Influence of dispersing additives on the conductivity of carbon black pigment dispersion

The influence of dispersing additives on the electrical conductivity of carbon black pigments dispersed in an organic medium was studied. Two dispersing additives were examined in combination with two different carbon blacks, a conductive carbon black and a nonconductive one. These carbon blacks differ in the size of their aggregates and in the amounts of surface oxygen groups. Both of the additives form a monolayer when adsorbed on either of the pigment surfaces. FTIR studies showed that chemical bonding of one of the additives on the surfaces of both pigments had occurred. Conductivity decreases with increasing additive concentration, but in the case of the chemically bonded additive, the conductivity of the dispersion remained high even at higher additive loadings. This study helps in understanding the effects such additives have on the specific conductivity of composite materials that contain dispersed carbon black pigment particles.     

炭黑在橡胶中分散技术研究进展

对于炭黑补强橡胶复合材料,平衡生热、补强以及磨耗之间的关系是炭黑应用的瓶颈问题。炭黑在橡胶基体中的分散性是影响其补强的关键因素之一,从增强炭黑与橡胶之间的相互作用角度出发,炭黑在橡胶中分散技术的研究进展主要体现在炭黑改性、橡胶改性以及液相复合技术方面。重点阐述炭黑的表面改性、聚合物基体的功能化改性以及炭黑与橡胶湿法混炼制备母胶,旨在促进炭黑在橡胶中均匀纳米分散,提高炭黑对橡胶的补强作用,获得性能优异的炭黑/橡胶复合材料。     

Selection of dispersants for the dispersion of carbon black in organic medium

The dispersion of the carbon black pigment in non-aqueous medium requires the use of dispersant additives. Two carboxylic dispersants of different chemical nature and molar masses have been investigated regarding this purpose. Their adsorption behavior has been evaluated by means of adsorption isotherms. The molecular interactions taking place at the surface have been inferred from IR and ¹³C RMN spectroscopies. The rheological behavior of the dispersions has considerably been improved by the presence of the copolymer dispersant of higher molar mass. It might adsorb at the surface by hydrogen bindings while taking a flat conformation with tails and possibly few loops that contributed to the steric stabilization of particles. The consequences of the deflocculation of the suspension on the colorimetric properties are an enhanced tinting strength and improved color stability.     

Observation of carbon black agglomerate dispersion in simple shear flows

Experiments aimed at studying the mechanisms of agglomerate breakup due to the application of a simple shear flow field were performed in a cone and plate transparent device. Spherical compacts of carbon black (diameters 1-2 mm) in a range of different porosites were used in the experiments. Two distinct breakup mechanisms, denoted as “rupture” and “erosion”, were observed. The critical stress for erosion was found to be smaller than that for rupture. Once erosion starts, it continues for very long times. Rupture occurs shortly after reaching a critical stress and concludes abruptly. For this analysis of rupture, the dimen-sionless group $\alpha {\rm = \{ }\eta {\rm .}\mathop \gamma \limits^{\rm .} {\rm /K'}\phi ^{\rm 4} {\rm \} }$, which is the ratio of applied stress to cohesive strength, was found to be a significant parameter for determining the final particle size distribution. The size analysis of fragments produced by shearing pellets for 1 minute showed a lognormal distribution function.     

Preparation of reactive nanoscale carbon black dispersion for pad coloration of cotton fabric

A reactive dispersant (SMA–ESA) was synthesised from poly(styrene‐alt‐maleic anhydride) (SMA) and 4‐(beta‐sulfatoethylsulfonyl)aniline (ESA), and its dispersing ability for carbon black (CB) was investigated. Fourier transform infrared (FTIR) and ¹H–nuclear magnetic resonance (NMR) spectroscopies showed that an amidation reaction took place between ESA and SMA. The optimal preparation conditions for reactive nanoscale CB dispersion were a mole ratio of ESA to SMA of 4:3, with a mass ratio of SMA–ESA and CB at 3%, sonication time 20 min, and pH 8. The reactive nanoscale CB dispersion prepared under optimal conditions showed excellent stability and small mean particle size. A cotton fabric coloured with reactive nanoscale CB dispersion could obtain a high K/S value, and excellent rubbing and washing fastness.     

Surface modifications for the effective dispersion of carbon nanotubes in solvents and polymers

The preparation of effective dispersions of carbon nanotubes (CNTs) presents a major impediment to the extension and utilization of CNTs. CNTs intrinsically tend to bundle and/or aggregate. The prevention of such behavior has been explored by testing various surface modification techniques to improve the dispersibility of CNTs in a variety of solvents and polymer matrices. General guidelines for the design of end-use tailor-fit surface modifications to achieve a particular CNT dispersibility have not thus far been articulated. This review aims to identify such guidelines by providing a perspective of the state of the art in surface modifications and the resultant dispersibility of CNTs. Surface modifications and dispersion properties must first be defined by agreeing upon a few new terms, such as the degree of surface modification, degree of substitution, and degree of dispersion, to determine the possible relationship(s) that may exist between surface characteristics and the dispersibility of CNTs. Furthermore, several critical issues that require concerted in-depth studies are discussed with particular emphasis on the quantitative characterization of CNT surface modifications and dispersions. This discussion describes the Flory–Huggins interaction parameter based on the solubility parameter for CNTs, which is correlated with the dispersibility in the surrounding media.     

