Preparation and optical properties of transparent epoxy composites containing ZnO nanoparticles

Polymer nanocomposites are usually made by incorporating dried nanoparticles into polymer matrices. This way not only leads to easy aggregation of nanoparticles but also readily brings about opaqueness for nanocomposites based on functionally transparent polymers. In this letter, transparent ZnO/epoxy nanocomposites with high‐UV shielding efficiency were prepared via two simple steps: first, in situ preparation of zinc hydroxide (Zn(OH)₂)/epoxy from the reaction of aqueous zinc acetate (Zn(Ac)₂·2H₂O) and sodium hydroxide (NaOH) at 30°C in the presence of high‐viscosity epoxy resin; second, thermal treatment of the as‐prepared Zn(OH)₂/epoxy hybrid into ZnO/epoxy composites. Optical properties of the resultant ZnO/epoxy nanocomposites were studied using an ultraviolet–visible (UV–vis) spectrophotometer. The nanocomposites containing a very low content of ZnO nanoparticles (0.06 wt %) possessed the optimal optical properties, namely high‐visible light transparency and high‐UV light shielding efficiency. Consequently, the as‐prepared ZnO/epoxy nanocomposites are promising for use as novel packaging materials in lighting emitting diodes technology. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis of EP‐POSS mixture and the properties of EP‐POSS/epoxy,SiO2/epoxy,and SiO2/EP‐POSS/epoxy nanocomposite

The hybrid material of EP‐POSS mixture was synthesized by the hydrolysis and condensation of (γ‐glycidoxypropyl) trimethoxysilane. A series of binary systems of EP‐POSS/epoxy blends, epoxy resin modified by silica nanoparticles (SiO₂/epoxy), and ternary system of SiO₂/EP‐POSS/epoxy nanocomposite were prepared. The dispersion of SiO₂ in the matrices was evidenced by transmission electron micrograph, and the mechanical properties, that is, flexural strength, flexural modulus, and impact strength were examined for EP‐POSS/epoxy blends, SiO₂/epoxy, and SiO₂/EP‐POSS/epoxy, respectively. The fractured surface of the impact samples was observed by scanning electron micrograph. Thermogravimetry analysis were applied to investigate the different thermal stabilities of the binary system and ternary system by introducing EP‐POSS and SiO₂ to epoxy resin. The results showed that the impact strength, flexural strength, and modulus of the SiO₂/EP‐POSS/epoxy system increased around by 57.9, 14.1, and 44.0% compared with the pure epoxy resin, T_i, T_max and the residues of the ternary system were 387°C, 426°C, and 25.2%, increased remarkably by 20°C, 11°C and 101.6% in contrast to the pure epoxy resin, which was also higher than the binary systems. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 810‐819, 2013     

Mechanical,thermomechanical, and creep performance of CNT embedded epoxy at elevated temperatures: An emphasis on the role of carboxyl functionalization

In contrast to polymeric composites, the role of interface/interphase has been widely acknowledged to govern their overall properties and performance. Environmental temperature has substantial effects on the interfacial durability of polymer nanocomposites. In this regard, present investigation has been carried out to study the mechanical performance of pristine (UCNT) and carboxylic functionalized CNT (FCNT) embedded epoxy nanocomposites under different elevated temperatures. Higher flexural strength and modulus of FCNT‐EP nanocomposite were recorded over UCNT‐EP and neat epoxy at room temperature environment. Flexural testing at elevated temperatures revealed a higher rate of strength degradation in polymer nanocomposites over neat epoxy. Postfailure analysis of specimens has been conducted to understand the alteration in failure micro‐mechanisms upon UCNTs and FCNTs addition in epoxy. Variation in viscoelastic properties with temperature has been studied from dynamic mechanical thermal analysis and significant reduction in glass transition temperature (T_g) is observed for nanocomposites. In the studied temperature and stress combinations, FCNT‐EP nanocomposites exhibited better creep resistance over UCNT‐EP and neat epoxy. Room temperature strengthening, elevated temperature strength degradations, improved creep resistance and reduction in T_g in nanocomposites over neat polymer have been discussed in terms of dynamic nature and gradient structure of CNT/epoxy interphase. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44851.     

