多级拉伸PP/PA1010/CB导电复合材料的结构与性能

利用自主设计的多级拉伸挤出设备,制备了含不同长径比的聚酰胺/炭黑（PA1010/CB）纤维的原位微纤聚丙烯/聚酰胺/炭黑（PP/PA1010/CB）导电复合材料,炭黑仅选择性分散在PA1010中,形成一种特殊的双逾渗现象。扫描电子显微镜观察、电学性能测试结果表明,随着分割叠加单元个数的增加,（PA1010＋CB）导电相...     

Percolation threshold and morphology of composites of conducting carbon black/polypropylene/EVA

Conducting carbon black (CB), one of the intrinsic semi-conductors, was added into matrix polypropylene (PP) to prepare conducting composites by means of the melt processing method. Another component EVA was mixed into the composites in order to lower the percolation threshold. The percolation threshold of the ternary CB/PP/EVA composites was merely 3.8 vol%, while it was up to 7.8 vol% for the binary CB/PP composites without EVA. The conductivity of the ternary CB/PP/EVA composites was up to 10^–2 S/cm when the CB percentage was 5 vol%, while that of the binary CB/PP was lower than 10^–2 S/cm when the CB percentage was up to 10 vol%. DSC thermograms of the CB/PP/EVA composites showed that the melting peak shifted to low temperature with increasing CB content. The addition of CB and EVA resulted in the decrease of the crystallinity of PP in the ternary composites. The mechanical properties are also discussed. SEM and TEM were employed to study the morphology of the blend system. The results indicated that CB existed in the form of aggregations in the blend system. The smallest unit that formed a percolation network was grape-like aggregates with some small branches, which consisted of some CB particles, rather than the individual particles. This distribution was very valuable for forming conducting paths and for lowering the percolation value.     

Preparation and properties of carbon black/polymer composites with segregated and double-percolated network structures

A carbon black (CB)/low-density polyethylene (LDPE)/ultrahigh-molecular-weight polyethylene (UHMWPE) composite with a segregated and double-percolated structure has been fabricated using the solution mixing and high-speed mechanical mixing method. Structural observations show that the conducting CB/LDPE layers were only dispersed at the interface of UHMWPE granules and formed a well-developed CB conductive network with a percolation threshold of 0.26 vol%. The low percolation threshold in CB/LDPE/UHMWPE composites can be explained by the segregated and double-percolated networks of CB within the polymer matrix. A noticeable double positive temperature coefficient of resistivity can be observed around the melting temperature of LDPE and UHMWPE followed by a negative temperature coefficient of resistivity. The microstructure evolution of CB/LDPE/UHMWPE composites can be observed and explained by in situ optical micrographs.     

特殊形态结构导电高分子复合材料的电学性能

先使聚丙烯接枝马来酸酐(PP-g-MAH)与炭黑(CB)反应,再与聚丙烯/尼龙6(PP/PA6)共混制备出CB位于两相界面处的PP/PA6/PP-g-MAH/CB导电高分子复合材料,研究了材料的特殊结构和电学性能。结果表明,在PP/PA6/CB体系中CB粒子分布在PA6相,体系的逾渗阈值为2%;而在PP/PA6/PP-g-MAH/CB体系中,CB被PP-g-MAH诱导分布在两相界面处。PP/PA6两相为海岛结构时,PP/PA6/PP-g-MAH/CB体系仍可导电。PP/PA6/PP-g-MAH/CB体系的逾渗阈值降至1.6%,低于PP/PA6/CB体系。体系的正温度效应(PTC)强度远高于PP/PA6/CB体系,在90-135℃范围内不出现负温度效应(NTC)。PP/PA6/PP-g-MAH/CB体系的电学性能归结于其特殊的界面形态结构:导电通道由位于共混物界面处的PP-g-MAH和CB构建而成。     

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。     

High-performance conductive materials based on the selective location of carbon black in poly(ether ether ketone)/polyimide matrix

