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With the development of high-density electronics, polymer-based thermal conductive composites with excellent thermal and mechanical performance are receiving great attention. For the development of polymer-based thermal conductive composites with superior properties, it is essential to reduce the agglomeration of fillers and enhance the interfacial interactions between thermal conductive fillers and the polymer matrix. Among the several thermal conductive materials, graphene nanoplatelets (GNPs) and cellulose nanofiber (CNFs) are attracting attention. However, poor interfacial interaction between GNP and CNF leads to interfacial separation, which in turn, deteriorates its properties. Herein, we synthesized a pyranine-functionalized polyether dispersant (PyPE), which can significantly improve the interfacial interactions between GNPs and CNFs. The effect of PyPE on the dispersion behavior of GNPs and the thermomechanical properties of GNP-CNF composite were monitored. Furthermore, we also performed molecular dynamics (MD) simulations to investigate the impact of applying PyPE dispersant on the interfacial interactions between the GNPs and CNF matrix. The application of PyPE significantly enhanced the dispersibility of GNPs within the CNF matrix, resulting in a 15.5 % increase in-plane thermal diffusivity and a 24.5 % enhancement in tensile strength of the composite, demonstrating their potential applications in high power density electrical equipment and electronic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

This study focuses on enhancing thermal properties of aramid copolymer nanocomposites by integrating hexagonal boron nitride (hBN). Pristine hBN (P -hBN) is first subjected to oxidative heat treatment at 900 °C, producing thermally treated hBN (T-hBN), which significantly improves thermal conductivity while also increasing the tensile properties of composites. The study further explores the effect of different diamine co-monomers, 3,4′- and 4,4′-oxydianiline (ODA), on the nanocomposite properties. Both types of ODA-based composite films show improvement in various properties containing T-hBN. With 20 wt% of T-hBN, the 3,4′-ODA and 4,4′-ODA-based films exhibit 33.2 % and 290 % increase in tensile strength and thermal conductivity, respectively. The functionalization of hBN by heat treatment enhances the interaction between aramid copolymer and hBN and prevents the aggregation of hBN. The rough interface was shown in fractured images for films with T-hBN, suggesting that the composite films with T-hBN withstand higher external forces. In addition, it was observed that T-hBN exhibits better dispersion compared to P -hBN. This is supported by molecular dynamics (MD) simulation, and, in addition, it also provides the underlying mechanism for the property differences between both types of co-monomers. [Display omitted] [ABSTRACT FROM AUTHOR]

Drawing inspiration from the robustness and resilience of spider silk, this study harnessed a combination of polydopamine (PDA), cellulose nanofibers (CNFs), polyvinyl alcohol (PVA), and aminated carbon nanotubes (CNTs) to create a synergistic network through hydrogen and covalent bonding on the surface of carbon fibers (CFs). This strategy significantly bolstered the interfacial properties of the resulting composites. The enhancements in flexural strength, flexural modulus, interlaminar shear strength (ILSS), tensile strength, and interfacial shear strength (IFSS) were measured at 47.8 %, 75.2 %, 54.3 %, 55.6 %, and 51.8 %, respectively. These improvements are attributed to the formation of robust covalent and hydrogen bonds among PDA, CNF, PVA, and aminated CNTs. Furthermore, the thermal conductivity of the CF composites saw a 59.7 % increase, owing to the CNFs and CNTs. These nanofillers are instrumental in forming an efficient thermal conductivity pathway within the resin matrix, which contributes to the improved thermal conductivity. This study introduces a straightforward, eco-friendly, and innovative approach for the production of high-performance CF composites. [Display omitted] [ABSTRACT FROM AUTHOR]

In view of the diversified demands for thermal management materials in soaring developments of electrical systems, the high thermally conductive composites often suffer from their poor mechanical properties and electrical insulation. Targeting at enhancing simultaneous thermal conductivity, dielectric and mechanical properties, the fibers reinforced gradient structured polyethylene-based composites consisting of ultrahigh molecular weight polyethylene (UHMWPE) fiber layer and hybrid-filled layer are proposed and successfully prepared by simple overlapping-hot pressing. The fibers collaborated with gradient arrangement of hybrid-filled layer in modulating the temperature, electric and stress field distribution. The resultant as-designed composites exhibit excellent thermal conductivity of 0.91 W/(m·K), ultrahigh tensile strength of 104.7 MPa and superior breakdown strength of 161.5 kV/mm, which are increased by 18%, 1374% and 37% than those of the homogeneous composites, respectively. This work provides a new strategy for manufacturing high-performance polymer-based composites. [Display omitted] • A new strategy was proposed to design PE-based composites with high thermal-dielectric-mechanical performances. • The UHMWPE fibers reinforced gradient structure was constructed through simple overlapping-hot pressing. • The structured composites have ultrahigh tensile strength, superior breakdown strength and high thermal conductivity. • The fibers collaborated with hybrid-filled layer in modulating the temperature, electric and stress field distribution. [ABSTRACT FROM AUTHOR]

The demand for biopolymer-based green packaging has attracted growing attention because of its outstanding properties and consistency with clean environmental principle, unfortunately, its slow crystallization rate and narrow processing window are challenging. Inspired by combined functions in nanocellulose-based conductive hybrids, this work developed high-performance polylactic acid (PLA) composites using conductive cellulose nanofiber (CNFene). Interestingly, CNFene has multiple functions as highly graphitized carbon and abundant hydroxyl groups, delivering stimulating properties to PLA composites. As nucleating agents, 3 wt% CNFene has a carbon layer on the surface combined with a hydrogen bonding network synergistically enhancing the tensile and crystallization properties of PLA-C3, with a tensile strength of ∼ 53.7 MPa, crystallinity of ∼ 33.9 %, and 6.6 °C decrease in the cold crystallization temperature. Additionally, the compatibility between CNFene and PLA can form a multi-level "reinforcement" network structure, further improving thermal stability and barrier properties. The resultant PLA-C3 showed higher thermal decomposition onset temperature (T 0), wider melt-processing window (197.6 °C) and extremely lower overall migration levels in ethanol (68.6 μg/kg) and isooctane (16.3 μg/kg), due to that improved interaction between CNFene and PLA positively affects crystallization ability and kinetic/mechanism of PLA to meet the requirements of industrial and green biopackaging applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Needle-punched fabric reinforced nanoporous phenolic composite (NPC) is a kind of promising ablative thermal protection material for spaceflight. However, in practical applications, typically anisotropic microstructure of NPC may lead to different performances and damage mechanisms under various directional mechanical or thermal loads. Herein, NPC is prepared and cut into specimens along three typical plane directions including XY -plane (0°), Z -plane (90°), and transitional-plane (45°), and their mechanical, thermal insulation, and ablation behaviors are systematically investigated. Benefiting from the woven fabric in XY -plane, NPC in 0°-plane direction exhibits highest tensile strength (169.2 ± 12.6 MPa), and CT image-based simulation further verifies that woven fabrics are primary load-bearing structure. Meanwhile, NPC in 45°-plane direction shows highest compressive strength (443.1 ± 18.2 MPa) but low compressive stress at low strain, demonstrating a weak bonding between two layers of woven fabrics. Moreover, the heat transfer simulation indicates that horizontally stacked woven fabrics effectively protect the internal material from thermal erosion, thus NPC in 0°-plane direction exhibits optimal thermal insulation. The ablation testing and micro-CT observations further demonstrate that the angle between woven fabric and thermal load significantly influences the ablation mechanism. The present work will further promote the structural reliability and optimization of needle-punched composites. [Display omitted] [ABSTRACT FROM AUTHOR]