Effects of amino‐functionalized carbon nanotubes on the properties of amine‐terminated butadiene–acrylonitrile rubber‐toughened epoxy resins

Amino‐functionalized multiwalled carbon nanotubes (MWCNT‐NH₂s) as nanofillers were incorporated into diglycidyl ether of bisphenol A (DGEBA) toughened with amine‐terminated butadiene–acrylonitrile (ATBN). The curing kinetics, glass‐transition temperature (T_g), thermal stability, mechanical properties, and morphology of DGEBA/ATBN/MWCNT‐NH₂ nanocomposites were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis, a universal test machine, and scanning electron microscopy. DSC dynamic kinetic studies showed that the addition of MWCNT‐NH₂s accelerated the curing reaction of the ATBN‐toughened epoxy resin. DSC results revealed that the T_g of the rubber‐toughened epoxy nanocomposites decreased nearly 10°C with 2 wt % MWCNT‐NH₂s. The thermogravimetric results show that the addition of MWCNT‐NH₂s enhanced the thermal stability of the ATBN‐toughened epoxy resin. The tensile strength, flexural strength, and flexural modulus of the DGEBA/ATBN/MWCNT‐NH₂ nanocomposites increased increasing MWCNT‐NH₂ contents, whereas the addition of the MWCNT‐NH₂s slightly decreased the elongation at break of the rubber‐toughened epoxy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40472.     

Compatibilized the thermosetting blend of epoxy and redistributed low molecular weight poly(phenylene oxide) with triallylisocyanurate

Vinyl‐containing low molecular weight PPO (R‐PPO) was prepared by redistribution reaction between commercially available PPO and maleic anhydride (MAH) and used to modify epoxy resin (EP). TAIC was furthermore used as the compatibilizer of EP/R‐PPO system in this study. The curing reaction kinetics, compatibility of the components, morphology, dielectric properties and impact toughness of EP/R‐PPO/TAIC systems were investigated. The experimental results showed that the cured EP/R‐PPO (80/20) system had two phase morphology, the R‐PPO particles of about 1 µm were evenly dispersed in continuous epoxy phase. After addition of TAIC, the EP/R‐PPO/TAIC systems were transferred to single phase. The glass transition temperature of cured EP/R‐PPO/TAIC (80/20/10) system was 150.2 °C. With the increase of TAIC content, the dielectric constant (D_k) and dissipation factor (D_f) of cured EP/R‐PPO/TAIC systems were both reduced. The dielectric constant and dissipation factor at 1MHz of cured EP/R‐PPO/TAIC (80/20/10) system was 2.72 and 0.006, respectively. Compared with those of cured EP/R‐PPO (80/20) system (D_k = 2.82 and D_f = 0.0078 at 1MHz), they decreased by 3.6% and 23.1%, respectively. With the increase of TAIC content, the impact strength of cured EP/R‐PPO (80/20) system increased and reached to a maximum value (2.41 kJ/m²) when TAIC content was 10 phr, which was improved by 23% compared with that of cured EP/R‐PPO (80/20) system (1.96 kJ/m²). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43293.     

In situ solvothermal synthesis and characterization of transparent epoxy/TiO2 nanocomposites

A solvothermal process was developed to in situ prepare epoxy (EP)/TiO₂ hybrid precursors. The chemical structure of samples was confirmed by X-ray and Fourier transformed infrared spectroscopy. Field emission scanning electron microscope micrographs of cured EP/TiO₂ hybrid composites showed that well-dispersed TiO₂ nanoparticles were successfully in situ formed in epoxy matrix through the solvothermal process. The thermogravimetic analysis, DSC, and gel content measurements showed that EP/TiO₂ hybrid precursors were fully cured with the glass transition temperature decreasing gradually. The effect of TiO₂ contents on optical and surface properties was investigated in detail. The results indicated that epoxy/TiO₂ nanocomposites exhibited excellent UV shielding effect and high visible light transparency. The contact angle of EP/TiO₂ nanocomposites, when the content of silane-coupling agent (KH560) was 5 g and the content of tetrabutyl titanate (TBT) was 3 g, can reach as high as 101°, which was 36° higher than that of pure EP, representing for the increase of hydrophobicity. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effects of epoxy resin‐modified zinc‐ion‐coated nanosilica on structural,thermal and dynamic mechanical properties of propylene‐ethylene copolymer

