Showing papers on "Polymer nanocomposite published in 2019"

Highly Thermally Conductive Yet Electrically Insulating Polymer/Boron Nitride Nanosheets Nanocomposite Films for Improved Thermal Management Capability.

Abstract: Thermally conductive yet electrically insulating polymer composites are urgently required for thermal management applications of modern electrical systems and electronic devices because of their multifunctionality and ease of processing. However, the thermal conductivity enhancement of polymer composites is usually at the price of the loss of lightweight, the deterioration of flexibility, and electrical insulation. Here we report advanced polymer nanocomposites containing orientated boron nitride nanosheets (BNNSs), which simultaneously exhibit high thermal conductivity enhancement, excellent electrical insulation, and outstanding flexibility. These nanocomposite films can be easily constructed by electrospinning polymer/BNNSs nanocomposite fibers, vertically folding the electrospun nanocomposite fibers and the subsequent pressing. The nanocomposite films exhibit thickness-dependent in-plane thermal conductivity, which can reach 16.3 W/(m·K) in the 18 μm thick nanocomposite film with 33 wt % BNNSs. In add...

Some basic aspects of polymer nanocomposites: A critical review

Abstract: 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 zero-dimensional (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.

Superior electromagnetic interference shielding 3D graphene nanoplatelets/reduced graphene oxide foam/epoxy nanocomposites with high thermal conductivity

Abstract: How to rationally design the microstructure of polymer nanocomposites to significantly improve their electromagnetic interference shielding effectiveness (EMI SE) is still a great challenge. Herein, we developed a template method for fabricating 3D porous graphene nanoplatelets/reduced graphene oxide foam/epoxy (GNPs/rGO/EP) nanocomposites, in which 3D rGO foam embedded with GNPs constructs a 3D electrical and thermal conductive network in the EP matrix. The 3D rGO framework resolves the agglomeration problem of GNPs, acts as an efficient bunch of channels for electrical transport and attenuates the entered electromagnetic wave. Benefiting from this 3D nanohybrid framework, the GNPs/rGO/EP nanocomposites containing 0.1 wt% rGO and 20.4 wt% GNPs exhibit an EMI SE value of 51 dB in the X-band range, an almost 292% improvement relative to the rGO/EP nanocomposites (∼13 dB) and 240% enhancement compared with the GNPs/EP nanocomposites without 3D microstructures (∼15 dB) and an excellent thermal conductivity of 1.56 W mK−1 and electrical conductivity up to 179.2 S m−1. This work provides a new strategy for the design of muti-functional epoxy nanocomposites for EMI shielding and efficient heat dissipation.

Facile Preparation of Hierarchical AgNP-Loaded MXene/Fe3O4/Polymer Nanocomposites by Electrospinning with Enhanced Catalytic Performance for Wastewater Treatment

Abstract: MXene as a kind of two-dimensional nanomaterial has aroused people’s strong research interest because of its excellent properties. In the present study, we introduced a new poly(vinyl alcohol)/poly...

Scalable Polymer Nanocomposites with Record High‐Temperature Capacitive Performance Enabled by Rationally Designed Nanostructured Inorganic Fillers

Abstract: Next-generation microelectronics and electrical power systems call for high-energy-density dielectric polymeric materials that can operate efficiently under elevated temperatures. However, the currently available polymer dielectrics are limited to relatively low working temperatures. Here, the solution-processable polymer nanocomposites consisting of readily prepared Al2 O3 fillers with systematically varied morphologies including nanoparticles, nanowires, and nanoplates are reported. The field-dependent electrical conduction of the polymer nanocomposites at elevated temperatures is investigated. A strong dependence of the conduction behavior and breakdown strength of the polymer composites on the filler morphology is revealed experimentally and is further rationalized via computations. The polymer composites containing Al2 O3 nanoplates display a record capacitive performance, e.g., a discharged energy density of 3.31 J cm-3 and a charge-discharge efficiency of >90% measured at 450 MV m-1 and 150 °C, significantly outperforming the state-of-the-art dielectric polymers and nanocomposites that are typically prepared via tedious, low-yield approaches.

