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To reach the full potential of polymer dielectrics in advanced electronics and electrified transportation, it calls for efficient operation of high-energy-density dielectric polymers under high voltages over a wide temperature range. Here, the polymer composites consisting of the boron nitride nanosheet/polyetherimide and TiO2 nanorod arrays/polyetherimide layers are reported. The layered composite exhibits a much higher dielectric constant than the current high-temperature dielectric polymers and composites, while simultaneously retaining low dielectric loss at elevated temperatures and high applied fields. Consequently, the layered polymer composite presents much improved capacitive performance than the current dielectric polymers and composites over a temperature range of 25-150 °C. Moreover, the excellent capacitive performance of the layered composite is achieved at an applied field that is about 40% lower than the typical field strength of the current polymer composites with the discharged energy densities of >3 J cm-3 at 150 °C. Remarkable cyclability and dielectric stability are established in the layered polymer nanocomposites. This work addresses the current challenge in the enhancement of the energy densities of high-temperature dielectric polymers and demonstrates an efficient route to dielectric polymeric materials with high energy densities and low loss over a broad temperature range.

A novel compatibilizer tannic grafted poly(12-hydroxy stearate) (TA-g-PHS) was synthesized using tannic and 12-hydroxystearic acid as raw materials through the esterification reaction. The compatibilizer was used to improve the compatibility between polypropylene (PP) and microcrystalline cellulose fibers (MCF). The impact strength and tensile strength of MCF/PP composites modified with the TA-g-PHS were 38.51 kJ/m2 and 30.45 MPa when the content loading of TA-g-PHS is 3 wt% and MCF is 10 wt%, which were improved by 40.5% and 76.9%, respectively, compared to the MCF/PP composites alone. The melt flow rate improved with the addition of TA-g-PHS. And the thermal properties have slightly improved. Moreover, the SEM images of the fracture surfaces display that MCF is relatively well dispersed in the PP matrix by adding TA-g-PHS. It can be inferred that the PP and MCF matrix interfacial bonding was strengthened. POLYM. COMPOS., 2016. © 2016 Society of Plastics Engineers

An efficient method was reported to fabricate boron nitride (BN) nanosheets using a sonication–centrifugation technique in DMF solvent. Then non-covalent functionalization and covalent functionalization of BN nanosheets were performed by octadecylamine (ODA) and hyperbranched aromatic polyamide (HBP), respectively. Then, three different types of epoxy composites were fabricated by incorporation of BN nanosheets, BN-ODA, and BN-HBP. Among all three epoxy composites, the thermal conductivity and dielectric strength of epoxy composites using BN-HBP nanosheets display the highest value, efficiently enhancing to 9.81 W/m K at 50 vol% and 34.8 kV/mm at 2.7 vol% (increase by 4057% and 9.4% compared with the neat epoxy), respectively. The significantly improved thermal conductivity and dielectric strength are attributed to the large surface area, which increases the contact area between nanosheets and nanosheets, as well as enhancement of the interfacial interaction between nanosheets and epoxy matrix. Copyright © 2015 John Wiley & Sons, Ltd.

We reported a facile approach to fabricate graphene nanoplatelets (GNPs)/epoxy composites with a novel blend method. The influence of GNPs on the thermal and electrical properties was investigated. Compounds with different GNPs content (0-8 wt%) were mixed with a Flacktek speedmixer at a speed of 3000 rpm for 5 min. The thermal conductivity of the epoxy composites with 8 wt% GNPs was 1.181 W/m K, which is increased by 627% compared with those of the neat epoxy. It is found that the thermal stability and electrical property also have a certain degree of improvement. Scanning electron microscopy images demonstrate that the structures of the composites have a closed relationship with their properties. In addition, the incorporation of GNPs in epoxy matrix indicated excellent Vickers hardness at the low weight fractions of GNPs. POLYM. COMPOS. 36:556-565, 2015. (c) 2014 Society of Plastics Engineers

Aluminum nitride (AlN) nanoparticles were firstly treated with a silane coupling agent, γ-aminopropyl-triethoxysilane (γ-APS), to introduce amine groups (AlN-APS), then grafting of the hyperbranched aromatic polyamide started from the modified surface (AlN-HBP). The surface modified AlN nanoparticles were characterized by Fourier transform infrared, nuclear magnetic resonance, and thermogravimetric analyzer. Then the nanoparticles with these three different interface structures were selected as reinforcing fillers for epoxy composites. The study reports the influence of interfacial structure of nanoparticles on the morphology and thermal properties of epoxy composites. It was found that the AlN-HBP nanoparticles result in a strong interface and thus the incorporation of the AlN-HBP nanoparticles not only improved the dispersion of the nanoparticles in the epoxy matrix but also enhanced the thermal conductivity, thermal stability, glass transition temperatures, and dynamical thermomechanical properties. Copyright © 2013 John Wiley & Sons, Ltd.

