose nanocrystal reinforced poly(butyl acrylate‐co‐methyl methacrylate) nanocomposites

Poly(butyl acrylate‐co‐methyl methacrylate) (BA‐co‐MMA) nanocomposite latexes were synthesized in the presence of sodium montmorillonite (Na‐MMT) and cellulose nanocrystal (CNC) as fillers. Nanocomposite preparation with 3 wt% Na‐MMT based upon the total monomer amount was conducted by semi‐batch emulsion polymerization. Furthermore, direct blending of neat copolymer latex with Na‐MMT was performed for comparison. CNC/BA‐co‐MMA nanocomposites were obtained via blending process with varying CNC content (1, 2, and 3 wt %). Good dispersion of both Na‐MMT and CNC within the copolymer matrix was achieved as demonstrated by X‐ray diffraction and transmission electron microscope. Particle size of the nanocomposite latexes was around 120 nm. Thermal, mechanical, and barrier properties of the copolymer showed great improvement with the addition of both Na‐MMT and CNC. CNC nanocomposites displayed enhanced properties with increasing CNC level. Tensile strength of copolymer latex with 3 wt% CNC reached 262.5% of the pristine latex, while tensile strength of Na‐MMT nanocomposite at the same content was 187.5% of the pristine latex. POLYM. ENG. SCI., 55:2922–2928, 2015. © 2015 Society of Plastics Engineers     

Segregated highly conductive linear low-density polyethylene/graphene nanoplatelet composite through aqueous dispersing and self-leveling method

Construction of segregated structure is an effective way of preparing highly conductive composite. Here, we report an environmentally friendly method to prepare highly conductive linear low-density polyethylene/graphene nanoplatelets composite with segregated structure (s-LLDPE/GN) and low GN content. Firstly, GN coated LLDPE granules are prepared through aqueous dispersing and gradually drying. Then, the s-LLDPE/GN composites are obtained by melting and self-leveling without extra pressure. This method not only favors the forming of GN segregated network, but also allows certain fusing of the polymer at the interfaces that contribute to good mechanical strength of the composite. The electrical conductivity of the composite increases to 4.5 S/m when the GN content is 1.0 wt%. The composite with 0.5 wt% GN shows 10⁻¹ S/m electrical conductivity, and retains 82% of the tensile strength of pure LLDPE. The facile and green process in this method can be applied in many other polymer composites and show high potential for industrial application.     

Sub-micron calcium carbonate isolated carbon nanotubes/polyethylene composites with controllable electrical conductivity

The dispersion and distribution of carbon nanotubes (CNTs) on/in the polymer composites are greatly affected by the molding technology progress, which results in different electrical conductivity. The uncontrollable electrical conductivity has limited the application of conductive polymer composites, for example, sensor components. In this work, to enhance the dispersion stability of CNTs in polyethylene (PE) matrix, sub-micron calcium carbonate isolated CNTs (smCaCO₃@CNTs) were selected based on the fact that smCaCO₃ is much easier to disperse in polymer in comparison with CNTs. This good distribution of CNTs in smCaCO₃@CNTs/PE was characterized by transmission electron microscope and Raman mapping. The electrical performance test results show that when 0.5 wt% of CNTs filled in smCaCO₃@CNTs/PE, the percolation network begins to form; when CNTs filled increases to 1-2 wt%, the surface resistance of smCaCO₃@CNTs/PE ranges from 10⁶ to 10⁹Ω almost not affected by the molding technology process (compression molding or injection molding). The possible reason is that the isolated CNTs by smCaCO₃ in polymer matrix are favorable for the formation of the stable conductive network.     

