基于空间限域强制组装法制备短切碳纤维/乙烯-醋酸乙烯导电复合材料性能

采用空间限域强制组装法（SCFNA）制备短切碳纤维/乙烯-醋酸乙烯共聚物（SCF/EVA）导电复合材料,研究SCFNA方法制备SCF/EVA复合材料中导电填料分布形态的演变规律及该方法对复合材料导电性能和力学性能的影响。与传统共混方法相比,采用SCFNA方法制备的SCF/EVA复合材料,导电网络上SCF的间距变小,网络密实度显著提高,导电性能得到大幅度提升并具有良好的力学性能。实验表明:通过SCFNA方法制备的SCF/EVA复合材料的逾渗阈值为6.5 wt%,低于共混自组装法的8.2 wt%。相同SCF质量分数下,SCF/EVA复合材料的电导率比共混法自组装最高提高4个数量级。随着SCF质量分数的增加,SCF/EVA复合材料的力学性能呈先提高后降低的趋势,其中10 wt%SCF/EVA复合材料的力学性能最优,拉伸强度达到19.86 MPa。      

空间限域强制组装法制备聚二甲基硅氧烷/短切碳纤复合材料的密炼参数对其导电导热性能的影响

为了深入分析空间限域强制组装法(SCFNA)的均相体系制备工艺参数对复合材料导电和导热性能的影响,以10%的短切碳纤维(SCF)作为导热导电填料,以聚二甲基硅氧烷作为聚合物基体材料,分析了密炼转速、密炼时间对复合材料导电和导热性能的影响。实验结果表明,密炼转速为40 r/min时,密炼时间由25 min缩短到5 min,复合材料中的碳纤维在哈克密炼机中受到剪切扭矩作用,复合材料的导电性能逐渐增强,电导率提高了58.46倍,其相同点处能传递的温度提高了2℃,导热能力提高;密炼时间由5 min缩短到3 min时,复合材料受到密炼扭矩作用,材料的电导率保持不变;在密炼时间为25 min时,密炼转速由60 r/min降低到20 r/min,复合材料的导电导热性能也呈现逐渐增强的趋势,材料的电导率提高了30.23倍,其相同点处能传递的温度提高了4℃。通过分析物料在密炼机中受到的扭矩变化情况,选择最佳的密炼转速和密炼时间,从而提高复合材料的导电和导热性能。     

短切碳纤维导电复合材料渗流和PTC行为的唯象分析

为研究短切碳纤维含量和温度对导电复合材料渗流行为的影响,通过Landau相变理论导出了复合材料电导率与填料体积分数及温度的方程,并用该方程分析了短切碳纤维/乙烯基酯树脂复合材料的渗流和PTC行为。结果表明:复合材料的渗流阈值随温度升高而增加,PTC温度随碳纤维含量增加而上升。当温度由24.6℃上升到108.4℃时,其渗流阈值的理论值由1.06%增加到1.60%;当碳纤维体积分数由3.1%增加到4.6%时,其PTC温度的理论值由120℃上升到170℃。复合材料渗流阈值和PTC温度理论值与实验值符合得很好。      

碳纳米管/聚苯乙烯复合材料的制备及导电性能研究

用溶液共混的方法将碳纳米管(CNTs)分散在聚乳酸聚己酸内酯(PLLA-PCL)嵌段共聚物中,再采用熔融共混的方法,制备了CNTs/PLLA-PCL/PS复合材料.扫描电镜和高分辨率光学显微镜观察发现,CNTs能够较均匀地分散在PLLA-PCL.电导率的测定表明,CNTs的加入大幅度提高了聚苯乙烯的导电性能,与CNTs//PS复合材料相比,PLLA-PCL的加入对更加有效地分散CNTs.     

