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Abstract High-performance and environment-friendly biomass-based composite films have drawn much attention recently. Here, bio-nanocomposites of TEMPO-oxidized cellulose nanofibrils (TOCNs) reinforced with layered double hydroxides (LDHs) were prepared through an environmentally benign pathway by aqueous dispersion. The results showed that LDHs could be uniformly dispersed in the cellulose nanofibril matrix to form an intercalated nanolayered structure due to good compatibility and the formation of ionic and hydrogen bonds between LDHs with positive charges and TOCNs with negative charges. The TOCN-LDH composite films exhibited high light transmittance, which exceeded 80% with an LDHs content of less than 10%. Moreover, the incorporation of LDHs improved not only the mechanical properties of the cellulose nanofibrils, but also their thermal stability, flame retardancy and hydrophobicity. More specifically, the highest Young's modulus and tensile strength reached 39.3 GPa of TOCN-LDH20 and 358 MPa of TOCN-LDH5, which were 364% and 178% of the neat TOCN film, respectively. The water contact angle and limiting oxygen index of the TOCN-LDH composite film increased from 46° to 103°, and from 25 to 31, respectively, with the LDH content increase from 0 to 20 wt%. [ABSTRACT FROM AUTHOR]

Abstract Nanocomposites of Polyvinylidene Flouride (PVDF) with Multi-walled Carbon Nanotubes (MWCNTs) possess excellent thermal, piezoelectric and conductive behaviors. However, the potential of MWCNTs as filler in polymer composites is hampered by their poor dispersion into the matrix, corresponding to the strong inter-tubular and weak inter tubular-polymer chain interactions. This issue is successfully overcome by utilizing di-glycidyl ether of bisphenol-A (DGEBA) grafted MWCNTs (DG-MWCNTs) as reinforcement in PVDF matrix. To synthesize the desired nanocomposites, the easier to manipulate, solution casting technique was employed. The resulting PVDF/DG-MWCNTs nanocomposites have different loadings of filler ranging from 1.0 wt% to 10 wt% , and have shown variation in the phase transformation from α-phase to β-phase along with improvements in thermal and dielectrical behaviors. It was revealed by the impedance spectroscopy (IS) that the reinforcement of PVDF with DG-MWCNTs leads to an increase in the dielectric permittivity. This increase was found higher enough to reach up to ∼5288 (at ∼100 Hz) and 214 (at ∼102 Hz) for filler loading of 10 wt %. The increase is several hundreds of magnitude i.e. , ∼204 at ∼102 Hz higher than the PVDF matrix, while retaining a low level conductivity (4.18 × 10−6 S/cm). This enhancement in the dielectric permittivity is attributed to the strong interfacial interaction between PVDF and DG-MWCNTs, and was explained by the Maxwell-Wagner-Sillar (MWS) effect. [ABSTRACT FROM AUTHOR]

Epoxy resins are inherently brittle caused by their highly cross-linked network structure. Herein, we report an effective method of toughening without loss of mechanical properties. Carboxylated carbon nanotubes (CNT-COOHs) were added to an epoxy (EP)/polysulfone (PSF) blend to control the phase separation behavior, fracture toughness and mechanical properties of the resultant ternary composites. Although CNT-COOHs did not change the phase separation mechanism of the EP/PSF blend they had an important influence on the final phase morphology. Rheological analysis showed that the complex viscosity and the cure-reaction rate of EP/PSF were increased by adding CNT-COOHs, leading to a significant suppression of the phase separation process which stopped at an earlier stage. Also, the fracture, mechanical and thermal properties of the EP/PSF/CNT-COOH composites were found to be increased due to the presence of CNT-COOHs. [ABSTRACT FROM AUTHOR]

In this work, a flowering-branch like CNTs/Bi 2 Se 3 hybrids was synthesized by a facile in-situ method. CNTs as carrier could provide low agglomeration of layered Bi 2 Se 3 . As-prepared nanomaterials were added into epoxy resin (EP) to enhance its fire safety. Compared with neat EP, there were more than 44% and 23% decrease in the value of peak heat release and total heat release with 2 wt% content of CNTs/Bi 2 Se 3 , respectively, confirmed the enhancement of flame retardancy of EP composites. Meanwhile, the release of smoke and CO were also suppressed during EP combustion. From results of thermogravimetric analysis-infrared spectrometry, the addition of CNTs/Bi 2 Se 3 obviously reduced the release of organic gaseous products, which contributed to the improved fire safety of EP matrix. Based on the analysis of gas and condensed phases, the possible enhancement mechanisms can be mainly concluded as the barrier effect of as-synthesized binary hybrids and enhanced char layers. Meanwhile, the addition of CNTs/Bi 2 Se 3 enhanced the mechanical performance of EP composites. This work broadens the application fields of Bi 2 Se 3 and enriches the membership of CNTs-based binary compounds, which were used as flame retardants. [ABSTRACT FROM AUTHOR]

