Use of carbon black as a reinforcing nano-filler in conductivity-reversible elastomer composites

This study presents an innovative approach to the production of reinforced elastomer composites filled with carbon black Printex XE-2B, using the calendering process and ionic liquids (ILs) as dispersing agents. The effect of Printex XE-2B on the mechanical and electrical properties of acrylonitrile-butadiene rubber (NBR) composites was compared to that of conventional carbon black Humex N339. It was found that the highly structured Printex XE-2B significantly enhanced both the mechanical and electrical properties of the NBR composites, in contrast to standard Humex N339. To obtain uniform filler dispersion in the polymer matrix, several different ILs were employed as dispersing agents. The application of ILs had a considerable effect on the properties of the prepared composites, due to the improved dispersion of the filler particles in the composite matrix, which favored the formation of ‘conductive paths.’ Importantly, the prepared NBR/Printex XE-2B/IL composites were found to have reversible and repeatable electrical properties following exposure to chloroform vapors.     

Roles of work of adhesion between carbon blacks and thermoplastic polymers on electrical properties of composites

The effect of the work of adhesion between carbon blacks and different thermoplastic polymers on the positive temperature coefficient (PTC) of composites was investigated. Thermoplastic polymers, such as EVA, LDPE, LLDPE, HDPE, and PP, were used with the addition of 30 wt% of carbon blacks. The work of adhesion based on the surface free energy of a composite was studied in the context of two-liquid contact angle measurements using deionized water and diiodomethane. It was observed that the resistivity on PTC behavior was greatly increased near the crystalline melting temperature, due to the thermal expansion of polymeric matrix. It was shown that the PTC intensity defined as the ratio of the maximum resistivity (rho(max)) to the resistivity at room temperature (rho(RT)) had the largest value on CB/HDPE composites. From the experimental results, the decrease in the work of adhesion induced by interactions between carbon black surfaces and polymer chains is an important factor in the fabrication of a PTC composite.     

Thermoanalytical testing of rubber-grade carbon blacks

The thermoanalytical behaviours of 9 carbon black types alone and in mixtures with rubber were studied. It was shown that the thermoanalytical tests carried out with rubber-grade carbon blacks help to predict their reinforcing effects. In measurements in the temperature range around 250° the weight losses indicate the activities of carbon blacks in rubber compounds. This test method may well supplement other test methods applied earlier to characterize carbon blacks.

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Zusammenfassung Das thermoanalytische Verhalten von 9 Typen von Ruß und in Gemischen mit Gummi wurde untersucht. Es wurde gezeigt, daß die an Ruß-Arten für die Gummi-Industrie durchgeführten thermoanalytischen Prüfungen sich für Voraussagen bezüglich der Verstärkungswirkung derselben eignen. Bei Messungen im Temperaturbereich um 250° zeigt der Gewichtsverlust die Aktivität des Rußes in den Gummiverbindungen an. Diese Testmethode kann die früher zur Charakterisierung von Ruß-Arten eingesetzten anderen Testmethoden gut ergänzen.

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Résumé On a étudié le comportement thermique de 9 types de noirs de fumée, seuls et en mélanges avec du caoutchouc. Les tests d'analyse thermique effectués sur des noirs de fumée destinés à l'industrie du caoutchouc permettent de prévoir l'effet renforçant de ceux-ci. Si les mesures sont effectuées vers 250°, la perte de poids indique l'activité des noirs de fumée dans le cautchouc. Cette méthode apporte des indications complémentaires des autres essais effectués précédemment pour caractériser les noirs de fumée.

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Paper presented at the Scientific Session on Thermal Analysis held at Balatonfüred, Hungary, on 14–16 October, 1976.     