短切碳纤维/羟基磷灰石生物复合材料的制备及性能

以短切碳纤维为增强相, 采用原位复合法制备短切碳纤维(C_f)/羟基磷灰石(HA)生物复合材料。为提高材料的界面结合, 对C_f表面进行氧化处理。对纯HA结构、 C_f表面以及复合材料断口形貌分别采用XRD、 FTIR、 SEM进行分析表征; 采用万能试验机对复合材料进行力学性能测试。结果表明: 氧化处理后C_f表面变粗糙, 有羟基羧基官能团出现; C_f质量分数为3%时C_f/HA复合材料相对密度最大, 力学性能最好, 弯曲强度和弯曲模量分别约为130 MPa和36 GPa。C_f/HA复合材料断口SEM照片表明, C_f质量分数低于6%时能够实现在HA基体中的均匀分布。      

碳纳米管/导电聚苯胺复合材料的制备及相互作用研究进展

综述了近年来通过原位聚合法和化学共价法制备碳纳米管/导电聚苯胺复合材料的最新研究进展,并且重点分析了碳纳米管、聚苯胺之间的相互作用.与原位聚合法相比,化学共价法制备的碳纳米管/导电聚苯胺分子间除了π-π相互作用外,还存在着强烈的化学键作用,能够显著提高导电聚苯胺的热稳定性,同时,导电聚苯胺可提高官能化碳纳米管的电化学氧化还原稳定性.     

碳纳米管/聚乙烯/聚苯乙烯多相复合材料的制备及导电性能研究

用熔融共混的方法分别制备了两相复合材料MWNT(多壁碳纳米管)/LDPE、MWNT/PS和多相复合材料MWNT/LDPE/PS,以上3种复合材料的导电渗滤阈值分别为8%(wt,下同)、6%和4%.SEM观察发现,MWNT选择性的分布于MWNT/LDPE/PS复合材料的LDPE相中.当LDPE/PS的质量比为50/50时,聚合物基体形成双连续结构,由于双重渗滤的作用,复合材料的渗滤阈值降低到4%.     

短切碳纤维增强HA/PMMA生物复合材料的制备及性能

以丙烯腈短切碳纤维(C)为增强相,纳米羟基磷灰石(HA)为改性体,聚甲基丙烯酸甲酯(PMMA)为基体,采用原位合成与溶液共混相结合的方法,制备了C_f-HA/PMMA生物复合材料。用X射线衍射仪(XRD)、红外吸收光谱仪(FTIR)、扫描电子显微镜(SEM)和能谱仪(EDS)等对材料的结构组成及断面的微观形貌等进行测试和表征,使用万能材料试验机测试其力学性能。结果表明：该合成工艺可以保证短切碳纤维和HA 在基体PMMA中均匀分布;所制备的复合材料具有较好的力学性能。随着碳纤维含量的增加,复合材料的弯曲强度和模量均呈先增大后减小的趋势。当碳纤维含量为4 %、HA含量为2%时(质量分数),复合材料的弯曲强度和弯曲模量达到极大值97.41 MPa和3.06 GPa。从复合材料的SEM照片可以看出,当碳纤维含量增加到6%时,纤维在基体PMMA中出现部分聚集现象。     

镀镍碳纤维-碳纤维-玻璃纤维/乙烯基酯树脂导电复合材料的设计制备及其电磁性能

本研究旨在设计制备兼具电和磁功能的新型导电复合材料。采用具有良好导电性的短切碳纤维（CF）与兼具磁性和导电性的短切镀镍碳纤维（Ni-CF）作为功能体,以短切玻璃纤维（GF）作为填料,以乙烯基酯树脂（VER）作为基体,设计制备电磁性能可调控的导电复合材料。分别研究了CF含量对CF-GF/VER导电复合材料体积电阻率的影响、Ni-CF长度对（Ni-CF）-CF-GF/VER导电复合材料体积电阻率的影响,重点研究了Ni-CF含量对（Ni-CF）-CF-GF/VER导电复合材料体积电阻率和磁导率的影响,并初步探索了导电复合材料的电磁屏蔽性能。结果表明：（Ni-CF）-CF-GF/VER导电复合材料体积电阻率在0.35~36.48 Ω·cm范围内可调,磁导率在0.2~0.7内可调。CF和Ni-CF的含量和长度都会对（Ni-CF）-CF-GF/VER导电复合材料电磁性能产生较大影响。制备的（Ni-CF）-CF-GF/VER导电复合材料有望应用于电磁屏蔽领域。     