High performance composites not only pursue high strength, light weight, but also need to have multifunctional characteristics. To further improve curing efficiency and mechanical properties of phthalonitrile resin (PN75) and give full play to its excellent thermal and dielectric properties, mica as reinforcement was introduced into PN75 to form particle-filled resin (Mica/PN75) and CFRP (Mica/PN75/CF) composites. The introduction of mica reduced the curing temperature of PN75 and improved the curing efficiency. The thermal stability of resin and composites was further improved. The bending strength of the two groups of mica reinforced resin increased by 44.87% and 55.97%, and the dielectric constant decreased from 3.3 to 2.7 and 2.5, respectively. The bending strength of the composites was increased by up to 19.9%, and the glass transition temperature of composites was increased by up to 26 °C after reinforcement. The multidirectional reinforcement of PN75 by mica was studied and analyzed in this work. [Display omitted] • Mica was used for the first time to particle reinforce phthalonitrile resin. • Powder blending was used to complete the mixing of inorganic particlesand phthalonitrilephtha resins. • The structure of reinforced resin is more stable, the bending toughness and dielectric property are greatly improved. • The reinforced composites have better thermal stability and improved toughness. [ABSTRACT FROM AUTHOR]

Due to the different coefficients of thermal expansion between the heat generation and heat dissipation units, the applications of soft high filled composite gels as thermal interface materials require both high stretchability and excellent resilience. However, high stretchable composite gels reported far usually contain sacrificial species to dissipate energy, thus compromising their resilience. Herein, a soft (0.13 MPa), stretchable (172%), and resilient (>70%) composite gel with ultrahigh filler loading (90 wt %) is developed. The stretchability and resilience are realized by lengthening free polymer strands to form appropriate entanglements, in which the loose entanglements transfer the applied force into a large area and the stiff crosslinks prevent the entanglements from disentangling. In additional, the reversible elasticity of the filler network also dictates the resilience, so delaying its deconstruction allows for excellent resilience. The ultrahigh filler loading also endows the composite gel with high thermal conductivity (4.04 W·m−1·k−1), and the potential of the as-prepared composite gel for a TIM is discovered. [Display omitted] [ABSTRACT FROM AUTHOR]

Aramids are materials with high-performance properties and used in advanced applications, including bulletproof vests and aerospace industry components. Consequently, research is focused on improving their properties and reducing their density to achieve fuel reduction and enhanced comfort. Herein we describe the preparation of dense, micro, and nanoporous aramid films containing hexagonal boron nitride (hBN) with two objectives: improving mechanical performance and increasing thermal conductivity (TC) in porous films for specific applications. The preparation procedure is simple and scalable, involving the addition of hBN and a porosity promoter to control the porous structure in the film's casting solution. Tensile tests revealed that the inclusion of 10% of hBN in microporous aramids led to a 130% increase in Young's modulus and 63% reduction in material's density compared to the dense commercial aramid. The orientation of the hBN in the films was also evaluated by considering the XRD and the thermal properties of the films. The films containing hBN exhibited enhanced TC and thermal diffusivity (TD) together with a very low density and improved mechanical performance, which can benefit applications in the aerospace industry, protective equipment, and battery separators. Obtention of dense, micro- and nanoporous aramid films containing hexagonal boron nitride with increased mechanical performance and thermal conductivity following a casting procedure. [Display omitted] • Dense, micro and nanoporous hBN-reinforced aramid films were obtained. • The cellular structure is controlled by the nature of the porosity promoter. • Young's Modulus increase 130% in 10% hBN-μP films compared to commercial aramid. • Thermal conductivity increased 167% in dense films and 75% in porous films. [ABSTRACT FROM AUTHOR]

High-performance composites that are mechanically strong and thermally stable are widely used in many fields, introducing additional functionalities into these composites accompanied with improved physical properties can further expand their applications. In this paper, reversibly cross-linked composites consisted of aromatic polyamide (fPA) with pendent furan groups and fullerene C 60 was fabricated. The Diels-Alder (D-A) reaction between furan groups and C 60 allowed the cross-linking of fPA at moderate temperature, and the cross-linking effect greatly improved the mechanical and thermal properties of composites at a small loading (0.3 wt%) of C 60. The retro D-A reaction permitted the dissociation and reprocessing of cross-linked C 60 /fPA composites at high temperature. Tensile test revealed the similar mechanical properties of reprocessed composites in comparison to their original samples, confirming the good recyclability of C 60 /fPA composites. Moreover, the improved high-temperature shape memory property of C 60 /fPA composites as compared to neat fPA was also demonstrated. These fascinating features as well as the easy processing of our C 60 /fPA composites make them promising materials for various applications. [ABSTRACT FROM AUTHOR]

Nano-sized silver nanowires (Ag NWs) always suffer from chemical and thermal instability for their high surface energy. To address these issues, a tri-layer structure, consisting of reduced graphene oxide (rGO) top-layer, Ag NW mid-layer and graphene oxide (GO) bottom-layer, is designed and fabricated by convenient spray and pressure transfer process. Different with water-soluble GO covered film, the rGO covered tri-layer film shows better chemical stability (1000 s without apparent changes) in stroke-physiological saline solution than pure Ag NW sample (failed after 200 s) and GO/Ag NWs/GO sample (failed after 240 s). The film also exhibits superior stability when heating at 200 °C for 30 min and mechanical robust at a bending radius of 3 mm for 1500 cycles. Moreover, the tri-layer film-based heater can reach 148 °C with highly thermal stability during cycling heating and long-time working (>5 h), indicating its possible applications in flexible and wearable electronics. [ABSTRACT FROM AUTHOR]