Adding thermal conductive filler is an effective method to improve the thermal conductivity of polymer matrix. In this research, we demonstrated that the polymer composites with much improved thermal conductivity while maintaining low electrical conductivity, which could be achieved via using hybrid 2D stacked filler and controlling the alignment of the filler in polymer matrix. In order to do this, the graphene oxide (GO) was prepared and simultaneously reduced/functionalized by diethylenetriamine (DETA) to obtain NH 2 -functionalized graphene (NfG) which designed to be immobilized on the surface of large-sized insulating hexagonal boron nitride (h-BN) via π-π stacking interaction. In this situation, since the NfG sheets were fixed on the surface of h-BN, the NfG sheets were well separated from each other and participated in the resin curing process. Hence, not only significantly enhanced thermal conductivity (∼3.409 W/m·K, in-plane direction) was obtained, but also a very low electrical conductivity was achieved. The low electrical conductivity was believed to be ascribed to both embedded insulating network of h-BN to inhibit the mobility of charge carrier and well-separated NfG sheets via π-π stacking interaction. In addition, the nanocomposites also exhibited good thermal stability and adhesive properties. We believed that this special structure will provide a new thought for fabricating thermal interface materials (TIMs) with much high thermal conductivity as well as low electrical conductivity. [ABSTRACT FROM AUTHOR]

Pickering emulsion-templated polystyrene (PS)/graphene oxide (GO) composite microspheres were successfully prepared using surface-functionalized silica as the stabilizer. These preformed polymer/GO composite microspheres were then melt-blended into polymer matrix to prepare nanocomposite materials in a short minute using HAAKE torque rheometer. Transmission electron microscope (TEM) images of the nanocomposites demonstrate that GO is uniformly dispersed into PS matrix. A significant decrease of coefficient of thermal expansion (CTE) values from more than 150 to 50 ppm/K is realized with the introduction of well-dispersed GO nanosheets. The glass transition temperature (T g ) and the temperature of 5% weight loss (T 0.05 ) are increased by 5 and 17 °C, respectively. Furthermore, the impact energy of the composite sample with a GO loading of 0.86% is 64% greater than that of pure PS, and is nearly twice as high as that of the composite which was prepared by direct melt-blending of surface-modified GO and commercial PS. The tensile strength and elongation at break of the composites are also obviously improved. The work provides an economic and convenient method which eliminates the dispersion problem of GO in polymer matrix to prepare GO-based nanocomposite materials for industrial application on a large scale. [ABSTRACT FROM AUTHOR]

To improve the flame retardancy of epoxy resin (EP), copper phenylphosphate (CuPP) nanoplates were designed and prepared by mixed solvothermal technique, which were incorporated into EP matrix and fabricated EP/CuPP nanocomposites. The results showed that the product was Cu(HO 3 PC 6 H 5 ) 2 with appropriate thermal stability, and EP/CuPP nanocomposites displayed excellent catalytic charring performance compared with pure EP. The combustion results indicated that pure EP had no rating and its LOI value was only 23.0%. With incorporation of 4 wt% CuPP, EP/4 wt% CuPP nanocomposites passed the UL-94 V1 rating and the LOI value reached 38.2%. The improved flame retardancy of EP/CuPP nanocomposites was proved by cone calorimeter test, and the peak heat release rate, total smoke production, peak CO production value of EP/4 wt% CuPP nanocomposites dramatically decreased by 51.7%, 52.4% and 47.3%, which were attributed to the formation of hard and condensed residues layers on the surface of EP nanocomposites. Additionally, the incorporation of CuPP improved the dynamic mechanical performance of EP nanocomposites, which may be due to the reinforcement effect of CuPP with rigid structure. [ABSTRACT FROM AUTHOR]

Polypropylene (PP)/TiO 2 and PP/Al 2 O 3 nanocomposites were fabricated based on a new technology that involves the impregnation of metal alkoxide precursors in the porosity of PP reactor granule and subsequent conversion of the precursors into oxides during melt mixing. The so-called reactor granule technology enabled in-situ generation of highly dispersed oxide nanoparticles over a wide range of the loading extending up to 20 wt% without the use of dispersants. The confinement of metal alkoxide precursors in the porosity of the PP reactor granule and their facile chemical conversion into oxides were found to be crucial for the dispersion of the nanoparticles. The excellent dispersion of Al 2 O 3 nanoparticles led to significant improvements in tensile properties, dielectric constants, and thermal conductivity as compared to conventional nanocomposites using a compatibilizer. It was concluded that the reactor granule technology is a simple and versatile way for the fabrication of polyolefin-based nanocomposites with superior functionalities. [ABSTRACT FROM AUTHOR]

Melamine resin/graphite nanoflakes hybrids (MGNH) were synthesized by in situ polymerization. The SEM and TEM demonstrate that melamine resin was self-deposited on the surface of the flakes. MGNH is uniform sheeted hybrids which exhibits excellent dispersiveness. MGNH/epoxy composite (MGNH/EP) is prepared via vacuum-assisted method. The special prepared method endows MGNH/EP with interesting anisotropic thermal conductivity. The coefficient of thermal conductivity of the composite in normal direction is 0.4024 W m −1 K −1 , while that of MGNH/EP in horizontal direction is 1.5596 W m −1 K −1 . The optical microscope image of the composite suggests that the nanoflake is arranged as a parallel conduction medium, it is demonstrated that direct flake-flake conduction can form heat-transfer passages, which contributes to the higher thermal conductivity of the composite in horizontal direction. Also, MGNH/EP shows excellent flame retardant properties, evidenced by the dramatically reduced peak heat release rate and 51% of total heat release values compared with neat EP obtained from a microcombustion calorimeter. The reduced fire hazard can mainly attributed to the synergistic effects of melamine resin and graphite nanoflakes. [ABSTRACT FROM AUTHOR]