碳纳米管/环氧树脂复合材料的静电自组装制备及性能

采用静电自组装法制备了均匀分散的碳纳米管环氧树脂复合材料,并对比分析了普通碳纳米管和功能化碳纳米管对环氧树脂热学和电学性能的影响。采用透射电镜(TEM)观察到碳管和树脂乳液自组装形成"葡萄藤"状结构,扫描电镜(SEM)观察发现,碳管可在环氧树脂中均匀分散并形成网络。电、热性能研究发现,添加3%普通碳纳米管可降低环氧树脂表面电阻率7个数量级,导热系数较纯树脂提高112%,而羧基化碳纳米管表面电阻率仅降低4个数量级,导热系数仅提高86%。     

Improved thermal conductivity of polydimethylsiloxane/short carbon fiber composites prepared by spatial confining forced network assembly

Traditional compounding method is a common way to construct network to improve thermal conductivity (TC) of polymeric composites. However, the TC of the composites increases slowly when the network has been constructed. There is no percolation threshold in TC, unlike in electrical conductivity. Thus, a method of spatial confining forced network assembly (SCFNA) was used to prepare polydimethylsiloxane (PDMS)/short carbon fiber (SCF) composites to improve the TC. The content of SCF ranging from 2 to 18 wt% was used to illustrate availability of SCFNA method. When the content of SCF was 18 wt%, the TC of PDMS/SCF composites prepared by SCFNA method increased by 7.79 times over the TC of PDMS/SCF composites prepared by traditional compounding method and 10.93 times over the TC of pure PDMS. Comparing the SEM of PDMS/SCF composites prepared by SCFNA method with that prepared by traditional compounding method, the gap between fillers of former was much smaller than that of latter. Moreover, the gap decreased when compression ratio increased. Therefore, the TC of composites prepared by SCFNA method could be improved significantly compared with traditional methods, which provides the possibility to replace thermally conductive materials such as metal with polymeric composites.     

多壁碳纳米管增强炭黑/聚丙烯导电复合材料导电行为

为了充分利用不同导电粒子的导电作用,在炭黑(CB)/聚丙烯(PP)导电复合体系中引入了多壁碳纳米管(CNTs)。研究发现：引入的CNTs分散在CB粒子间起到“桥梁”作用,使体系的导电性能得到明显改善,并且CB∶CNTs为19∶1时其协同导电效果最好,该复合体系出现逾渗现象,对应的导电填料体积分数明显降低。在导电填料总体积分数为4.76%时,少量CNTs的引入就可使复合体系的体积电阻率从109Ω·cm下降到105Ω·cm;同时少量的CNTs能明显抑制炭黑/聚丙烯导电复合材料的正温度效应(PTC),使PTC强度从6.10降低到1.48,PTC转变峰温度从166℃升高到174℃。少量的 CNTs可以使PP的结晶温度提高12℃,对PP结晶的成核作用比CB更加明显。复合体系力学性能随导电填料体积分数增加而明显降低,但因为体积电阻率一定时CB-CNTs/PP体系所需导电填料体积分数较CB/PP体系明显降低,因此少量CNTs的引入能够使复合体系的力学性能得到更大程度的保持。     

Microstructure of carbon nanotubes/PET conductive composites fibers and their properties

