CF/ASA复合材料的电磁屏蔽性能影响因素

通过填料分散复合法制备CF/ASA(苯乙烯、丙烯晴和丙烯酸酯类橡胶体的接枝共聚物)复合材料,研究CF的长度及含量对复合材料电磁屏蔽效能的影响,并且,对其导电性和微观形貌进行表征。激光共聚焦显微镜研究结果显示,复合材料内部碳纤维分散均匀,碳纤维之间相互搭接形成了较好的导电网络。分析表明,随着导电性的提升,复合材料电磁屏蔽性能逐渐提升;随着纤维含量的增加,复合材料的膜电阻逐渐减小,其电磁屏蔽效能得到提高,当碳纤维含量为29%、碳纤维长度为6 mm的复合材料样品膜电阻最小,其值为23.36Ω/sq,而有效屏蔽带宽达到最大,其值为6 GHz,电磁屏蔽性能最优。电磁波频率在10～15 GHz范围内,复合材料具有较好的电磁屏蔽性能,并且,碳纤维长度越长,复合材料电磁屏蔽效能越好。     

多层纤维增强环氧树脂复合材料结构设计与电磁屏蔽效能预测模型

构建渐进导电网络结构是一种降低导电材料电磁波反射率的有效策略。利用芳纶纤维(AF)、还原氧化石墨烯负载芳纶纤维(rGO@AF)与碳纤维(CF),制备多层纤维增强环氧树脂复合材料(AF/rGO@AF/CF/EP),研究CF/EP和AF/rGO@AF/CF/EP的电磁屏蔽性能。通过单层纤维的电磁参数和电导率预测,得到多层纤维增强环氧树脂复合材料电磁屏蔽效能的简化模型。结果表明：单层CF/EP的反射损耗效能(SER)为12.3 dB,总电磁屏蔽效能(SE_T)为40.2 dB,与之相比,AF/rGO@AF/CF/EP的SER降至9.6 dB,SE_T提高至43.6 dB,说明梯度导电网络结构在保证材料屏蔽效能的同时降低复合材料的反射损耗。利用简化模型得到AF/rGO@AF/CF/EP的电磁屏蔽效能为42.6 dB,表明该模型准确预测多层结构复合材料的电磁屏蔽性能。     

金属化碳纤维对PC/ABS电磁屏蔽塑料性能的影响

使用自行研发的碳纤维连续电镀镍生产设备生产镀镍碳纤维(NCF),并用不同用量NCF填充聚碳酸酯/丙烯腈-丁二烯-苯乙烯塑料(PC/ABS)合金基材,采用包覆工艺制备PC/ABS电磁屏蔽塑料。研究了NCF用量对电磁屏蔽塑料力学性能、热性能、电性能和电磁屏蔽效能的影响。结果表明,NCF能够在PC/ABS中均匀分散,且两者很好地结合在一起,形成完善的导电网络结构;NCF可以提高电磁屏蔽塑料的力学性能、热性能、导电性能;在NCF质量分数为18%时,电磁屏蔽塑料的综合性能最优,拉伸强度为108.18 MPa,拉伸弹性模量为15 GPa,缺口冲击强度为6.82 kJ/m~2,热变形温度为120℃,体积电阻率为7.10×10~(–3) Ω·cm,屏蔽效能可达到52～72 dB。     

镀覆工艺对镀镍铝粉/硅橡胶复合材料电磁屏蔽性能的影响

采用不同镀覆工艺(置换法、还原法和先置换后还原法)制备镀镍铝粉,研究镀覆工艺对镀镍铝粉/甲基乙烯基硅橡胶(MVQ)复合材料电磁屏蔽性能的影响。结果表明:采用置换法制备的镀镍铝粉镍镀层厚度较小;采用还原法制备的镀镍铝粉镀层结合强度较低;采用先置换后还原法制备的镀镍铝粉镀层厚度较大,镀层结合强度较高;采用先置换后还原法制备的镀镍铝粉/MVQ复合材料电磁屏蔽性能优异,在30～3 000 MHz频段内,其电磁屏蔽效能在55～95 dB之间。     

