高韧性绝缘环氧基复合材料的研制

采用聚砜改性环氧树脂为基体,通过高温模压成型法制备环氧树脂/玻纤/BN复合材料.探讨了BN用量对复合材料力学性能、电性能和热性能的影响.结果表明,当BN用量为10wt％时,复合材料的力学性能较佳.电阻率随着BN用量增加,呈下降趋势.通过DSC和TGA综合分析表明,聚砜的加入提高了树脂基体的热稳定性能,随BN用量增加,复...     

Improving the performance of carbon/graphite composites through the synergistic effect of electrostatic self-assembled carbon nanotubes and nano carbon black

Superior performance fillers are considered as an effective means to enhance the performance of carbon/graphite composites. However, poor interfacial properties and incomplete filler networks limit the performance enhancement of the composites. In this study, a new method was proposed to weaken this impact through the synergistic effect of the electrostatic self-assembly of nano carbon black (NCB) onto carbon nanotubes (CNTs). The results showed that the synergistic effect between NCB and the CNTs significantly improved the mechanical and electrical properties of the composites. NCB reduces the porosity of the composites and increases the interaction between the CNTs and matrix. The compressive strength of the composite was 143.2 Mpa, and the flexural strength was 46.3 MPa, which is 210% higher than that of the pristine carbon/graphite composites. Moreover, NCB and CNTs form a globally connected synergistic network in the carbon skeleton. Composites filled with CNTs/NCB exhibited the lowest resistivity and highest thermal conductivity, with a resistance that was 42% lower than that of pristine carbon/graphite composites at 44.8 μΩ m. All of these results suggest that the synergistic effect of CNTs/NCB show great potential to improve the performance of carbon/graphite composites.     

耐高温高导热环氧树脂／玻纤／BN复合材料的制备

以4,4-二氨基二苯砜（DDS）和内亚甲基四氢邻苯二甲酸酐（NA）为复配固化剂,采用高温模压成型法制备耐高温高导热环氧树脂／玻纤／氮化硼（BN）复合材料。探讨了BN用量和偶联剂处理对复合材料冲击强度、导热性能和电阻率的影响。结果表明：当nDDS：nNA=3：1时,复合材料的耐热性能最佳。当BN质量分数为8％时,复合材料的冲击强度最高;导热性能随BN用量的增加而增加,当BN用量为15％时,热导率为0．7560W／（mk）,此时复合材料仍保持较高的体积、表面电阻率;当BN填充量为一定值时,偶联剂处理使冲击强度和导热性能得到进一步提高。     

Effect of the filler structure of carbon nanomaterials on the electrical,thermal, and rheological properties of epoxy composites

Carbon nanotubes (CNTs) and graphene nanosheets (GNSs) were used as fillers in epoxy composites with the aim of increasing the electrical and thermal conductivities of the composites. The filling of pristine CNTs produced the highest electrical conductivity (σ), whereas a high CNT functionalization and the two‐dimensional planar structure of GNSs were promising for improving the thermal conductivity. A combination of CNTs and GNSs exploited the advantages of both. When the CNT fraction was larger than 50 wt %, a higher σ was obtained. When a small amount of functionalized CNTs was added to the GNSs, the thermal conductivity was also increased. The rheological measurements revealed the lowest complex viscosity for the GNS filling and showed the exciting advantages of an easy processing. As a result, the mixed filling also exhibited a much lower viscosity than the pure CNT fillings. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of CNT decoration with silver nanoparticles on electrical conductivity of CNT-polymer composites

A simple approach to decorate carbon nanotube (CNT) with silver nanoparticles (Ag-NPs) was developed to enhance the electrical conductivity of CNT. CNTs were functionalized using ball milling in the presence of ammonium bicarbonate, followed by reduction of silver ions in N, N-dimethylformamide, producing silver decorated CNTs (Ag@CNTs). The Ag@CNTs were employed as conducting filler in epoxy resin to fabricate electrically conducting polymer composites. The electrical, thermal and mechanical properties of the composites were measured and compared with those containing pristine and functionalized CNTs. It was found that when pH was about six, highly dispersed Ag-NPs can be decorated on functionalized CNTs. The electrical conductivity of composites containing 0.10 wt% of Ag@CNTs was more than four orders of magnitude higher than those containing same content of pristine and functionalized CNTs, confirming the advantage of the Ag@CNTs as effective conducting filler. The ameliorating effect of improved electrical conductivity was not at the expense of thermal or mechanical properties.     

