纤维状填料/HDPE复合体系的导电渗流与流变渗流行为的关系

研究了纤维状导电材料不锈钢纤维(SSF)填充高密度聚乙烯(HDPE)导电复合体系的导电渗流与流变渗流行为之间的关系,并与颗粒状导电颗粒炭黑(CB)/HDPE导电复合体系进行了比较.发现当SSF含量极低(0.3vol%)时,SSF/HDPE体系即发生导电渗流现象,且导电渗流转变区域极窄;而仅当SSF含量达到4.8vol%时,该复合体系才表现出流变渗流现象,这一结果与CB/HDPE体系及纳米级导电纤维填充体系截然不同.此外,通过正温度系数效应的研究发现SSF形成的导电通路稳定性高于CB/HDPE体系.我们认为,SSF/HDPE体系呈现的这些特点均与SSF较大的直径及长径比且其导电通路及流变渗流网络的形成机理不同有关.     

加工工艺对炭黑填充聚合物双基体复合材料导电性能的影响

制备了炭黑(CB)填充高密度聚乙烯(HDPE)/乙烯-醋酸乙烯酯共聚物(EVA)双基体复合材料,研究了加料顺序、混合时间对复合材料导电性能的影响.结果表明,CB主要分布在HDPE相中;采用CB首先填充EVA然后与HDPE混合,或采用EVA/HDPE共混物与CB混合的加工策略,均可获得导电性较优的导电复合材料.然而,混合过程显著影响CB填充双基体复合材料的导电性.采用EVA/HDPE共混物与CB混合法加工复合材料,导电性受相形态演化影响较小.     

iPP/HDPE/CB三元导电复合材料的导电与流变行为

利用界面能原理使CB选择性分布于HDPE中成为复合导电相,固定CB在HDPE中的质量分数(20 wt％),控制CB/HDPE导电相在iPP中的含量,制备出一系列三元(iPP/HDPE/CB)导电复合材料,并研究其导电逾渗和流变逾渗行为.结果表明,在复合导电相含量为20 wt％时复合材料内即形成导电网络,在复合导电相含量30 wt％时出现流变网络.只有当复合导电相在材料中形成连续相时(60 wt％),损耗因子在频率扫描中才出现峰值.     

不同粒径炭黑混合对复合型导电材料PTC性能的影响

研究了炭黑分散效果对具有PTC效应的高密度聚乙烯／炭黑导电复合材料性能的影响。实验结果表明，由不同粒度和比表面积的两种炭黑混合后填充的复合材料同由导电性能较好的乙炔炭黑填充复合材料比较，前者具有较低的渗滤阀值、较高的临界温度、优良的PTC特性以及电阻稳定性好的特点．     

炭黑的“impurity-free”改性及其在聚酰亚胺薄膜中的分散特性研究

利用聚酰胺酸(PAA)在研磨过程形成炭黑(CB)的"impurity-free"分散剂制备纳米CB填充聚酰亚胺(PI)高性能复合薄膜.球磨CB和PAA/N-甲基-2-吡咯烷酮(NMP)溶液的混合液,PAA在研磨过程中降解形成活性分子,原位生成与CB表面具有反应活性和强烈物理吸附能力的"impurity-free"分散剂.拉曼、红外以及紫外-可见光吸收光谱证实了降解PAA分子对CB的改性作用.经改性的CB与PAA溶液共混,涂覆固化制备PI/CB复合薄膜.TEM照片表明该分散剂可以显著促进CB粒子在PI基体中的均匀分散,分散粒径约为200nm.力学性能测试和导电性能测试表明PI/CB复合薄膜的断裂伸长率大幅提高,电阻率(ρ)重复性浮动范围从2个数量级降到1个数量级.进一步研究发现,研磨过程中添加高分子量PAA更有利于CB在PI基体中的均匀分散.     

HDPE/HIPS/CB复合材料的制备及PTC性能

以高抗冲击聚苯乙烯(HIPS)和高密度聚乙烯(HDPE)为基体,炭黑(CB)为导电填料,采用熔融法制备聚合物基正电阻率温度系数效应(PTC)复合材料.通过扫描电子显微镜(SEM)研究了CB在复合材料两相基体中的选择分布,采用热敏电阻温度(RT)曲线测试仪研究复合材料PTC性能随CB含量的变化规律.结果表明,在HIPS/CB体系中加入HDPE后,复合材料的渗流阈值降低,PTC强度增强,耐电压强度有所提高.     

流变-导电同步测试法研究炭黑填充高密度聚乙烯的等温结晶行为

采用流变-导电同步测试法,研究炭黑(CB)填充高密度聚乙烯(HDPE)在124.3～125.3℃范围的等温结晶行为,发现应变、频率与预降温速率均显著影响等温结晶过程中动态流变与导电行为.动态储能模量(G')与电阻均在结晶过程中发生显著变化.其中,CB粒子在熔体中发生扩散,造成原有逾渗网络结构破坏,导致复合体系电阻在结晶诱导期内增大.随结晶度增加,G'在结晶诱导期附近开始显著增大,其临界时间对应1%～2%相对结晶度;同时,CB粒子在无定形区相互聚集而形成渗流网络结构,使得复合体系电阻显著降低.电阻的变化被认为与CB粒子在熔体中的迁移以及在HDPE晶体生长过程中的聚集行为有关,且比依时性动态流变行为更敏感.     