Barium titanate at the nanoscale: controlled synthesis and dielectric and ferroelectric properties

Abstract: The current trend in the miniaturization of electronic devices has driven the investigation into many nanostructured materials. The ferroelectric material barium titanate (BaTiO3) has garnered considerable attention over the past decade owing to its excellent dielectric and ferroelectric properties. This has led to significant progress in synthetic techniques that yield high quality BaTiO3 nanocrystals (NCs) with well-defined morphologies (e.g., nanoparticles, nanorods, nanocubes and nanowires) and controlled crystal phases (e.g., cubic, tetragonal and multi-phase). The ability to produce nanoscale BaTiO3 with controlled properties enables theoretical and experimental studies on the intriguing yet complex dielectric properties of individual BaTiO3 NCs as well as BaTiO3/polymer nanocomposites. Compared with polymer-free individual BaTiO3 NCs, BaTiO3/polymer nanocomposites possess several advantages. The polymeric component enables simple solution processibility, high breakdown strength and light weight for device scalability. The BaTiO3 component enables a high dielectric constant. In this review, we highlight recent advances in the synthesis of high-quality BaTiO3 NCs via a variety of chemical approaches including organometallic, solvothermal/hydrothermal, templating, molten salt, and sol-gel methods. We also summarize the dielectric and ferroelectric properties of individual BaTiO3 NCs and devices based on BaTiO3 NCs via theoretical modeling and experimental piezoresponse force microscopy (PFM) studies. In addition, viable synthetic strategies for novel BaTiO3/polymer nanocomposites and their structure-composition-performance relationship are discussed. Lastly, a perspective on the future direction of nanostructured BaTiO3-based materials is presented.

Air-Stable Polyphosphazene-Functionalized Few-Layer Black Phosphorene for Flame Retardancy of Epoxy Resins.

Abstract: Similar to graphene, few-layer black phosphorus (BP) features thermal stability, mechanical properties, and characteristic dimension effects, which has potential as a new member of nanofillers for fabricating polymer nanocomposites. Herein, a cross-linked polyphosphazene-functionalized BP (BP-PZN) is developed with abundant -NH2 groups via a one-pot polycondensation of 4,4'-diaminodiphenyl ether and hexachlorocyclotriphosphazene on the surface of BP nanosheets. Whereafter, the resulting BP-PZN is incorporated into epoxy resin (EP) to study the flame-retardant property and smoke suppression performance. Cone results show that the introduction of 2 wt% BP-PZN distinctly improves the flame-retardant property of EP, for instance, 59.4% decrease in peak heat release rate and 63.6% reduction in total heat release. The diffusion of pyrolysis products from EP during combustion is obviously suppressed after incorporating the BP-PZN nanosheets. Meanwhile, the EP/BP-PZN nanocomposites exhibit air stability after exposure to ambient conditions for four months. The air stability of the BP nanosheets in EP matrix is assigned to surface wrapping by PZN and embedded in the polymer matrix as dual protection. As a new member of the 2D nanomaterials, BP nanosheets have potential to be a new choice for fabricating high-performance nanocomposites.

Molecular dynamics modeling of the structure, dynamics, energetics and mechanical properties of cement-polymer nanocomposite

