The roles of polymer-graphene interface and contact resistance among nanosheets in the effective conductivity of nanocomposites

The effective conductivity of graphene-based nanocomposites is suggested by the characteristics of polymer-filler interfacial areas as well as the contact resistance between the neighboring nanosheets.The interfacial properties are expressed by the effective levels of the inverse aspect ratio and the filler volume fraction.Moreover,the resistances of components in the contact regions are used to define the contact resistance,which inversely affects the effective conductivity.The obtained model is utilized to predict the effective conductivity for some examples.The discrepancy of the effective conductivity at various ranks of all factors is clarified.The interfacial conductivity directly controls the effective conductivity,while the filler conductivity plays a dissimilar role in the effective conductivity,due to the incomplete interfacial adhesion.A high operative conductivity is also achieved by small contact distances and high interfacial properties.Additionally,big contact diameters and little tunnel resistivity decrease the contact resistance,thus enhancing the effective conductivity.

Synthesis, properties, and applications of graphene oxide/reduced graphene oxide and their nanocomposites

Thanks to their remarkable mechanical, electrical, thermal, and barrier properties, graphene-based nanocomposites have been a hot area of research in the past decade. Because of their simple top-down synthesis, graphene oxide (GO) and reduced graphene oxide (rGO) have opened new possibilities for gas barrier, membrane separation, and stimuli-response characteristics in nanocomposites. Herein, we review the synthesis techniques most commonly used to produce these graphene derivatives, discuss how synthesis affects their key material properties, and highlight some examples of nanocomposites with unique and impressive properties. We specifically highlight their performances in separation applications, stimuli-responsive materials, anti-corrosion coatings, and energy storage. Finally, we discuss the outlook and remaining challenges in the field of practical industrial-scale production and use of graphene-derivative-based polymer nanocomposites.

Recent Advances in Fabrication and Characterization of Graphene-Polymer Nanocomposites

Graphene has attracted considerable interest over recent years due to its intrinsic mechanical, thermal and electrical properties. Incorporation of small quantity of graphene fillers into polymer can create novel nanocomposites with im- proved structural and functional properties. This review introduced the recent progress in fabrication, properties and potential applications of graphene-polymer composites. Recent research clearly confirmed that graphene-polymer na-nocomposites are promising materials with applications ranging from transportation, biomedical systems, sensors, elec-trodes for solar cells and electromagnetic interference. In addition to graphene-polymer nanocomposites, this article also introduced the synergistic effects of hybrid graphene-carbon nanotubes (CNTs) on the properties of composites. Finally, some technical problems associated with the development of these nanocomposites are discussed.

Morphology Dynamical Mechanical and Flame Retardant Properties of Nylon 1212/Organic Montmorillonite Nanocomposites Prepared by Melt Compounding

Nylon 1212/organic montmorillonite(OMMT)nanocomposites were prepared using the melt compounding method.The morphology and dynamical mechanical properties of the nanocomposites were investigated using transmission electron microscope(TEM)and dynamic mechanical analysis(DMA).The storage modulus of nylon 1212/OMMT nanocomposites was increased with increasing OMMT.The flame retardant properties were characterized by cone calorimetry,scanning electron microscope(SEM)and X-ray photoelectron spectroscopy(XPS).The flame retardant properties were characterized using cone calorimetry,whereby nylon 1212/OMMT nanocomposites were improved compared with pure nylon 1212 because of the carbonaceous-silicate granular materials which were formed during combustion,thus proposing the flame retardant mechanism.

Effect of nano powder(Al2O3-CaO)addition on the mechanical properties of the polymer blend matrix composite

This work describes the preparation and study of the properties of composite nanoparticles prepared by the sol-gel method which consists of two materials(Al2 O3-CaO),and study the effect of these nanoparticles on the mechanical behavior of a polymer blend(EP 4%+96%UPE).The powder was evaluated by X-ray diffraction analysis,scanning electron microscopy analysis(SEM),particle size analysis,and energy dispersive X-ray analysis(EDX).The mechanical behavior of the co mposite material was assessed by tensile test,bending test and hardness test.The evaluation results of the composite nanoparticles showed good distribution of the chemical composition between aluminum oxide and calcium oxide,smoothness in particles’size at calcination in high and low temperatures,formation of different shapes of nanoparticles and different(kappa and gamma)phases of the Al2 O particles.The results of mechanical behavior tests showed marked improvement in the mechanical properties of the resulted composite material,especially at 1.5%,compared with polymer blend material without nano powder addition.The tensile properties improved about(24 and 14.9)%and bending resistance about(23.5 and16.8)%and hardness by(25 and 22)%when adding particles of size(63.8 and 68.6)respectively.Therefore,this reflects the efficiency of the proposed method to manufacture the nanoco mposite powder and the possibility of using this powder as a strengthening material for the composite materials and using these composite materials in bio applications,especially in the fabrication of artificial limbs.