A novel high performance conductive material with excellent comprehensive properties was prepared by melt-blending, and its performances were adjusted by controlling the selective location of carbon black (CB) in poly(ether ether ketone) (PEEK)/thermoplastic polyimide (TPI) matrix. With increasing the CB loadings, the morphology of PEEK/TPI blends changed from sea-island to co-continuous structure, which was owing to the selective location of CB in TPI phase. Notably, with the selective location of CB in the induced co-continuous PEEK/TPI matrix, the electrical percolation threshold was reduced to 5 wt%, which was significantly lower than that of binary PEEK/CB (9 wt%) and TPI/CB (10 wt%) composites. And the electrical conductivity of ternary PEEK/TPI/CB composites was 10⁴ to 10⁶ times higher than that of binary composites at identical 7.5 wt% CB loading, which was attributed to the double percolation effect. Moreover, the incorporation of CB could improve the thermal and mechanical properties effectively.     

Enhancement of thermal and electrical conductivities of cyanoacrylate by addition of carbon based nanofillers

Nanocomposites with addition of graphite nanoparticles, multi-walled carbon nanotubes (MWCNTs), and graphene in cyanoacrylate from 0.1 to 0.5 or 0.6 vol% were fabricated. The influences of morphology towards thermal and electrical conductivities of cyanoacrylate nanocomposites were studied. Microstructure based on field emission scanning electron microscopy and transmission electron microscopy images indicated that nanofillers have unique morphologies which affect the thermal and electrical conductivities of nanocomposites. The maximum thermal conductivity values were measured at 0.3195 and 0.3500 W/mK for 0.4 vol% of MWCNTs/cyanoacrylate and 0.5 vol% of graphene/cyanoacrylate nanocomposite, respectively. These values were improved as high as 204 and 233% as compared with the thermal conductivity of neat cyanoacrylate. Nanocomposites with 0.2 vol% MWCNTs/cyanoacrylate fulfilled the requirement for ESD protection material with surface resistivity of 6.52?×?10⁶ Ω/sq and volume resistivity of 6.97?×?10⁹ Ω m. On the other hand, 0.5 vol% MWCNTs/cyanoacrylate nanocomposite can be used as electrical conductive adhesive. Compared with graphene and graphite nanofillers, MWCNTs is the best filler to be used in cyanoacrylate for improvement in thermal and electrical conductivity enhancement at low filler loading.     

Microstructure and electrical property of copper films on a flexible substrate formed by an organic ink with 9.6 % of Cu content

An organic copper ink with 9.6 wt% of Cu content derived from a short carbon chain organic copper precursor was successfully applied on a modified PI substrate and easily formed a favorable conductive copper film by self-reduction in the sintering process, which showed excellent conductivity. The effects of sintering temperature and time on the microstructure and conductivity action of the copper films were studied by XRD, EDS and SEM and electrical measurements, respectively. The sheet resistance and resistivity were determined to be as low as 0.11 Ω/□ and 2.2 × 10^?5 Ω·cm. The conduction mechanism is discussed in terms of the percolation theory.     

Fullerene-modified polyamide 6 by in situ anionic polymerization in the presence of PCBM

Activated anionic ring-opening polymerization of ε-caprolactam (ECL) was carried out for the first time in the presence of [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) to prepare polyamide 6 (PA6)-based composites comprising up to 3 wt% of this fullerene derivative. This in situ polymerization process produced high molecular weight composites containing 52–80 % of gel fraction at PCBM concentration ≥0.5 wt%. Spectral, thermo-mechanical, synchrotron X-ray, and scanning electron microscopy data were used to elucidate the structure and morphology of the PA6/PCBM composites. A mechanism of the chemical structure evolution was proposed starting with incipient complexation between ECL and PCBM, via subsequent chemical linking of ECL moieties on the C₆₀ spheroid and final formation of star-burst and cross-linked morphologies. PCBM amounts of 0.1 wt% and more decreased the volume resistivity from 10¹² Ω cm (neat PA6) to 10⁹–10⁷ Ω cm, thus opening the way for new applications of anionic PA6.     