Abstract: Efforts to tune the performance of organic/inorganic composites are hindered owing to a lack of knowledge related to the interfacial interaction mechanisms. Here we investigated the interfacial structure, dynamics, energetics and mechanical properties between calcium silicate hydrates (C-S-H) and polymers by molecular dynamics (MD) simulation. In this work, polyethylene glycol (PEG), polyvinyl alcohol (PVA) and polyacrylic acid (PAA) are intercalated into nanometer channel of C-S-H sheets to construct the model of polymer/C-S-H composite. In the interfacial region, the calcium ions near the surface of C-S-H play mediating role in bridging the functional groups in the polymers and oxygen in the silicate chains by forming Os-Ca-Op bond. In addition to ionic bonding, the bridging oxygen (C-O-C) in the PEG, hydroxyl (C-OH) in the PVA and carboxyl groups (-COOH) in the PAA provide plenty oxygen sites to form H-bonds with silicate hydroxyl, interlayer water and calcium hydroxyl in C-S-H substrate. The interfacial binding energy is dependent on polarity of functional groups in the polymers, the stability of the H-bond and Ca-O bond, ranking in the following order: E(PAA)> E(PVA) > E(PEG). The PVA with small number of H-bonds formed between oxygen in PVA and water molecules, resulting in increasing the mobility of confined water in the interlayer region. On the other hand, PAA and PVA, with strong polarity, can provide more number of non-bridging oxygen sites that widely distributed along the polymer chains to associate with more calcium ions and H-bonds. Furthermore, uniaxial tensile test is utilized to study the mechanical behavior of the composites. The incorporation of polymers, strengthening the H-bonds in the interfacial region and healing the defective silicate chains, can inhibit the crack growth during the loading process, which both enhance the cohesive strength and ductility of the C-S-H gel. In particular, the intercalated PAA increases the Young's modulus, tensile strength and fracture strain of C-S-H gel to 22.27%, 19.2% and 66.7%, respectively. The toughening mechanism in this organic/inorganic system can provide useful guidelines for polymer selection, design, and fabrication of C-S-H/polymer nanocomposites, and help eliminate the brittleness of cement-based materials from the genetic level.

Phase-field modeling and machine learning of electric-thermal-mechanical breakdown of polymer-based dielectrics

Abstract: Understanding the breakdown mechanisms of polymer-based dielectrics is critical to achieving high-density energy storage. Here a comprehensive phase-field model is developed to investigate the electric, thermal, and mechanical effects in the breakdown process of polymer-based dielectrics. High-throughput simulations are performed for the P(VDF-HFP)-based nanocomposites filled with nanoparticles of different properties. Machine learning is conducted on the database from the high-throughput simulations to produce an analytical expression for the breakdown strength, which is verified by targeted experimental measurements and can be used to semiquantitatively predict the breakdown strength of the P(VDF-HFP)-based nanocomposites. The present work provides fundamental insights to the breakdown mechanisms of polymer nanocomposite dielectrics and establishes a powerful theoretical framework of materials design for optimizing their breakdown strength and thus maximizing their energy storage by screening suitable nanofillers. It can potentially be extended to optimize the performances of other types of materials such as thermoelectrics and solid electrolytes.

Millefeuille-Inspired Thermally Conductive Polymer Nanocomposites with Overlapping BN Nanosheets for Thermal Management Applications.

Abstract: Increasing power density makes modern electronic devices and power equipment generate excess heat, which greatly restricts the applications of polymeric materials because of their poor thermal conductivity. In the present work, inspired by the structure and production process of millefeuille cakes, we show that electrostatic spraying of boron nitride nanosheets (BNNSs) onto electrospun poly(vinyl alcohol) (PVA) nanofibers can produce highly thermally conductive, electrically insulating, flexible, and lightweight nanocomposites via a scalable method of building a multilayer PVA/BNNS nanonetwork structure. The PVA/BNNS nanocomposites exhibit an ultrahigh in-plane thermal conductivity of 21.4 W/(m·K) at 22.2 vol % BNNS addition, realized by an orientated BNNS network structure with overlapping interconnections. The BNNS networks exhibit low thermal resistance and interfacial heat scattering between BNNSs. Moreover, for heat dissipation applications, the nanocomposites with an overlapping BNNS network show higher efficiency in dissipating hot spots than randomly dispersed BNNS or directly hot-pressed BNNS composites. These PVA/BNNS nanocomposites can be used as high-performance lateral heat spreaders in next-generation thermal management systems.

Polymer nanocomposites having a high filler content: synthesis, structures, properties, and applications.