碳纳米管增强环氧／石墨复合材料的制备与性能研究

采用粉末冶金法制备了碳纳米管增强环氧／石墨复合材料,并研究了酸洗处理对复合材料弯曲强度、硬度和导电性能的影响。结果表明：与未处理碳纳米管相比,酸处理的碳纳米管增加了环氧／石墨复合材料的弯曲强度和硬度,降低了电阻率。酸处理的碳纳米管增强环氧／石墨复合材料的弯曲强度达到21．9MPa,比未添加碳纳米管时提高了近22％;同时复合材料的硬度达到最大值21．7HS,比未添加碳纳米管时提高了近10％;复合材料的电阻率达到了最小值45036μΩ·cm,比未添加碳纳米管时复合材料的电阻率降低了近17％。     

BN／Al2O3／环氧树脂导热复合材料的制备与性能

分别采用氮化硼（BN）、氧化铝（Al2O3）和复配BN／Al2O3作为导热填料制备环氧树脂导热复合材料。结果表明,环氧树脂热导率随导热填料用量的增加而增大;同等用量下,BN／Al2O3／环氧树脂复合材料的导热性能均优于BN／环氧树脂和Al2O3／环氧树脂。当BN／Al2O3质量分4~50％[m（BN）／m（Al2O3）=3／1J,复合材料热导率为08194W／mK。此外,随BN／Al2O3用量的增加,环氧树脂的介电常数和介电损耗角正切增加,而弯曲强度和冲击强度则先增加后降低。     

环氧树脂/氧化锌晶须/氮化硼导热绝缘复合材料的研究

以环氧树(脂EP)为基体,分别以氧化锌晶(须ZnOw)和ZnOw/氮化硼(BN)混合物为导热填料,制备了EP导热绝缘复合材料。研究了填料含量对复合材料导热性能、电绝缘性能及力学性能的影响,并利用扫描电镜对复合材料的断面形貌进行了观察。结果表明:随着导热填料含量的增大,复合材料的导热系数和介电常数增大,体积电阻率下降,而拉伸强度呈先增大后减小的趋势;在填料含量相同的情况下,EP/ZnOw/BN复合材料比EP/ZnOw复合材料具有更好的导热性能;当填料体积分数为15%时,EP/ZnOw/BN复合材料的热导率为1.06W/(mK)而,EP/ZnOw复合材料的热导率仅为0.98W/(mK)。     

Preparation and properties of epoxy/BN highly thermal conductive composites reinforced with SiC whisker

A simple method is reported to increase the thermal conductivity and improve the poor mechanical properties caused by high filler loadings of epoxy composites, simultaneously. Epoxy composites were prepared with micro‐boron nitride (BN) and silicon carbon whisker (SiCw) chemically treated by 3‐aminopropyltriethoxysilane (KH550) and 3‐glycidyloxypropyltrimethoxysilane (KH560), respectively. Effects of surface modification of BN particles on the thermal conductivity and flexural strength of epoxy/BN composites were investigated. About 3% SiCw particles grafted with KH560 were incorporated into composites with BN grafted with KH550, which led to about 13.8–17.8% increase of the flexural strength as well as a marginal improvement of the thermal conductivity of composites, and they possessed good dielectric properties. In addition, dynamic mechanical analysis results showed that the storage modulus of composites increased significantly with the addition of fillers, while the glass transition temperature exhibited a slight decrease. POLYM. COMPOS., 37:2611–2621, 2016. © 2015 Society of Plastics Engineers     

Thermal conductivity and mechanical properties of polyimide composites with mixed fillers of BN flakes and SiC@SiO2 whiskers

Polyimide (PI) composites with mixed fillers of BN flakes and SiC whiskers exhibit enhanced thermal conductivity and mechanical properties. In order to improve dispersion and interaction of these mixed fillers within the PI matrix, BN flakes were modified by a titanate coupling agent while SiC whiskers were oxidized at 750°C for 60 minutes to produce SiC@SiO₂ followed by silane coupling agent modification. PI composites reached a maximum thermal conductivity of 0.95 W/m K at volume fraction of mixed fillers of 27.6 vol% when the weight ratio of BN flakes to SiC@SiO₂ whiskers was 1:4. The enhanced thermal conductivity is likely attributed to the formation of heat conductive networks constructed by BN flakes and SiC@SiO₂ whiskers and the improved interfacial affinity between fillers and matrix. The optimized Nielsen-mold confirms the distribution and morphology of fillers affect the thermal conductivity of PI composites. In addition, SiC whiskers enhanced the mechanical property of PI composites and the influence of fillers on the mechanical property was further elaborated.     