A highly efficient phenylphosphonate-based flame-retardant epoxy resin (FREP) was firstly prepared from phenylphosphonic dichloride (PPDCl) and allylamine (AA). Functionalized graphite nanoplatelets ( f GNPs) fillers were then performed to fabricate the f GNPs/FREP nanocomposites via mixing followed by casting method. The thermally conductive coefficient ( λ ), thermal diffusivity ( α ), flame retardancy, electrical conductivities and thermal stabilities of the f GNPs/FREP nanocomposites were all enhanced with the increasing addition of f GNPs fillers. The λ and α value of the f GNPs/FREP nanocomposite with 30 wt% f GNPs fillers was increased to 1.487 W/mK and 0.990 mm 2 /s, about 7 times and 6 times for that of pure FREP matrix (0.234 W/mK and 0.170 mm 2 /s), respectively. And the corresponding electrical conductivity was also increased to 5.0 × 10 −4 S/cm, far better than that of pure FREP matrix (1.0 × 10 −12 S/cm). In comparison with that of pure FREP, the THR and TSP value of the f GNPs/FREP nanocomposite with 15 wt% f GNPs fillers was decreased by 37% and 32%, respectively, char yield was increased by 13%, and LOI value was increased from 31% to 37%. However, the peak of heat release rate of the f GNPs/FREP nanocomposite became worse due to its high thermal conductivity. Nanoindentation revealed that there was negligible influence of f GNPs fillers on the hardness values and Young's modulus of the f GNPs/FREP nanocomposites. [ABSTRACT FROM AUTHOR]

To simultaneously resolve an undesirable electromagnetic wave and heat emissions that were caused by an electronic device, an electromagnetic interference (EMI) shielding material with excellent electrical insulation and high thermal conductivity was urgently required. However, keeping the EMI shielding material on electrical insulation still remained a challenge due to the superior electrical conductive network in it. We fabricated an ordered multilayer film through casting layer (graphene oxide/poly(-hydroxybenzate- co -DOPO-benzenediol dihydrodiphenyl ether terephthalate)) by layer (boron nitride/(maleated styrene-ethylene/butylene-styrene)), and the special architecture of the film not only simultaneously built the superior electrical and thermal conductive network in-plane direction, but also effectively blocked the electrical conductive path through-plane direction. Moreover, the ordered multilayer film (11 layers) exhibited a good EMI shielding effectiveness (37.92 dB), excellent electrical insulation (breakdown strength was 1.52 MV/m) and high thermal conductivity (12.62 W/mK) in-plane direction, indicating that the ordered multilayer film was a novel promising candidate for an ideal EMI shielding material with excellent electrical insulation and high thermal conductivity in today's electronic devices. [ABSTRACT FROM AUTHOR]

Improving the dispersion of graphene nanosheets (GN) in a polymer matrix is a critical step in lowering the percolation threshold of nanocomposites. In this paper, an effective method based on an electrostatic assembly process is reported. Polystyrene (PS) latex was first prepared by using hexadecyl trimethyl ammonium bromide (CTAB) as a cationic surfactant, which created positive charges on the surface of the PS micelles. An in situ demulsification process was then conducted by adding negatively charged graphene oxide (GO) particles into the positively charged PS latex. Thus, GO sheets were attached spontaneously to the surfaces of PS particles through electrostatic adsorption. Followed by in situ reduction and hot pressing, the agglomeration of GN was largely prohibited by the PS microspheres and facilitated the formation of GN networks in the PS matrix. The obtained PS/GN nanocomposites exhibited excellent electrical properties with a percolation threshold as low as 0.054 vol.% GN. When the GN content reached 1.53 vol.%, the electrical conductivity was 46.32 S/m and the thermal conductivity 0.47 W/mk. This strategy represents a new environment-friendly pathway, which is also applicable for other polymer matrices, for large-scale production of polymer composites with fully interconnected graphene networks at ultra-low GN content. [ABSTRACT FROM AUTHOR]

Anisotropic thermal conductive polymer composite provides a bright prospect for thermal management in modern electronics device. Via infiltration, biphenyls mesogenic epoxy nanocomposite (AEO) is prepared based on mesogenic epoxy and reduced graphene oxide (rGO) bulk. Unlike common polymer composites, AEO shows an interesting anisotropic thermal conductivity phenomenon. The rGO sheet is prepared from reduction of graphene oxide (GO) via grafting phosphorus-containing compound, and then rGO bulk can be obtained by vacuum-assisted self-assembly method. In rGO bulk, basal plane of most rGO nanosheet is nearly parallel and it displays aligned laminated structure in in-plane direction. Between rGO nanosheets, an intercalated morphology and cramped spaces can be observed. As a result, in AEO, rGO- rGO linkages heat transfer channel in in-plane direction is formed and epoxy nanocomposite exhibits anisotropic thermal conductivity. In-plane and through-plane thermal conductivity of AEO is 1.3209 W m −1 K −1 and 0.1725 W m −1 K −1 , respectively. Moreover, AEO exhibits excellent flame retardancy and mechanical strength. [ABSTRACT FROM AUTHOR]

