导电硅橡胶泡沫材料的制备与性能研究

在硅橡胶基体中添加碳系导电填料(CB、CNT),利用超临界CO2发泡技术,制备了CB/硅橡胶、CNT/硅橡胶以及CB/CNT/硅橡胶复合导电泡沫材料,研究了混料胶料的流变行为以及发泡前后复合材料电导率、电磁屏蔽效能的变化规律。结果表明,CB与CNT均会阻碍硅橡胶复合材料的初始交联,导电填料含量越多交联越迟缓。CB/CNT/硅橡胶复配体系中更容易形成导电通路,当CB/CNT(1∶1)总含量为8%(质量分数)时,硅橡胶复合材料的电导率可达10^-5 S/cm,其电磁屏蔽效能(EI)为14~26 dB。发泡后,硅橡胶复合材料的电导率及EI值均有所下降。     

碳系导电填料性质对PVB基功能薄膜结构及电磁屏蔽效能的影响

分别以形状和电导率不同的石墨、镀镍石墨和镀银碳纤维为功能填料,采用溶液流延法制备了聚乙烯醇缩丁醛基导电薄膜,并对薄膜的微观结构和电学性能进行了研究。结果表明:填料性质(包括形状、密度和电导率)对复合材料的分布结构和电学性能有重要影响,纤维状的填料更容易搭接成导电网络。石墨和镀银碳纤维填充体系中,填料在聚合物基体内部分布基本均匀;而镀镍石墨填充体系中,填料在聚合物基体内部形成了梯度分布。不同的分布状态导致材料的导电性能在薄膜的上下表面产生差异并对复合材料的电磁屏蔽效能产生影响。在同等体积含量下,复合材料的电磁屏蔽效能主要受材料电导率的影响,三种复合材料中,镀银碳纤维填充体系的屏蔽效能最高,镀镍石墨填充体系次之,石墨填充体系最低。     

低温热处理对Fe@Ag复合粒子结构及性能的影响

为了降低Fe@Ag复合粒子的电阻率,研究了低温热处理对其微观形貌、电阻率、磁性能及复合粒子作为屏蔽填料制备的电磁屏蔽橡胶的屏蔽效能(SE)的影响.结果表明:随热处理温度的升高,在140℃获得的Fe@Ag复合粒子的银壳层最致密,电阻率最低,饱和磁化强度基本保持不变;以其作为屏蔽填料制备的电磁屏蔽橡胶的SE在-28~-53 dB,比未处理时提高了-10 dB~-15 dB.同时以界面润湿理论和晶体生长理论合理解释了复合粒子壳层形貌演变规律与屏蔽效能提高的原因.为制备具有高导电导磁的屏蔽填料提供了一种简单方便的处理方法.     

环氧树脂电磁屏蔽涂料的研究

以环氧树脂为基料、银粉为导电填料制备了环氧树脂电磁屏蔽涂料。研究了电磁屏蔽涂料的导电性能、屏蔽效能以及高、低温实验对材料性能的影响,确定了环氧树脂电磁屏蔽涂料在-60℃—125℃温度范围内屏蔽效能可以达到60 dB,并保持稳定工作。     

多功能聚吡咯/聚酰亚胺电磁屏蔽复合膜的制备与性能研究

目的 开发具有优异屏蔽效率、轻质且热稳定性良好的电磁屏蔽材料。方法 以聚酰亚胺(PI)为聚合物基体,聚吡咯(PPy)为添加相,采用静电纺丝-低温原位聚合技术制备PPy/PI电磁屏蔽复合膜。通过在薄膜内部的多孔结构中构建致密的导电网络,赋予复合膜优异的导电性和高效的电磁屏蔽效能。结果 在聚合PPy浓度为0.1 mol/L时,复合膜的电导率和电磁屏蔽效能分别为2.23 S/cm和26.04 dB,且其单位厚度电磁屏蔽效能可达到110.81 dB/mm,展现出优异的电磁屏蔽性能。结论 PPy/PI复合纤维膜表现出良好的力学性能(拉伸强度为11.73 MPa)、优异的热稳定性(>400 ℃)和力学传感性能,具备在恶劣环境下广泛应用的潜力。     