High performance epoxy composites are highly required in many applications. In this work, polyimide electrospun nanofibers (PIENFs) with excellent thermal and mechanical properties were used to reinforce the epoxy matrix by a vacuum-assisted hot-pressing procedure. The morphologies of PIENFs and PI/epoxy composites were investigated by scanning electron microscopy (SEM). Thermogravimetric analyses (TGA) was used to characterize the thermal properties of PI/epoxy composites and calculated the actual weight amount of PIENFs in the composites. The effects of nanofiber amount and the degree of fiber alignment on the mechanical properties of PI/epoxy composites have been studied. Owing to the superior mechanical performance of PIENFs and the strong interfacial adhesion, the PI/epoxy composites presented significantly mechanical improvement as compared to the pure epoxy. Image 1 [ABSTRACT FROM AUTHOR]

Abstract Owing to the integration of power electronic devices and the development of flexible devices, demands for high quality thermal conductive composites have substantially increased. Thus highly flexible poly (vinylidene fluoride)/boron nitride (i.e. PVDF/BN-x) composite films were prepared in this work, and a low quantity of graphite nanoplatelets (GNP) was added to simultaneously improve the thermal and mechanical properties of the film (i.e. PVDF/BN-30/GNP-y). The synergistic effect of the two fillers has been discussed, and results show that the thermal conductivity of PVDF/BN-30/GNP-2.5 reaches up to 0.720 Wm−1K−1 compared with 0.634 Wm−1K−1 of PVDF/BN-30. And the tensile strength is also increased from 12.43 MPa to 20.21 MPa, which has been improved by 63%. In addition, the experiment results validate that the films possess high electrical insulation and satisfactory breakdown strength, which proves its applicability to high-voltage environment. Besides, the thermal conductivity of films can be preserved after 300 thermal shocks with extreme temperature changes. This study provides a kind of flexible thermal interface material with excellent comprehensive properties for application in field of power electronics. [ABSTRACT FROM AUTHOR]

Developing polymer composites with high thermal conductivity is a must to improve the thermal-management ability for modern electronic applications, in which power densities rapidly increase. Boron nitride nanotubes are one of the most promising fillers due to their high thermal conductivity and electrical insulator, but the overall thermal conductivity of the obtained polymer composites is limited by high interfacial thermal resistances. Here, we present an approach to reduce the interfacial thermal resistance between adjacent boron nitride nanotubes through low-melting effect of nanoscale silver particles. A sharp increase in thermal conductivity (20.9 Wm −1 K −1 ) is observed in cellulose nanofibers (CNFs)/boron nitride nanotubes (BNNTs) composites, which is approximately 14.3 times larger than that of conventional polymers. The underlying mechanism is understood through Foygel model, and demonstrated that the interfacial thermal resistances play key role in the thermal conductivity. This strategy can become a quotable method for design and prepared of highly thermal conductivity materials in the future. [ABSTRACT FROM AUTHOR]

A facile strategy was applied to transfer chemically exfoliated molybdenum disulphide (MoS 2 ) nanosheets from aqueous medium to organic solvents. The MoS 2 nanosheets were then modified by trisilanol-phenyl-POSS (T 7 POSS) which was confirmed by Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS) and Powder X-Ray Diffraction (PXRD). The modified MoS 2 nanosheets were then incorporated into poly (methyl methacrylate) (PMMA) via a simple solution blending method. The Scanning Electron Microscope (SEM) and Transmission electron microscope (TEM) were employed to demonstrate the well-dispersion of nanosheets in polymeric matrix. Compared to neat PMMA, the decomposition temperatures (T d ) and the half weight decomposition temperatures (T half ) of POSS-MoS 2 /PMMA nanocomposites at nanosheets concentration of 0.2 wt% were dramatically increased by 35.2 °C and 35.3 °C, respectively. Meanwhile, according to the measurements of Dynamic Mechanical Analysis (DMA), the storage modulus at 30 °C is significantly improved by 5.2 times and the glass transition temperature (T g ) is also enhanced by 6.2 °C. Remarkably, POSS-MoS 2 /PMMA nanocomposites possess low optical limiting differential transmittance T c (0.5%), low nonlinear optical absorption onset threshold F ON (0.02 J⋅cm −2 ), low optical limiting threshold F OL (0.4 J⋅cm −2 ) and high nonlinear coefficient β (297⋅cm GW −1 ), highlighting their vast potential in the development of solid-state optical limiting materials. [ABSTRACT FROM AUTHOR]

Continuous carbon fiber (CCF) reinforced polymeric composites have attracted significant attention in the aeronautic and automobile industries. In this study, novel CCF/poly(ether ether ketone) (PEEK) composites with robust solvent resistance, excellent thermal stability and outstanding mechanical properties were successfully fabricated via a facile solution impregnation process, mainly ascribed to the introduction of the crosslinkable phenylethynyl pendant to PEEK (PEP-PEEK) with excellent solubility. After the crosslinking reaction, PEP-PEEK presented robust solvent resistance, good thermal stability, and high mechanical properties. The longitudinal tensile strength of the CCF/PEP-PEEK composites significantly improved to 1610 MPa, which was 19 times stronger than the longitudinal tensile strength of PEP-PEEK. In the meantime, the CCF/PEP-PEEK composites also had a higher long-term operating temperature, excellent thermal stability and high heat distortion temperature. This study was performed as part of a larger effort to provide a simple and feasible method for the preparation of high quality continuous fiber reinforced poly(ether ether ketone) composites. [ABSTRACT FROM AUTHOR]

10-hydroxy-9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-OH) has been successfully covalently grafted onto the surfaces of multi-walled carbon nanotubes (MWCNTs) to obtain DOPO-functionalized MWCNTs (MWCNT-DOPO-OH) by a three-step process. The resultant core-shell nanostructured MWCNT-DOPO-OH was introduced into aluminum hypophosphite/poly(lactic acid) (AHP/PLA) flame retardant systems via melt blending to improve both flame retardancy and mechanical properties. AHP/PLA/MWCNT-DOPO-OH nanocomposites with synergistic effect of 1 wt.% MWCNT-DOPO-OH and 14 wt.% AHP were shown to be effective in improving flame retardancy with UL 94 V-0 rating and limiting oxygen index (LOI) value of 28.6. And these flame-retardant nanocomposites show a usable T g higher than 57.8 °C and much higher char yield for preventing the anti-dropping. Moreover, a cold rolling process was performed for AHP/PLA/MWCNT-DOPO-OH nanocomposites to further improve the mechanical properties for secondary processing. For 1 wt.% MWCNT-DOPO-OH loading PLA nanocomposites, the tensile strength increased from 69.5 MPa to 77.9 MPa and 82.0 MPa, and the fracture strain increased from 17.9% to 27.5% and 120%, at rolling ratios of 30% and 50%, respectively, indicating that MWCNT-DOPO-OH modified PLA was homogenized plastic deformation during the rolling process. [ABSTRACT FROM AUTHOR]

