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。     

基于磁控溅射技术的碳基电磁屏蔽材料

利用磁控溅射技术在碳纤维表面沉积铜膜制备了高效的电磁屏蔽材料,并通过调整磁控溅射时间和碳纤维单向布铺层层数,分析了磁控溅射改性方式和铺层层数对碳纤维织物及其复合材料电磁屏蔽性能的影响。结果表明,磁控溅射碳纤维表面铜膜沉积有利于碳纤维电磁屏蔽性能的改善。经磁控溅射改性处理后,碳纤维电磁屏蔽效能最小提高了37.73%,且电磁屏蔽性能随着磁控溅射时间的延长而增强,但碳纤维电磁屏蔽效能增加率则随磁控溅射时间的增加而逐渐减小。增加碳纤维织物铺层层数有利于碳纤维织物集合体电磁屏蔽性能的改善,但织物层间的不连续性对织物集合体电磁屏蔽性能起消极作用。环氧树脂经碳纤维复合后,电磁屏蔽效能显著增强,增加了约30 dB,但由于环氧树脂对碳纤维的包覆性能,影响了复合材料对电磁波的屏蔽效果,不随碳纤维复合材料中碳纤维织物铺层层数的增加和改性碳纤维导电性能的增加而增强。     

LDPE/不锈钢纤维电磁屏蔽材料的性能研究

以不锈钢纤维作为导电填料，添加到低密度聚乙烯（LDPE）中，制备了一种电磁屏蔽材料。分析了不锈钢纤维的加入对复合材料电磁性能、导电性能和力学性能的影响。结果表明，LDPE/不锈钢纤维复合材料的电磁屏蔽效能与不锈钢纤维的长径比成正比，添加了长径比大的不锈钢纤维的LDPE的导电性能更佳。随着不锈钢纤维用量的增加，LDPE／不锈钢纤维复合材料的拉伸强度和断裂伸长率都有较大幅度的下降。     

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。     

聚氨酯掺杂铜粉涂层的电磁特征及其涂层织物的吸波性能

将掺杂了不同含量微米铜粉的聚氨酯（PU）涂料通过涂层工艺涂敷在棉织物上制成吸波涂层织物,并利用扫描电子显微镜、红外光谱和矢量网络分析仪等测试了不同铜粉含量聚氨酯涂层的介电常数、磁导率和电磁损耗等电磁性能,同时还探讨不同铜粉含量涂料对涂层织物电磁吸收性能的影响。结果表明,在 8~13 GHz 的频段范围内,随着涂层中铜粉含量增加,涂层介电常数实部与虚部均增大,铜粉具有良好的介电性能,在外加电场的作用下产生极化,对电磁波产生介电损耗;铜粉不属于磁损耗材料,对电磁波产生磁损耗较小;当铜粉的含量较低（3 %,质量分数,下同）时,涂层材料的吸波与电磁屏蔽性能较弱,当含量由5 %增加至11 %时,在9.0、10.5、12.8 GHz处反射损耗最低分别为-20.4、-28.3、-25.6 dB,有效吸收带宽分别为0.2、1.3、1.1 GHz,电磁屏蔽效能分别由12.24、16.59、21.1 dB增加至25.92 dB。     

两种电磁屏蔽纺织品屏蔽效能及耐水洗性能比较

分析了含银离子织物和金属纤维混纺织物两种电磁屏蔽纺织品的屏蔽效能和耐水洗性能，测试了两种织物在辐射频率0～6 000 MHz范围下的电磁屏蔽效能，并比较评估了两种织物水洗处理前后的耐水洗性能。结果表明，金属纤维混纺织物在低频率辐射环境下电磁屏蔽效能不及含银离子织物，但在多次洗涤的情况下电磁屏蔽效能变化不大，具有更强的稳定性。通过对两种电磁屏蔽纺织品的屏蔽效能和耐水洗性能的对比研究，为消费者购买防辐射产品提供了科学指导，也为相关产品的研制提供了参考。     