Epoxy resin has been intensively used as an electronic packaging material for its good mechanical strength and electrical insulativity. However, the low thermal conductivity of epoxy resin limits its applications. Inorganic fillers with a high loading fraction (>30 vol%) is typically used to enhance the thermal conductivity. But the high loading fraction could degrade the mechanical property and challenge the processing. In this work, we develop a new class of epoxy composites comprising very long (up to tens of micrometers) single-crystalline copper nanowires (a diameter of ∼20 nm and a length of up to ∼40 μm) as filler. A high thermal conductivity of 2.59 W/mK was obtained at a very low loading fraction of Cu nanowires at 0.12 vol%, corresponding to an 8-fold enhancement in thermal conductivity of plain epoxy resins. We also demonstrate that ytterbium and erbium codoped sodium yttrium tetra-fluoride (NaYF 4 :Yb/Er) upconversion nanoparticles can be concomitantly incorporated into the epoxy composite, providing an accurate temperature of the composite. The dual functionality should render the epoxy composite an attractive candidate in electronic device. [ABSTRACT FROM AUTHOR]

A thermodynamic model for transient heat conduction in ceramic-polymer nanocomposites is proposed. The model takes into account particle’s size, particle’s volume fraction, and interface characteristics with emphasis on the effect of agglomeration of particles on the effective thermal conductivity of the nanocomposite. The originality of the present work is its basement on extended irreversible thermodynamics, combining nano- and continuum-scales without invoking molecular dynamics. The model is compared to experimental data using the examples of SiO 2 , AlN and MgO nanoparticles embedded in epoxy resin. The analysis is limited to spherical nanoparticles. The dependence of the degree of agglomeration with respect of the volume fraction of particles is also discussed and a power-law relation is established through a kinetic mechanism and experiments performed in our laboratory. This relation is used in our theoretical model, resulting into a good agreement with experiments. It is shown that the effective thermal conductivity may either increase or decrease with the degree of agglomeration. [ABSTRACT FROM AUTHOR]

In this study, we report a sharp increase of both thermal and electrical conductivity in polypropylene (PP) via formation of double percolated filler network with dense small-sized multi-wall carbon nanotubes (MWCNT) network located within loosened large-sized expanded graphite (EG) network. The electrical conductivity of PP/EG composites which levels off after the percolation threshold can be further enhanced by adding MWCNT and is increased two orders of magnitude as the content of MWCNT reaches to its threshold. Besides, the thermal conductivity of PP/EG-MWCNT increases by 38.5% compared to PP/EG and is much higher than PP/MWCNT. Furthermore, an excellent electromagnetic interference shielding effectiveness of ∼60 dB is obtained at the sample thickness of only 1.3 mm. Then, effective medium theory model is applied to analyze the mechanism for the largely enhanced thermal and electrical conductivity. It is suggested that formation of double percolated filler network, in which three types of connections exist between EG and EG, EG and MWCNT as well as MWCNT and MWCNT, could effectively reduce the interface thermal resistance. Our work is important and provides some new idea for the preparation of polymer composites with excellent thermal and electrical conductivity via constructing double percolated filler network. [ABSTRACT FROM AUTHOR]

Electrically insulating polymeric nanocomposites with high thermal conductivity have great potential for use as thermal-management materials in increasingly high-power-density electronics and optoelectronics. Conventional composite materials require a large amount, over 70 vol%, of electrically conducting fillers such as carbon allotropes to attain thermal conductivities of 1–5 W/mK, [Balandin, 2011] [1] which restricts the utility of these materials to applications that require both electrical and thermal conductivities. Here, we introduce a strategy to achieve the strongest enhancement of thermal conductivity to date at a low level of filler loading (≤15 vol%) in insulating polymer nanocomposites with hexagonal boron nitride (BN) nanosheets. The combination of electric-field switching and the application of fillers with various aspect ratios enables the rearrangement of the BN nanofillers into linear densely packed BN structures (LDPBNs). Flexible nanocomposite films with LDPBNs exhibit electrical resistivity greater than 1.50 × 10 −6 MΩ cm and a thermal conductivity of 1.56 W/mK, a dramatic enhancement over that of pristine polysiloxane with the same BN loading (0.4 W/mK). Our strategy of electric-field-induced BN nanosheet assembly offers insight into the possibility of solving thermal-management problems using ideal thermal interface materials, thus enabling improved next-generation integrated circuits and nanoelectronics. [ABSTRACT FROM AUTHOR]

A facile and effective approach by incorporating silica nanoparticles (SNPs) to fabricate high performance epoxy-based electronic packaging materials which are both thermally conductive and electrically insulating was presented. Because of the strong interaction between SNPs and silver nanowires (AgNWs), uniformly dispersed SNPs-modified epoxy was employed to promote the dispersion of AgNWs in epoxy matrix. Further, the enhanced modulus of epoxy matrix by the incorporation of SNPs effectively alleviates the modulus mismatch between stiff AgNWs and epoxy matrix. Compared with epoxy/AgNWs composites without SNPs, the resulting hybrid materials, that is, epoxy/SNP/AgNWs, showed distinct improvements in thermal conductivity without degrading their mechanical properties. Also, the SNPs were absorbed onto the surface of AgNWs forming an electrical insulation layer to disrupt the electron flows between adjacent AgNWs, hence retaining the electrical insulation of epoxy matrix. Finally, this new fabrication method is easily scalable owing to its simple procedure and use of commercial well-dispersed SNPs-modified epoxies. [ABSTRACT FROM AUTHOR]