Herein, we report a fabrication of epoxy resin/oriented BN composites via a facile hot-pressing strategy. Benefitting from the force exerted vertically on the BN platelets, a well-ordered BN microstructure in the composites has been achieved, which renders the prepared composites an elevated thermal conductivity up to 6.09 W m −1 K −1  at 50 wt% loading, while it is only 2.44 W m −1 K −1 for epoxy resin/random BN composites. In addition, the composites show an enhanced tensile strength (31.79 MPa) and Young's modulus (4.63 GPa) when comparing with epoxy resin/random BN composites at the same 50 wt% loading (21.21 MPa and 1.48 GPa). We attribute the improved thermal conductivity to the well-aligned BN platelets in higher heat conduction direction based on the anisotropic thermal conduction ability of BN. The enhanced mechanical properties are ascribed to the increased friction area along the tensile in-plane direction and the decreased defects which are easily incorporated during the fabrication process. This study sheds a light for exploring future thermal management materials to meet the increasing heat dissipation demands. [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]

Hybrid inorganic/polymer composite aerogels combine the advantages of both components which can overcome the brittle fracture of inorganic aerogels as well as high flammability of polymeric aerogels. Herein, we reported a facile approach to prepare polyvinyl alcohol (PVA)-hydroxyapatite (HAP) composite aerogel by freeze-casting process towards multi-functional aerogel materials. The incorporation of HAPs led to significant reduction in the peak heat release rate (−79%), total heat release (−76%), specific extinction area (−65%) and CO production (−45%). Vertical burning tests also manifested that PVA-HAP composite aerogels displayed excellent fire resistance and self-extinguishing behaviours. The resultant PVA-HAP composite aerogels also showed a low thermal conductivity (33.6–38.7 mW m −1  K −1 ). The hydrogen bonding formed between the HAP and the PVA matrix endowed the resultant composite aerogels with a specific modulus (58.7 kN m −1  kg −1 ) which was comparable to or even higher than those reported by state-of-the-art foams, including polystyrene foams, polyurethane foams and silica aerogels. After a facile polydimethylsiloxane treatment, the resultant PVA-HAP composite aerogels also exhibited water-repellent and self-cleaning capacity, which is a promising candidate as building insulating materials. [ABSTRACT FROM AUTHOR]

Herein, we studied the homogeneous transfer of graphene oxide (GO) into photocurable SU-8 photoresist for fabricating GO/SU-8 three-dimensional (3D) composite micropillar arrays by modified photolithography. SU-8 is a negative toned epoxy based photoresist, which includes 8 epoxy groups in each SU-8 monomer. The effects of the concentration of GO flakes on the thermal, mechanical and specific surface area (SSA) properties of the resultant composites were investigated. The large amount of oxygen functional groups on the GO plane and at the edges allowed uniform distribution of GO sheets within the SU-8 resin. The GO/SU-8 micropillar arrays were fabricated by a versatile ultraviolet (UV) photolithography technique that allowed the synthesis of various 3D micro–nano integrated carbon microelectrode arrays. The integrated GO flakes were bonded to the surface or embedded within the primary structure of SU-8 micro-pillars. These SU-8 micropillars having surface-bonded or embedded GO flakes showed superior thermal stability, strength, and SSA characteristics than bare SU-8 micropillars. Thus, this new synthesis approach provides a novel route for developing high performance catalysts, sensors, and adsorbents, among other materials. [ABSTRACT FROM AUTHOR]

Dispersing nanoparticles in polymers is a key requirement for the development of polymer-matrix composites. In this study, cationic ligand and anionic ligand were designed to serve as dispersant, emulsifier and comonomer in different stages of nanocomposites preparation. Commercial BaTiO 3 , TiO 2 , Ag and Al 2 O 3 nanoparticles were incorporated and dispersed uniformly in polystyrene (PS) and polymethyl methacrylate (PMMA) matrices by designed cationic/anionic ligand. As dispersants, the sizes of nanoparticles aggregates were reduced from thousands of nanometers to dozens of nanometers by cationic/anionic ligand. Then ligands served as emulsifiers to prepare polymer nanocomposites. At the end of emulsion polymerization, the ligands copolymerized with polymer matrices. At this stage, the sizes of nanoparticles in polymer matrices fell to several nanometers. After hot-pressing, nanoparticles maintained the stable dispersion state in polymer matrices. The tensile strength of P(MMA-co-VDAC)/BaTiO 3 increased by 77% compared with PMMA. The thermal decomposition temperature of P(St-co-MAMS)/Al 2 O 3 was improved by 24 °C compared with PS. A facile and efficient approach was exhibited for preparing polymer nanocomposites with a large variety of chemically different nanoparticles in diversified polymer matrices. [ABSTRACT FROM AUTHOR]

The thin flexible film heater made of carbon fibers is widely considered to be an ideal material for the use as self-heating devices because of its safe, low-cost, no noises, small size and fast heating as well as energy saving. Presently thin flexible film heater is mostly fabricated by mixing method using the long cellulose fibers as film-forming materials and carbon fibers as self-heating materials, which mostly suffer from opaque or uneven heating field. In this work, we firstly reported a flexible and transparent thin film heater (FTFH) composed of carbon fibers and regenerated cellulose. The use of regenerated cellulose for membrane materials brings high transmittance, strong adhesion, fast temperature response and high generated temperature. More importantly, the FTFH using novel carbon fibers as self-heating materials and regenerated cellulose as membrane materials show a rapid heating response (12 s), higher power density (2577 w/m 2 ) and long-term stability of generated temperature (162.3 °C). [ABSTRACT FROM AUTHOR]

The synthesis of poly(propylene carbonate) (PPC) consumes carbon dioxide, which forms a promising route to fix greenhouse gas. Developing the applications of PPC could enhance the recycle of carbon dioxide. However, PPC typically has low mechanical strength and thermal stability, and its glass transition temperature (T g ) is low as well, which restrict its use in practice. In this study, we have for the first time found that wool powder (WP) can be an efficient additive to modify PPC. By adding just 2.0wt% wool powder (WP) to PPC, the mechanical properties, glass transition temperature, and thermal decomposition temperature can be improved significantly. PPC containing 2.0wt% WP shows comparable tensile properties to commonly-used polymers such as poly(butylene succinate), polypropylene and high-density polyethylene. We further showed that PPC can form strong interfacial interaction with WP, responsible for the improvement in PPC mechanical properties. Addition of wool powder may offer a promising way to boost the applications of PPC. [ABSTRACT FROM AUTHOR]