A Perspective on the Dynamics Properties in Polymer Nanocomposites

Polymer nanocomposites(PNCs)usually have superior properties than pristine polymers.Understanding the dynamics properties in PNC system is crucial to reveal the mechanism of property change unpon the addition of nanoparticles(NPs),and therefore for a better design of the material properties.In this short perspective,we summarize recent advances mainly from theoretical and simulation studies of dynamics properties in polymer nanocomposite system.One is the"vehicle model"which reveals that diffusion dynamics of sticky NP is coupled to surrounding chain segments.Similarly,recent simulations demonstrate that such coupling also exists in all-polymer nanocomposite wich is composed of linear polymer chains and single-chain nanoparticles(SCNPs).These SCNPs have almost the same chemical composition as the matrix chain.Therefore,it is assumed that such all-polymer nanocomposite can act as a model system where there are no enthalpic interactions between NPs and polymer chains.Although the above dynamic coupling was found in the above two different systems containing inorganic NPs or relatively small organic SCNPs,it was found that the length scale of such dynamic coupling(the thickness of the matrix/NP interface)is comparable to the NP size,which is surprisingly consistent in the above two different systems.In addition,a chain-length dependence of the NP influence on the chain dynamics reported from a recent joint simulaiton and experimental study of all-polymer nanocomposite system,and a theoretical model developed for such phenomena are also reviewed.At the end,we give an outlook of this field,especially for possible chainlength dependence of complex dynamics in sticky-NP systems.

Some basic aspects of polymer nanocomposites: A critical review

Polymer nanocomposites have been investigated for about three decades. To get deep insights into the modifying effects of various nanofillers on mechanical and physical properties of polymer nanocomposites, the three basic aspects of processing, characterization and properties are critically reviewed in this paper. Nanofillers can be classified into three major types of two-dimensional (2D) layered, one-dimensional (1D) fibrous and zerodimensional (0D) spherical ones and this review thus discusses in detail the processing, characterization and properties of the three types of polymer nanocomposites. It starts with an introduction of various nanoscale fillers such as two-dimensional (2D) nano-clay, graphene and MXene, one dimensional (1D) carbon nanofibers and nanotubes, zero dimensional (0D) silica nanoparticles and ZnO quantum dots as well as nanofiller-polymer interfaces. The processing of these polymer nanocomposites using different methods and the characterization of nanofillers and polymer nanocomposites using various techniques are described. Finally, the mechanical and physical properties of these polymer nanocomposites are discussed by considering the effects of nanofiller type, dispersion and contents;also, interface properties show significant effects on the mechanical properties of polymer nanocomposites and are discussed in some details.

Modeling of the Mechanical Properties of Blend Based Polymer Nanocomposites Considering the Effects of Janus Nanoparticles on Polymer/Polymer Interface

Blend based polymer nanocomposites, comprising Janus nanoparticles at their polymer/polymer interface, were analytically/experimentally evaluated. The modeling procedure was performed in two stages: first, modeling of polymer/polymer interface region comprising Janus nanoparticles and second, modeling of the entire systems as a function of the variation of the blend morphology.In the first stage, the modeling procedure was performed based on the development of the model proposed by Ji et al. and in the second stage, the fundamental of Kolarik's model was used in order to propose a developed and more practical model. It was shown that Janus nanoparticles may form dual polymer/particle interphase at polymer/polymer interface which can drastically affect the final mechanical properties of the system. Comparing the results of tensile tests imposed on different prepared samples with the predictions of the model proved its accuracy and reliability(error < 9%).

