641125电磁屏蔽复合导电无酸PSA胶带的研制

以无酸丙烯酸酯系压敏胶为导电胶基体,苯二亚甲基二异氰酸酯（XDI）为交联剂,镍／银混合粉体为导电填料,制备了铜箔导电胶带。讨论了导电粒子的种类及其添加量、交联剂的用量、老化存放时间等对导电胶带的粘接性能、导电性能及电磁屏蔽性能的影响。结果表明,当镍银混合粉添加15％,交联剂用量25％,干胶厚度45μm时,制备的胶带综合性能良好。其粘接强度大于19N／25mm,体积电阻率为6×10^-3Ω·cm,电磁屏蔽效能大于90dB（频率从30-1500MHz）,且耐高温性能稳定。     

Improving the electrical and electromagnetic shielding properties of conductive silicon rubber filled with Ni-coated carbon fibre by magnetic field

In this work, the effects of magnetic field induction on electrical and electromagnetic shielding properties of conductive silicon rubbers (CSRs) filled with Ni-coated carbon fibres (Ni/CFs) have been investigated. When the magnetic field intensity is above the threshold value of 0.10?T during the vulcanisation, it is beneficial to their electrical property that the volume resistivity decreases from 48.7?Ω·cm to 1.57?Ω·cm, owing to the orientation alignment of Ni/CFs in CSRs filled with Ni/CFs (40?phr). Moreover, with the aids of magnetic field induction, the prepared CSRs with lower amount of Ni-CF filler can receive better electromagnetic shielding of 65?dB in 500?MHz–3?GHz, which reduce cost effectively. This vulcanisation process shows promises for various applications in power transmission and transformation industries.     

镀银铜粉导电涂料的制备及性能

采用自制的镀银铜粉制备了导电涂料,研究了导电填料的用量和涂层厚度对涂层导电性的影响,以及导电涂层的抗电迁移和老化性能.结果发现,导电涂层的电阻率随导电填料的用量及涂层厚度的增加而逐渐下降,然后趋于平缓.适宜的镀银铜粉的用量为60％,涂层厚度为120 μm.在100℃以内,涂层具有良好的导电性;超过100℃后,涂层电阻率急剧增大,导电性下降.含镀银铜粉的涂层较含纯银粉涂层具有明显的抗电迁移性.     

Fine-grained and electrically conductive NdB6/SiO2: A promising electromagnetic interference shielding material with good thermal and mechanical properties

Searching for thermal conductive materials with high electromagnetic interference (EMI) shielding effectiveness (SE) is the key to protect electronic equipment against electromagnetic pollution and excess heat emission. Herein, NdB₆/SiO₂ bulks with high EMI SE and thermal conductivity which also exhibit good mechanical properties were prepared by liquid phase sintering (LPS). The NdB₆/SiO₂ bulk prepared by LPS at 1550 °C has fine grain-size, which is beneficial to improving mechanical property and EMI shielding performance. It exhibits high conductivity of 1.47 × 10⁴ S/cm, high EMI SE of 55.1 dB in K band, and high thermal conductivity of 37.9 W/m K. It also possesses flexural strength of 266 MPa and Vickers hardness of 14.8 GPa. Thus, NdB₆/SiO₂ composite ceramics are promising candidates for EMI shielding with good heat dissipation and mechanical load-bearing capabilities.     

Highly conductive and flexible bilayered MXene/cellulose paper sheet for efficient electromagnetic interference shielding applications

In this work, a robust and flexible bilayered MXene/cellulose paper sheet with superhigh electrical conductivity was prepared via vacuum-assisted filtration and a subsequent hot-pressing process for electromagnetic interference (EMI) shielding applications. By tightly assembling few-layered MXene (f-Ti₃C₂T_x) on the cellulose substrate via hydrogen bonds, an effective and interconnected conductive network was constructed in the paper sheet, resulting in a high electrical conductivity of 774.6–5935.4 S m^?1 at various f-Ti₃C₂T_x loadings. The highly conductive MXene layer can promptly reflect a great amount of incident EM waves, a process which preceded the transmission of EM waves in the cellulose matrix. Owing to the highly efficient reflection-dominated EMI shielding mechanism, the resultant bilayered MXene/cellulose paper sheets exhibit excellent EMI shielding effectiveness of 34.9–60.1 dB and specific EMI shielding efficiency of 290.6–600.7 dB mm^?1. Moreover, the MXene/cellulose paper sheets demonstrated improved mechanical strength (up to 25.7 MPa) and flexibility due to the mechanical frame effect acted by the cellulose substrate. Consequently, the robust and flexible bilayered MXene/cellulose paper sheet is a promising candidate for application in next-generation electric devices.     