Poly(ethylene terephthalate) (PET) resin has been compounded with carbon nanotubes (CNTs) using a twin-screw extruder. The composites of 4 wt% CNTs in PET had a volume electrical resistance of 10³ Ω cm, which was 12 orders lower than pure PET. The volume electrical conductivity of CNTs/PET composites with different CNTs containing followed a percolation scaling law of the form σ = κ(ρ − ρ_c)^t well. Scanning electron microscopy (SEM) micrograph showed that CNTs had been well dispersed in PET matrix. Optical microscopy micrograph showed that discontinuity of conductive phase existed in some segments of composite fiber. Rheological behavior of CNTs/PET composites showed that the viscosity of CNTs/PET composites containing high nanotube loadings exhibited a large decrease with increasing shear frequency. Crystallization behavior of CNTs/PET composites was studied by differential scanning calorimetry (DSC) and the nucleating effect of CNTs in the cooling crystallization process of PET was confirmed. Composite fiber was prepared using the conductive CNTs/PET composites and pure PET resin by composite spinning process. Furthermore, cloth was woven by the composite fiber and common terylene with the ratio 1:3. The cloth had excellent anti-static electricity property and its charge surface density was only 0.25 μC/m².     

Structure and tensile properties of polypropylene/carbon nanotubes composites prepared by melt extrusion

Polypropylene/carbon nanotubes (PP/CNTs) nancomposites were prepared with a single screw extruder by adding maleic anhydride-grafted poplypropylene (PP-g-MAH) as compatibilizer to polypropylene (PP) with different amounts of carbon nanotubes (CNTs) in the range of 0.1–0.7 wt.%. Structure and morphology of the prepared samples were examined by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), polarizing light microscopy (PLM) and X-ray diffraction (XRD). The results showed that PP spherulites decreased in size when CNTs were introduced into the polymer. Mechanical properties of the samples were also studied. Tensile tests showed that with increasing amount of CNTs the strain at break decreased whereas the Young’s modulus was improved of 16.41 % to 36.05 % and tensile strength of 36.67 % to 64.70 % compared to pristine PP. The SEM microphotographs showed that majority of the CNTs were dispersed individually and oriented along the shear flow direction.     

Properties of polypropylene composites containing aluminum/multi-walled carbon nanotubes

Polypropylene/aluminum–multi-walled carbon nanotube (PP/Al–CNT) composites were prepared by a twin-screw extruder. The morphology indicates that the CNTs are well embedded or implanted within Al-flakes rather than attached on the surface. During preparation of composites, the CNTs came apart from Al–CNT so that free CNTs as well as Al–CNT were observed in PP/Al–CNT composite. The crystallization temperatures of PP/CNT and PP/Al–CNT composites were increased from 111 °C for PP to 127 °C for the composites. The decomposition temperature increased by 55 °C for PP/CNT composite and 75 °C for PP/Al–CNT composite. The PP/Al–CNT composite showed higher thermal conductivity than PP/CNT and PP/Al-flake composites with increasing filler content. PP/Al–CNT composites showed the viscosity values between PP/CNT and PP/Al-flake composites. PP/Al–CNT composite showed higher tensile modulus and lower tensile strength with increasing filler content compared to PP/CNT and PP/Al-flake composites.     

脉冲FCVI制备炭/炭复合材料的微观结构及力学性能

采用脉冲强制流动热梯度化学气相渗透（IFCVI）法制备了毡基炭／炭复合材料。借助偏光显微镜及扫描电子显微镜观察了基体热解炭的微观组织结构及断口形貌特征；用弯曲实验测定了材料的力学性能。结果表明：采用脉冲FCVI，经1000℃～1250℃，100h致密化，2300℃热处理后，炭／炭复合材料的密度可达1．7g／cm^3，弯曲强度为125．4MPa，挠度为0．61mm。该工艺致密化速率快，所制备材料的密度分布均匀、力学性能好。研究表明，温度是影响材料组织结构的主要因素，高温条件下有利于粗糙层热解炭组织的生成，而低温有利于光滑层热解炭组织的生成，一般因沉积环境复杂多变，常得到混合型组织。