稀土氧化物和碳纳米管共掺导电纸的电磁屏蔽性能研究

以纸纤维作为基体,稀土掺杂碳纳米管作为导电剂,采用高速剪切分散工艺混合均匀,通过真空抽滤制备碳纳米管复合导电纸,并研究了其电磁屏蔽性能。采用扫描电子显微镜、四探针电阻仪和矢量网络分析仪对其进行表征。结果表明,分别采用CeO_2、Pr_6O_(11)和Sm_2O_3掺杂碳纳米管作为导电添加剂。CeO_2作为稀土添加剂时,电磁屏蔽性能最佳,导电纸的电磁屏蔽性能提高了约2dB。CeO_2稀土氧化物在碳纳米管中掺杂量从15%(wt,质量分数,下同)增加到35%时,碳纳米管导电纸的电磁屏蔽性能先增强后减弱,在CeO_2掺杂量为20%时达到最大值,在1000MHz时屏蔽效能达到-29.4dB。     

镀银玻璃珠导电橡胶条的研制

采用镀银玻璃珠为导电填料,甲基乙烯基硅橡胶为原胶制备导电橡胶条,主要应用于军品、民品电台,满足高频环境下电台的电磁屏蔽和水汽密封要求,并对其性能进行研究。结果表明:用硅烷偶联剂A-151对镀银玻璃珠进行表明改性,采用挤出硫化的方式制备的导电橡胶条导电性能和机械性能较好。     

铝镀银微珠/有机硅导电压敏胶的制备及性能研究

以107硅橡胶和甲基乙烯基硅树脂为原料制备了有机硅压敏胶,傅里叶变换红外光谱分析表明反应生成物具有典型的甲基聚硅氧烷结构;采用有机溶剂化学镀法制备出铝镀银微珠,采用扫描电子显微镜、X射线衍射仪、能谱分析仪对铝镀银微珠及铝镀银微珠/有机硅导电压敏胶的形貌、微观结构及元素含量进行分析和测试,结果表明铝镀银微珠表面被致密银层包覆且银质量分数大于95%,铝镀银微珠/有机硅导电压敏胶与导电橡胶板具有有效电连接。电性能与力学性能测试结果表明,当铝镀银微珠体积分数为5%时,铝镀银微珠/有机硅导电压敏胶综合性能最优。     

炭黑填充粒子对导电硅橡胶压阻特性的影响

阐述了复合型导电高分子材料的导电机理,分析了4种导电炭黑填充量对导电硅橡胶导电特性的影响,实验分析了相同导电填料、不同质量分数情况下的导电硅橡胶压阻特性,分析了相同质量分数、不同导电填料对复合材料压阻特性的影响。研究表明,随着炭黑填充量的不断增加,复合材料体积电阻率均呈下降趋势;4种炭黑填充的导电硅橡胶渗流阀值较接近;导电硅橡胶的电阻-压力变化规律符合隧道效应理论模型;为保证导电硅橡胶具有良好的压阻特性,应根据原料控制好导电炭黑的添加量。     

镀Ni-Cu硅酸钙镁晶须/镍粉/环氧树脂电磁屏蔽涂料研究

以一种新型镀Ni-Cu硅酸钙镁矿物晶须和羰基镍粉作为屏蔽复合填料,研制出了一种新型镀Ni-Cu硅酸钙镁晶须/镍粉/环氧树脂电磁波屏蔽复合涂料,并研究了其导电和电磁波屏蔽性能.结果表明,添加4%(wt)的镀Ni-Cu硅酸钙镁晶须能显著改善涂层的电磁性能,膜厚300μm,涂层电阻率为1.09Ω·cm,涂层屏蔽效能在0.3-...     