An investigation on the structural characteristics and reinforcement of melt processed polyamide 66/multiwalled carbon nanotube composites

Properties of melt processed polyamide 66 (PA66)/multiwalled carbon nanotube composite were first characterized experimentally. The experimental results exhibited the formation of crystalline layer around the nanotubes and a considerable enhancement in mechanical properties by incorporation of multiwalled carbon nanotube up to 1 wt%. Mechanical properties were analyzed in terms of structural parameters using micromechanical models proposed in this study. It was suggested that the mechanical properties were greatly dominated by crystalline layer and nanotube length. It was also deduced that the melt mixing process caused a significant nanotube breakage restricting further enhancement of nanocomposite properties at higher nanotube contents. Surface modification of nanotube provided better polymer‐nanotube interaction; however, it increased the mechanical properties marginally. Copyright © 2014 John Wiley & Sons, Ltd.     

Toughness mechanism of polypropylene/elastomer/filler composites

The toughening mechanisms of polypropylene filled with elastomer and calcium carbonate (CaCO₃) particles were studied. Polypropylene/elastomer/CaCO₃ composites were prepared on a twin‐screw extruder with a particle concentration of 0–32 vol %. The experiments included tensile tests, notched Izod impact tests, scanning electron microscopy, and dynamic mechanical analysis. Scanning electron microscopy showed that the elastomer and CaCO₃ particles dispersed separately in the matrix. The modulus of the composites increased, whereas the yield stress decreased with the filler concentration. The impact resistance showed a large improvement with the CaCO₃ concentration. At the same composition (80/10/10 w/w/w), three types of CaCO₃ particles with average diameters of 0.05, 0.6, and 1.0 μm improved the impact fracture energies comparatively. The encapsulation structure of the filler by the grafting elastomer had a detrimental effect on the impact properties because of the strong adhesion between the elastomer and filler and the increasing ligament thickness. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1113–1123, 2005     

Polypropylene/carbon nanotube magnetic composites obtained using carbon nanotubes from sawdust

Magnetic polypropylene (PP) nanocomposites with different loadings (from 0.5 to 20 wt %) of carbon nanotubes with iron (CNT‐Fe) were fabricated using the melt‐mixing method. The carbon nanotubes were synthesized by pyrolysis of sawdust from the furniture industry. The morphological characterization shows homogenous dispersion of the filler in the polymer matrix. The addition of only 0.5 wt % CNT‐Fe already results in ferromagnetic behavior in the diamagnetic polymer matrix. The thermal properties were investigated using thermogravimetric analysis and differential scanning calorimetry. The results show an increase in the maximum degradation, crystallization, and melting temperatures of the nanocomposites compared with neat PP. The nanocomposites showed improvement in terms of mechanical and oxygen permeability properties. A very significant result of the work is the high remnant magnetization and coercivity values of the nanocomposites at room temperature whereas most of the works on similar systems show magnetic properties only at very low temperatures.     

An investigation on the kinetics of direct carbon solid oxide fuel cells

A direct carbon solid oxide fuel cell (DC-SOFC) is an all-solid-state electricity generation device that operates directly with solid carbon as fuel, without any liquid medium and feeding gas. Tubular electrolyte-supported solid oxide fuel cells (SOFCs), with silver-gadolinium doped ceria (Ag-GDC) as both anode and cathode materials, are fabricated and operated directly with activated carbon as fuel. The kinetics of the DC-SOFCs is carried out through analyzing the correlations of the cell reaction rates to the emitting rates of CO and CO₂. It turns out that higher operating current corresponds to higher rates of consuming and producing CO, through electrochemical oxidation at the anode and the Boudouard reaction at the carbon fuel, respectively. The rate of consuming CO can be maintained constant by controlling the operating current while the rate of producing CO decreases with time because of carbon consumption. When the CO producing rate becomes smaller than the CO consuming rate, the operation will be terminated. Compared to the rates of the chemical reactions, the diffusion rates of CO and CO₂ are so fast that their impeding effect on the cell performance can be neglected.     