This paper reports a comparative study of propylene–ethylene copolymer (EP) nanocomposites synthesized using zinc‐ion (Zn²⁺)‐coated nanosilica (ZNS) and the diglycidyl ether of bisphenol‐A (DGEBA, an epoxy resin)‐modified zinc‐ion‐coated nanosilica (EZNS) as nanofillers. These nanocomposites were prepared using the ‘melt mixing’ method at a constant loading level of 2.5 wt%. This loading level is much lower than that used for fillers in conventional composites. The EP nanocomposites were characterized using wide‐angle X‐ray diffractometer (WAXD), a thermo gravimetric analyzer (TGA), a differential scanning calorimeter (DSC), a dynamic mechanical analyzer (DMA) and scanning electron microscopy (SEM). DMA results showed a higher storage modulus for EP‐epoxy‐modified Zn²⁺‐coated nanosilica nanocomposite (EP‐EZNS) with respect to EP and EP‐Zn²⁺‐coated nanosilica nanocomposite (EP‐ZNS). In addition, TGA thermograms showed an increase in degradation temperature of EP in the presence of EZNS. Copyright © 2006 Society of Chemical Industry     

Evaluation of PP/EPDM nanocomposites filled with SiO2, TiO2 and ZnO nanofillers as thermoplastic elastomeric insulators

Abstract

Thermoplastic elastomer, which has important characteristics for cable insulation, was developed by melt blending of polypropylene (PP) with ethylene propylene diene monomer (EPDM) at various blend ratios together with SiO₂, TiO₂ and ZnO nanofillers at fixed loading of 2 vol.-%. The influence of EPDM content and the presence of nanofillers in the blend on burning rate, hydrophobicity and dielectric breakdown strength were investigated. Burning rate of PP/EPDM/ZnO was significantly reduced, implying that there was an improvement in fire retardancy with the addition of ZnO nanofillers in the polymer blend. Both SiO₂ and ZnO filled system showed an improvement in hydrophobicity. Furthermore, dielectric breakdown strength showed higher value in EPDM rich blends. In addition, the presence of nanofillers deteriorated the dielectric breakdown strength of PP/EPDM nanocomposites.     

Fabrication and characterization of vapor grown carbon nanofiber/epoxy magnetic nanocomposites

Co₃O₄ nanoparticle‐decorated vapor‐grown carbon nanofiber (VGCNF) hybrid materials were successfully synthesized and served as nanofillers for preparing magnetic epoxy (EP) nanocomposites. The Co₃O₄‐decorated VGCNF (Co₃O₄‐VGCNF) and Co₃O₄‐VGCNF/EP nanocomposites were systematically and explicitly investigated by combined analytical techniques. The composition and phase structure of Co₃O₄‐VGCNF hybrid materials were characterized by Fourier transform infrared spectroscopy and X‐ray diffraction analyses. The morphology of Co₃O₄ was investigated using field‐emission scanning electronic microscopy (FE‐SEM). Results revealed the presence of Co₃O₄ nanoparticles firmly immobilized on VGCNF sidewalls. The tensile mechanical, thermomechanical, and magnetic properties of Co₃O₄‐VGCNF/EP nanocomposites were also investigated in detail. Results indicated that the tensile strength of Co₃O₄‐VGCNF/EP nanocomposites (filler = 0.5 wt%) improved by 44.6% compared with that of raw VGCNF/EP nanocomposites (filler = 0.5 wt%). Magnetization measurements revealed that Co₃O₄‐VGCNF/EP nanocomposites exhibited ferromagnetic behavior, and the saturation magnetization and coercivity of the nanocomposites with 2 wt% of Co₃O₄‐VGCNF were 0.055 emu g⁻¹ and 0.75 kOe, respectively. POLYM. COMPOS., 37:1728–1734, 2016. © 2014 Society of Plastics Engineers     

Morphology and thermal/mechanical properties of alkyl‐imidazolium‐treated rectorite/epoxy nanocomposites