多壁碳纳米管/聚乙烯醇复合材料电磁屏蔽性能研究

通过熔融共混、流延成膜法制备了多壁碳纳米管/聚乙烯醇(MWCNTs/PVA)复合材料,并研究了碳纤维作为增强体的作用。扫描电子显微镜、傅里叶变换红外光谱、热重分析表明:MWCNTs在PVA基体中均匀分散且形成了良好的空间导电网络;MWCNTs的加入会使吸收峰转移并与PVA发生键合反应;MWCNTs/PVA复合材料具有优异的热稳定性,热分解温度低于105℃时只有少量水分蒸发。导电性和电磁屏蔽测试表明,MWCNTs/PVA复合材料电磁屏蔽性能随其导电性的增强而提高,MWCNTs质量分数为1.2%的复合材料样品,在干扰电磁波频率为1~18GHz频段上具有良好的屏蔽性能,当干扰电磁波频率为13.3GHz时,其屏蔽效能为36.7dB。碳纤维可以增强MWCNTs/PVA复合材料的屏蔽性能,MWCNTs质量分数为0.6%的碳纤维增强MWCNTs/PVA复合材料样品,在干扰电磁波频率为1~18GHz频段时,其电磁屏蔽效能大于40dB。     

Electromagnetic shielding effectiveness of thin film with composite carbon nanotubes and stainless steel fibers

Using the polymer blending method, conductive materials and waterborne polyurethane (WPU) were mixed to fabricate conductive composite films for application in electromagnetic shielding. First, nitric acid was used to purify the multi-walled carbon nanotubes (MWCNT). Second, sodium dodecyl sulfate (SDS) was utilized to disperse the carbon nanotubes, and then they were mixed with 8 microm diameter and 2 mm long stainless steel fibers (SSF) in the WPU by the polymer blending method. Finally, the thickness of 0.25 mm of conductive composite film was fabricated by means of coating. According to the ASTM D4935-99 standard, a coaxial transmission line was used to measure the electromagnetic shielding effectiveness (EMSE) of conductive composite film within the range of 50 MHz approximately 3.0 GHz. Moreover, the influence of the prior and posterior dispersion of carbon nanotubes dispersed on electromagnetic shielding was dealt with in the paper. Results demonstrated that the conductive composite film, within 50 MHz approximately 3.0 GHz, fabricated by the 15 wt% of the multi-walled carbon nanotubes and 30 wt% of the stainless steel fibers can achieve the maximum of the electromagnetic shielding effectiveness, 34.86 dB, and its shielding effect, 99.9%.     

TiO<Subscript>2</Subscript> hybrid polypropylene/nickel coated glass fiber conductive composites for highly efficient electromagnetic interference shielding

A highly efficient electromagnetic interference shielding composite based on nickel coated glass fibers (NCGFs) and titanium dioxide (TiO₂) filled polypropylene (PP) is fabricated via the simple melt blending method. Superior shielding effectiveness of 44.5 dB can be achieved with only 1.12 vol% Ni and 0.8 vol% TiO₂ loadings owning to the well-formed conductive network and interfacial polarization effect of TiO₂. The conductive Ni layer coating on the surface of glass fibers constructs an efficient conductive network due to its interfacial distribution between GF and PP. This interconnected Ni network provides fast electron transport channels to absorb the electromagnetic waves. Meanwhile, TiO₂ dispersed among the network of NCGFs induces more interfacial polarization, and thus produces a synergistic effect to enhance the shielding effectiveness of composite. Such composite would be considered as a promising electromagnetic shielding material in aerospace and electronics.     

钢纤维混凝土电磁屏蔽性能实验研究

实验研究了纤维体积掺量相同情况下，4种不同纤维长度的钢纤维混凝土电磁屏蔽性能，并对其屏蔽规律进行了分析、比较。探讨了纤维长度对钢纤维混凝土电磁屏蔽性能的影响机理。当纤维体积掺量为2A％，纤维长度为18或12mm时，钢纤维混凝土电磁屏蔽效能在0-3～1000MHz频带内达到20dB以上。其中掺入长度为18mm钢纤维时，在0．3MHz最高达到65dB，掺入长度为6mm钢纤维时，在1．0GHz最高达到41dB。     

Electromagnetic shielding effectiveness of copper/glass fiber knitted fabric reinforced polypropylene composites