Ethylene–propylene–diene terpolymer rubber (EPDM)-based nanocomposites containing carbon black (CB), graphene nanoplatelets (GNPs), and mixtures of the two fillers were prepared. The influence of the relative amounts of the two fillers on the dynamic and static friction coefficients was examined. The static analysis of the coefficient of friction suggests that the partial substitution GNPs into the EPDM/CB blend did not produce a significant variation of the surface grip. The sample comprising EPDM/CB composite and an effective amount of GNPs dispersed in the matrix provides an increase of the thermal conductivity, damping (i. e. shock absorbing properties) and mechanical properties of the nanocomposites. The field-emission scanning electron microscopy and micro tomography analyses showed that the replacement of CB with GNPs reduces the CB aggregation and, hence, improving the percolation of the hybrid fillers and the interface resistance of the composite. The development of thermally conducting elastomeric nanocomposites could envisage their utilization in the processing of rubber blends satisfying the increasing demand to reduce both the duration of the vulcanization process and thus the cost of the vulcanized rubbers. [ABSTRACT FROM AUTHOR]

To develop high-performance dielectric materials, we report a novel strategy to fabricate core-shell structured BaTiO 3 @polymer nanoparticles through rotary coating technology combined with a post-treatment bonding process, by using carboxyl-functionalized poly(arylene ether nitrile) (CPAEN) as the polymeric surface-grafting agent. The results demonstrated that the CPAEN was chemically bonded on the surface of BaTiO 3 core through monodentate coordination of carboxyl groups, and the BaTiO 3 core was completely wrapped by a stable CPAEN shell with a uniform thickness of 4–7 nm. Furthermore, polymer nanocomposites were prepared by using core-shell structured BaTiO 3 @CPAEN nanoparticles as hybrid nanofillers and poly(arylene ether nitrile) (PAEN) as the polymer matrix. The results indicated that the nanocomposites exhibited enhanced dielectric properties, such as relatively high dielectric permittivity, quite low loss tangent and good permittivity-frequency stability, and excellent thermal stability, high mechanical strength and good flexibility. Therefore, it provides a path to obtain a new class of high-temperature-resistant dielectric materials for various engineering applications. [ABSTRACT FROM AUTHOR]

The terephthalic acid(TPA)-modified amine-polyhedral oligomeric silsesquioxane(M-AM-POSS)/poly (ethylene terephthalate) (PET) nanocomposites were prepared using in-situ polymerization. The thermal decomposition temperature of the composite, measured at a 5wt% weight loss, was 350 °C and much higher than those of neat PET and AM-POSS/PET composite. The SEM observation suggests that there was an obvious phase separation in the POSS/PET composite. The nanocomposite fiber that contained 1 wt% of AM-POSS and M-AM-POSS showed a uniform dispersion at all cross sectional regions, which arose from the strong interfacial interactions between POSS and PET during the polymerization. However, at magnified region AM-POSS with distribution of 30–100 nm, the M-AM-POSS showed narrow distribution of 50–80 nm. This suggests that the particles resulted from the reaction between M-AM-POSS and PET reaction. The storage moduli retention of the nanocomposite fibers with 1 wt% of AM-POSS and M-AM-POSS at 120 °C increased by 5% and 15%, respectively, and glass transition temperature, by 4 °C and 10 °C, respectively. [ABSTRACT FROM AUTHOR]

Novel superparamagnetic nanocomposites based on covalently linked waterborne polyurethane (WPU) and Ni 0.3 Zn 0.7 Fe 2 O 4 ferrite nanospheres (NZFO) were successfully synthesized using an in situ polymerization method. The Ni 0.3 Zn 0.7 Fe 2 O 4 nanoparticles prepared by a typical solvothermal method were modified with 3-(triethoxysilyl) propyl isocyanate (IPTS) to improve the compatibility with monomers. The functionalized NZFO nanoparticles (NZFO-IPTS) served as effective cross-link points and reacted with the WPU matrix, forming chemical bonds. It was found that the NZFO-IPTS greatly improved the dispersibility of NZFO nanoparticles in the WPU matrix, and the introduction of NZFO-IPTS enhanced the thermal behavior and mechanical properties of the WPU polymer. What's more, the WPU/NZFO nanocomposites presented superior magnetic properties and a maximum saturation magnetization (Ms) of 16.58 emu/cm 3 was observed, thus illustrating the potential applications of the generated materials in microwave-absorbing fields. [ABSTRACT FROM AUTHOR]

Filler particle shape and size influence interconnectivity within a polymer matrix and both play a significant role in controlling the effective thermal conductivity of a composite. This study examines the effect of nanofiller particle shape in a polytetrafluoroethylene (PTFE) matrix on thermal energy transport. Experimental measurements using a laser flash analysis method are performed on PTFE with three different shaped carbon fillers: nano-diamond spheres, carbon nanotubes (CNT) and graphene flakes. Filler concentration ranged from 0 to 30%. The experimental results are coupled with a particle connectivity model to understand the relationship between energy transport and filler connectivity. Results show filler particles with more micron scale dimensions form better interconnected networks at lower volume concentrations than fillers with fewer micron scale dimensions. Filler connectivity influences effective conductivity: specifically, nano-diamond spheres showed negligible interconnectivity and result in negligible change in thermal conductivity. The CNT, with one-micron scale dimension (i.e., length) and flakes, with two-micron scale dimensions (i.e., length and height), both exhibited linear increases in interconnectivity and effective thermal conductivity. Graphene interconnectivity in PTFE is six times that of CNT and thermal conductivity is 0.5 W/mK, two times that of CNT, respectively. These results provide new insights on how to optimize nanoparticle structure to enhance thermal energy transport. [ABSTRACT FROM AUTHOR]