Preparation and properties of poly(lactic acid)/lipophilized graphene oxide nanohybrids

Poly(lactic acid) (PLA)/lipophilized graphene oxide (LGO) nanohybrids were prepared using a solution blending method. Graphene oxide (GO) was synthesized using a modified Hummers method and then lipophilized by functionalization with alkylamines such as octylamine, dodecylamine or octadecylamine (ODA). PLA/GO nanohybrids were also prepared for comparison. Among the LGOs, ODA‐GO was chosen to produce the PLA/LGO nanohybrids because ODA‐GO exhibited obvious intercalation behavior and the best dispersibility in chloroform. The properties of the PLA/GO and PLA/LGO nanohybrids were investigated using scanning electron microscopy, wide‐angle X‐ray diffraction, differential scanning calorimetry, thermogravimetric analysis, a universal testing machine, chemical resistance measurements and hydrolytic degradability analysis. The hydrophobic ODA‐GO was dispersed on the nanoscale within the PLA matrix and the resulting nanohybrids showed significantly higher chemical resistance and reduced hydrolytic degradation. © 2017 Society of Chemical Industry     

Novel electrochemical sensing platform based on palygorskite nanorods/Super P Li carbon nanoparticles-graphitized carbon nanotubes nanocomposite for sensitive detection of niclosamide

We reported an one-pot ultrasonic-assisted method for the preparation of palygorskite nanorods/Super P Li carbon nanoparticles-graphitized carbon nanotubes (PNRs/SPCNPs-g-CNTs) nanocomposite, which was used to modify the glassy carbon electrode (GCE) for the fabrication of PNRs/SPCNPs-g-CNTs/GCE sensor. For the PNRs/SPCNPs-g-CNTs nanocomposite, PNRs with good stability presented large specific surface area and high adsorption, which promoted the enrichment of NA molecules on the electrode surface. SPCNPs with pearl chain-like nanostructure exhibited good electrical conductivity, and the combination of SPCNPs and g-CNTs with high graphitization degree formed an interconnected carbon conductive network with excellent electrical conductivity, which enhanced the charge transport efficiency. Moreover, the interconnected carbon conductive network of SPCNPs-g-CNTs not only promoted the dispersion degree of PNRs but also made up for the poor conductivity property of PNRs. When used for the detection of niclosamide (NA), an acceptable limit of detection (3.6 nM) was achieved at the PNRs/SPCNPs-g-CNTs/GCE sensor in linear NA concentration range of 0.01–10 μM. The PNRs/SPCNPs-g-CNTs/GCE sensor exhibited good reproducibility, repeatability, and anti-interference performance. For the practicability measurement, the fabricated sensor showed good practicability with satisfactory recoveries (97.0–102.7%) and low RSD values of 0.99–4.78% for the detection of NA in tap water and lake water samples.     

一段混炼时间对石墨烯/天然橡胶/溶聚丁苯橡胶复合材料性能的影响

采用一段密炼和二段开炼的两段混炼工艺制备氧化石墨烯(GO)/天然橡胶(NR)/溶聚丁苯橡胶(SSBR)和还原氧化石墨烯(rGO)/NR/SBR复合材料,研究一段混炼时间对GO/NR/SSBR和rGO/NR/SSBR复合材料性能的影响。结果表明:随着一段混炼时间的延长,GO/NR/SSBR和rGO/NR/SSBR复合材料的Fmax和FL增大,t90缩短;邵尔A型硬度、300%定伸应力、拉伸强度和撕裂强度呈先增大后减小的趋势,导电性能和导热性能呈先提高后降低的趋势,气密性能呈先提高后平稳再降低的趋势。     

Effect of the compression molding parameters on the in-plane and through-plane conductivity of carbon nanotubes/graphite/epoxy nanocomposites as bipolar plate material for a polymer electrolyte membrane fuel cell

The main challenges for commercialization of a single-filler graphite (G) polymer-matrix composite as bipolar plates are its low electrical conductivity and flexural strength. The minimum requirements set by the US Department of Energy (DOE) are the electrical conductivity and flexural strength to be greater than 100 S/cm and 25 MPa, respectively. In this study, the electrical conductivity of a G/epoxy (EP) composite (single filler) is only 50 S/cm (in-plane conductivity) at 80 wt% G. However, flexural strength is greater than 25 MPa. Using carbon nanotubes (CNTs) as the second filler at a concentration of 5 wt% in a CNTs/G/EP nanocomposite resulted in the in-plane and through-plane electrical conductivity and flexural strength being 180 S/cm, 75 S/cm, and 45 MPa, respectively. The density of the CNTs/G/EP nanocomposite is also less than that of G/EP composite, which demonstrates that a total weight reduction is achievable.