Electrical and thermal conductivity and tensile and flexural properties of carbon nanotube/polycarbonate resins

Adding conductive carbon fillers to insulating thermoplastic polymers increases the resulting composite's electrical conductivity. Carbon nanotubes (CNTs) are very effective at increasing composite electrical conductivity at low loading levels without compromising composite tensile and flexural properties. In this study, varying amounts (2–8 wt %) of CNTs were added to polycarbonate (PC) by melt compounding, and the resulting composites were tested for electrical conductivity (1/electrical resistivity), thermal conductivity, and tensile and flexural properties. The percolation threshold was less than 1.4 vol % CNT, likely because of CNTs high aspect ratio (1000). The addition of CNT to PC increased the composite electrical and thermal conductivity and tensile and flexural modulus. The 6 wt % (4.2 vol %) CNT in PC resin had a good combination of properties for electrical conductivity applications. The electrical resistivity and thermal conductivity were 18 Ω‐cm and 0.28 W/m · K, respectively. The tensile modulus, ultimate tensile strength (UTS), and strain at UTS were 2.7 GPa, 56 MPa, and 2.8%, respectively. The flexural modulus, ultimate flexural strength, and strain at ultimate flexural strength were 3.6 GPa, 125 MPa, and 5.5%, respectively. Ductile tensile behavior is noted in pure PC and in samples containing up to 6 wt % CNT. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Enhancement of thermal conductivity of BN-Ni/epoxy resin composites through the orientation of BN-Ni fillers by magnetic field and hot-pressing

The construction of high thermal conductivity polymer composites by the orientation of fillers is of great significance in electronic devices. Herein, a novel strategy to prepare boron nitride-Ni nanoparticles/epoxy resin composites (hmBN-Ni/EP) through the synergistic effect of magnetic field and hot-pressing on the orientation of BN-Ni fillers has been reported. hmBN-Ni/EP composites have better BN orientation in the in-plane direction than other BN-based/EP composites obtained by hot-pressing or magnetic field orientation only. The thermal conductivity of hmBN-Ni/EP reached 2.42 W m^?1 K^?1 at 30 wt% BN-Ni loading, which was 1145% higher than pure EP. The enhancement of thermal conductivity of hmBN-Ni/EP was attributed to the high in-plane orientation of BN-Ni through the synergistic effect of magnetic field orientation and hot-pressing. Meanwhile, the as-prepared hmBN-Ni/EP composites showed good insulation and mechanical properties which were facilitated to its industrial application in electronic packaging. This work provided a new strategy for better orientation of BN-Based fillers in polymer matrix by combining the magnetic field orientation and hot-pressing.     

Thermal,electrical, and mechanical properties of addition-type liquid silicone rubber co-filled with Al2O3 particles and BN sheets

The addition-type liquid silicone rubber (ALSR) co-filled with spheroidal Al₂O₃ and flaky BN was prepared by the mechanical blending and hot press methods to enhance the thermal, electrical, and mechanical properties for industrial applications. Morphologies of ALSR composites were observed by scanning electron microscopy (SEM). It was found that the interaction and dispersion state of fillers in the ALSR matrix were improved by the introduction of BN sheets. Thermal, electrical, and mechanical performances of the ALSR composites were also investigated in this work. The result indicated that the thermal conductivity of ALSR can reach 0.64 W m⁻¹ K⁻¹ at the loading of 20 wt% Al₂O₃/20 wt% BN, which is 3.76 times higher than that of pure ALSR. The addition of Al₂O₃ particles and BN sheets also improve the thermal stability of ALSR composites. Moreover, pure ALSR and ALSR composites showed relatively lower dielectric permittivity (1.9–3.1) and dielectric loss factor (<0.001) at the frequency of 10³ Hz. The insulation properties including volume resistivity and breakdown strength were improved by the introduction of flaky BN in the ALSR matrix. The volume resistivity and characteristic breakdown strength E₀ are 6.68 × 10¹⁵ Ω m and 93 kV/mm, respectively, at the loading of 20 wt% Al₂O₃/20 wt% BN. In addition, the mechanical characteristics including elongation at break and tensile strength of ALSR composites were also enhanced by co-filled fillers. The combination of these improved performances makes the co-filled ALSR composites attractive in the field of electrical and electronic applications.     