Preparation, Characterization and Frictional Properties of Silane Self-Assembled Elastomeric Nanocomposite Polymer Layers

A novel surface modification method was proposed to improve the tribological property of Si. Multilayers were grown on Si（100） substrate by self-assembling monolayer （SAMs） method and filtered catholic vacuum arc （FCVA） technique. The film composition and structure were characterized by using x-ray photoelectron spectroscope （XPS） and Raman spectroscopy （Raman）. Surface morphology and the roughness were also analyzed by an atomic force microscope （AFM） and a scanning electron microscopy （SEM）. The frictional behaviors of the films were evaluated by a UMT tester. Results showed that elastomeric nanocomposite monolayer prepared by SAM was uniformly distributed and isotropy, and the diamond-like carbon （DLC） film was successfully deposited by the FCVA technique. The friction coefficients of the prepared samples were in the range of 0.108-0.188. Furthermore, the friction coefficient slightly increased but the surface quality of the wear trace was improved after adding the copolymer elastomeric macromolecules SEBS on aminopropyl-triethoxysilane （APS） layer due to the inherent long chain of SEBS which abated the immediate impulsion at the interface and changed the kinetic energy into elastic potential energy, and stored it in SEBS.

Stress Transfer in Polymer Nanocomposites:A Coarse-grained Molecular Dynamics Study

In this work,we used coarse-grained molecular dynamics simulation methods to investigate the dispersion and percolation behavior of nanoparticles in polymer nanocomposite.Our aim was to investigate the correlation between particle arrangement in nearby layers and the stretching performance in composite systems by exploring the stress transfer processes during different stages of the stretching process.The machine learning technique of linear regression was used to quantitatively measure the efficiency of stress transfer between particles nearby.According to our research,increasing the strength of attraction can significantly enhance the particle dispersion and affect the percolation threshold.We also noticed a non-monotonic relationship between the interaction strength and the tensile stress.Additionally,we quantified the efficiency of nanoparticles and polymers at transferring stress to nearby nanoparticles.As a result,the stress value provided by each particle in the aggregation body is significantly increased by the aggregation behavior of nanoparticles.The non-monotonic behavior is caused by two variables:the rapid disintegration of aggregates and the improved stress transfer efficiency from polymers to nanoparticles.Significantly,it was discovered that the structural rearrangement of nanoparticles during stretching is the main reason that causes the yield-like behavior seen in poorly dispersed systems.

3D printing of ABS Nanocomposites.Comparison of processing and effects of multi-wall and single-wall carbon nanotubes on thermal,mechanical and electrical properties

The following paper reports on a comparative study of the effects of two types of carbon nanotubes,namely multiwall(MWCNT)and single-wall(SWCNT)carbon nanotube,on the properties of 3D-printed parts produced with acrylonitrile-butadiene-styrene(ABS)nanocomposites with various CNT loadings of5-10 wt.%.Quasi-static tensile properties and Vicat softening temperature of 3D-printed parts were enhanced with the increasing CNT content.The highest enhancement in tensile properties was observed for the ABS/CNT nanocomposites at 10 wt.%filler loading.3D-printed ABS/SWCNT composites showed higher tensile modulus,better creep stability and higher Vicat temperature.However,the strength of ABS/SWCNT 3D samples is relatively lower than that of ABS/MWCNT.In addition,3D-printed parts exhibited anisotropic electrical conductive behaviour,which has a conductivity of through-layer of about2-3 orders of magnitude higher than cross-layer.The highest conductivity of 3D-printed samples reached25.2 S/m,and 9.3 S/m for ABS/MWCNT and ABS/SWCNT composites at 10 wt.%,respectively.The results obtained,i.e.the successful fuse filament fabrication and the consequent electromechanical properties,confirm that these 3D printable nanocomposite could be properly utilized for the production,and application up to about 90°C,of thermoelectric devices and/or resistors for flexible circuits.

Improved photoconductive properties of composite nanofibers based on aligned conjugated polymer and single-walled carbon nanotubes

We successfully address the challenge of aligning single-walled carbon nanotubes （SWNTs） and conjugated polymer chains in composite nanofibers for enhancing their opto-electrical properties. A pore-filling template strategy has been developed to prepare such nanocomposites from SWNTs and poly（para-phenylene vinylene） （PPV） chains, with both species well-oriented aligned along the pore axis. Addition of the SWNTs leads to a remarkable increase in photocurrent of four orders of magnitude as compared to equivalent pristine PPV nanofibers. Further analysis indicates that the strong photocurrent enhancement is not simply an effect of alignment, but additionally benefits from alignment-enhanced interaction of polymer chains with SWNTs, as supported by density functional theory （DFT） calculations.

