预制炭黑/尼龙6纤维网络在导电高分子复合材料中的逾渗行为

通过超声法将炭黑(CB)粒子固定在静电纺丝尼龙6(PA6)纤维膜表面,制备出一系列具有不同CB含量的CB/PA6导电纤维薄膜。利用热压成型法将制备的导电纤维膜与高密度聚乙烯(HDPE)粉末热压复合,制备出CB/PA6/HDPE导电高分子复合材料(CPC)。扫描电子显微镜图片显示,CB粒子均匀地锚固在PA6纤维表面,且CB/PA6导电纤维膜在HDPE基体中形成连续的导电网络结构。研究了材料的导电逾渗行为,发现CB/PA6/HDPE复合材料的逾渗值仅为2.5%,显著低于传统的CB/HDPE复合材料的逾渗值(8.5%)。同时,由于CB/PA6/HDPE复合材料具有特殊的预制CB/PA6导电纤维网络状结构,PA6电纺纤维膜的含量在复合材料体系中也呈现出有趣的逾渗行为。     

低逾渗MWCNTs-CB/UHMWPE导电复合材料的制备及性能

采用溶液法及机械共混法分别制备了均匀结构的炭黑(CB)/超高分子量聚乙烯(UHMWPE)及隔离结构的多壁碳纳米管(MWCNTs)-CB/UHMWPE复合薄膜。扫描电镜分析显示,虽然大部分CB均匀分散于UHMWPE基体中,但依然存在明显的局部团聚,而隔离结构中的MWCNTs-CB分布于UHMWPE界面间,更易形成导电通道。导电测试结果表明,复合材料的导电逾渗值由均匀分布的4.91%(体积分数)下降到隔离结构的0.42%。MWCNTs的加入完善了CB间的导电网络,使复合材料的逾渗值进一步下降,当CB∶MWCNTs=15∶1时,复合薄膜的逾渗值由0.42%(体积分数)下降到0.24%,然而混合填料中MWCNTs含量的进一步增加几乎对逾渗值没有影响。力学性能研究表明,隔离型复合材料的拉伸强度和断裂伸长率随填充剂含量的增加呈现出先上升后下降的趋势。     

炭黑／聚丙烯／聚碳酸酯复合材料导电性能和PTC特性

以聚丙烯（PP）／聚碳酸酯（PC）共混物为基体,采用不同种类炭黑（CB）填充制备导电复合材料并对其导电性能和PTC特性进行研究。结果表明：在常温时,PP／PC共混基体中PP含量大于40wt％时,材料的电阻率急剧下降;共混比为50：50（wt％）复合材料的电阻率达到最小值。加热时,两者均未出现明显NTC现象,说明PP／PC的共混可以有效的消除NTC效应。但PTC强度仅为1个数量级,远低于PP／CB二元复合材料。CB是影响PTC效应的重要因素之一,达到逾渗值时随着体系CB含量减少PTC效应会增强;乙炔炭黑与炉法CB填充的CB／PP／PC复合材料相比较,前者的体积电阻率较低,而两者的逾渗阈值相近,均为6．6％;乙炔CB为填料的CB／PP／PC三元复合材料的阿C突变温度在140℃附近,以炉法CB为填料时,PTC效应突变点出现在150℃（PC的Tg）附近。DSC分析结果表明,复合材料中PP的结晶度随着CB含量增加呈上升趋势,CB含量为15％时,PP的结晶度为32．75％,对于整个PP／PC／CB体系而言结晶部分的含量较低,因此该体系的PTC效应强度较低。     

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。     

用定向冷冻干燥法制备具有一维取向微孔结构的炭黑/聚乙烯醇导电复合材料

通过定向冷冻干燥法,制得了具有一维取向微孔结构的导电炭黑(CB)/聚乙烯醇(PVA)复合材料。对CB/PVA复合材料的导电性测试结果表明,该复合材料的导电逾渗行为并不完全符合经典的逾渗理论。由于CB/PVA复合材料特殊的取向微孔结构和炭黑于PVA基体的非均匀分布,使得其电阻率临界指数t值高于经典的逾渗理论的取值范围。     

基于共凝聚PTFE/炭黑粒子复合材料的制备和性能

在不使用凝聚剂的情况下采用下压式机械搅拌方式使聚四氟乙烯(PTFE)乳液和炭黑(CB)共凝聚,得到颗粒大小均匀的PTFE/CB粒子,然后用冷压成型和高温烧结工艺制备PTFE/CB复合材料,研究了烧结温度和CB含量对PTFE/CB复合材料的力学性能、导电性能和结晶度的影响。结果表明,烧结温度为390oC时复合材料中形成了均匀分布的微纤结构,力学性能最好;CB的填充明显提高了PTFE的力学性能和导电性能,当CB含量(质量分数)为2%时复合材料的力学性能最佳,拉伸强度从19.1 MPa增加至27.3 MPa,断裂伸长率从420%增加到525%。CB含量提高到3%的PTFE/CB复合材料结晶度最大,且CB在PTFE基体中形成了导电网络,电导率出现"逾渗",PTFE/CB复合材料具有抗静电性能。     