The main objectives of this research work are to develop conductive knitted fabric composite materials and to determine their electromagnetic shielding effectiveness (EMSE). Polypropylene is the matrix phase and glass fibers are the reinforcement phase of the composite material. Copper wires are incorporated as conductive fillers to provide the electromagnetic shielding properties of the composite material. The amount of copper in the composite material is varied by changing the yarn composition, fabric knit structure and stitch density. The EMSE of various knitted fabric composites is measured in the frequency range of 300 kHz to 3 GHz. The variations of EMSE of knitted fabric composites with fabric structure, stitch density and yarn compositions are described. Suitability of conductive knitted fabric composites for electromagnetic shielding applications is also discussed.     

表面改性和复合工艺对金属纤维/聚合物复合材料性能的影响

以不锈钢纤维为导电填料,分别与ABS和PP复合,制得了电磁屏蔽用导电高分子复合材料。考察了表面改性和复合工艺对金属纤维／聚合物复合材料性能的影响。结果表明,用不同表面处理剂处理不锈钢纤维后,随纤维表面张力增加,复合材料的电阻率增加。使用母料法工艺可以有效地改善金属纤维在聚合物基体中的分散,从而提高复合材料的导电性能和电磁屏蔽性能。     

Electromagnetic interference shielding of composites consisting of a polyester matrix and carbon nanotube-coated fiber reinforcement

We investigated the electromagnetic interference shielding effectiveness (EMI SE) of composites consisting of an unsaturated polyester matrix containing woven glass or carbon fibers that had been coated with multiwalled carbon nanotubes (MWCNTs). Composite panels consisting of fiber fabrics with various combinations of fabric type and stacking sequence were fabricated. Their EMI SE was measured in the frequency range of 30 MHz–1.5 GHz. The underlying physics governing the EMI shielding mechanisms of the materials, namely, absorption, reflection, and multiple reflections, was investigated and used in analytical models to predict the EMI SE. Simulation and experimental results showed that the contributions of reflection and absorption to EMI shielding is enhanced by sufficient impedance mismatching, while multiple reflections have a negative effect. For a given amount of MWCNTs in the glass-fiber–reinforced composite, coating the outermost, instead of intermediate, glass fiber plies with MWCNTs was found to maximize the conductivity and SE.     

电磁屏蔽复合材料的屏蔽性能预测

建立了填充椭球颗粒电磁屏蔽复合材料等效电磁参数的物理模型,基于变分原理和电磁波传输理论推导出其电磁屏蔽性能的预测公式,计算了不同填充条件下复合材料的屏蔽效能及反射率,分析了填料显微结构特征(浓度、形状、尺寸、分布方式)对复合材料屏蔽性能的影响规律.结果表明,复合材料屏蔽效能和反射率随填料填充浓度、长径比的增加而增大;针形和片形填料优于球形填料且定向分布好于随机分布;材料的反射率在特定的填充浓度及填料尺寸下存在峰值。屏蔽效能的计算结果与实验上填充球形银包羰基铁和镀镍短碳纤维的屏蔽复合材料的测试数据拟合较好。     

Thermoplastic Polyurethane Reinforced with Continuous Carbon Fiber Tows: Manufacturing Technique and Fabric Property Evaluation

Co-extrusion technique is used to combine carbon fiber tows and thermoplastic polyurethane (TPU) blends into composite carbon fibers (CCFs). The TPU blends serve as the shell and the carbon fiber tows serve as the core. CCFs are fabricated into woven composites and knitted composites with electromagnetic interference shielding effectiveness (EMI SE). The effects of the content of carbon fiber tows on different fabrics are examined. The failure mechanism of CCFs is improved as the fiber slippage along the axial direction replaces the fiber fracture. Fabrics made of CCFs are soft. The laminated woven composites have an average EMI SE of -27.20 dB at 0–3000 MHz and -44.99 dB at 2450 MHz, suggesting a good EMI attenuation capability. This study proposes the use of co-extrusion technique followed coating and fabrication of carbon fibers. This brand-new concept would be vital in the development of carbon fiber composites.