Effects of Synthetic and Processing Methods on Dispersion Characteristics of Nanoclay in Polypropylene Polymer Matrix Composites

This work presents the effect of synthetic procedures (extrusion and casting) on the dispersion characteristics of nano layered silicate clay particles in the polypropylene (PP) polymer matrix. Three different molecular weights PP samples are taken and filled with nanoclay of 1 wt% and 3 wt%, and these nanocomposites were synthesized by using an extrusion or casting methods. The X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) is used to characterize the structure and morphology of nanocomposites. Rheological and mechanical results show that the extruded products are better than that of cast products. The outcome of this work is discussed in this paper.

Preparation,Morphology and Damping Property of PU/UP Interpenetrating Polymer Networks

Interpenetrating polymer networks （IPNs） composed of acrylate-modified polyurethane （PU）/unsaturated polyester （UP） resin via simultaneous polymerization with various component ratios of PU/UP were prepared. The polymerization processes of IPNs were traced through infrared spectrum （IR） techniques, by which the phase separation in systems could be controlled effectively. Results for the morphology and miscibility among multiple phases of IPNs, obtained by transmission electron microscope （TEM） indicated that the domains between two phases were constricted in nanometer scales. The dynamic mechanical thermal analyzer （DMTA） detection results revealed that the loss factor （tanS） and loss modulus （E″） increased with the polyurethane amounts in system, and the peak value in curves of tanδ and E″ appeared toward low temperature ranges. Maximum tanδ values of all samples were above 0.3 in the nearly 50℃ ranges. Also, the mechanical properties of PU/UP IPNs were studied in detail.

Study of microstructure and flexural properties of microcellular acrylonitrile-butadiene-styrene nanocomposite foams: experimental results

In this paper, acrylonitrile-butadiene-styrene （ABS） nanocomposite foams are produced using carbon dioxide through the solid-state batch process. Microcellular closed-cell foams are produced with the relative density ranging from 0.38 to 0.97. The effects of the processing conditions on the density, morphology, and flexural properties of ABS and its nanocomposite foams are studied. It is found that nanoclay particles, as nucleating sites, play an important role in reducing the size of cells and increasing their number in the unit volume of foamed polymer, as well as increasing the flexural modulus of foam through reinforcing its matrix.

Towards suppressing dielectric loss of GO/PVDF nanocomposites with TA-Fe coordination complexes as an interface layer

In this work, graphene oxide(GO) nanosheets with surface modification by Tannic and Fe coordination complexes(TA-Fe) were incorporated into poly(vinylidene fluoride)(PVDF) to prepare high constant but low loss polymer nanocomposites, and the effect of TA-Fe interlayer on dielectric properties of the GO@TA-Fe/PVDF nanocomposites was investigated. The results indicate that the dosage, mixing ratio, and reaction time of TA-Fe complexes have obvious influences on the dielectric properties of the nanocomposites. Furthermore, the TA-Fe interlayer significantly influences the electrical properties of GO@TA-Fe nanoparticles and their PVDF composites, and the GO@TA-Fe/PVDF composites exhibit superior dielectric properties compared with raw GO/PVDF. Dielectric losses of the GO@TA-Fe/PVDF are significantly suppressed to a rather low level owing to the presence of TA-Fe layer, which serves as an interlayer between the GO sheets, thus preventing them from direct contacting with each other. Additionally, the dynamic dielectric relaxation of the GO/PVDF and GO@TA-Fe/PVDF nanocomposites was investigated in terms of temperature.

Carbon nanotube-reinforced elastomeric nanocomposites: a review

This review is focused on carbon nanotube(CNT)-elastomeric polymer nanocom-posites,which have attracted industrial and academic interest over the years due to their enhanced properties.Major factors notably CNT type,surface modifica-tion,dispersion of CNT,and processing techniques that affect the physical properties of CNT-elastomeric polymer nanocomposites are reviewed,and several key physical properties,including tensile,electrical,and thermal properties,were also included in this review.Some of the key challenges that undermine the effectiveness of CNTs and their composites with elastomeric polymers,and the potential applications of CNT-elastomeric composites are also captured.