Owing to the growing electromagnetic interference (EMI) shielding and heat removal issues in modern electronics, polymer composites with remarkable EMI shielding performance and thermal management capability have attached much attention. In this work, vertical edge-rich graphene (ERG) were in-situ grown on the reduced graphene oxide (rGO) aerogel skeleton, constructing a unique 3D hybridized carbon nanostructures with covalent bonding, which were applied to modify epoxy resin for EMI shielding and thermal management. Impressively, the obtained rGO-ERG/epoxy nanocomposites possessed an improved EMI shielding performance of 45.9 dB in the X-band, which mainly attributes to the structural defects and strong charge polarization ability of ERG. Furthermore, theoretical models qualitatively prove that the construction of phonon-matching 3D rGO-ERG networks results in efficient phonon transport, providing an enhanced thermal conductivity of 1.96 W m−1 K−1. Meanwhile, the 3D hybrid structure from total 2D ingredients which exhibits a remarkable thermal management capability is further corroborated. More importantly, this strategy endows rGO-ERG/epoxy nanocomposites comprehensive functions, providing a bright application prospect for next-generation electronic packing. [Display omitted] [ABSTRACT FROM AUTHOR]

Lightweight and multiscale nanocomposites are considered to be the most promising materials applied in the field of advanced aerospace and modern building industry, owing to their outstanding mechanical, thermal and flame-resistant properties served in high-temperature oxidizing environments. Herein, a novel siliconoxycarbide (SiOC) modified needle quartz fiber felt reinforced phenolic resin nanocomposite (SiQF/PR) with a hierarchical macro-/micro-/nano-scaled structure is reported. The as-prepared highly porous SiQF/PR nanocomposite exhibits a multiscale three-dimensional network and the micro-sized SiOC particles, derived from the hydrolysis of methyltrimethoxysilane (MTMS) and dimethyldiethoxysilane (DDS), are uniformly incorporated into the phenolic aerogel. The resultant nanocomposite has a bulk density of 0.30–0.35 g/cm3, and the maximum compressive strength reaches 4.20 MPa and 3.34 MPa in xy and z directions, respectively. Thermal stability and oxidation resistance experiments show that the SiQF/PR multiscale composite has a good ablation and heat insulation performance under oxyacetylene test condition, and the backside temperature of SiQF/PR is only 55.5 °C under 1.8mw/m2 for 120 s, and line ablation rate of SiQF/PR multiscale nanocomposite decreases by 20.1% at 1.8 MW/m2 and 59.5% at 0.4 MW/m2 compared to non-SiOC modified composite. These results indicate that the lightweight SiQF/PR nanocomposite fabricated by this method is very suitable for architectural or aerospace applications as high-performance insulation material. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Polylactide (PLA) nanocomposites reinforced with commercially available organoclays, Nanomer I.28E and Nanomer I.34TCN, were prepared using a melt intercalation technique. In this work, two different clay concentrations (2 and 4wt.%) were considered. The morphology of the resulting nanocomposites was observed by TEM micrographs while the interaction between polymer and clay was measured by FTIR analysis and contact angle measurements. Better dispersion quality and interaction with the polymer matrix was observed for I.34TCN organoclay. The effect of clay dispersion and its interaction with PLA was investigated by measuring the thermal, oxygen barrier and mechanical properties of the prepared nanocomposites; consequently, higher improvements were observed in the properties of nanocomposites containing I.34TCN compared to the I.28E counterpart. Besides, 2wt.% clay content was found as an optimum concentration for enhancing the different properties of the resulting nanocomposites with respect to neat PLA. However, higher improvements in oxygen permeability and tensile modulus were achieved by embedding 4wt.% organoclay into the PLA matrix. [Copyright &y& Elsevier]

Abstract: Sonication-induced scission was used to obtain carbon nanotubes (CNTs) with aspect ratios averaging 50 (short CNTs) and 500 (long CNTs). A series of carbon nanotube/epoxy nanocomposite samples with CNT content up to 1.0wt.% were prepared using these tubes. Electrical and thermal characterisation was conducted to identify changes in such properties and the extent of these changes as a function of aspect ratio and CNT content. Results show significantly enhanced electrical conductivities and a modest increase in the thermal conductivities in both sets of samples. Further analysis of electrical conductivity of the long CNT and short CNT-based epoxy nanocomposites was carried out in order to understand their viability for EMI shielding and electrostatic dissipation applications. The processing behaviour of the long and short CNT-based composites and the corresponding electrical properties is also discussed which will help the researchers to select the right type of carbon nanotube aspect ratio achieve specific electrical properties as well as good processing behaviour. [Copyright &y& Elsevier]