Abstract: The recent development of nanoscale fillers, such as carbon nanotubes, graphene, and nanocellulose, allows the functionality of polymer nanocomposites to be controlled and enhanced. However, conventional synthesis methods of polymer nanocomposites cannot maximise the reinforcement of these nanofillers at high filler content. Approaches for the synthesis of high content filler polymer nanocomposites are suggested to facilitate future applications. The fabrication methods address the design of the polymer nanocomposite architecture, which encompasses one, two, and three dimensional morphologies. Factors that hamper the reinforcement of nanostructures, such as alignment, dispersion of the filler and interfacial bonding between the filler and polymer, are outlined. Using suitable approaches, maximum potential reinforcement of nanoscale fillers can be anticipated without limitations in orientation, dispersion, and the integrity of the filler particle–matrix interface. High filler content polymer composites containing emerging materials such as 2D transition metal carbides, nitrides, and carbonitrides (MXenes) are expected in the future.

Polymer Nanocomposites with Interpenetrating Gradient Structure Exhibiting Ultrahigh Discharge Efficiency and Energy Density

Abstract: In recent decades, electrostatic capacitors have inspried extensive studies. As the only type of energy storage device simultaneously exhibiting an ultrahigh power density (≈MW), high reliabitity (up to 106 charge/discharge cycles), and highest operating voltage (≈kV), which can not be achieved by any other energy storage devices, the elctrostatic capacitors have been the major enabler for a number of modern electronic and electrical applications, such as pulsed power systems, electric vehicles (EVs), smart grid and sensors applications..[1–3] As the key component in electrostatic capacitors, dielectric materials with high breakdown strength, high energy density, and discharge efficiency are critical for the continuing miniaturization of integrated circuits and the scalingdown of power systems.[4] However, with low energy density dielectric materials of current use, such as the bench-mark biaxially-oriented poly propylene (BOPP) with a low energy density of ≈2 J cm−3, the state-of-the-art electrostatic capacitors only deliver a low energy density of <2 J cm−3 and are therefore bear large Poly(vinylidene fluoride) (PVDF) based polymer nanocomposites with high-permittivity nanofillers exhibit outstanding dielectric energy storage performance due to their high dielectric permittivities and breakdown strength. However, their discharge efficiency is relatively low (usually lower than 70%), which limits their practical applications. Here, polymer nanocomposites with a novel interpenetrating gradient structure are designed and demonstrated by cofilling a PVDF matrix with barium zirconate titanate nanofibers and hexagonal boron nitride nanosheets via modified nonequilibrium processing. The interpenetrating gradient structure is highly effective in breaking the trade-off between discharge energy density and efficiency of the corresponding nanocomposite, as indicated by the concomitantly enhanced discharge energy density (Ue ≈ 23.4 J cm−3) and discharge efficiency (η ≈ 83%). The superior performance is primarily attributed to the rational distribution of nanofillers in the polymer matrix, which raises the height of the potential barrier for charge injection at the dielectric/electrode interface, suppresses electric conduction and contributes to enhanced apparent breakdown strength. Meanwhile, the gradient configuration allows higher volume fraction of high-permittivity nanofillers without compromising the breakdown strength, leading to higher electric polarization compared with the random configuration. This work provides new opportunities to PVDF-based polymer nanocomposites with high energy density and discharge efficiency for capacitive energy storage applications. Polymer Nanocomposites

Creep performance of CNT polymer nanocomposites -An emphasis on viscoelastic interphase and CNT agglomeration