Carbon nanotube/epoxy composites fabricated by resin transfer molding

Carbon nanotube (CNT)/epoxy composites with controllable alignment of CNTs were fabricated by a resin transfer molding process. CNTs with loading up to 16.5 wt.% were homogenously dispersed and highly aligned in the epoxy matrix. Both mechanical and electrical properties of the CNT/epoxy composites were dramatically improved with the addition of the CNTs. The Young’s modulus and tensile strength of the composites reach 20.4 GPa and 231.5 MPa, corresponding to 716% and 160% improvement compared to pure epoxy. The electrical conductivity of the composites along the direction of the CNT alignment reaches over 1 × 10⁴ S/m.     

Noncovalent functionalization of carbon nanotubes using branched random copolymer for improvement of thermal conductivity and mechanical properties of epoxy thermosets

A branched random copolymer, poly[(hydroxyethyl acrylate)‐r‐(N‐vinylcarbazole)] (BPHNV), was synthesized through a facile one‐pot free radical polymerization with hydroxyethyl acrylate and N‐vinylcarbazole monomers, using 4‐vinylmethylmercaptan as the chain transfer agent. BPHNV was employed to noncovalently modify multiwall carbon nanotubes (MWCNTs) by π–π interaction. The as‐modified MWCNTs were then incorporated into epoxy resin to improve the thermal conductivity and mechanical properties of epoxy thermosets. The results suggest that, due to both the conjugation structure and the epoxy‐philic component, BPHNV could form a polymer layer on the wall of MWCNTs and inhibit entanglement, helping the uniform dispersion of MWCNTs in epoxy matrix. Owing to the unprecedented thermal conductivity of MWCNTs and the enhancement in the interfacial interaction between fillers and matrix, the thermal conductivity of epoxy/MWCNTs/BPHNV composites increases by 78% at extremely low filler loadings, while the electrical resistivity is still maintained on account of the insulating polymer layer. Meanwhile, the mechanical properties and glass transition temperature (T_g) of the thermosets are elevated effectively, with no significant decrease occurring to the modulus. The addition of as little as 0.1 wt% of MWCNTs decorated with 1.0 wt% of BPHNV to an epoxy matrix affords a great increase of 130% in impact strength for the epoxy thermosets, as well as an increase of over 13 °C in T_g. © 2018 Society of Chemical Industry     

Barrier properties of thermal and electrical conductive hydrophobic multigraphitic/epoxy coatings

Epoxy composites doped with different content of graphene nanoplatelets (GNPs) and/or carbon nanotubes (CNTs) have been manufactured. Their chemical, thermal, electrical, and mechanical behaviors have been studied, evaluating also their performance as coatings of glass fiber composite substrates. It is confirmed that the graphitic nanofillers present different efficiency as nanofillers as a function of their geometry. CNTs are much higher efficient electrical nanofillers than graphene, but an important synergetic effect is determined in the electrical conductivity of hybrid GNP/CNT/epoxy composites. In contrast, the thermal conductivity scarcely depends on the geometry of graphitic nanofillers but on the graphitic nanofiller content. Adding up to 12 wt% GNP and 1 wt% CNT, the thermal conductivity of the epoxy resin can be increased more than 300%. GNP presents high efficiency to increase the barrier properties, reducing the water absorption up to 30%. The stiffness of nanocomposites proportionally increases with graphitic addition, up to 50%, regard to the modulus of the neat epoxy resin. The adherence of coatings over glass fiber composite substrates increases by nanofiller addition due to the nanomechanical anchoring. However, the water uptake induces a higher weakening on nanodoped composites due to the preferential water absorption by the interface.     

Synergistic effect of boron nitride and tetrapod‐shaped zinc oxide whisker hybrid fillers on filler networks in thermal conductive HDPE composites