Clay‐Assisted dispersion of carbon black in thermoplastic nanocomposites

The poor dispersion of carbon black (CB) in thermoplastic polymers has provided a space for improving the various properties of nanocomposites. In this study, nanoclay (NC) was introduced into CB/thermoplastic composites to improve the dispersion of CB and, finally, to improve the thermal or mechanical performance. We noticed that there was a simultaneous enhancement in the mechanical and thermal performances of the nanocomposites because of the combination of the NC and CB. The information obtained from the mechanical and thermal studies indicated that the properties were improved to an appreciable extent because of the plastic–plastic/CB/NC combination. The tensile strength of polycarbonate (PC) was observed to be enhanced by 9.4% only because of the addition of CB, although when poly(methyl methacrylate) (PMMA) was used as a matrix material along with PC, the tensile strength improved by 25%, although the tensile strength of PMMA is much lower than that of PC. This confirmed that the tensile properties of the polymer composites also depended on the plastic–plastic interaction phenomenon. Moreover, the tensile strengths of the different blended nanocomposites system increased by around 42.5% with the addition of NC. A significant improvement of 22% was achieved in the thermal stability of the PMMA composites with the addition of CB. However, the addition of NC provided further improvement in the thermal decomposition temperature by only 3.7%. This showed that the thermal stability of the polymer nanocomposites was slightly affected by the addition of NC. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41477.     

Fine dispersion of carbon black in fluorene‐based resin

The dispersion ability of fluorene‐based epoxy resin (FBE), bisphenol A based epoxy resin (PBE), fluorene‐based polyester (FBP), and polycarbonate (PC) in carbon black (CB) was evaluated. CB/FBE composite had a lower L value (reflectance, blackness) than that of CB/PBE composite, for the same CB content. Aggregations of CB in CB/FBE composites were much smaller than those in CB/PBE composites. The strong interaction between fluorene with cardo structure and CB resulted in a fine dispersion of CB in FBE. FBP had much higher dispersion ability of CB than PC. CB (50 wt%) was dispersed into FBP compared with the 10 wt% of CB dispersed in PC by melt blending. The effect of CB on the mechanical properties of FBP was much higher than that on PC due to fine dispersion of CB in FBP. The effect of CB addition on the T_g of FBP was also higher than that of CB on the T_g of PC. Computational simulation indicates that most stable energy between fluorene with a cardo structure and graphite structure was smaller than the energy between bisphenol A and graphite. It was also shown that the minimum energy appeared when the fluorene structure was almost parallel to the graphite plane. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Use of ultrasound to determine variation of carbon dispersion in carbon black filled HDPE melts

Abstract

An ultrasonic technique was used to determine whether differences in the degree of dispersion of carbon filler in high density polyethylene (HDPE) melts could be identified. Ultrasonic transit time measurements were used to identify differences between three grades of HDPE with different degrees of filler dispersion (designated high, medium and low dispersion). Tests were carried out on static melts (off line) over a range of temperatures and pressures, and during extrusion (inline). Tests carried out on samples of static melt showed a significant increase in ultrasonic transit time for the poorly mixed (low dispersion) sample, compared with the medium and high dispersion samples. Differences measured during off line tests were not observed during extrusion tests.     

论黑色陶瓷色料的制备

前言 黑色陶瓷色料是装饰材料中很重要的一种色料，黑釉以其纯正、凝重的装饰效果，倍受人们青睐，更被高档装修商视为珍品。一般制备黑色色料采用的是晶体着色：铬、铁、锰、镍、铜、钴等金属氧化物形成同晶混合型尖晶石晶体。这些元素在周期表中属于第四周期的过渡金属元素，它们的电子最外层为d轨道，是非球形对称轨道，当这些离子处于不同形状的配位场中时，     

Synthesis and characterization of carbon black modified by polylactic acid (PLA-g-CB) as pigment for dope dyeing of black PLA fibers

Dope dyeing is a clean method to produce a color polylactic acid (PLA) fiber. In order to investigate the influence factors of dope dyed PLA fiber, three kinds of PLA modified carbon black (PLA-g-CB) pigments with different particle size were prepared by open-ring polymerization method, which were further used for dope dyed black PLA fiber. The resultant black fiber was characterized by TEM, SEM, and DSC. The effect of particle size and concentration of PLA-g-CB pigments on color, mechanical property, and crystallization behavior of dope dyed PLA fiber were studied. Dope dyed black PLA fiber reached its good color property including K/S and leveling property when PLA-g-CB (I) pigment was the colorant with a concentration of 1.5%. Moreover, the dope dyed black PLA fiber containing PLA-g-CB (I) pigment had high breaking strength, crystallinity, fastness, and migration resistance to water and ethanol. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48784.     