Abstract: The use of carbon nanotubes (CNTs) as an additive in polymer nanocomposites (PNCs) is being driven by a need to improve the mechanical, electrical, and thermal properties of composite materials for a variety of applications including advanced aerospace vehicles. The magnitude of electrical conductivity in CNT-containing PNCs is primarily influenced by the volume fraction, dispersion, interconnectivity and alignment of CNTs as well as the individual CNT properties, which are a function of diameter, chirality, and defects. Measurement techniques used to quantify the electrical conductivity of composites containing CNTs suffer from a host of issues including the influence of contact resistance, poor sample preparation leading to inadequate electrical contact of all concentric shells in aligned multi-walled CNT PNCs, and poor spatial resolution, which can obscure the micrometer- to millimeter-scale effects of inhomogeneities. In this study we demonstrate a new technique for measuring the local (∼100μm resolution) conductivity of PNCs fabricated by infusing aligned CNT arrays with a non-conductive polymer, where the CNTs are continuous through the thickness of the composite. The technique involves the use of improved surface preparation processes, prior to the formation of electrical contacts, to ensure good electrical engagement of the CNTs. Furthermore, this technique provides a systematic process to remove the contribution of contact resistance and therefore measure the conductivity of the polymer nanocomposite alone. Using this technique we have measured a conductivity of 2.2×104 S/m for aligned CNTs (20% volume fraction) in RTM-6 aerospace epoxy. [Copyright &y& Elsevier]

Abstract: In this study, wood polymer nanocomposites (WPNCS) were manufactured from five Malaysian tropical wood species by vacuum-impregnation attended by in situ polymerization using phenol–formaldehyde resin and montmorillomite nanoclay. Percentage weight gain and density of wood polymer nanocomposites depended on wood species. Thermo-mechanical properties of wood samples were investigated by the dynamic mechanical thermal analysis (DMTA) over the temperature range of −100°C to 200°C. The intrinsic properties of the components, morphology of the system and the nature of interface between the phases were also determined through DMTA test. Storage modulus (E′) of WPNC samples exhibited significant improvement over the temperature range, in both glassy region and rubbery plateau in relation to their corresponding raw wood samples and wood polymer composites (WPCs). Furthermore, damping (loss tan δ) peaks of all wood species were lowered by PF-Nanoclay system treatment, an indication of improved surface interphase of wood. Dynamic Young’s modulus (Ed ) of wood was also calculated using free–free vibration testing. A significant increment was obtained for the PF-Nanoclay impregnated WPNC samples. [Copyright &y& Elsevier]

Abstract: A facile technique was developed to modify boron nitride (BN) nanosheets with iron oxides in order to fabricate highly-oriented polysiloxane/BN nanosheet composite films and their thermal properties were evaluated according to the orientation of BN. The surfaces of the BN nanosheets were modified with iron oxide nano particles by chemical vapor deposition, and their one-dimensional arrangement with variation of BN content was controlled under a magnetic field. The homogeneous suspension of BN nanosheets and pre-polymers of polysiloxane was cast on a glass spacer, and subjected to a magnetic field before the mixture was crosslinked. X-ray diffraction, transmission electron microscopy, and superconducting quantum interference device measurements were employed to identify the phases and amounts of iron oxide nano particles deposited on the BN nanosheets. The results revealed that the modified BN nanosheets were aligned either horizontally or vertically to the film plane, depending on the direction of magnetic flux with high anisotropy. The transmittance and thermal conductivity of the nano composite films were improved due to the orientation of the BN nanosheets inside the polymer matrix. [Copyright &y& Elsevier]

Abstract: Carbon materials, such as graphite oxides, carbon nanotubes and graphenes, have exceptional thermal conductivity, which render them excellent candidates as fillers in advanced thermal interface materials for high density electronics. In this paper, these carbon materials were functionalized with 4,4′-diaminodiphenyl sulphone (DDS), to enhance the bonding between the carbon materials and the resin matrix. Their visibly different properties were investigated. It seems that DDS-functionalization can obviously improve the interfacial heat transfer between the carbon materials and the epoxy matrix. The thermal conductivity enhancement of D-Graphene composites (0.493W/mK) was about 30% higher than that of D-MWNTs composites (0.387W/mK) at 0.5vol.% loading. The different effects among EGO, D-EGO, MWNTs, D-MWNTs and D-Graphene in polymer composites were also discussed. It was demonstrated that DDS-functionalized carbon materials had an obvious effect on the thermal performances of composite materials and were more effective in thermal conductivity enhancement. [Copyright &y& Elsevier]

Abstract: Two types of montmorillonite (MMT), natural sodium montmorillonite (Na-MMT) and organically modified montmorillonite (OMMT), in different amounts of 1, 2, 5, 10 and 25phr (parts per hundred resin), were dispersed in rigid poly (vinyl chloride) by two different methods: solution blending and solution blending+melt compounding. The effects on morphology, thermal and mechanical properties of the PVC/MMT nanocomposites were studied by varying the amount of Na-MMT and OMMT in both methods. SEM and XRD analysis revealed that possible intercalated and exfoliated structures were obtained in all of the PVC/MMT nanocomposites. Thermogravimetric analysis revealed that PVC/Na-MMT nanocomposites have better thermal stability than PVC/OMMT nanocomposites and PVC. In general, PVC/MMT nanocomposites prepared by solution blending+melt compounding revealed improved thermal properties compared to PVC/MMT nanocomposites prepared by solution blending. Vicat tests revealed a significant decrease in Vicat softening temperature of PVC/MMT nanocomposites prepared by solution blending+melt compounding compared to unfilled PVC. The mechanical properties of the PVC/MMT nanocomposites were, in general, greatly improved compared to unfilled PVC. Nanocomposites with 2phr and 5phr of OMMT have demonstrated enhanced results in Young’s modulus, tensile strength and elongation. The Mori–Tanaka method along with an orientation distribution function was used to predict the effective stiffness of the PVC/OMMT nanocomposites prepared by solution blending+melt compounding method. Experimental values for 1 and 2phr are larger than the calculated values which directly suggest that the MMT particles are exfoliated. [Copyright &y& Elsevier]