A novel organic rectorite (OREC) was prepared by treating the natural sodium‐rectorite (Na‐REC) with ionic liquid 1‐hexadecyl‐3‐methylimidazolium bromide ([C₁₆mim]Br). X‐ray diffraction (XRD) analysis showed that the interlayer spacing of the OREC was expanded from 2.23nm to 3.14nm. Furthermore, two types of OREC/epoxy nanocomposites were prepared by using epoxy resin (EP) as matrix, 2‐ethyl‐4‐methylimidazole (2‐E‐4‐MI) and tung oil anhydride (TOA) as curing agents, respectively. XRD and transmission electron microscope (TEM) analysis showed that the intercalated nanocomposite was obtained with addition of the curing agent 2‐E‐4‐MI, and the exfoliated nanocomposite was obtained with addition of the curing agent TOA when the OREC content was less than 2 wt %. For the exfoliated nanocomposite, the mechanical and thermal property tests indicated that it had the highest improvement when OREC content was 2 wt% in EP. Compared to pure EP, 60.3% improvement in tensile strength, 26.7% improvement in bending strength, 34% improvement in bending modulus, 14°C improvement in thermal decomposition temperature (T_d) and 5.7°C improvement in glass transition temperature (T_g) were achieved. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Microwave processing of SiC nanoparticles infused polymer composites: Comparison of thermal and mechanical properties

The goal of this study is to compare thermal and mechanical properties of an epoxy resin system reinforced with SiC nanoparticles using both conventional thermal curing and microwave irradiation techniques. The microwave curing technique has shown potential benefits in processing polymeric nanocomposites by reducing the curing time without compromising the thermo‐mechanical performances of the materials. It was observed from this investigation that, the curing time was drastically reduced to ～30 min for microwave curing instead of 12 h room temperature curing with additional 6 h post curing at 75°C. Ductile behavior was more pronounced for microwave curing technique while thermal curing showed brittle like behavior as revealed from flexural test. The maximum strain to failure was increased by 25–40% for microwave‐cured nanocomposites over the room temperature cured nanocomposites for the same loading of nanofillers. The glass transition temperature (T_g) also increased by ～14°C while curing under microwave irradiation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41708.     

Microwave responsive epoxy nanocomposites reinforced by carbon nanomaterials of different dimensions

This study fabricated nanocomposites consisting of epoxy‐based shape memory polymer (ESMP) matrix and carbon nanofillers. The nanofillers include zero‐dimensional carbon black, one‐dimensional multiwalled carbon nanotubes, two‐dimensional (2D) graphene nanoplatelets, and three‐dimensional (3D) functionalized graphene sheets, which are all efficient microwave‐absorbing materials that can transform microwaves into heat energy. As a result, the temperatures of the nanocomposites increased more rapidly than pristine ESMP in microwaves. The functionalized graphene sheets were found to transform the microwaves into heat more efficiently than the other nanofillers. Possible microwave propagation paths in the nanocomposites were proposed. Moreover, the nanocomposites displayed significantly higher mechanical strengths than pristine ESMP. The low cost and strong nanocomposites with fast microwave responses may be applied as actuators or deployable devices in medical treatments. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45676.     

Synthesis,characterization, and thermo mechanical properties of siloxane‐modified epoxy‐based nano composite

In this study, polymer hybrid composites were synthesized by sol‐gel process. 3‐Amino‐propyltrimethoxysilane [APTMS)/γ‐Glycidoxypropyl trimethoxy‐silane (GPTMS); (4, 4′‐Methylene‐dianiline (DDM)] and 1,4‐Bis(trimethoxysilylethyl) benzene (BTB) were added to DGEBA type epoxy resin for anticipated to exhibit excellent thermal stability. Boron trifluoride monoethylamine (BF₃MEA) was used as catalyst. The structure of nanocomposites was characterized by attenuated total reflectance (ATR) and solid‐state ²⁹Si NMR which suggest EP‐APTMS‐BTB/EP‐GPTMS‐BTB possesses T³; T¹–T⁰, and T¹ structures when the BTB content was lower than 10 wt % and higher 20 wt %, respectively. BF₃MEA was proved to be an effective catalyst for the sol‐gel reaction of APTMS, but it could not promote for GPTMS. From TEM microphotographs, EP‐APTMS‐BTB (10 wt %) possesses a dense inorganic structure (particle size around 5–15 nm) compare with the loose inorganic structure of EP‐GPTM‐/BTB (10 wt %). DSC, TGA were use to analyze the thermal properties of the nanocomposites and DMA was used to analyze the dynamic mechanical properties of hybrid composites. The T_gs of all nanocomposites decreased with the increasing BTB content. A system with BTB content lower than 10 wt % showed good dynamic mechanical property and thermal stability (Td₅ increased from 336°C to 371°C, char yield increased from 27.4 to 30.2%). The structure of inorganic network affects the Td₅ and dynamic mechanical properties of composite. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40984.     