Halloysite nanotubes loaded with nano silver for the sustained-release of antibacterial polymer nanocomposite scaffolds

It is challenging for antibacterial polymer scaffolds to achieve the drug sustained-release through directly coating or blending.In this work,halloysite nanotubes(HNTs),a natural aluminosilicate nanotube,were utilized as a nano container to load nano silver(Ag)into the lumen through vacuum negativepressure suction&injection and thermal decomposition of silver acetate.Then,the nano Ag loaded HNTs(HNTs@Ag)were introduced to poly-l-lactic acidide)(PLLA)scaffolds prepared by additive manufacturing for the sustained-release of Ag^+.Acting like a’shield’,the tube walls of HNTs not only retarded the erosion of external aqueous solution on internal nano Ag to generate Ag^+but also postponed the generated Ag^+to diffuse outward.The results indicated the PLLA-HNTs@Ag nanocomposite scaffolds achieved a sustained-release of Ag^+over 28 days without obvious initial burst release.Moreover,the scaffolds exhibited a long-lasting antibacterial property without compromising the cytocompatibility.Besides,the degradation properties,biomineralization ability and mechanical properties of the scaffolds were increased.This study suggests the potential application of inorganic nanotubes as drug carrier for the sustained-release of functional polymer nanocomposite scaffolds.

纳米颗粒填充玻璃纤维增强环氧树脂复合材料的力学性能

为探究纳米颗粒[纳米氧化铁(NFe)、纳米二氧化硅(NS)、多壁碳纳米管(MWCNT)]填充玻璃纤维增强环氧树脂复合材料(GFRP)的力学性能,对纳米颗粒质量分数分别为0.1%、0.2%、0.5%、1.0%的纳米颗粒/GFRP材料开展了拉伸、压缩、弯曲及冲击力学性能试验,并结合扫描电镜(SEM)分析了纳米颗粒的种类及质量分数对试件力学性能的影响规律。结果表明,随着纳米颗粒质量分数的增加,试件拉伸强度均先增大后降低,纳米颗粒的良好分散性及与树脂间的黏聚力能够提升试件的拉伸强度,但过量纳米颗粒的掺入会形成积聚现象,使得试件拉伸强度降低。相较于GFRP试件,掺入纳米颗粒的质量分数为0.1%、0.2%、0.5%和1.0%时,MWCNT/GFRP抗压强度的增幅分别为25.31%、36.04%、26.84%和27.25%,弯曲强度的增幅分别为58.74%、63.21%、40.89%及43.11%,纳米颗粒的掺入使得试件抗压强度、弯曲强度、冲击强度均得到改善,颗粒种类及质量分数的不同使得试件力学性能提升效果存在差异。SEM试验结果表明,外荷载作用下纤维出现断裂、分层现象,纤维与纳米颗粒间存在的摩擦效应增强其力学性能,颗粒的积聚使得试件力学性能降低。

氨基酸功能化二硫化钼/环氧树脂复合材料耐水性能的研究

环氧树脂因其优异物理化学性能在各种高新领域得到了重要发展。近年来随着材料科学在某些极端环境下的需求越来越多,对提高环氧树脂的耐水性需求日渐迫切。本文首先制备了氨基乙酸(Gly)改性二硫化钼(MoS_(2))纳米片,然后用其改性环氧树脂,制备了Gly-MoS_(2)/环氧树脂复合材料。对其结构、微观形貌、力学性能、热机械性能和吸水率等指标进行表征。研究结果表明:(1)成功制备了目标产物,经氨基乙酸剥离和改性的MoS_(2)纳米片在树脂基体中分散更均匀,在保证适宜的横向尺寸的同时厚度更薄,与基体树脂相容性更好。(2)随着纳米片添加量的增加,树脂体系水煮后的常温和高温剪切强度、拉伸强度和抗冲击强度均有提升。这是由于改性后纳米片在基体中分散均匀,且与环氧基形成更稳定的海岛结构,从而提升了材料本身的耐水性。(3)热机械性能测试表明,Gly-MoS_(2)纳米片对增强材料水煮后的耐温性有着重要的作用。吸水率测试表明,Gly-MoS_(2)极大地改善了环氧树脂的耐水性能,并且随着Gly-MoS_(2)纳米片的增加,吸水率随之降低。其中1.00%Gly-MoS_(2)/环氧树脂体系的耐水效果最好,水煮192 h后最终吸水率仅为1.2%。