Abstract: The present work is aimed at presenting a multi-stage hierarchical micromechanical model to investigate creep response of polymer nanocomposites containing randomly dispersed carbon nanotubes (CNTs). Two frequently real situations-encountered fundamental aspects affecting the polymer nanocomposite mechanical behavior including the CNT/polymer interphase region and CNT agglomeration are taken into account. It is assumed that the CNT to be a transversely isotropic material and the polymer matrix obeys a viscoelastic constitutive law. The multi-stage procedure homogenizes the nanocomposite by exploiting a unit cell-based micromechanical model coupled with Eshelby method. Generally, an excellent agreement is found between the results of the current model and available experiment. The outcomes clearly prove that for a more realistic prediction in the case of creep performance of CNT-polymer nanocomposites, considering the (i) random dispersion and (ii) transversely isotropic behavior of CNTs as well as (iii) viscoelastic interphase region is essential. Moreover, when CNTs are not well-dispersed into the polymer nanocomposites, the three significant factors together with the CNTs agglomerated state must be precisely incorporated in the analysis to achieve a more accurate estimation of the creep response. It is shown that the CNT agglomeration dramatically influences and degrades the creep resistance of the CNT-polymer nanocomposites. Also, the effects of CNT volume fraction and interphase characteristics on the nanocomposites creep behavior are extensively examined.

Enhanced performance of 3D printed highly elastic strain sensors of carbon nanotube/thermoplastic polyurethane nanocomposites via non-covalent interactions

Abstract: Strain sensors based on conductive polymer composites have been widely investigated due to their excellent elasticity and sensitivity. Such sensors may be manufactured using additive manufacturing techniques but there are some challenges to overcome in terms of performance if this technique is to be used. In this work, a high-performance strain sensor of carbon nanotube/thermoplastic polyurethane (CNT/TPU) nanocomposites was printed by fused deposition modeling (FDM), and 1-pyrenecarboxylic acid (PCA) was introduced to non-covalently modify the CNTs and improve the polymer-nanofiller interactions. It is shown that the tensile and electrical properties of the modified composites are increased as a result of more uniform CNT dispersion. The 3D printed sensors demonstrate excellent properties with high gauge factor (GF = 117213 at a strain of 250%), large detectable strain (0–250%), good stability (up to 1000 loading/unloading cycles) and wide frequency response range of 0.01–1 Hz. Also, the strain sensing ability of the sensor is greatly improved with the introduction of PCA. The working mechanism of strain sensor was further studied based on the Simmons’ tunneling theory. In addition, the sensor demonstrates the capability to monitor human body movements and voice, showing its potential for applications in intelligent robots and wearable electronics where customizability is demanded.

Significantly Enhanced Energy Density by Tailoring the Interface in Hierarchically Structured TiO2–BaTiO3–TiO2 Nanofillers in PVDF-Based Thin-Film Polymer Nanocomposites

Abstract: Dielectric polymer nanocomposites with a high breakdown field and high dielectric constant have drawn significant attention in modern electrical and electronic industries due to their potential app...

Reinforcement of the optical, thermal and electrical properties of PEO based on MWCNTs/Au hybrid fillers: Nanodielectric materials for organoelectronic devices

Abstract: Polymer nanocomposite samples of polyethylene oxide (PEO) embedded with multi-walled carbon nanotubes and gold nanoparticles (MWCNTs/Au NPs) were prepared through the casting method The polymer–nanoparticle interactions had been examined by Fourier transform infrared (FT-IR) measurement. X-ray diffraction (XRD) analysis depicted that these samples were semi-crystalline and the crystalline phases of PEO were reduced due to the incorporation of MWCNTS/Au NPs. The TEM micrographs indicated that the diameter range of MWCNTs is 10–25 nm and the shape of Au NPs was spherical with size range 2–25 nm. The redshift of absorption edge in the spectra of ultraviolet/visible (UV–Vis.) spectroscopy for the nanocomposite samples indicated a good reactivity between the polymer matrix and the nanofillers which in turn the decrement of optical energy gap value was expected, which was calculated from Tauc's relation. The thermal stability of nanocomposite samples was improved as indicated by the thermogravimetric analysis (TGA) technique. The electrical and dielectric spectra of these samples had been measured using broadband dielectric spectroscopy. The electrical and dielectric measurements realize the favorable uses of these nanocomposite samples in the production of electroactive materials and further their use as the electrical insulating polymeric nanodielectrics in the production of organoelectronic devices. The Mechanical properties of the prepared samples were calculated by the tensile universal testing machine.