Electrical properties of graphene nanoplatelets/ultra-high molecular weight polyethylene composites

Graphene nanoplatelets (GNPs)/ultra-high molecular weight polyethylene (UHMWPE) composites with a segregated structure had been fabricated using ethanol-assisted dispersion and hot compression at 180 °C. A percolation threshold of 3.5 wt% was achieved because of the formation conductive network. The positive temperature coefficient (PTC) and the negative temperature coefficient (NTC) effects of GNPs/UHMWPE composites had been investigated. The PTC behavior enhanced with increasing GNPs content but this was not always the case. The maximum PTC effect was observed in GNPs/UHMWPE composites (GNPs, 3.8 wt%) with the relatively low room temperature resistivity and the relatively high peak resistivity. The structure for GNPs/UHMWPE composites was examined by the SEM. The fact revealed that the slight interaction between GNPs and UHMWPE matrix may be changed by thermal cycles, and this can explain why thermal cycles could increase PTC and NTC intensity.     

炭黑/聚丙烯-聚(苯乙烯-乙烯/丁烯-苯乙烯)复合材料的介电性能和压阻性能

为了制备柔性较好的聚合物基压阻材料,利用熔融共混法制备了炭黑/聚丙烯-聚(苯乙烯-乙烯/丁烯-苯乙烯)(CB/PP-SEBS)复合材料,并研究了CB含量对CB/PP-SEBS复合材料介电性能和压阻性能的影响。结果表明:随着CB含量的增加,CB/PP-SEBS复合材料的介电常数、介电损耗及电导率均提高;CB/PP-SEBS复合材料发生导电逾渗时,CB的含量为12.2wt%;在CB/PP-SEBS复合材料发生弹性形变时,由于外力破坏了CB的导电网络,复合材料的电阻随着应变的增大而增大;循环压阻测试结果显示,在弹性变形区CB/PP-SEBS复合材料的电阻随着应变呈现周期性变化。研究结果可为制备具有稳定电阻变化的聚合物基压阻材料提供借鉴。     

炭黑结构度对HDPE/CB导电复合材料导电网络形成与破坏的影响

采用熔融混合方法制备高密度聚乙烯/炭黑(HDPE/CB)导电复合材料,比较不同结构度CB填充体系的逾渗曲线和温度-电阻行为,并研究了不同含量、不同结构度CB填充的HDPE的结晶行为。实验结果表明,高结构度CB可使填充体系逾渗值显著下降(本研究中可降低为2.7%);低结构度CB填充体系的正温度系数(PTC)效应强度比高结构度CB填充体系高出约3;降温过程中,温度-电阻率曲线上出现电阻突变峰的强度随着CB结构度的降低而增强;差示扫描量热(DSC)和广角X射线衍射(WAXD)结果显示,CB粒子的加入对HDPE的结晶行为没有显著影响。     

CNTs/ UHMWPE composites with a two-dimensional conductive network

A low percolation threshold can be achieved for the conductive polymer composites(CPC) materials having a segregated structure in which the conductive particles like carbon black (CB), carbon nanotubes (CNTs), etc. are only located on the interface of the polymer matrix particles instead of being randomly distributed in the whole system. Multiwalled carbon nanotubes (MWNTs) were experienced alcohol-assisted dispersion under ultrasonication and intense mechanical mixing, and only located on the interfaces of the ultrahigh molecular weight polyethylene (UHMWPE) matrix particles to form a segregated structure. The morphological observation and the critical exponent t value obtained from the classical threshold mechanism indicate that the MWNTs/UHMWPE composites form a 2-dimension conductive network, which leads to a very low percolation of 0.072vol%.     