镀银铝粉填充型电磁屏蔽硅橡胶的制备与性能

研究了镀银铝粉填充量和环境试验对电磁屏蔽硅橡胶电学和力学性能的影响。结果发现,镀银铝粉填充量为210份(质量)是电磁屏蔽硅橡胶的逾渗阈值;最佳的镀银铝粉填充量为230份(质量),此时电磁屏蔽硅橡胶的体积电阻率为6.75×10-3Ω.cm,拉伸强度为2.3MPa,扯断伸长率为571%,邵尔A硬度为65;镀银铝粉填充型电磁屏蔽硅橡胶具有较好的耐高低温和热空气老化性能,而耐盐雾性能较差。     

Effects of conductive fibers and processing conditions on the electromagnetic shielding effectiveness of injection molded composites

This paper investigates the electromagnetic interference shielding effectiveness (EMI SE) of injection molded ABS disks filled with stainless steel fibers (SSF) and nickel-coated graphite fibers (NGF). The effects of fiber type, fiber length and weight percentage on SE were studied. Optical microscope (OM) and scanning electron microscopy (SEM) observations of the fiber distribution and dispersion were used to aid interpretation of the deviation on SE. The effects of processing conditions such as ring gate angles and injection speed on SE and fiber dispersions were also investigated. It is found that the SE of SSF filled disks is better than that of NGF with the same fiber length and weight percentage. The SEM shows that the SSF with severe twists connect with each other to form a three-dimensional network. Nevertheless, the NGF break into straight fragments, which make it difficult to form networks. With the same type of fiber (SSF), the critical concentration of 6mm was similar to that of 4mm. But the SE of 6mm is a little higher than that of 4mm. Minor improvements of SE values were obtained with expanded ring gate angles. Gate design and injection speed both change filling patterns.     

PET表面金属银涂层的制备与性能

以聚对苯二甲酸乙二酯(PET)为基体,基于化学刻蚀和敏化处理的表面改性,采用双组分喷涂法在改性基体表面制备了高性能的银涂层.改变喷涂过程中银氨溶液和还原溶液的浓度以及喷涂次数,研究它们对银涂层的微观形貌、宏观形貌、沉积量和光学常数的影响,考察了最佳喷涂条件下所得银涂层的成分和性能.结果表明:化学刻蚀后表面产生大量凹坑,...     

AAS/GPNs电磁屏蔽复合材料的制备及其性能

对石墨烯进行功能化改性,以丙烯腈-丙烯酸丁酯-苯乙烯共聚物(AAS)为基体,采用溶液分散法制备了AAS/功能化石墨烯(GPNs)复合材料,并研究了其性能.结果表明:GPNs与AAS基体融合性和结合力均较好;AAS/GPNs复合材料的耐候性远优于丙烯腈-丁二烯-苯乙烯共聚物/石墨烯复合材料;GPNs用量为0.5％(w)时...     

Measurement of the electromagnetic shielding properties of mechanically loaded composites

The use of fiber reinforced plastic (FRP) composites for large structures is becoming more widespread. With composites increasingly called upon to replace structures traditionally fabricated from metals the requirement to find suitable methods of providing adequate electromagnetic shielding (EMS) is often of prime importance. This paper describes a measurement technique employing induced magnetic eddy currents for assessing electromagnetic shielding. The technique does not require costly screened rooms or large test panels and is portable and easy to use. The effectiveness of the technique for comparing the electromagnetic shielding of material samples after mechanical loading is demonstrated, and it is concluded that the method offers a cheap and reliable means of comparing screening solutions for composite materials in high loading or fatigue applications. The potential for development of the method into a through-life shielding monitoring tool is also highlighted.     

导电型室温硫化硅橡胶的屏蔽性能及拉敏特性研究

以a，w-二羟基聚二甲基硅氧烷为基胶、正硅酸乙酯为交联剂、二月桂酸二丁基锡为催化剂、特导电华光炭黑(HG-1B)或中超耐磨炭黑(N234)为填料、环己烷为稀释剂，制成了适于灌封的导电型硅橡胶；研究了导电硅橡胶的屏蔽性能及拉敏特性。结果发现，在低阻值下可用Schelkunoff理论较好地描述其屏蔽效果；根据量子力学隧道效应推导出的电阻值随拉力的变化关系可近似地用二次多项式表示，且与实验结果很吻合；当硅橡胶具有最大的拉敏特性时，其导电性能与力学性能具有最佳的结合点，此时N234和HG-1B的用量分别为30～40份和8～12份。     

Toughening strategies of carbon nanotube/polycarbonate composites with electromagnetic interference shielding properties

The effect of different toughening strategies on the mechanical properties of multiwalled carbon nanotube/polycarbonate composite (PC/MWNT) for electromagnetic interference shielding was analyzed from the mechanical and fracture tests using linear elastic fracture mechanics. The effect of processing (injection and compression molding) and manufacturing (annealing) conditions in the mechanical properties and electrical conductivity has been studied. The classic electromagnetic theory predicts a shielding effectiveness around 40 dB for nanocomposites with 5 wt% of MWNT in the frequency range studied. These values make these compounds to be very interesting materials for potential applications as electronic housings. Therefore, a combination of cyclic form of polybutylene terephthalate addition and annealing strategies let to optimize flexural parameters and improve the flexural modulus of PC composites. The rheology results showed that the dynamic moduli and the viscosity grew with increasing MWNT content. A significant change in frequency dependence of the moduli was observed, with respect to pure PC, which indicates a transition from a liquid‐like to a solid‐like behavior. Finally, the morphological study proves that the composites display different toughening mechanisms as function of carbon nanotube quantity. This fact could explain the different fracture behaviors of materials. In summary, it has been proved that it is possible to obtain PC/MWNT nanocomposites with relatively high conductivity, minimizing the loss of mechanical properties, using processing techniques easily scalable at industrial level. POLYM. COMPOS., 34:1938–1949, 2013. © 2013 Society of Plastics Engineers     