Liquid paraffin microcapsules (LPMs) were incorporated into epoxy resin to prepare fluid-filler/polymer composite materials in this work, with the objective of introducing fluid heat convection into thermally conductive and electrically insulting materials. The LPMs were fabricated by coating urea resin onto liquid paraffin via in-situ polymerization, enabling the as-prepared LPMs to experience no weight loss below 240 °C. The heat dissipation efficiency of the LPM/epoxy-resin composite with 25 vol% LPM content was remarkably improved above 50 °C, although its thermal conductivity was only 0.25 W/(m·K) at room temperature. The enhancement of heat dissipation efficiency above 50 °C could be ascribed to the effect of fluid heat convection in the LPM filler increased with increasing temperature. The LPM/epoxy composites containing 20 vol% of LPM filler exhibited tensile strengths, bending strengths, and breaking elongations that were 14.3%, 12.5%, and 30.5% higher, respectively, than those of the pure epoxy resin. The results of this study indicate that fluid heat convention is of great significance in the development of thermally conductive and electrically insulting materials. [ABSTRACT FROM AUTHOR]

The short length hemp fibers treated with 5% NaOH (THF) were sandwiched in bisphenol A-aniline based benzoxazine (BA-a) to form the resin-fiber-resin composite. The effects of fluctuating fiber volume on the curing behavior, mechanical, thermomechanical, and thermal properties of the resulted composites were studied through fourier transform infrared (FTIR), differential scanning calorimetry (DSC), dynamic mechanical analyzer (DMA), thermogravimetric analysis (TGA), and scanning electron microscope (SEM). The results confirmed that the rich -OH groups on THF can promote the ring-opening of oxazines at lower curing temperature, and improve the adhesion between fiber and matrix. In addition, an increase of 185% in impact strength, 1.3 GPa in flexural modulus, and 109% in tensile strength was recorded for 25 vol% THF content cured composites. The slight diminution in thermal stability was observed as THF content increased, at 25 vol% THF content, weight loss temperature ( T 5% ) and char yield at 800 °C ( Y c ) were 11 °C, and 0.4% lower than pristine poly(BA-a), respectively. [ABSTRACT FROM AUTHOR]

Electrically insulating polymer materials having high thermal conductivity and elastic modulus are in high demand for next-generation electric machines and electronic devices. Carbon nanotubes (CNTs) show extremely high thermal conductivity and elastic modulus; however, even the addition of a few CNTs to polymers leads to them losing their electrically insulating properties. Herein, morphologically controlled multiwalled CNT (MWCNT)/polyamide-6 (PA6)/poly( p -phenylene sulfide) (PPS) composites, having high thermal conductivity, electrical insulation and elastic modulus, were designed and fabricated. First, MWCNT/PA6/PPS/EGMA composites comprising a PA6 matrix and MWCNT-localized PPS domains surrounded by shell-layers formed from poly(ethylene- co -glycidyl methacrylate) (EGMA) were prepared. The thermal conductivity of the composites was improved without losing the volume resistivity. However, these composites showed low elastic modulus, especially at high temperature, due to MWCNT localization and the existence of EGMA. Therefore, MWCNT/PA6/PPS/(3-glycidyloxypropyl)trimethoxysilane (GOPTS) composites having a novel morphology were designed and fabricated using GOPTS as a highly reactive shell-forming agent. In this composite, the MWCNT ends were capped with nano-sized PPS domains (MWCNT-PPS nanodomain-linked structure) to prevent electrically conductive paths forming, and MWCNT-PPS nanodomain-linked structures were uniformly dispersed in the PA6 matrix, leading to much enhanced elastic modulus and heat resistance in addition to improved thermal conductivity and electrically insulating properties. These composites containing CNT-nanodomain-linked structures are promising as electrically insulating materials for various applications including high-performance electric machines and electronic devices. [ABSTRACT FROM AUTHOR]

Our pilot research revealed that the dielectric constant of polyimide (PI) can be reduced and the modulus can be improved by assembling necklace-like interlocking complexes with crown ethers. Not only did we find that these properties of the PI complex still cannot adequately meet the demand of practical applications but also that there was a deterioration in its thermal stability. A functional octa(aminopropyl)silsesquioxane (OAPrS) with a significantly rigid Si-O-Si cage was incorporated into an 18-crown-6 (CE6)-PI (CE6-PI) complex to produce inorganic-organic OAPrS/CE6-PI nanocomposites. By exploiting the synergetic effect of OAPrS and CE6, most properties of the PI were clearly improved. In the case of 3.9 wt% OAPrS and 7.8 wt% CE6, the dielectric constant of PI was reduced by 30%, and Young's modulus and the tensile strength were increased by 106% and 23%, respectively. In addition, the thermal stability of the CE6-PI complex was modified, and its 5% weight loss temperature and glass transition temperature were increased by 31.2 and 11.2 °C, respectively, with the incorporation of 3.9 wt% OAPrS. The indispensable nano-reinforcing role of aggregated OAPrS crystal in the nanocomposite was carefully analysed and verified. [ABSTRACT FROM AUTHOR]

A novel lightweight needled carbon fibre felt/phenolic resin (NCF-PR) aerogel composite was fabricated through vacuum impregnation using NCF as matrix and PR aerogels as filler. The PR aerogels was synthesized through polymerization-induced phase separation (PIPS), accompanied by solvent exchange and ambient pressure drying, from a resin mixture of PR with ethylene glycol (EG) as the porogen and hexamethylenetetramine (HMTA) as the catalyst. A homogeneous microstructure without macroscopic cracking and agglomeration was achieved in the composite, and the macropores between the fibres in the NCF were fully and uniformly filled by PR aerogels with high porosity and with large amounts of mesopores. The resulting NCF-PR aerogel composites exhibit low densities between 0.270 and 0.370 g/cm 3 , relatively high compressive strength, ranging from 0.83 to 11.02 MPa, and low thermal conductivities of 0.093–0.230 W/(mK) at room temperature. The thermal ablative properties of the aerogel composite were studied under arc jet conditions at a heat flux of 1.5 MW/m 2 for 33 s. The ablation results demonstrate that the NCF-PR aerogel composite could deliver good thermal ablative and insulative properties (linear ablation rates as low as 0.029 mm/s and internal temperature peaks below 90 °C at 38 mm in-depth position as the surface temperature exceeded 2000 °C). Therefore, this lightweight carbon/phenolic composite is an excellent heat-insulation and thermal-protection material with applications in the fields of energy-saving and aerospace. [ABSTRACT FROM AUTHOR]