Blends of carbon blacks and multiwall carbon nanotubes as reinforcing fillers for hydrocarbon rubbers

The reinforcement of a styrene‐butadiene rubber (SBR) by single fillers—carbon black (CB) or multiwall carbon nanotubes (MWNTs)—or by mixtures of CB and MWNTs, is investigated. The morphologies, mechanical and electrical properties of the composites, are analyzed. A significant improvement in the tensile properties is observed for samples containing a dual phase. Using atomic force (AFM) and transmission electron (TEM) microscopies, we demonstrate that the double loading improves the dispersion of the nanotubes in SBR. Electrical measurements show lower resistivity and a lower percolation threshhold for composites containing blends of fillers, which provides further evidence of better dispersion. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 46: 1939–1951, 2008     

Degradation process investigation of thermoplastic polyurethane elastomer in supercritical methanol

The depolymerization of thermoplastic polyurethane elastomer (TPU) was investigated in sub- and supercritical methanol. The raw TPU was based on 4,4′-diphenylmethane diisocyanate (MDI), poly(1,4-butylene adipate) (PBA) and extended with 1,4-butanediol (BDO). GC–MS, IR were used in product analysis which shown that the degradation products consisted of the monomers of TPU and their methylates. The quantitative analytical approaches were internal standard method of GC-FID and external standard method of HPLC-UV after derivatization with methanol. The morphological change of the reaction residues in degradation process was observed by SEM, combined with the influences of the degradation temperature and time, the depolymerization mechanisms were proposed, i.e. in HTHP methanol, the degradation started with the broken of the urethane group, the chain of TPU was separated into soft segment and hard segment by transesterification. Subsequently, the transesterification acted between methanol with the urethane group of the hard segment and the ester group of the soft segment, respectively. In the subcritical region, the main products were BDO, dimethyl adipate (DMA), and 4,4′-methylene diphenyl carbamate (MDC) which can be used in the innocuous production of MDI; and BDO, DMA, amines, tetrahydrofuran (THF), macrolides were mainly obtained in supercritical region.     

废轮胎回转窑中试热解炭表面组分XPS分析

以X射线光电子能谱（XPS）对废轮胎回转窑中试热解炭表面组分进行实验分析,研究热解炭本体与表面的异同,热解温度、热解炭粒径的影响。与商用炭黒比较,废轮胎热解炭本体中含有更多的Zn、Si、S、Mg等杂质元素,各组分与热解温度没有大的相关性;热解炭表面在热解过程中形成了一吸附沉积层,表面层中杂元素的质量分数极低;低于500℃时,热解不完全,吸附沉积物较少。热解炭按粒径存在一定分布,粒度<0.074 mm的粉末状热解炭来自表面磨损脱落的粉末,各种杂元素的质量分数很低;Zn元素的相对质量分数随热解炭粒径的减小而减少。对热解炭进行深度剖析发现,吸附层是极薄的,表面层对本体的影响是极小的;定量分析结果表明,以C质量分数为100,则O为4～6,S、N约为1,Zn小于0.6,而商用炭黑中S约为0.3,不含N、Zn。     

Preparation of carbon nanotubes/BiOBr composites with higher visible light photocatalytic activity

A novel flower-like photocatalyst CNTs/BiOBr was successfully prepared by a facile hydrothermal method. The morphology and the physicochemical properties of the prepared samples were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectrometry (EDX), and UV-visible diffuse reflectance spectroscopy (UV-vis DRS). The photocatalytic activity was evaluated by degradation of Rhodamin B (RhB) dye. It was demonstrated that CNTs/BiOBr photocatalyst could effectively photodegrade RhB under visible light (VL) irradiation.     