Processing conditions for electromagnetic interference shielding effectiveness and mechanical properties of acrylonitrile-butadiene-styrene based composites

A conductive plastic was compounded in a twin screw extruder by incorporating conductive carbon fiber (CF) into an acrylonitrile-butadience-styrene (ABS) copolymer. The effects of various processing parameters prior to injection molding were investigated; then, the electromagnetic interference shielding effectiveness (EMI SE), fiber length, processability, and mechanical properties of the composite were studied. Results showed that the EMI SE of the composite increased as the final fiber length increased. The longer final fiber was produced by feeding fibers into the ABS melt at 240°C and 60 rpm. A more conductive network was formed by adding lubricants to the composite to reduce fiber damage and increase fiber dispersion. The increase of the fiber content affected processability. When the fiber content was higher than 40 phr (parts per hundred resin) in the composite, the average fiber length shortened. This study shows that better shielding can be obtained by adding a fiber at a rate higher than 30 phr. The best shielding obtained is about 30 decibels (dB).     

Enhanced electromagnetic interference shielding properties of silicon carbide composites with aligned graphene nanoplatelets

Graphene nanoplatelets (GNPs) were successfully incorporated into silicon carbide (SiC) ceramic matrix in a self-aligned pattern and the obtained materials displayed extremely high value of shielding effectiveness (SE) over 40?dB by adding only 3?wt.% GNPs, which was the highest SE value in all SiC-based composites reported in literature up to now. It was found that the texture distribution of GNPs was crucial to achieve the high electromagnetic interference shielding performance of SiC/GNPs composites, which can contribute to the significant improvement of both absorption and reflection. The improved absorption originated from the formation of network of mini capacitors comprised of self-aligned GNPs and multiple reflections. The improvement of reflection was attributed to the high electrical conductivity of the composite due to the introduction of GNPs. These results indicate that SiC/GNPs composites can be used as high-performance ceramic-based EMI shielding materials.     

Colloidal graphite as an admixture in cement and as a coating on cement for electromagnetic interference shielding

A water-based colloid of submicron graphite particles is an effective admixture for enhancing the EMI shielding effectiveness of cement paste, though it is ineffective for lowering the electrical resistivity. As an admixture, it is more effective for shielding than 15-μm-diameter discontinuous carbon fibers, though it is less effective than 0.1-μm-diameter discontinuous carbon filaments. A shielding effectiveness of 22 dB at 1 GHz is reached by cement paste at a solid graphite content of 0.92 vol.%, compared to a value of 11 dB for a coating made from the graphite colloid and a value of 14 dB for graphite-colloid-coated cement paste (without admixture).     

电磁屏蔽与导电胶粘剂研制

介绍了导电胶粘剂的导电机理,讨论了导电载体(填料)的类型、形状以及粘料(树脂)等对导电胶粘剂性能的影响。根据电磁屏蔽产品的性能要求和成型工艺条件,研制出一种能满足电磁屏蔽要求的环氧-银粉型导电胶粘剂。     

The effect of chemical exposure on the EMI shielding of conductive plastics

The electrical properties of a number of filled plastics were examined after subjecting the materials to exposure to isopropyl alcohol, a 25°C detergent/water solution, an 80°C detergent/water solution, and at various chemical plant sites. Compositions which contained metal fillers maintained their conductivity only when a high temperature thermally stable polymer was used as the polymer matrix, while compositions which are made conductive through a carbon filler network maintained their conductivity under most of the exposure conditions examined even when low temperature polymers were used as matrices.     

Well-integrated ZnO nanorod arrays on conductive textiles by electrochemical synthesis and their physical properties

We reported well-integrated zinc oxide (ZnO) nanorod arrays (NRAs) on conductive textiles (CTs) and their structural and optical properties. The integrated ZnO NRAs were synthesized by cathodic electrochemical deposition on the ZnO seed layer-coated CT substrate in ultrasonic bath. The ZnO NRAs were regularly and densely grown as well as vertically aligned on the overall surface of CT substrate, in comparison with the grown ZnO NRAs without ZnO seed layer or ultrasonication. Additionally, their morphologies and sizes can be efficiently controlled by changing the external cathodic voltage between the ZnO seed-coated CT substrate and the counter electrode. At an external cathodic voltage of −2 V, the photoluminescence property of ZnO NRAs was optimized with good crystallinity and high density.