Polyhedral oligomeric silsesquioxanes (POSSs) are ideal particles to reduce the dielectric constant (k) and loss (tan δ) values of resin matrixes for electronic packaging, but greatly limited by its finite addition due to phase-separation. Herein, tetra(epoxy)-terminated open-cage TG-POSS was synthesized and utilized as a unique building block to crosslink with bisphenol A or hexafluoro-bisphenol A, respectively, for the preparation of novel high performance low-k composites (POSS/BPA or POSS/FBPA). Results reveal that such rational design endows these two materials with homogeneous hybridization even at high POSS loading (>72.0 wt%), which is the main reason for superior dielectric, thermal and hydrophobic properties as compared with counterparts reported previously. Especially, fluorinated POSS/FBPA shows the lowest k value of 2.38, lowest tan δ value of 0.008, highest initial decomposition temperature of 396.1 °C and largest water contact angle of 117.0°, under the extra-contribution of trifluoromethyl units. In addition, its well-dispersed, moderate-crosslinked and rigid-flexible polymer network also leads to outstanding mechanical properties (elongation at break of 3.50% and modulus of 2.75 GPa) for practical applications. Summarily, this work highlights a useful strategy to fabricate high performance low-k composites with high POSS content, which is not only potential for advanced microelectronic industry but also instructive for academic fields. [Display omitted] • A tetra(epoxy) TG-POSS with inorganic open-cage structure was synthesized. • TG-POSS was utilized to thermo-crosslink with diphenols for novel low-k composites. • The prepared composites show advanced low-dielectric and other comprehensive properties. • The superior properties are mainly attributed to the open-cages from TG-POSS. • The prepared composites have broad application prospects for electronic packaging. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) attract considerable scientific and engineering interest because of their excellent mechanical, electrical and thermal properties. Today, when manufacturers use CNTs, purification, chemical modifications and dispersion techniques are usually applied rendering them cost-effective in large-scale applications. Our research shows that multi-wall CNTs bundles (MWCNTBs) with the same alignment, orientation and high surface defects for each CNT can be directly incorporated into the elastomer matrix through melt compounding. A uniform dispersion of CNTs and strong interfacial interactions between elastomers and CNTs due to the silane-coupling agent can be simultaneously produced. The resulting elastomer/MWCNTBs nanocomposites demonstrate excellent mechanical properties, high thermal conductivity and low volume resistivity. Note that this nanocomposite is achieved using common compounding equipment that is easy to industrialize. Through further scale-up, we confirmed that this elastomer/MWCNTBs nanocomposite has the most optimized comprehensive performance with practical applications for fuel-savings and engineering tires. These advantages include fuel efficiency, anti-static electricity and long-time fatigue resistance. In light of the large number of tires used worldwide, this work is promising for future large-scale industrial applications of CNTs. [ABSTRACT FROM AUTHOR]

Tin oxide (SnO 2 ) nanorods (NRs) were successfully grown using a two-step seed-mediated hydrothermal method in the absence of surfactants. The enhanced mechanical properties of the impact absorbed energy (71.65%), ultimate tensile strength (35.07%), in-plane shear strength (49.07%) and elastic modulus (44.15%) were obtained for 70 mM of SnO 2 –woven carbon fiber (WCF) composites. The higher electrical resistive heating in the interlaminar region of electrified SnO 2 (70 mM)–WCF composite sheets was observed at 108.92% improvement of an average temperature under an applied current of 3 A for 20 min. It was attributed to the fact that a higher SnO 2 NR content provided secondary reinforcement and subsidiary electrified heat traps by modifying the interphase region between the CFs and polymers. X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to examine the morphology and phase structure of one-dimensional (1D) grown SnO 2 NR arrays. The crystalline 1D SnO 2 nanostructure evolved via a self-assembly mechanism that depended on nuclei of Sn 4+ /OH − ions in a supersaturated solution at a pH of about 13. This facile controlled growth of SnO 2 embedded in CF composites is relevant to engineering applications requiring higher mechanical performance and thermal heating than attainable with conventional CF-reinforced polymer composites. [ABSTRACT FROM AUTHOR]

Phenolic-based composites are the most promising ablative thermal protection materials for space applications, but optimizing their thermal insulation performance while maintaining high strength remains extremely challenging. Herein, phenolic-based composites with co-optimized thermal insulation and mechanical properties are prepared via 2.5D quartz fabric reinforcing nanoporous phenolic. The pore size of phenolic matrix is efficiently refined to ∼35 nm by adjusting resin concentration, enabling composites to exhibit high density but low thermal conductivity by enhancing Knudsen diffusion. Finite element analysis shows that low braiding angle of 2.5D fabric can further weakening heat transfer of composites due to anisotropic thermal conductivity of fiber yarns. In-situ X-ray micro-CT results indicate that 2.5D fabrics can reinforce composites through interwoven yarns, and straighter weft yarns result in higher strength along weft direction than that along warp direction. Compared with dense quartz/phenolic composite, the resulting composites exhibit 16.5% lower density (1.32 g/cm3), 58.8% lower thermal conductivity (0.21 W/(m·K), ≥372.7% higher tensile strength (≥182.0 ± 9.6 MPa) and comparable ablation resistance. The present results will further advance the application of phenolic-based composites in more extreme re-entry environments. [Display omitted] [ABSTRACT FROM AUTHOR]

For the better operation of future electronic devices in complex situations, higher requirements of mechanical performance, especially bearing capacity, were put forward to functional composites. Therefore, the mechanical performance enhancement of functional composites had important practical application value. In this work, we reported a short carbon fiber-graphene nanoplatelets-polydimethylsiloxane (SGP)/epoxy acrylic resin (EA resin) composites with integrated thermal conductivity, electromagnetic interference (EMI) shielding, and mechanical performances using a combination method of 3D printing and vacuum impregnation. In the SGP/EA resin composite, EA resin skeleton with different cell shapes was responsible for the bearing capacity of composite samples, while the thermal conductivity and EMI shielding performance were provided by the SGP compound. When the cell shape of skeleton was circular and the filling contents in SGP compound was 15 wt% SCF and 6 wt% GNP, the SGP/EA resin composite presented best combination properties of 323.5 kPa compressive modulus, 2.13 W/(m·K) thermal conductivity, and 45.93 dB EMI shielding performance at 12.4 GHz. This work provided a facile, low-cost, and scalable method to fabricate composite samples with integrated thermal conductivity, EMI shielding, and mechanical performances. These multifunctional composites are highly promising for applications concerning heat dissipation, EMI shielding, and load-bearing devices. [Display omitted] [ABSTRACT FROM AUTHOR]

We proposed a method to prepare double modified amino phenolic resin (D-APS) particles, which includes a hydrothermal synthesis and subsequent two-step modification. The prepared D-APS particle has a uniform spherical morphology. There were abundant and evenly dispersed amino hydrogen and phosphaphenanthrene groups on its surface. The formed D-APS/epoxy composite possesses improved mechanical properties at room and cryogenic temperature. At room temperature, the tensile strength of epoxy composite firstly increased and then decreased with the increase of D-APS loading. A maximum tensile strength of 98.4 MPa was obtained when the D-APS loading was 3.0 wt%. The fracture toughness of D-APS/epoxy composite containing 3 wt% D-APS particle was 1.68 MPa m1/2. At 90 K, a maximum tensile strength of 208.4 MPa was obtained when the D-APS loading was 3.0 wt%. The corresponding K IC is 3.23 MPa m1/2. A 49 °C increase in 50 wt% mass loss temperature for epoxy composite containing 3 wt% D-APS particle is observed. DMA tests show that D-APS was also helpful to increase the glass transition temperature of epoxy composites. Possible modification mechanism of D-APS/epoxy composites was also discussed. [Display omitted] [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]