炭黑填充聚丙烯/尼龙6/玻璃纤维复合材料的制备及表征

以聚丙烯(PP)和尼龙6(PA6)的共混物为基体材料,以导电炭黑(CB)和玻璃纤维(GF)作为填料,通过熔融共混的方法制备了导电复合材料。研究了GF和CB质量分数对复合材料热稳定性、导电性能、力学性能和微观形貌的影响。结果表明:CB粒子选择性分散在PA6中,同时PA6包覆在GF表面,通过具有较大长径比的纤维相互搭接形成连续的网络结构,从而显著降低复合材料的逾渗阈值。在相同CB质量分数下(2%),PP/PA6/GF/CB的表面电阻率相对于PP/PA6/CB体系降低了5个数量级。此外,引入GF后,材料的热稳定性和拉伸强度都有所提高。     

炭黑填充橡胶复合材料的高频介电特性

研究了炭黑(CB)结构和橡胶基体极性对复合材料在高频区介电特性的调控作用.结果表明,与极性较强的丙烯酸酯橡胶体系相比,非(弱)极性硅橡胶体系与CB相互作用较弱,渗流阈值较低,界面极化弱,高频区介电常数随频率增大衰减较小. CB粒径大且比表面积小,虽不利于渗流网络的形成,但高频介电特性随频率衰减较小.比表面积小且结构度低的CB填充弱极性的硅橡胶体系在高频区具有较大介电常数,有望实现人体肌肉和脂肪的宽频化介电特性仿真.     

CB在PET-PE复合材料中的选择分散及电性能

用Haake转矩流变仪制备了聚对苯二甲酸乙二酯-聚乙烯-炭黑(PET-PE-CB)复合材料.通过溶解性试验、扫描电镜测试对CB在PET-PE多相体系中的选择性分散进行了研究,考察了CB分布对电性能的影响.结果表明:CB倾向于分布在PET相,改变CB填充量、基体配比以及加料次序对CB微观分布的影响不大.当m(CB)/m(PET-PE)=0.07时,出现渗滤现象.固定炭黑含量,当PET的质量分数由20%增加到60%时,材料的体积电阻率下降了6个数量级,一次性加料更有利于形成导电通路,可以获得较低的体积电阻.     

Black lipid membranes

New techniques have been introduced or pushed forward to render this model system more powerful. Dynamical light scattering allows us to quantify, in non-pertubative way, viscoelastic properties. Ion current fluctuation analysis gives information on channels on a single molecular level. Highly promising is the current development in fluorescence detection.     

The Electrochemistry of Black Carbons

“Modifications” of carbon—as long as they predominantly have the layered graphite structure—exhibit the following properties: (1) electrical conductance, (2) the ability to accomodate ions or molecules between the layers of the lattice, and (3) the ability to react via functional groups at their surfaces (largely at the layer edges). The first of these properties has led to carbon being used as an “inert” electrode material; this aspect will not be considered in this article. The combination of the first and second properties leads to the possibility of electrochemical intercalation. This aspect of black carbon's properties will be described, using both literature data and our own results, in terms of both the basic information and the methodology associated with its uses. In addition to the formation of graphite salts the origin of graphite oxide and the various methods which have been used to analyze these materials will be reviewed. The functional groups [(cf. 3) above] can also be reacted electrochemically. Here, particular emphasis will be placed on detailed results obtained from chemically modified carbon electrodes and also from surface oxides and fluorides. Reference will be made to the technological uses of surface oxidized carbon fibers in composite materials and also generally to possible future uses of graphite based compounds.     

Electrochemical Synthesis of Black Cobalt

The possibility of depositing black cobalt coatings from fluoride-containing electrolytes based on cobalt sulfate was studied.     

Noncovalent Functionalization of Black Phosphorus

Black phosphorus (BP) was functionalized with organic moieties on the basis of liquid exfoliation. The treatment of BP with electron‐withdrawing 7,7,8,8‐tetracyano‐p‐quinodimethane (TCNQ) led to electron transfer from BP to the organic dopant. On the other hand, the noncovalent interaction of BP with a perylene diimide was mainly due to van der Waals interactions but also led to considerable stabilization of the BP flakes against oxygen degradation.     