石墨烯微片对尼龙6的改性研究

采用共混法制备尼龙6/石墨烯微片(GNPs)复合材料,研究了其导电性能、摩擦磨损性能及力学性能,并利用扫描电镜观察分析了材料磨损表面形貌,同时将其结果与炭黑(CB)体系进行了比较。结果表明,PA6/GPNs的渗滤阀值为15%(质量分数,下同),远低于PA6/CB的30%;GNPs的加入降低了材料的摩擦系数和磨损率,并在其含量为10%时达到最佳,分别降低30%和50%;提高了材料的拉伸强度、断裂伸长率、硬度,但冲击强度下降。CB的加入提高了材料的耐磨性、硬度,但摩擦性能、拉伸强度、断裂伸长率和冲击强度均下降。     

Effect of carbon nanotubes shape on the properties of multiwall carbon nanotubes/polyethylene flexible transparent conductive films

Transparent conductive material is used in a wide range of applications and is particularly interesting. In the present work, a series of multiwall carbon nanotubes/low density polyethylene nanocomposites with different carbon nanotubes were prepared via solution casting method. The optical transparency, morphology, and resistivity of transparent conductive films have been characterized by using UV–Vis Spectrophotometer, Field emission scanning electron microscope and Multimeter, respectively. Their electrically conductive and optically transparent properties were studied and compared. The result showed that thinner and longer multiwall carbon nanotubes were more suitable for the fabrication of flexible transparent conductive nanocomposites. The sample filled with 1 wt% of T.1 (outside diameter <8 nm, length 10–30 μm) had good transparent conductive properties (volume conductivity of 3.12 × 10^?3 S m^?1 and optical transmittance of 62.8 % at the light wavelength of 600 nm). The high volume conductivity and optical transparency demonstrated that such kind of nanocomposite films had favorable potential in the applications from electromagnetic interference shielding to transparent electrodes.     

Preparation and characterization of sulfonated poly(1,3,4-oxadiazole)/multi-walled carbon nanotube composite films with high performance in electric heating and thermal stability

For manufacturing thermally stable electric heating composite films, a sulfonated poly(1,3,4-oxadiazole) (sPOD) was synthesized and it was composited with pristine MWCNT of 0.1–10.0 wt% by an ultrasonicated solution mixing and casting. SEM images revealed that the pristine MWCNTs were dispersed well in the composite matrix via π–π interaction between the MWCNTs and the aromatic rings of sPOD backbone. The electrical resistivity of the composite films decreased considerably from ∼10⁹ Ω cm to ∼10⁰ Ω cm with the increment of the MWCNT content by forming a percolation threshold at ∼0.026 wt%. The composite films with 5.0–10.0 wt% MWCNT contents, which had sufficiently low electrical resistivity of ∼10³–10⁰ Ω cm, exhibited excellent electric heating performance by attaining high maximum temperatures as well as electric energy efficiency. Since the dominant thermal decomposition of the composite films took place at ∼500 °C, sPOD/MWCNT composite films with low electrical resistivity could be used for high performance electric heating materials for advanced applications.     

多元碳纳米材料协同改性玻璃微珠/环氧树脂复合材料

采用静电自组装法制备了还原氧化石墨烯表面修饰中空玻璃微珠（rGO@HGB）,与导电炭黑（CB）、石墨烯纳米片（GNPs）一起与环氧树脂（EP）共混,制备了CB-GNPs-rGO@HGB/EP复合材料,并系统研究了复合材料的微观结构、导电性能和介电性能。结果表明,rGO@HGB的加入能够显著提高rGO@HGB/EP复合材料的导电性能和介电常数,进一步引入CB和GNPs后,形成了被rGO@HGB隔离的导电逾渗网络,rGO、CB和GNPs三者对提高CB-GNPs-rGO@HGB/EP复合材料性能具有协同作用。在CB与GNPs的总含量固定为0.2vol%,且二者的体积比为10:1时,CB-GNPs-rGO@HGB/EP复合材料的导电与介电性能最优,对应的体积电阻率为1.88×104 Ωcm,在1 kHz下的介电常数高达454.5,分别比CB-rGO@HGB/EP和GNPs-rGO@HGB/EP复合材料提高了11.3%和10.7%,而其介电损耗仅为0.065。      

Synergistic effects of micro-/nano-fillers on conductive and electromagnetic shielding properties of polypropylene nanocomposites