Polyvinyl alcohol (PVA) is a biocompatible, semi-crystalline and water soluble polymer with moderate tensile properties. To improve the thermal and mechanical properties of PVA, as well as to reduce water uptake, structural modification by glutaric acid (GA) and nanoparticle reinforcement by tungsten disulphide nanotubes (WSNTs) were used to prepare PVA based composites. We observed a significant drop in the water uptake of GA crosslinked PVA, an indication of the formation of a network. Fourier transform infrared spectroscopy was applied to confirm the presence of covalent bonds formed during the crosslinking. Crosslinked PVA and composites are found to have higher thermal stability and mechanical properties compared to their un-crosslinked counterparts. Tensile tests show that the presence of WSNTs increases the strength (up to 25%), modulus (up to 120%) and toughness (up to 80%) of the pristine as well as the crosslinked PVA. [ABSTRACT FROM AUTHOR]

Lithium intercalated molybdenum disulfide (Li x MoS 2 ) was synthesized using a simple one-step solvothermal technique, followed by the formation of few-layer suspension of chemically exfoliated molybdenum disulfide (c-MoS 2 ) in aqueous solution. The c-MoS 2 was introduced into the waterborne polyurethane (WPU) emulsions to obtain the nanocomposite films by a simple blending method. As a comparison, MoS 2 /WPU composite film was prepared by directly blending bulk MoS 2 particles into WPU. The incorporation of chemically exfoliated MoS 2 significantly enhanced the thermal stability and mechanical properties of WPU film: with the incorporation of 4 wt% of c-MoS 2 , the 5% mass loss temperature of WPU nanocomposite film was increased by 30 °C relative to neat WPU; the tensile strength and Young's modulus were increased by 140% and 85%, respectively. Furthermore, the moisture permeability coefficient was reduced by about 37% at a MoS 2 content of 4 wt%. These results demonstrate that such a facile and rapid technique presented herein will provide an effective and promising strategy to design and fabricate high barrier MoS 2 /polymer nanocomposite films. [ABSTRACT FROM AUTHOR]

The introduction of block copolymer with low T g blocks and epoxy host miscible blocks is one of most effective approaches to toughen epoxy thermosets. Nevertheless, this enhancement in toughness is always accompanied by decrease in tensile strength of the resulting materials, which is also extremely important in practical applications. In this work, we demonstrated a new strategy to overcome this challenge by adding the chemically reduced graphene oxide (C-RGO) 1 to a triblock copolymer toughen epoxy system. For epoxy thermoset toughened by 30 wt% PCL-PPC-PCL, 2 the fracture toughness was 1099 J/m 3 and tensile strength was 31.5 MPa, while that of pristine epoxy thermoset is 688 J/m 3 and 80.6 MPa respectively. By introducing 0.25 wt% of C-RGO, the resulting nanocomposite not only maintained high fracture toughness (c.a. 1102 J/m 3 ), but also exhibited significantly increased strength of 51.9 MPa. Moreover, the temperature of 5% thermal weight loss was increased by more than 10 °C compared to the toughened system without C-RGO. Our work provides a simple and feasible approach to prepare epoxy thermosets with balanced toughness, strength and thermal properties. [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]

Surface-modified montmorillonite (mMMT) and graphene nanoplatelets (GNPs), both possessing plate-like structure, were adopted as property enhancers for a blend based on poly(lactic acid) and poly(butylene adipate- co -terephthalate). Unlike mMMT, GNPs contributed to higher stretchability of the solvent-cast films compared to that of the polymer-clay composite films. Fine dispersion of GNPs throughout the polymer host promoted several improved properties of the blend. Compared to the mMMT at identical filler amount, GNPs enhanced thermal stability and water vapor barrier property while decreased light transmittance in controllable fashion by simply tuning the GNP loading content (0.1–1 phr). In contrast, the clay did not show any obvious trend of property enhancement. Thus, GNPs functioned as promising property improver for this selected blend. Finally, the polymer-graphene composite could find further application in conductive coating of metal electrodes. This paper shows the simple preparation of polymer composite films by using fillers without any complicated functionalization. The findings will also benefit further facile processing of engineering composites. [ABSTRACT FROM AUTHOR]

Hyperbranched polymers (HBP6) with polyethylene glycol (PEG) chains were synthesized via bulk polymerization of diepoxide, primary amine, and monoepoxide. Polylactide (PLA) composites, with aluminum trihydroxide (ATH) and HBP6, were prepared via direct melt compounding using a brabender. The limiting oxygen index (LOI) could be raised to 44% for the PLA composite with 29 wt% ATH and 1% HBP6. A UL-94 V-0 rating could be achieved by adding ATH and HBP6 to the PLA matrix. The HBP6 has a lower glass transition temperature ( T g ), approximately −31 °C, and its incorporation as a plasticizer could increase the impact strength of a PLA blend or composite. The elongation at break could be increased from 5% for neat PLA to 83% for the PLA composite with an addition of 10% of HBP6 and 20% ATH. The enhancement of impact strength of the composite was not only attributed to the decrease in T g , but also the dispersion of second-phase HBP6 domains formed by the phase separation. [ABSTRACT FROM AUTHOR]

Based on their extraordinary mechanical, electrical and thermal properties carbon nanotubes (CNT) are attributed as high potential filler material for polymer matrices. Besides the CNT material and functionalization, the properties of the polymer matrix, stabilization additives as well as the production process have a significant influence on the maximum CNT content and the resultant composite properties. Adapted from a modification of commonly used solvent based approaches a production process for high loaded epoxy based composites is presented in this study. In this process high loadings of up to 80 wt% CNTs are embedded in the epoxy composite matrix. The resultant mechanical, electrical and thermal properties are investigated for various CNT types, CNT modification, stabilization and loadings. Moreover, a model for the electric conductivity of CNT reinforced composites above the percolation threshold is presented. This model describes the electric conductivity as a function of the composite structure including CNT content as well as a theoretical value for the number of contacts within such a composite network. [ABSTRACT FROM AUTHOR]