An experimental investigation on the conductive behavior of carbon nanotube-reinforced natural polymer nanocomposites

It is well known that carbon nanotubes (CNTs) have excellent electrical properties and can be used as the nanofiller in natural polymers to produce conductive CNT/polymer nanocomposites. In this study, the conductive behavior of CNT-reinforced natural polymer nanocomposites was investigated. The effect of CNT concentration on the conductivity of CNT/natural polymer nanocomposites was also investigated. The natural polymers used were plasticized starch (PS) and chitosan (CS). FTIR spectroscopy was used to examine the interactions between PS, CS, and CNTs. TEM analysis on both nanocomposites were made to study the dispersion states of CNTs in both polymers. The results showed that the surface resistivities of both CNT/PS and CNT/CS nanocomposites decreased steeply with increasing CNT concentration. Particularly, the CNT/CS nanocomposites showed a better conductivity than the CNT/PS composites at the same CNT concentration. The TEM result showed that CNT/CS nanocomposites had better dispersibility and formation of fully connected, three-dimensional network structures between the CNTs than the CNT/PS nanocomposites, which results in the superior conductive property of CNT/CS nanocomposites compared to the CNT/PS nanocomposites.     

An investigation on dispersion of carbon nanotubes in chitosan aqueous solutions

The dispersion of carbon nanotubes (CNT) in water of different pH and in chitosan aqueous solution of three acids, acetic acid, formic acid, and hydrochloric acid, was investigated. Chitosan was soluble in water of pH ≤3 and could well disperse untreated CNT and acid-treated CNT, both of which had poor dispersion in water of pH ≤3. With the presence of 0.1 wt% chitosan in solution, particle sizes of the CNT dispersion were found to decrease with increasing COOH contents on the CNT. Particle sizes of CNT, untreated and acid-treated, in the three acidic aqueous solutions were found to increase with increasing chitosan contents in solutions. Among the three acids, hydrochloric acid gave the smallest particle size of the CNT dispersion. Without chitosan, the dispersibility of the acid-treated CNT in aqueous solutions of three acids was in the order of acetic acid > formic acid > hydrochloric acid.     

废轮胎回转窑中试热解炭的重金属离子吸附特性

对废轮胎回转窑中试热解炭的重金属离子Pb2＋、Cr3＋和Cr6＋吸附特性进行了研究,分析了溶液pH值、接触时间、吸附剂用量以及溶液初始浓度对重金属去除率的影响。结果表明,溶液pH值对热解炭的重金属去除率有显著影响,阳离子Pb2＋、Cr3＋的去除率随pH的增加而增大,在弱酸和中性环境中去除率接近100％;Cr6＋在强酸性溶液中被还原成为Cr3＋,经二次吸附,总Cr去除率可达99％以上;Pb2＋和Cr3＋的去除率随热解炭用量和吸附时间的增大而增加,热解炭用量和吸附时间有一个最佳值。Pb2＋和Cr3＋的吸附为单分子层吸附,可用Langnuir和两段Freundlich等温吸附式描述,Freundlich拟合指数表明,热解炭具有较好的吸附性能。经酸洗后的热解炭对Pb2＋的去除率变低。     

Size analysis of industrial carbon blacks by sedimentation and flow field-flow fractionation

Carbon black is one of the most useful particulate materials in the industrial field. Among the various physical properties of carbon black, size and size distribution are the most important properties to affect the quality of a final product. However, it is difficult to measure the exact particle size of carbon black since it suffers unavoidable interference from flocculation. In this study, the effects of various factors on the dispersion of industrial carbon blacks were investigated for the determination of size and size distribution of carbon black particles. Sedimentation and flow field-flow fractionations (FIFFF) were used to determine the size of carbon black, and their optimum analytical conditions were tested by changing surfactant, pH, ionic strength, and method of dispersion. The results showed that surfactant structure and its concentration played significant roles in dispersion stability. Carbon black was dispersed well with a nonionic surfactant with a pH of around 8 and an ionic strength of 0.003 M. The mean diameters measured from two types of FFF and photon correlation spectroscopy are in good agreement. This study demonstrates the potential of sedimentation and flow FFF for analyzing highly adsorptive industrial particles and guides for sample preparation.