This study presents the synergistic effects of graphene nanosheets (GNSs) and carbon fibers (CFs) additions on the electrical and electromagnetic shielding properties of GNS/CF/polypropylene (PP) composites. These composites were fabricated by the melt blending of different ratios of GNSs and CFs (20:0, 15:5, 10:10, 5:15 and 0:20 wt/wt%) into a PP polymer matrix using a Brabender mixer. Besides, the chemical and crystalline structures and the thermal stability of the resultant GNS/CF/PP composites were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and thermogravimetric analysis (TGA). FT-IR and XRD showed that with the addition of GNSs content, transmittances at 1373.4?cm^?1 and 1454.4?cm^?1 became smaller and the characteristic peak at 26.82° became stronger. TGA showed that the GNS/CF/PP composite can be used at high temperature below 456°C. Blending 10?wt% CFs and 10?wt% GNSs into the PP polymer resulted in excellent conductivity (0.397 S/cm), which indicated the occurrence of the critical percolation threshold phenomenon, and also reached the maximum electromagnetic shielding effectiveness (EMSE) of 20?dB at 1.28–2.00?GHz. Laminated with five layers of composites, its EMSE achieved 25–38?dB at 0.3–3.0?GHz, corresponding to blocking of 94.38–98.74% electromagnetic waves.     

熔融酯交换法原位合成炭黑/聚碳酸酯导电复合材料

利用原位聚合法合成具有导电性能的炭黑(CB)/聚碳酸酯(PC)复合材料。在聚合反应过程中, CB与PC在较低黏度下更好地混融, 而且通过负载催化剂连接CB和PC分子, 使CB参与PC链增长过程, 从而使CB有效分散。与传统的熔融共混法相比, 利用原位聚合法制备的CB/PC导电复合材料的渗滤阈值低, 当复合材料的体积电阻率为1.56×10⁶ Ω·mm时, CB的质量分数仅为4.32%。通过SEM观察发现, 原位法得到的样品中CB与PC充分混融, 形成导电网络更充分有效。利用原位聚合法得到的样品的正温度系数(PTC)的对数值达到4.69, 具有作为自控温材料的潜力。     

Self-sensing and mechanical performance of CNT/GNP/UHMWPE biocompatible nanocomposites

Ultra-high molecular weight polyethylene (UHMWPE)-based conductive nanocomposites with reduced percolation and tunable piezoresistive behavior were prepared via solution mixing followed by compression molding using carbon nanotubes (CNT) and graphene nanoplatelets (GNP). The effect of varying wt% of GNP with fixed CNT content (0.1 wt%) on the mechanical, electrical, thermal and piezoresistive properties of UHMWPE nanocomposites was evaluated. The combination of CNT and GNP enhanced the dispersion in UHMWPE matrix and lowered the probability of CNT aggregation as GNP acted as a spacer to separate the entanglement of CNT with each other. This has allowed the formation of an effective conductive path between GNP and CNT in UHMWPE matrix. The thermal conductivity, degree of crystallinity and degradation temperature of the nanocomposites increased with increasing GNP content. The elastic modulus and yield strength of the nanocomposites were improved by 37% and 33%, respectively, for 0.1/0.3 wt% of CNT/GNP compared to neat UHMWPE. The electrical conductivity was measured using four-probe method, and the lowest electrical percolation threshold was achieved at 0.1/0.1 wt% of CNT/GNP forming a nearly two-dimensional conductive network (critical value, t = 1.20). Such improvements in mechanical and electrical properties are attributed to the synergistic effect of the two-dimensional GNP and one-dimensional CNT which limits aggregation of CNTs enabling a more efficient conductive network at low wt% of fillers. These hybrid nanocomposites exhibited strong piezoresistive response with sensitivity factor of 6.2, 15.93 and 557.44 in the linear elastic, inelastic I and inelastic II regimes, respectively, for 0.1/0.5 wt% of CNT/GNP. This study demonstrates the fabrication method and the self-sensing performance of CNT/GNP/UHMWPE nanocomposites with improved properties useful for orthopedic implants.