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。     

基于渗流网络的聚合物基柔性应变传感复合材料研究进展

基于渗流网络的柔性导电高分子复合材料具有制备简便、加工性良好、成本低、电学与应变传感性能可调等优点,是构筑柔性应变传感材料的重要方式,也是目前研究的热点.文中首先介绍柔性力敏材料的渗流网络、导电机理、性能参数及相关数值模拟,并详细介绍了逾渗曲线,然后总结了导电填料含量、形貌与维数、导电填料协同作用、填料与基体间的相互作...     

高电导率炭系复合高分子材料的研制

炭黑(CB)、石墨(C)、炭纤维(CF)炭系与基体树脂以特殊的工艺复合改性制得体积电阻率小于0.1Ω.cm的高导电高分子复合材料。研究了不同的复合体系(CB/PP)/SEBS、(PP/SEBS)/CB、(CB/SEBS)/PP及不同的配方与工艺获得的复合材料对导电性能的影响,结果表明,(PP/SEBS)/CB复合体系是最佳加工方式。采用扫描电镜(SEM)、力学性能测试等方法研究了炭系导电材料在PP/SEBS树脂中的分散机理及复合材料的力学性能。实验结果表明炭系复合组分含量为60%的PP/SEBS导电复合材料具有超高电导率、优良的力学性能和加工性能。     

CB/CNTs/PP导电高聚物力/温度作用下介电性能的研究

以聚丙烯(PP)为基体,炭黑(CB)和碳纳米管(CNTs)为填料,通过熔融共混、注塑成型制备导电复合材料,测定电场频率、填料种类、填料含量以及温度、载荷等因素对其介电性能的影响。结果表明,室温下,随着填料含量的增加,材料介电常数和介电损耗均呈增大趋势;随着频率的增加(100 Hz～10MHz),介电常数和介电损耗首先迅速降低,然后逐渐趋于稳定;随着CNTs的加入,CB/CNTs/PP导电复合材料的介电常数明显增大,但是当填料含量达到某一定值时,继续增大CNTs的含量,介电常数反而下降;同一频率下,随着温度的升高(30～100℃),由热膨胀引起炭黑粒子间距的变化会导致介电常数减小。复合材料压缩实验表明:压缩载荷作用下,材料发生形变,基体中的CB粒子间相对位置改变,引起介电常数减小。     

填充型聚合物基复合材料的导电和导热性能

研究了高密度聚乙烯为基体、炭黑和炭纤维为填料复合体系的导电和导热性能。发现当导电填料的含量达到渗流阈值时,复合材料的电导率急剧升高;而在渗流阈值附近,其热导率未出现突变。这表明电导渗流现象不完全是由导电粒子通过物理接触生成导电链所致。其导电机制是相当数量的导电粒子相互发生隧道效应。     

Complementary percolation characteristics of carbon fillers based electrically percolative thermoplastic elastomer composites

Electrically percolative composites of thermoplastic elastomers (TPE) filled with different concentrations of carbon nanotubes (CNT), carbon black (CB) and (CNT–CB) hybrid fillers were fabricated by melt blending. The effects of filler type and composition on the electrical properties of the percolative TPE composites were studied. Percolation threshold for CB-, CNT- and (CNT–CB)-based composites was found to be 0.06, 0.07 and 0.07 volume fraction respectively. Compared to CB-based composites and earlier reported results, CNT- and (CNT–CB)-based ones revealed an unexpectedly high percolation threshold, which otherwise considered an unwelcome phenomenon, lead to distinct and rare percolation characteristics of CNT filled percolative composites like per-percolation conductivity and a relatively steep percolation curves. CB-based composites showed a comparatively sharp insulator–conductor transition curve complementing the percolation characteristics CNT- and (CNT–CB)-based composites. Percolation threshold conductivity of the fillers was in the order of CB > CNT > (CNT–CB), while maximum attained conductivities followed the order of CNT > (CNT–CB) > CB. Conductivity order of fillers not only denied much reported synergic effect in (CNT–CB) filler but also highlighted the effect of percolation characteristics on the outcome of conductivity values. Results obtained were of theoretical as well as practical importance and were explained in the context of filler morphology and different dispersion characteristics of the carbon based fillers.     