Properties of nanofillers/crosslinked polyethylene composites for cable insulation

In this work, we report the effect of nanofillers and filler loading on mechanical, physical, dielectric, and thermal properties of the crosslinked polyethylene (XLPE) matrix. XLPE filled with 0.5–2% of zinc oxide (ZnO), aluminium oxide (Al₂O₃), and organoclay (OMMT) nanofillers prepared by melt mixing with a single screw extruder followed by hot press moulding. Nanocomposites were tested as per ASTM standard methods and characterized with tensile test, water absorption, linear rate of burning, dielectric breakdown strength, and thermal stability. Scanning electron microscopy (SEM) was used to examine the surface morphology of the nanocomposites. The results showed that addition of nanofillers improved tensile strength, elongation at break, Young's modulus, burning rate, dielectric breakdown strength, and decomposition temperature. However, water absorption increased with time due to the hydrophilic properties of nanofillers. In general, based on the properties measured Al₂O₃ exhibits the highest properties than those of ZnO and OMMT nanofillers. Addition of 1.5% of Al₂O₃ in XLPE matrix has led to the improvement in tensile strength, elongation at break, Young's modulus, burning rate, and dielectric breakdown strength as compared to the unfilled polymer. J. VINYL ADDIT. TECHNOL., 25:E147–E154, 2019. © 2018 Society of Plastics Engineers     

Functionalized graphene sheets‐epoxy based nanocomposite for cryotank composite application

Multifunctional high performance functionalized graphene sheets (FGSs) based epoxy nanocomposites were investigated to understand the feasibility that these FGSs‐epoxy nanocomposites can be applied to cryotank composite applications. The FGSs were successfully synthesized from graphite flakes through preparing graphite oxides by oxidizing graphite flakes first and next, thermally exfoliating the formed graphite oxides. These high performance FGSs were next incorporated into epoxy matrix resin system to generate the uniformly dispersed FGSs reinforced epoxy nanocomposites. The resultant FGSs‐epoxy nanocomposites significantly enhanced resin strength and toughness about 30–80% and 200–700% at room and low temperatures of −130°C, respectively, and reduced the coefficient of thermal expansion (CTE) of polymer resin at both below and above T_g about 25% at loading of 1.6 wt% FGSs, and increased T_g of polymer resin about 8°C at low loading of 0.4 wt% FGSs without deteriorating their good processability. We found that these significantly improved properties of FGSs‐reinforced epoxy nanocomposite were closely associated with high surface area and wrinkled structure of the FGSs. The further optimization will result the high performance FGSs‐epoxy nanocomposite suitable for use in the next generation multifunctional cryotank carbon fiber reinforced polymer (CFRP) composite applications, where better microcrack resistance and mechanical and dimensional stability are needed. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Synthesis,characterization and properties of organoclay‐modified polyurethane/epoxy interpenetrating polymer network nanocomposites

organoclay‐modified polyurethane/epoxy interpenetrating network nanocomposites (oM‐PU/EP nanocomposites) were prepared by adding organophilic montmorillonite (oMMT) to interpenetrating polymer networks (IPNs) of polyurethane and epoxy resin (PU/EP) which had been prepared by a sequential polymerization technique. Wide‐angle X‐ray diffraction (WAXD) and transmission electronic microscopy (TEM) analysis showed that the interpenetrating process of PU and EP improved the exfoliation and dispersion degree of oMMT. The effects of the NCO/OH ratio (isocyanate index), the weight ratio of PU/EP and oMMT content on the phase structure and the mechanical properties of the oM‐PU/EP nanocomposites were studied by tensile testing and scanning electronic microscopy (SEM). Water absorption tests showed that the PU/EP interpenetrating networks and oMMT had synergistic effects on improvement in the water resistance of the oM‐PU/EP nanocomposites. Differential scanning calorimetry (DSC) analysis showed that PU was compatible with EP and that the glass transition temperature (T_g) of the oM‐PU/EP nanocomposites increased with the oMMT content up to 3 wt%, and then decreased with further increasing oMMT content. The thermal stability of these nanocomposites with various oMMT contents was studied by thermogravimetric analysis (TGA), and the mechanism of thermal stability improvement was discussed according to the experimental results. Copyright © 2005 Society of Chemical Industry     