With the electronic device advancing to miniaturization, higher integration and flexibility, flexible polymer composites with high thermal conductivity are desirable for efficient removal of accumulated heat to maintain normal operation of electronics. In this work, a polydimethylsiloxane/boron nitride nanosheets (PDMS/BNNS) foam scaffold was prepared by the sugar-templated method, and the corresponding PDMS/BNNS composites were manufactured with vacuum-assisted PDMS impregnation and curing. The PDMS/BNNS composites exhibit a three-dimensional (3D) BNNS interconnected network with curved BNNS pathways due to the intensive compression during hot-pressing curing, providing thermally conductive network and corresponding prestrains for deformable application. The PDMS/BNNS composites finally can achieve a high thermal conductivity of 7.55 W m−1 K−1 in the in-plane direction and 1.12 W m−1 K−1 in the through-plane direction with 25 vol% BNNS, which represent 153% and 78% increases over the composites prepared by randomly mixing method, respectively. In addition, the composite still maintains superior heat dissipation property under repeated stretching and bending conditions, which indicates a broad and bright application for thermal management in flexible electronic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Based on the rapid development of electronic device performance, heat dissipation has become an urgent problem in packaging materials relating to polymeric composites. Meantime, the severe environmental pollution and energy crisis have also become great problems. Therefore, the development of renewable polymers with high thermal conductivity is a considerable way to reduce the dependence on petroleum-based polymers. Here, we report a convenient method for the preparation of renewable high thermal conductivity composites. Firstly, the stereocomplex crystallites (SCs) granules are prepared through the melt blending of poly(l -lactic acid) (PLLA) and poly(d -lactic acid) (PDLA) at a mass ratio of 1:1. Then, the PLLA/graphene nanoplatelets (PLLA/GNP) composite is coated on the surface of the SC granules by solution blending. Finally, the segregated and double-percolated structures with multiscale SCs form in the PLLA/GNP@SC composites through the compression molding method. The results show that the thermal conductivity of the PLLA/GNP@SC composites are much better than that of the PLLA/GNP composite under the same load of GNPs. The thermal conductivity of the PLLA/GNP@SC composite containing only 2 wt % GNPs reaches 0.96 W m−1K−1, which is 336.4% and 71.4% higher than those of the pure PLLA (0.22 W m−1K−1) and the PLLA/GNP (0.56 W m−1K−1) composite, respectively. The PLLA/GNP@SC composites also exhibit good mechanical properties at high temperatures due to the formed SC microcrystals at the interface between segregated SC granules and continuous PLLA/GNP phase. Moreover, the PLLA/GNP@SC composites also exhibit ultrahigh thermal resistance, flame retardance, and electrical conductivity. This work provides a new way for manufacturing the green multifunctional high thermal conductivity composite. [Display omitted] Poly(l -lactic acid) composites with segregated structure were fabricated. Multiscale stereocomplex crystallites were constructed in the composites. The interfacial adhesion between granules and continuous phase was enhanced. The composites showed high thermal conductivity and thermo-mechanical properties. [ABSTRACT FROM AUTHOR]

The highly thermally conductive yet electrically insulating polymeric materials are exhibiting tremendous potential for thermal management materials. However, the practical application of these materials is restrained by the limited thermal conductivity (TC) and deterioration of mechanical properties. In this work, an ultraflexible polyamide-imide (PAI) film with a sandwich-like structure composed with assembled well-oriented functionalized boron nitride nanosheets (FBN) by facile layer-by-layer solution-coating strategy is constructed. The design of the layered structure and highly oriented arrangement of interconnected FBN (Herman's orientation parameter ƒ up to 0.847) endows the obtained PAI composite film with super-flexibility, ultrahigh in-plane thermal conductivity (λ //), superior thermal transfer capability (ΔT max = 24.4 °C) and excellent electrical insulation performance. The PBP composite film reaches an ultrahigh λ // of 45.7 W m−1 K−1 with only 23 wt% FBN loading and exhibits a remarkable TC enhancement factor over 23 because of the more continuous phonon transfer networks that constructed by interconnected well-oriented FBN which could effectively suppress the phonon scattering. Furthermore, the mechanical properties of the layered composite film (PB4P) exhibit noteworthy enhancement compared with uniform PBN composite film, in which the tensile strength is increased by 110% and toughness enhancement is 329%. Meaningfully, our fabrication strategy has the advantage of simplicity and adaptability for commercial amplification. The composite film developed in this work provides a promising prospect for the thermal management system of modern power electronic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Thermal insulation materials play an important role in energy conservation and the sustainable development of natural resources. Herein, novel silica composite nanofibers (SiO 2 NFs) with closed cell structure and excellent thermal insulation performance were designed and prepared via electrospinning technique using hollow SiO 2 /TiO 2 spheres (HSTSs) as pore-forming agent and infrared shielding agent. The addition of HSTSs broke the continuity of heat transfer pathways inside the NFs and enhanced the infrared thermal radiation shielding performance of SiO 2 NFs, endowed it with ultra-low thermal conductivity and low infrared transmittance. Meanwhile, the materials exhibited good flexibility, high tensile strength, low density and excellent thermal stability, indicating promising application as insulation materials. This research not only provides a novel strategy to prepare porous nanocomposite fibers for thermal insulation, but also offers a new insight for the development of porous materials with multiple functions. [Display omitted] • A novel strategy for constructing porous thermal insulators is reported. • Hollow SiO 2 /TiO 2 spheres broke the heat transfer pathways of the fiber and enhanced its infrared shielding performance. • The obtained SiO 2 composite nanofibers show great potential as thermal insulators in high-temperature. [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]

The uniform dispersion of multi-wall carbon nanotubes (MWNTs) in waterborne polyurethane (WPU) matrix was achieved by in-situ polymerization and latex particles assisted dispersion, endowing the MWNT/WPU composite film with the enhanced tensile strength, elongation at break and thermal stability. Compared with pure WPU, the breaking strength, elongation at break and initial decomposition temperature of the MWNT/WPU composite were increased by 69.6%, 16.4% and 130 °C, respectively. The decomposition amount at 400 °C of MWNT/WPU composite is only about half that of pure WPU. The latex particles assisted dispersion also effectively improved the exposure rate of MWNTs, making it easier for MWNTs to contact the target gas molecules. Increased exposure rate and uniform dispersion of MWNTs, and rich functional groups of WPU improved the gas sensing performance, making the response of the flexible MWNT/WPU to O 3 be 4.1 times of the responses of pure MWNTs. The limit of detection for O 3 reached 38.4 ppb. The enhanced mechanical properties endowed the flexible MWNT/WPU composite with the high bending stability and long-term stability. After one month, the response of the MWNT/WPU was changed by 3% and the responses decreased by no more than 10% after bending 5000 times. [Display omitted] • The uniform dispersion of MWNTs in WPU matrix was achieved by in-situ polymerization and latex particles assisted dispersion. • The evenly dispersed MWNTs endowed the MWNT/WPU composite with the enhanced mechanical and thermal properties. • Increased exposure rate of MWNTs and rich functional groups of WPU improved the gas sensing performance of flexible MWNT/WPU sensor. • The response of flexible MWNT/WPU was changed by 3% after one month and the responses decreased by no more than 10% after bending 5000 times. [ABSTRACT FROM AUTHOR]