电磁屏蔽复合材料包装箱的研究

采用复合材料树脂传递模塑（RTM）工艺，利用一层含不锈钢纤维的导电布为屏蔽材料，制备了具有电磁屏蔽效能的玻璃纤维增强树脂基复合材料包装箱，该包装箱材料在1．0～4．0GHz电磁波范围内，电磁屏蔽效能最高可高达36dB左右，且与未含导电布的相同体系的复合材料相比，力学性能基本保持不变。     

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。     

聚偏氟乙烯/导电炭黑填充聚偏氟乙烯层状复合材料的电磁屏蔽性能研究

以聚偏氟乙烯(PVDF)为基体、导电炭黑(CB)为填料,制备了PVDF/CB复合材料。研究了导电粒子含量、PVDF/CB与纯PVDF层层叠合等因素对PVDF电磁屏蔽效能的影响。结果显示,随着CB含量增加,PVDF/CB复合体系的屏蔽效能(SE)逐渐升高。根据电性能测试结果,导电粒子越多,体系的电阻率越低,因而对电磁波的反射作用增强,导致SE值提高。将质量分数为15%的CB填充的PVDF与纯PVDF按不同层厚比叠合成2层样品后进行电磁屏蔽测试发现,随着PVDF/CB层层厚增加,PVDF层层厚降低,层状体系的电磁屏蔽性能逐渐提高。与具有相同层厚度、相同CB含量的PVDF/CB复合体系相比,层状体系的屏蔽效果明显高于前者。与测试结果相比,理论曲线的趋势基本一致,但测试曲线中出现屏蔽峰的频率更低。分析认为,当电磁波作用在层状体系上时,PVDF/CB层中的CB粒子可能会影响到相邻PVDF层中的电荷移动,使其达到最大吸收需要更长的时间,这为宽频电磁屏蔽材料的制备提供了思路。     

电磁屏蔽膜国家标准介绍——《电磁屏蔽膜 化学镀铜溶液 镍离子和铜离子含量测定方法》和《光学功能薄膜等 离子电视用电磁波 屏蔽膜屏蔽效能测定方法》

随着日常生活、工作环境中电器设施的日益增多,人们意识到电磁辐射的危害性,电磁波屏蔽膜因此得到越来越广泛的应用。本文就2项电磁波屏蔽膜方面的国家标准,对电磁屏蔽膜制备所需化学镀铜溶液中镍离子、铜离子含量测定方法及等离子电视用电磁屏蔽膜的屏蔽效能测定方法制定二方面内容进行了推介。     

防电磁辐射混纺织物的设计与开发

20μm的不锈钢长丝与25 tex的竹浆/丝光羊毛(50/50)股线经过并线加捻设计开发出5种不锈钢长丝含量不同的纱线,设计并试织了不锈钢长丝质量分数分别为11%、15%、17%、22%、26%的5种2/2斜纹组织织物。测试和分析了这5种织物的防辐射性能、厚度、面密度、透气性、悬垂性、刺痒感、汽蒸收缩性、折皱回复性。结果表明:开发的5种织物均具有良好的防电磁辐射性能,且随着不锈钢长丝含量增加,织物的防辐射性能提高,厚度、面密度、刺痒分值逐渐增大,透气性、悬垂性、折皱回复性降低,汽蒸收缩性先降低后保持不变。     

抗静电织物的电荷面密度测试与分析

通过YG(B)403型织物摩擦带电测试仪测试各种无导电纤维织物、不锈钢纤维织物、有机导电纤维织物的电荷面密度,研究了摩擦次数和含水率对织物抗静电性能的影响。结果表明:大部分含导电纤维的织物抗静电性能优于普通织物;摩擦次数对织物的抗静电性能基本无影响;随着含水率的减少,含导电纤维的织物抗静电性能有提高趋势,普通织物抗静电性能会有所下降。     