In this study, CNT-doped carbon aerogel (CNT-CA) and carbon aerogel (CA) were used in different weight ratios (0.1, 0.3, and 0.5 wt%) to reinforce epoxy (Ep) nanocomposites. The relationship between the aerogels' structure deformation such as the average diameter, the total volume of pores, specific surface area, and interfacial (particle/matrix) interaction, distribution, rheological, mechanical, and thermal properties were investigated systematically. Also, the nanocomposites were investigated by ATR-FTIR, XRD, and Raman spectroscopy. In general, the fabricated nanocomposites showed enhanced properties compared to the neat epoxy which is attributed to the penetration of polymer chains into the porous three-dimensional structure of the distributed aerogels. This phenomenon resulted in a high filler/matrix interaction, resulted in a better load transfer. Ep/CNT-CA showed better properties than Ep/CA which is due to ultrahigh specific surface area in CNT-CA. The rheological analysis showed a significant change in behavior from a liquid-like state to a pseudo-solid state in Ep/CA0.3 and Ep/CNT-CA0.1. Mechanical and thermal investigations of nanocomposites showed 8–17% increment in young modulus, 39–52% in tensile strength, 47–69% in elongation at break, 28–53% in E′ at 40 °C, 2–6% in Tanδ, and 7–11 °C in T max (compared to the neat epoxy matrix). [Display omitted] • CNT-doped carbon aerogel was used as reinforcement in epoxy matrix. • Rheological properties of carbon aerogel/epoxy suspensions were investigated and evaluated with rheological parameters. • Physical, morphological and mechanical characterizations were performed on nanocomposite samples. • Physical structure of the aerogel was an effective parameter on the nanocomposite performance. • Penetration of the resin caused a high interaction with the large surface area of aerogels' mesoporous structure. [ABSTRACT FROM AUTHOR]

In this research, the novel nano-filled fluoroelastomer (FKM) composites with excellent thermal and mechanical properties were prepared using the Siligraphene (graphene-like SiC), g-C 3 N 4 , and Siligraphene/g-C 3 N 4 composites to improve the thermal and mechanical stability of FKM. The nanocomposites were exposed to heat aging test and characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), dynamic mechanical analysis (DMA), and tensile test. Results show that Siligraphene, g-C 3 N 4, and Siligraphene/g-C 3 N 4 improved the tensile properties of FKM before and after exposure to the aging test. Si and N dopants in the graphenic structure of Siligraphene and g-C 3 N 4 nanofillers are the effective parameter to reinforce the properties of nanocomposites. In general, these nanofillers provided better adhesion with FKM matrix. It can be justified by a better distribution of filler and higher interaction between filler and FKM which form the cellulation structure that can improve the mechanical properties and prevent the rubber decomposition at high temperatures by resisting molecular mobility. [Display omitted] [ABSTRACT FROM AUTHOR]

Polyethylene (PE) are in demand for electrical insulation and thermal management applications; however, their low mechanical and thermal properties pose major challenges. Herein, we report on novel properties of PE-boron nitride (BN) nanocomposites prepared by melt compounding followed by injection molding. The thermal and mechanical properties of silane-functionalized (sBN) and non-functionalized (pBN) PE-BN nanocomposites were studied in order to assess the role of silane functional groups at the interface of BN nanosheets and PE matrix. In comparison with PE materials, addition of 5 wt % BN nanosheets increases tensile modulus of elasticity by 37 and 42%, flexural modulus of elasticity by 24 and 30%, tensile strength by 15 and 27%, and storage modulus by 80 and 91% for pBN and sBN nanocomposites, respectively. Besides mechanical reinforcement, thermal and thermomechanical properties were evaluated for PE-BN nanocomposites. While thermal stability of PE-pBN and PE-sBN nanocomposites was comparable, coefficient of thermal expansion was decreased by 12 and 20% at 5 wt % pBN and sBN nanosheets, respectively. These polymer nanocomposites with enhanced mechanical and thermal properties can be an excellent choice for application in insulation materials, including thermal interface layers in electronic devices. Image 1 [ABSTRACT FROM AUTHOR]

In this study, polyamide 66 (PA66)/nanodiamond (ND) nanocomposites were prepared by in-situ polymerization and their chemical/physical structures and properties were investigated. Since ND was highly dispersed at the nanoscale in PA66, the nanocomposites with a low loading of ND (<0.3 wt%) exhibited high optical transparency similar to that of neat PA66. FTIR spectra revealed that the amide bond content of the nanocomposite was greater than that of neat PA66, indicating that the amide bond was formed at the interface between PA66 and ND in the process of in-situ polymerization. In terms of the mechanical properties, the Young's modulus and tensile strength considerably increased by the incorporation of ND. With the loading of only 0.5 wt% of ND, the Young's modulus and tensile strength increased by 140% and 39%, respectively. In addition, the nanocomposites showed excellent enhancement in the thermal stability as well as the thermal conductivity. The thermal decomposition temperature increased by 16 °C at an ND content of 0.5 wt%. The strong reinforcement effect of ND was assumed to be considerably greater than that of previously reported random oriented nanocarbons, related to not only the nano-dispersion and strong interfacial interaction but also the nanoconfined region at the interface. Image 1 [ABSTRACT FROM AUTHOR]