In this paper, in order to investigate and predict the synergistic effect of the tetra‐needle‐shaped zinc oxide whisker (T‐ZnO) and boron nitride (BN) hybrid fillers in the thermal conductive high‐density polyethylene (HDPE) composites, the filler networks were studied through dynamic rheological measurement. Moreover, the crystallinity of the HDPE in the composites, and the thermal and electrical conductivity of the composites were also investigated. It was found that when the ratio of the BN and T‐ZnO in hybrid fillers was 20:10, the HDPE/hybrid fillers composite not only had the highest thermal conductivity but also can maintain the electrically insulating. Furthermore, the gel point of the HDPE/hybrid fillers composites was 11.2 wt%, and it was close to the 10 wt%. Therefore, the synergistic effect of the T‐ZnO and BN hybrid fillers in the HDPE/hybrid fillers composites can be successfully predicted through dynamic rheology date. Simultaneously, the Scanning electron microscope results showed that the T‐ZnO and BN particles can contact each other to form the thermal conductive paths so that the thermal conductivity of the HDPE can be enhanced through addition of the hybrid fillers. In addition, it was also found that the improved thermal conductivity of the HDPE/hybrid fillers composites was not because of a change in the crystallinity of the HDPE in the HDPE/hybrid fillers composites. POLYM. COMPOS., 38:1902–1909, 2017. © 2015 Society of Plastics Engineers     

The comparison between the effects of solvent casting and melt intercalation mixing processes on different characteristics of polylactide‐nanographite platelets composites

This study investigates the influence of enhanced dispersion of nanographite platelets (NGP) fillers through solvent casting mixing process on rheological, electrical and thermal properties of polylactide (PLA)/NGP composites. PLA/NGP composites were fabricated at 1 to 5 wt% filler contents by means of three processing techniques: (i) dry mixing and melt intercalation; (ii) solvent casting using dichloromethane organic solvent; and (iii) combination of solvent casting and melt intercalation techniques. The extent of dispersion of nanofillers within polymer matrix was evaluated through X‐ray diffraction and transmission electron microscopy analysis of the composites. Morphological studies of the samples revealed that the maximum extent of dispersion of NGP fillers within PLA matrix was achieved when the combination of solvent casting and melt intercalation processes occurred. Rheological analyses of the samples were indicative of deterioration in the composites produced through solvent casting mixing process. Despite of initial reduction in electrical resistivity of the composites after the addition of 1 wt% of NGP fillers, further addition of nanofillers did not exhibit a considerable enhancement in their electrical conductivity of the composites. Thermogravimetric analysis of the composites was demonstrative of enhancing impact of nanofiller loading, along with detrimental effect of solvent casting on the thermal stability of the PLA matrix. POLYM. ENG. SCI., 55:1560–1570, 2015. © 2014 Society of Plastics Engineers     

A study of the electrical properties of carbon nanotube-NiFe2O4 composites: Effect of the surface treatment of the carbon nanotubes

Novel carbon nanotube-NiFe₂O₄ composite materials have been prepared for the first time by in situ chemical precipitation of metal hydroxides in ethanol in the presence of carbon nanotubes (CNTs) and followed by hydrothermal processing. The obtained composite powders were characterized using XRD, TEM and EDS. The effect of surface oxidation treatment of CNTs on their properties was investigated by FTIR, zeta potential and hydrodynamic radius distribution characterization. Electrical conductivity measurements show that surface oxidation treatment of CNTs can improve the electrical conductivity of the composites more pronouncedly than pristine CNTs do. With 10 wt.% addition of surface treated CNTs, the electrical conductivity is increased by 5 orders of magnitude. The surface oxidized CNTs are crucial for this significant increase in electrical conductivity, which provides strong adhesion between the nanotubes and the matrix to give a homogeneous carbon nanotube-NiFe₂O₄ composite.     

Preparation and properties of hierarchical composites based on carbon nanotubes‐coated glass babric preform

A strategy based on carbon nanotubes (CNTs)‐containing sizing dispersion has been implemented to fabricate nanocomposite preforms and their hybrid multiscale composites. The state of pristine CNTs and carboxylic acid functionalized CNTs (CNTs–COOH) in sizing dispersion was effectively monitored by on‐line measuring electrical conductivity. The effects of different CNTs coating applied onto glass fabric on wettability of nanocomposite fibrous reinforcement with epoxy matrix were evaluated using scanning electron microscopy and capillary experiment. A CNTs‐COOH loading of 0.5 wt% gave rise to 97% and 30°C increases in the storage modulus (G′) and glass transition temperature of the resulting hybrid composites, respectively. The enhanced thermomechanical properties of the CNTs hybrid composites are closely related to the stable CNTs sizing dispersion and uniform coating onto fiber reinforcement. The mechanism for reinforcing composites through toughening resin region with CNTs desorbing from primary fiber surface during impregnation has been identified. POLYM. COMPOS. 37:979–986, 2016. © 2014 Society of Plastics Engineers