A nanocomposite of Poly(vinylidene fluoride) (PVDF) was prepared with graphene sheets (GSs), which are a novel filler by a solution method. The structure-properties relationships of PVDF/GSs nanocomposites were studied. The results of differential scanning calorimetry and X-ray diffraction show that addition of GSs to the PVDF matrix promotes an α phase to β phase transformation of the polymer crystal. The nanocomposites exhibit significant increases in dynamic mechanical properties and thermal stability compared to the neat PVDF. In addition, the incorporation of GSs in PVDF indicated excellent optical transparency at the lowest weight fractions of GSs and modified wettability of PVDF. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

A novel flame retardant (SPDH) containing phosphorus was synthesized through the reaction of 10-(2, 5-dihydroxyphenyl)-9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-HQ) and synthesized intermediate product 3, 9-dichloro-2, 4, 8, 10-tetraoxa-3, 9-diphosphaspiro(5.5)undecane-3, 9-dioxide (SPDPC). The structure and properties of SPDPC and SPDH were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) spectroscopy and thermogravimetric analysis (TGA). After blending with poly(ethylene-co-vinyl acetate) (EVA), the flame-retardant properties of EVA/SPDH composites were estimated by cone calorimeter, limited oxygen index (LOI) and UL-94 tests, whereas the thermal stabilities were investigated using TGA. The morphological microstructure of the char formed by EVA/SPDH composite after combustion in cone calorimeter was investigated by scanning electron microscopy (SEM). The results indicate that the flame retardant and thermal stability were improved by incorporation of SPDH. The rich foamy char layers were observed from the residues after combustion in a cone calorimeter, which exactly benefits the improvement of thermal stability and flame retardant property of materials. Copyright © 2010 John Wiley & Sons, Ltd.

In this work, epoxy/tatania/silica ternary hybrid materials with covalent bonding interaction between polymer and inorganic phases have been prepared using titania/silica mesoporous particles, which were prepared by the sol–gel process from tetraethoxysilane (TEOS) and titanium tetra-butyltitanate (TBT) as precursors. The obtained hybrid particles were characterized by Nitrogen physisorption, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), etc. From the experimental results, the glass transition temperature (Tg) increases and the modulus of the modified systems decreases by adding mesoporous SiO2–TiO2 particles to epoxy matrix, the impact strength and tensile strength of the hybrid materials increase by 53.5% and 14% when the SiO2–TiO2 content is up to 3 wt %. The morphological, structure of the impact fracture surface and the surface of the hybrid were observed by scanning electron microscope (SEM) and atomic force microscopy (AFM), respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

To improve the performance of unsaturated polyester (UP) under cold-heat alternate temperature, self-synthesized reactive thermotropic liquid crystalline polymer (TLCP)-methacryloyl copolymer (LCMC), UP, and glass fiber (GF) hybrid composites was prepared by molding technology. The apparent activation energy and crystal behavior analysis of LCMC/UP blends were investigated by Differential scanning calorimetry and X-ray diffraction (XRD), respectively, the results showed that the addition of LCMC can reduce apparent activation energy and accelerate the curing reaction of UP, the XRD analysis indicated that the crystal phase of LCMC still exist in the blends after blending with UP. The effect of LCMC content on the properties of LCMC/UP/GF hybrid composites such as impact strength, bending strength, and ring-on-block wear were also investigated through static mechanical tests and wear tests. The mechanical properties of hybrid composites increased significantly because of the addition of LCMC. The wear tests showed that LCMC can improve the wear resistance of the UP/GF/LCMC hybrid composites even though the content of LCMC was at a relatively low level (5–7.5 wt %). This makes it possible to develop novel kind of UP-based materials with good wear resistance for various applications. The Worn surface was observed by scanning electron microscopy (SEM) and the mechanism for the improvement is discussed in this paper. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3899–3906, 2007

Ultra high molecular weight polyethylene/alumina (UPE/Al2O3) microcomposites with high loading micro alumina (Al2O3, 20 to 100 phr) were prepared by casting method. The composites were thermal treated (cooled slowly) and then the thermal properties were studied at temperatures from 25 to 125°C. Thermogravimetric analysis (TGA) and scanning electron microscopic (SEM) proves the homodispersion of Al2O3 microparticles in UPE. TGA indicates that the temperature of 5% weight loss of UPE/Al2O3 (100 phr) composite is 467.0°C, 10.5°C higher than that of pure UPE. Differential scanning calorimetry (DSC) shows that the melting point and the real degree of crystal (Xrc) of treated UPE/Al2O3 composite (100 phr) are 141.4°C and 65.7%, respectively, all higher than that of untreated composite, which can be described by crystal bridge mechanism. The density of the composite is also be enhanced because of crystal volume shrinkage induced by thermal treatment. The thermal conductivity of the treated UPE/Al2O3 composite (100 phr) is 1.920 W (m K)−1 at 25°C, 23.6% higher than that of the untreated composite. Crystal bridge thermal conduction mechanism is proposed. The thermal conductivity of UPE/Al2O3 composite has some dependency on the increasing Al2O3 content and also thermal treatment. These results can give some advice to design formulations for practical applications in pipe area and other wear area. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40528.