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。     

炭黑填充聚偏氟乙烯复合材料的PTC效应

以聚偏氟乙烯（PVDF）为基体,经与炭黑等混合后挤出成型辐照。研究了两种不同类型导电炭黑（CB）对复合物导电性和正电阻温度系数（PTC）的影响,辐射剂量对PTC性能的影响,以及HDPE/PVDF配比对复合物PTC性能的影响。通过CB在HDPE/PVDF中配比不同时分布的扫描电镜（SEM）观测,随着PVDF含量的增加,C...     

双逾渗PTC材料的制备研究

以CB为导电填料,HDPE和PC为聚合物基,采用两种工艺制备HDPE／PC／CB三元复合材料。研究表明CB在单一聚合物HDPE中的逾渗阈值约为20％。母料共混制备的HDPE／PC／CB三元复合材料的PTC行为及重复性优于直接共混制备的试样。在母料共混制备的HDPE／PC／CB三元复合体系中形成了双逾渗行为,当HDPE／PC-40／60时,复合材料具有较好的PTC效应及PTC效应重复性。     

Electrical properties of hybrid carbon black/carbon fiber polypropylene composites

The electrical conductivity and morphology of injection molded polypropylene based composites containing two conductive fillers, carbon black (CB) and carbon fibers (CF) were studied. Injection moldings containing both, CB and CF, where the content of each filler was above its own percolation threshold, resulted in similar or lower values of overall composite volume resistivity compared with the resistivity of systems filled only with CB at the corresponding content. However, the resistivity of two-filler systems is always higher than the resistivity of systems filled only with CF at the corresponding content. The morphology and fiber length analysis of the injection molded composites are quite intriguing. Fiber orientation in the injection molded two-filler systems was found to be almost perpendicular to the melt flow direction, with no significant skin-core fiber orientation patterns, contrary to the typically observed fiber orientation in injection molded fiber filled composites. Moreover, the CF breakage in the presence of the CB was found more intense than when just CF is used, resulting in shorter fibers with narrower length distributions. This unexpected fiber behavior is responsible for the unexpected electrical behavior. However, the coexistence of CB and CF electrically conductive networks, supporting each other, was confirmed, in spite of the mechanical disturbances caused by the presence of fibrilar and particulate fillers.     

Conductive network formation during annealing of an oriented polyethylene-based composite

The conductive polymer composite (CPC) based on carbon black (CB), polyethylene (PE), and poly(ethylene terephthalate) (PET) was fabricated, in which the majority of CB particles were selectively localized in the surface of in situ deformed, highly oriented PET microfibrils. The on-line measurement of the electrical resistivity of the CPC materials indicated that the critical time for conductive network formation decreased with the increase of the annealing temperature and the filler loading. The activation energy for conductive network formation was about 96 kJ/mol, which was much higher than that for common CB/PE composite due to the large size of the conductive microfibrils. By a thermodynamic percolation model, the percolation threshold at equilibrium state was 1.735 vol.%, below which the effective conductive network was never formed. The reorganization velocity of the conductive microfibrils was a function of annealing temperature. This study extended insight into the dynamic process of the conductive network formation during annealing.     

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。     

Low temperature electrical conductivity of low-density polyethylene/carbon black composites

The study deals with the electrical characteristics of carbon black/low-density polyethylene (CB/LDPE) composites of various CB filler concentrations (10, 15, and 20 wt.%). The DC electrical conductivity was studied as a function of filler concentration in low temperature range 25–285 K. It was found that the composites exhibit negative temperature coefficient of resistivity (TCR) at low temperatures and high enhancement in the electrical conductivity with both temperature and carbon black concentration. The observed increase of conductivity with the filler concentration was interpreted through the percolation theory. The dependence of the electrical conductivity of the given composites on temperature (25–285 K) was analyzed in terms of a formula in consistence with Mott hopping mechanism.Visiting scientist from the Jordan University of Science and Technology, Irbid-Jordan.     

炭黑碳纤维填充双组分聚合物体系的导电网络及其阻温特性

以2种不同形态尺寸的导电填料炭黑(CB)、 碳纤维(CF)填充双组分聚合物体系高密度聚乙烯(HDPE)聚丙烯(PP), 制备了四元导电复合材料。研究了导电网络的结构形态及其对材料阻温特性的影响。光学显微镜及SEM 观察表明: 炭黑选择性地分布于HDPE中, 体系中HDPE与PP呈双连续相分布, 形成双渗流导电网络结构。而具有较高长径比的碳纤维在两相基体中均匀分布并贯通多个相区, HDPE导电相区的碳纤维相互桥接形成导电网络。电性能测试结果表明: 体系的体积电阻率与CB/HDPEPP及CBCF/HDPE三元复合体系相比下降了1~5个数量级。同时, 双渗流导电网络的存在也有效抑制了负温度系数(NTC)效应, 提高了循环稳定性。与CBCF/HDPE体系相比, CBCF/HDPEPP体系的NTC效应从2个数量级下降到0.6个数量级, 电阻特征弛豫时间从951s增加到了2370s。