镀镍石墨/杜仲橡胶复合材料的制备及性能

用硅烷偶联剂对镀镍石墨(NCG)进行湿法处理,采用机械共混法制备了镀镍石墨/杜仲橡胶(EUG)复合材料,考察了NCG用量对NCG/EUG复合材料导电性能、电磁屏蔽效能和力学性能的影响。结果表明,随着NCG质量分数的增加,NCG/EUG复合材料的电导率和电磁屏蔽效能逐渐增大,拉伸强度先增大后减小,扯断伸长率逐渐降低,邵尔A硬度逐渐增大。当NCG质量分数为50%时,NCG/EUG复合材料的电导率可达到2.59 S/cm,电磁屏蔽效能最高可达到47.50 dB。     

环氧树脂/CF/亚麻纤维复合材料电磁屏蔽性能

电子电气设备等产生电磁辐射污染会严重影响到人体健康,并干扰设备的正常运行,解决电磁污染的关键是使用电磁屏蔽材料。采用模压工艺制备了具有电磁屏蔽功能的环氧树脂/碳纤维(CF)/亚麻纤维复合材料。借助矢量网络分析仪、热重分析仪、万能试验机、扫描电子显微镜(SEM)等研究CF粉对复合材料的电磁屏蔽性能(EMI SE)、热稳定性和力学性能的影响。结果表明,复合材料的弯曲强度随着CF粉含量的增加而增加,并在其质量分数为30%时达到最大值,为102.5 MPa,与未加CF的材料相比较,提高了31.1%,此后进一步增加CF粉含量,复合材料的弯曲强度开始下降。SEM证实,复合材料力学性能的提高来源于CF与环氧树脂界面性能的改善。CF粉的加入提高了环氧树脂/亚麻纤维复合材料的热稳定性,热分解温度从206℃提高到268℃。同时复合材料的体积电阻率随着CF粉含量的增加而下降,从0.65Ω·cm降至0.132Ω·cm。在8.4～12.4 GHz电磁波范围内,环氧树脂/CF/亚麻纤维复合材料的EMI SE达到20 dB以上,基本满足商业要求。     

CNT基木塑复合材料的力学性能、电磁屏蔽性能

采用碳纤维(CF)和碳纳米管(CNT)通过模压工艺制备出具有电磁屏蔽功能的丙烯酸酯木塑复合材料。借助材料试验机、动态热机械分析仪、微欧计和电磁屏蔽测量仪等详细研究CNT质量分数对丙烯酸酯木塑复合材料弯曲性能、动态力学性能、电阻率和电磁屏蔽效能的影响。结果表明,添加质量分数为2%的CNT,使得复合材料的弯曲强度和弯曲弹性模量分别增加了10%和16%。复合材料的储能模量也在CNT质量分数为2%时达到最大值,之后储能模量随着CNT的增加而逐渐下降,损耗因子在CNT质量分数多于2%时也逐渐增加。复合材料的吸水率和导电性能随着CNT含量的增加而增加。同时复合材料的电磁屏蔽效能也随着CNT含量增加而递增。在30~1 500 MHz范围内,电磁屏蔽效能从27 d B增加到40 d B。结果证明,当CNT质量分数在2%时,丙烯酸酯木塑复合材料具有较佳的力学性能和较好的电磁屏蔽效能(30 d B),能满足商业要求。     

G-MWNT/Fe/ABS屏蔽材料的性能和机理研究

采用熔融共混法制备G-MWNT(石墨化碳纳米管)/Fe/ABS新型屏蔽复合材料,研究材料的综合性能及其机理,初步探讨了该材料微观结构与性能之间的关系.G-MWNT质量分数为35%～40%,对复合材料的抗拉强度、拉伸模量、硬度能起到最大增强效果.而随着G-MWNT含量的增加,复合材料的屏蔽效能明显增强,在50 k～1.5 GHz均有良好的屏蔽性能.此外纳米铁粉能显著增强和改善碳纳米管的电磁屏蔽性能.     

碳纳米管填充聚合物基复合体系的电磁屏蔽性能

为防止和减轻电磁波的危害,研制电磁屏蔽材料有重要的实际意义.分别以聚碳酸酯(PC)以及聚碳酸酯/丙烯腈-丁二烯-苯乙烯共聚物(PC/ABS)为基体,以多壁碳纳米管(MWCNT,muliti-walled carbon nanotubes)为主要导电材料,采用熔融法制备填充型复合材料,并对其流变性能和电磁屏蔽效能(SE,shielding effectiveness)进行测试.复合体系在2.5%～3.0%的填充分数内发生了流变逾渗过程.研究制备SE大于35 dB的复合材料,达到民用屏蔽材料的实用标准.     