热塑性导电塑料在屏蔽电磁波干扰中的应用

介绍了复合型导电塑料，特别是导电纤维增强热塑性塑料在屏蔽电磁波干扰中的应用现状和技术发展趋势，讨论了3种主要的导电纤维即碳纤维，镀镍碳纤维和不锈钢纤维的优缺点；比较了不同的加工设备和加工方法对这类导电复合材料性能的影响。     

Enhancement in electrical conductive property of polypyrrole‐coated cotton fabrics using cationic surfactant

Recently, great efforts have been made to gain highly conductive fabrics for smart textiles and flexible electromagnetic shielding materials. Different from the conventional chemical synthesis method, fibrillar polypyrrole was synthesized on the cotton fabrics via a simple chemical polymerization process with micelles of cationic surfactant (cetyltrimethylammonium bromide, CTAB) as soft template. The modified cotton fabric exhibited excellent electrical conductivity and electromagnetic interference shielding effectiveness due to the formation of fibrillar polypyrrole on the fiber surface. Electrical conductivity of fabric surface were studied by four‐probe resistivity system. The highly conductive fabric with surface conductivity of 5.8 S cm^?1 could be obtained by changing cationic surfactant concentration. The electromagnetic interference shielding effectiveness (EMI SE) of the modified fabrics was evaluated by the vector network analyzer instrument. Compared with the sample without using surfactant, the EMI SE value of PPy‐coated cotton fabrics increased by 28% after using 0.03 M CTAB as soft template. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43601.     

LDPE不/锈钢纤维电磁屏蔽材料的性能研究

将不锈钢纤维填加到LDPE中,制备了一种电磁屏蔽材料。分析了不锈钢纤维的加入对复合材料电磁性能、导电性能和力学性能的影响。     

Electroless silver plating on the PET fabrics modified with 3‐mercaptopropyltriethoxysilane

The feasibility of adherent silver layers onto PET fabrics by electroless plating was explored and its optimal technology for modification and electroless plating was investigated. Morphology, structure, and thermal stability of silver plating PET fabrics were characterized by scanning electric microscope (SEM), X‐ray diffraction (XRD) and thermogravitric (TG) analysis. As the silver weight on the modified fabric is 25 g/m², the electromagnetic shielding effectiveness (SE) of silver plating PET fabric is more than 30dB at the frequency ranging from 1MHz to 5000 MHz. The results show that the silver plating PET fabric has good electrical conductivity and electromagnetic shielding property. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effects of molding conditions on the electromagnetic interference performance of conductive ABS parts

Polymers filled with conducting fibers to prevent electromagnetic interference (EMI) performance have recently received great attention due to the requirements of 3C (computer, communication, and consumer electronics) products. In the present article, the effect of fiber content and processing parameters, including melt temperature, mold temperature, and injection velocity, on the electromagnetic interference shielding effectiveness (SE) in injection molded ABS polymer composites filled with conductive stainless steel fiber (SSF) was investigated. The influence of fiber orientation and distribution resulting from fiber content and molding conditions on EMI performance was also examined. It was found from measured results that fiber content plays a significant role in influencing part EMI SE performance. SE value can reach the highest values of approximately 40 dB and 60 dB at 1000 MHz frequency for fiber content 7 wt % and 14 wt %, respectively, under the best choice of molding conditions. Higher melt and mold temperature would increase shielding effectiveness due to a more uniform and random fiber orientation. However, higher injection velocity leading to highly‐orientated and less uniform distribution of fiber reduces shielding effectiveness. Among all molding parameters, melt temperature affects SE performance most significantly. Its influence slightly decreases as fiber content increases. Injection speed plays a secondary importance in affecting SE values, and its influence increases as fiber content increases. Upon examination of fiber distribution via optical microscope and subsequent image analysis, it was found that the fiber becomes more densely and random distributed toward the last melt‐filled region, whereas fiber exhibits less concentration around the middle way of the flow path. This can be attributed to the combined effects of fountain flow, frozen layer thickness, and gapwise melt front velocity. The results indicate that molding conditions, instead of fiber content alone, are very important on the SE performance for injection molded SSF filled ABS composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1072–1080, 2005