N234/N660炭黑并用对炭黑在SBR1712橡胶中分散及物理性能影响

通过不同比例的N234/N660炭黑在SBR1712橡胶中的分散状态及物理性能分析,发现N234/N660以不同比例并用时分散度均较其加权平均值明显提高,扫描电镜观察胶料的脆断面发现炭黑结团数目降低,说明N234/N660炭黑的并用能促进炭黑在胶料中的分散。同时炭黑并用混炼胶的各项物理性能高于其加权平均值,说明炭黑分散度的提高对于胶料的各项物理性能的提高有明显效果。不同比例的N234/N660炭黑并用时均产生了协同效应。     

Influence of carbon black dispersion on the thermal diffusivity of an SBR vulcanizate

There are few investigations of the influence of filler dispersion on the thermal diffusivity of carbon black rubber compounds. In this article, experimental results of a cured styrene–butadiene rubber (SBR) compound are presented in the range of temperatures between 210 and 350 K at four levels of dispersion obtained in a laboratory mill. The results of thermal diffusivity measurements are discussed in the frame of competitive mechanisms appearing during mixing and involving the breakdown of agglomerates into aggregates and particles in the rubber matrix. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1379–1385, 1999     

Characterisation of dispersion of carbon black in high density polyethylene using dielectric measurements

Abstract

The use of dielectric measurements as a means of characterising the dispersion of carbon black in high density polyethylene has been investigated. The dispersion of carbon black is an important parameter to quantify because of its significant effect on the electrical properties of the material. Samples were prepared at 26 and 31% carbon black level by compounding on a twin screw extruder using different designs of screw to produce three degrees of mixing: low, medium, and high. Dielectric properties were measured as a function of temperature in the solid phase and through into the melt phase at various frequencies.

For a given level of carbon black, and at a fixed temperature, the frequency sensitivity of the alternating current (AC) resistivity was related to the dispersion of the carbon black. The AC resistivity and its frequency sensitivity decreased as the distance between the carbon black aggregates decreased, i.e. the frequency sensitivity decreased as the level of carbon black increased, as the degree of mixing decreased, and at lower measurement temperatures (especially below the melting point as opposed to above it). The frequency sensitivity of the AC resistivity is explained qualitatively in terms of a resistor-capacitor network model. In the manufacturing environment, the frequency sensitivity of the AC resistivity may be used as a practical measure of the dispersion of carbon black in high density polyethylene.     

The relationship of carbon black dispersion to electrical resistivity and vulcanizate physical properties

The degree of dispersion of carbon black in rubber is known to be a determining factor in the physical properties of the composite. It is important, therefore, to have a reliable, quantitative technique for assessing carbon black dispersion. It has been known for some time that the degree of dispersion of carbon black is reflected in its electrical resistivity. A resistivity instrument, developed by B. Boonstra, has been redesigned and constructed for use in this study. Factors that influence resistivity (i.e., black type, volume loading, and mixing time) are examined. Physical property and dynamic mechanical measurements are made, and their relationship to black dispersion is investigated. Light microscopy is also used to evaluate dispersion, and these data are compared to the resistivity results.     

Investigation of the dispersion of carbon black agglomerates of various sizes in simple-shear flows

The dispersion of spherical carbon black agglomerates suspended in polydimethyl siloxane liquid and subjected to simple shear flows has been studied in a cone-and-plate shearing device. Sets of dispersion experiments were carried out for agglomerates of various size and packing density. For agglomerates of equal density and under conditions of equivalent cone rotation rates, the dispersion rates of small agglomerates were smaller than those observed for larger agglomerates. Since the agglomerates occupy a significant fraction of the flow domain, the magnitude and distribution of shear stress acting on the agglomerate at a fixed cone rotation rate depends on the ratio of agglomerate size relative to the size of the gap between the cone and plate. To investigate whether this effect could cause the observed variation in dispersion behavior, we performed three-dimensional simulations of the flow fields within the cone-and-plate device and calculated the resulting stress fields acting on spherical agglomerates. These results helped guide additional experiments in which the peak stress acting on agglomerates of various sizes was matched. However, even under matched stress conditions, the dispersion kinetics was found to vary according to the agglomerate size. In addition, the dispersion kinetics for identical sized agglomerates was found to depend on their processing history. Both of these results lead to the conclusion that some other effect, likely the infiltration of the processing fluid within the agglomerate structure, also influences the dispersion behavior.