具有电磁屏蔽功能聚苯硫醚复合材料的制备与性能研究

本文采用粉末浸渍工艺制得连续玄武岩纤维和不锈钢纤维增强聚苯硫醚预浸料,预浸料的编织物经层压成型制备了聚苯硫醚复合材料,对复合材料的力学和电磁屏蔽性能进行了研究。结果表明:不锈钢纤维/聚苯硫醚预浸料与玄武岩纤维/聚苯硫醚预浸料层压所形成的复合材料其力学性能和电磁屏蔽性能均优于铝箔与玄武岩纤维/聚苯硫醚预浸料层压所形成的复合材料;当电磁波频率小于200 MHz时,复合材料的电磁屏蔽效能较高,不锈钢纤维/聚苯硫醚预浸料中不锈钢纤维质量分数(含量)为30%时,复合材料的电磁屏蔽效果达到较高值,当电磁波频率在200～1 500 MHz范围内,材料的屏蔽效能在20～30dB间波动。     

Electromagnetic interference shielding effectiveness and mechanical sliding behavior for electroless nickel/phosphorous–poly(tetrafluoroethylene) codeposition on carbon fiber/acrylonitrile–butadiene–styrene composites

Poly(tetrafluoroethylene) (PTFE) powders were mounted on an electroless nickel/phosphorous (Ni/P) film on the surface of a carbon fiber by an electroless codeposition method. This type of carbon fiber filler, denoted FENCF, was then compounded with acrylonitrile–butadiene–styrene (ABS) for use in electromagnetic interference shielding. For the suspension of the PTFE powders, a surfactant was used. Although the adhesion between the electroless Ni/P–PTFE films and the fiber was reduced, the PTFE powders on the surface of FENCF reduced the torque values when compounded into the ABS matrix because of a self‐lubricating effect. The two‐step FENCF composites exhibited particularly significant advantages. The torque values for the two‐step FENCF/ABS composites were about one‐half of those for carbon fiber/ABS composites in compounding processes; in addition, the former had an average mean fiber length almost 2.5 times that of the latter. The multiyield phenomena in stress–strain curves of FENCF/ABS composites implied that the PTFE powders mounted on Ni/P films slid during stress–strain action. The electromagnetic interference shielding effectiveness of FENCF/ABS composites did not decrease significantly even though the PTFE powders formed a discontinuous phase on the electroless Ni/P films. The mechanical properties of FENCF composites were enhanced because of the larger fiber length. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1661–1668, 2002     

Polymeric composites for use in electronic and microwave devices

The dielectric and conductive properties of thermoplastic (ABS) composites filled with ceramic powder (barium titanate), conductive powders (carbon black, copper) and conductive fibers (carbon, steel) were investigated for use in electromagnetic crystals and microwave devices. Barium titanate/ABS composites were produced that had dielectric constants over 8 and loss tangents of 0.01, which are the requirements for electromagnetic crystals. Carbon black/ABS and steel fiber/ABS composites were obtained with conductivities suitable for electromagnetic shielding (over 10^?3 S/cm). Fused decomposition modeling was tested as a method for building electromagnetic crystals and showed promising results. Polym. Eng. Sci. 44:588–597, 2004. © 2004 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).     

Effects of A,B, and S components on fiber length distribution,mechanical, and impact properties of carbon fiber/ABS composites produced by different processing methods

Carbon fiber/ABS composites with different acrylonitrile, butadiene, and styrene components were produced via extrusion/injection and long fiber thermoplastic (LFT)/injection molding processes, respectively. The effect of the components on fiber length distribution, tensile, flexural, impact, and dynamic mechanical properties of the composites was investigated. The properties of carbon fiber/ABS composites produced using 12 mm-long LFT pellets were markedly higher than those produced using extruded pellets made with 12 mm-long chopped carbon fibers. Uses of LFT pellets were preferable to enhancing the mechanical properties of carbon fiber/ABS composites. The tensile, flexural, and dynamic mechanical properties were increased in order of ABS750sw > ABS720 ≥ ABS780 > ABS740, whereas the impact strength was increased in order of ABS740 > ABS780 > ABS720 ≈ ABS750sw. Less carbon fiber damages and less carbon fiber length degradation upon LFT processing resulted in longer fiber length distribution and higher fiber aspect ratio in the composites with LFT pellets, indicating a beneficial reinforcing effect, which was responsible for the increased mechanical properties of ABS composites, particularly with ABS750sw. The results were agreed with each other, significantly depending on the A, B, and S components, being supported by fiber length distribution, fiber aspect ratio, and fracture surfaces.     