High‐performance flexible epoxy/ZnO nanocomposites with enhanced mechanical and thermal properties

Flexible epoxy/ZnO nanocomposites were prepared using different loadings of ZnO nanoparticles (NPs) and nanotubes (NTs) via in situ curing of epoxy with polyoxyethylene diamines (ED₆₀₀). ZnO precursor was synthesized via precipitation method and ZnO NPs with an average size of 25 nm were used in the preparation of the nanocomposites. ZnO NTs with an average outer diameter, length of 200 nm and 2.4 µm respectively, were prepared by the wet method (hydrothermal method). The morphology, structure, and composition of the nanocomposites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), and thermo‐gravimetric analysis (TGA). The effect of morphology and content of nano‐ZnO materials on the thermal and mechanical properties of flexible epoxy was studied. In addition, the hardness and indentation depth were calculated by means of nanoindentation. Results showed that the mechanical and thermal properties of flexible epoxy were enhanced by incorporation of ZnO nanostructure into the polymer matrix. POLYM. ENG. SCI., 57:932–946, 2017. © 2016 Society of Plastics Engineers     

Effect of poly(etherimide) chemical structures on the properties of epoxy/poly(etherimide) blends and their carbon fiber‐reinforced composites

Poly(etherimide)s (PEIs) with different chemical structures were synthesized and characterized, which were employed to toughen epoxy resins (EP/PEI) and carbon fiber‐reinforced epoxy composites (CF/EP/PEI). Experimental results revealed that the introduction of the fluorinated groups and meta linkages could help to improve the melt processability of EP/PEI resins. The EP/PEI resins showed obviously improved mechanical properties including tensile strength of 89.2 MPa, elongation at break of 4.7% and flexural strength of 144.2 MPa, and good thermal properties including glass transition temperature (T_g) of 211°C and initial decomposition temperature (T_d) of 366°C. Moreover, CF/EP/PEI‐1 and CF/EP/PEI‐4 composites showed significantly improved toughness with impact toughness of 13.8 and 15.5 J/cm², respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Electrical ac and dc behavior of epoxy nanocomposites containing graphene oxide

This article deals with the investigation of electrical properties of epoxy‐based nanocomposites containing graphene oxide nanofillers dispersed in the polymer matrix through two‐phase extraction. Broadband dielectric spectroscopy and dc electrical conductivity as a function of electric field have been evaluated in specimens containing up to 0.5 wt % of nanofiller. Nanocomposites containing pristine graphene oxide do not show significant changes of electrical properties. On the contrary, the same materials after a proper thermal treatment at 135°C, able to provoke the in situ reduction of graphene oxide, exhibit higher permittivity and electrical conductivity, without showing large decrease of breakdown voltage. Moreover, a nonlinear behavior of the electrical conductivity is observed in the range of electric fields investigated, i.e. 2–30 kV mm^?1. A new relaxation phenomenon with a very low temperature dependence is also evidenced at high frequency in reduced graphene oxide composites, likely associated to induced polarization of electrically conductive nanoparticles. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41923.     

Low dielectric and high thermal conductivity epoxy nanocomposites filled with NH2‐POSS/n‐BN hybrid fillers

Hybrid fillers of mono‐amine polyhedral oligomeric silsesquioxane/nanosized boron nitride (NH₂‐POSS/n‐BN) were performed to fabricate NH₂‐POSS/n‐BN/epoxy nanocomposites. Results revealed that the dielectric constant and dielectric loss values were decreased with the increasing addition of NH₂‐POSS obviously, but increased with the increasing addition of BN fillers. For a given loading of NH₂‐POSS (5 wt %), the thermal conductivities of NH₂‐POSS/n‐BN/epoxy nanocomposites were improved with the increasing addition of n‐BN fillers, and the thermal conductivity of the nanocomposites was 1.28 W/mK with 20 wt % n‐BN fillers. Meantime, the thermal stability of the NH₂‐POSS/n‐BN/epoxy nanocomposites was also increased with the increasing addition of n‐BN fillers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41951.