Heat-Resistant Polymer-Grafted Carbon Black: Grafting of Poly(Amide-Imide) Onto Carbon Black

Aromatic poly(amide-imide) with terminal isocyanate groups (PAINCO) was prepared by the polycondensation of trimellitic anhydride and a slight excess of 4,4′-diphenylmethane diisocyanate in N-methyl-2-pyrrolidone (NMP) at 160°C for 20 h. PAI was effectively grafted onto the surface by the reaction of PAI-NCO with carbon black: the percentage of grafting onto FW 200 and Neospectra II was determined to be 41.2 and 39.5%, respectively. When the carboxyl and phenolic hydroxyl groups on carbon black were blocked by treatment with diazomethane, the grafting of PAI-NCO onto the treated carbon black does not proceed. Therefore, it is concluded that PAI-NCO reacts with the carboxyl and phenolic hydroxyl groups on carbon black and PAI is grafted through amide and urethane bonds, respectively. The reaction of PAI-NCO with carbon black was accelerated by the addition of amines as catalyst and by raising of the reaction temperature. Thermogravimetric analysis indicated that PAI-grafted carbon black was stable in air up to about 300°C. The PAI-grafted carbon black was found to give a stable colloidal dispersion in NMP.     

高分子型炭黑分散剂的合成及其性能研究

研究了嵌段型分分子颜料分散剂的合成及其有炭黑分散体系中的分散稳定作用。结果表明，高分子嵌段分散剂在炭黑分散体系中能明显改善分散稳定性。同时发现，嵌段分散剂的组成、结构及分子量对分散作用有综合影响。     

Black Phosphorus Quantum Dots

As a unique two‐dimensional nanomaterial, layered black phosphorus (BP) nanosheets have shown promising applications in electronics. Although mechanical exfoliation was successfully used to prepare BP nanosheets, it is still a challenge to produce novel BP nanostructures in high yield. A facile top‐down approach for preparation of black phosphorus quantum dots (BPQDs) in solution is presented. The obtained BPQDs have a lateral size of 4.9±1.6 nm and thickness of 1.9±0.9 nm (ca. 4±2 layers). As a proof‐of‐concept application, by using BPQDs mixed with polyvinylpyrrolidone as the active layer, a flexible memory device was successfully fabricated that exhibits a nonvolatile rewritable memory effect with a high ON/OFF current ratio and good stability.     

Black Phosphorus Quantum Dots

As a unique two‐dimensional nanomaterial, layered black phosphorus (BP) nanosheets have shown promising applications in electronics. Although mechanical exfoliation was successfully used to prepare BP nanosheets, it is still a challenge to produce novel BP nanostructures in high yield. A facile top‐down approach for preparation of black phosphorus quantum dots (BPQDs) in solution is presented. The obtained BPQDs have a lateral size of 4.9±1.6 nm and thickness of 1.9±0.9 nm (ca. 4±2 layers). As a proof‐of‐concept application, by using BPQDs mixed with polyvinylpyrrolidone as the active layer, a flexible memory device was successfully fabricated that exhibits a nonvolatile rewritable memory effect with a high ON/OFF current ratio and good stability.     

Heat-Resistant Polymer-Grafted Carbon Black: Grafting of Poly(Organophosphazenes) onto Carbon Black Surface

Abstract

The grafting of poly(organophosphazenes) onto carbon black surface by the reaction of poly(dichlorophosphazene) (PDCP) with carbon black having sodium phenoxide groups was investigated. PDCP was prepared by the ring-opening polymerization of hexachlorocyclotriphos-phazene in solution using sulfamic acid as a catalyst. The introduction of sodium phenoxide groups onto carbon black was achieved by treatment of phenolic hydroxyl groups on the surface with sodium hydroxide in methanol. Poly(diphenoxyphosphazene) (PDPP) was successfully grafted onto carbon black by the reaction of PDCP with sodium phenoxide groups introduced onto the surface followed by the replacement of chlorine atoms in PDCP with phenoxy groups. The percentage of grafting onto carbon black increased to 206% at 30°C after 12 h. It was found that only 1.4% of sodium phenoxide groups on carbon black surface was used for the grafting of PDCP because of the blocking of the surface by grafted polymer chains. Poly(diaminophenylphosphazene) and poly-(diethoxyphosphazene) were also grafted onto carbon black surface by the treatment of PDCP-grafted carbon black with aniline and sodium ethoxide, respectively. Poly(organophosphazenes)-grafted carbon blacks produced stable colloidal dispersions in good solvents for grafted polymers. Furthermore, thermogravimetric analysis indicated that poly-(organophosphazenes)-grafted carbon blacks were stable in air about 300°C.     

LC–MS/MS法检测黑色粮谷类食品中的苏丹黑B和苏丹红B

采用液相色谱串联质谱(LC–MS/MS)法测定黑色粮谷类食品中苏丹黑B和苏丹红B含量。用正己烷、饱和乙腈提取目标物,以乙腈饱和的正己烷去除油脂,以固相萃取柱富集净化处理,外标法定量。苏丹黑B和苏丹红B的质量浓度在5~100 ng/m L范围内与色谱峰面积呈良好的线性,线性相关系数r20.999,检出限为5μg/kg。加标回收率为90.0%~96.0%,测定结果的相对标准偏差小于1.0%(n=6)。该方法分析时间短,准确性好,适用于黑色粮谷类食品中苏丹黑B和苏丹红B含量的检测分析。