Studies on processing parameters and thermal stability of ENCF/ABS composites for EMI shielding

Electroless nickel coated carbon fibers (ENCF) were blended with acrylonitrile-butadiene-styrene (ABS) to prepare composites for electromagnetic interference (EMI) shielding. The effects of processing parameters, such as additives, temperature, and fiber loading amount, on EMI shielding effectiveness (SE) were researched. The thermal stability of EMI SE of ENCF/ABS composites was tested by heat treating composites in a drying oven at 60°C, and SE was measured at an interval of one week to consider the degradation of SE. The best SE of ENCF/ABS composites could be reached was 44 dB at optimum processing parameters. The thermal stability of ENCF/ABS composites for EMI shielding was steady without obvious degradation after 60°C heat treatment for five weeks. © 1997 John Wiley & Sons, Inc.     

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.     

Preparation and EMI shielding properties of nickel‐coated PET fiber filled epoxy composites

Electrically conductive composites were prepared using epoxy resin (EP) as matrix and nickel‐coated polyethylene teraphthalate (PET) fibers as filler. The fibers were coated with nickel by plating and ultrasonic electroless deposition techniques. The coaxial transmission line method was used to measure the electromagnetic interference (EMI) shielding effectiveness of the nickel‐coated PET fiber/EP composites. The contents of nickel and phosphorus in the coating were determined by X‐ray photoelectron spectroscopy (XPS). As a result, the ultrasonic electroless nickel‐coated PET fiber/EP composites showed excellent electrical conductive capability and better EMI shielding effectiveness due to higher content of nickel and lower content of phosphorus in the coating than conventional plated nickel‐coated PET fiber/EP composites. POLYM. COMPOS., 27:24–29, 2006. © 2005 Society of Plastics Engineers     

Investigation of the Effects of Injection Molding Processing Parameters on Conductive Polymeric Composites for Electromagnetic Interference Shielding Effectiveness

Polycarbonate (PC) composites filled with conductive nickel-coated carbon fibers (NCFs) were injection-molded under different injection process conditions. They were then used to investigate the influence of the injection processing parameters of melt temperature, mold temperature, injection velocity and packing pressure on the electromagnetic interference (EMI) shielding effectiveness (SE). In order to study the effect of the molding variables using the minimum number of experiments, the Taguchi method was employed. The aim of the Taguchi method was to optimize the injection processing parameters for better EMI shielding of the conductive polycarbonate composites. It is found out that the packing pressure and mold temperature affect the EMI shielding efficiency most significantly.     

Effect of titanate coupling agent on electromagnetic interference shielding effectiveness and mechanical properties of PC–ABS–NCF composite

Nickel-coated carbon fibers (NCF) treated with a coupling agent (CA) have been used for preparing composites of polycarbonate (PC) and acrylonitrile—butadiene—styrene (ABS) (90/10%) by melt blending. These composites have been evaluated for electromagnetic interference shielding effectiveness (EMI SE), mechanical properties, dispersion, and adhesion of the polymer to a filler using the scanning electron microscope (SEM). There is an improvement in the EMI SE, tensile strength, and impact strength of the composite when the carbon fiber is coupled with titanate CA. In loading NCF in composite, the optimum concentration of the CA Lica 38 used is about 2.0 phf combined with 1.5 phf calcium stearate (Ca.st.) (on the weight percentage of fillers); the composite can reach an SE of 50 dB by the coaxial transmission line test method.     

镀镍碳纤维/镀镍石墨粉填充PC/ABS材料导电性能的研究

在PC/ABS材料中填充镀镍碳纤维（NiCF）和镀镍石墨粉,制备一种新型填充型导电复合材料,分析了NiCF与镀镍石墨粉的填充量及NiCF长度对复合材料导电性能的影响。结果表明,随着NiCF和镀镍石墨粉填充量的增加,复合材料的体积导电率会下降,即导电性能得到提高。与镀镍石墨粉相比,NiCF对复合材料导电性的影响更显著。NiCF/镀镍石墨粉/PC/ABS复合材料存在渗滤效应,当NiCF含量在10%~15%范围内时,材料的体积导电率急剧下降,导电性能迅速提高。当复合材料颗粒长度为10mm左右时,注塑成型的材料导电性能最佳。