The effect of calcium ions on carbon suspensions

A high degree of dispersion of carbon black in water is obtained only in the presence of adsorbing long-chain, amphipathic molecules. Calcium ions flocculate these dispersions, but agglomeration can be prevented if anionic detergents are adsorbed on the carbon. Fine dispersions of carbon coated with a fatty acid or alcohol were maintained in the presence of calcium ions with detergents which coadsorb with the acid or alcohol monolayer. The significance of these results in regard to detergency theory is discussed.     

Observations of bound Tween80 surfactant molecules on single-walled carbon nanotubes in an aqueous solution

The slow diffusion of Tween80 surfactant molecules in a single-walled carbon nanotube (SWCNT) aqueous dispersion was directly observed using the pulsed field gradient nuclear magnetic resonance method. The slow diffusion of Tween80 molecules was attributed to the strongly adsorbed molecules on the SWCNTs in the aqueous dispersion. The amount of bound Tween80 molecules was estimated to be approximately 12% of the total amount of Tween80 molecules, contributing to the stability of the SWCNT aqueous dispersion. Using dynamic light scattering and total organic carbon measurements, this SWCNT/Tween80 aqueous dispersion was found to be very stable for at least 3 weeks. The observed zeta potentials of this SWCNT dispersion are between −10 and 0 mV, indicating that the stability of the SWCNTs in the Tween80 solution was maintained by steric interactions between the small amount of adsorbed Tween80 molecules on the SWCNTs, while the effect of electrostatic interactions between adsorbed Tween80 was minimal. This proposed method to investigate the amount of bound Tween80 molecules on SWCNTs has potential benefits in the field of the production of functional materials and nano-toxicity assessments.     

Congo red- and Zn(II)-derivatized monosize poly(MMA-HEMA) microspheres as specific sorbent in metal chelate affinity of albumin

Monosize poly(methylmethacrylate-hydroxyethylmethacrylate) [poly(MMA-HEMA)] microspheres (4 μm in diameter) were produced by dispersion copolymerization of MMA and HEMA in an ethanol-water medium. Congo Red was attached to the poly(MMA-HEMA) microspheres, covalently. These Congo Red-derivatized microspheres were characterized by optical microscopy, Fourier transform infrared spectroscopy, and elemental analysis. Then, Zn(II) ions were incorporated by chelating with the immobilized Congo Red molecules. Different amounts of Zn(II) ions [1.2–17.6 mg of Zn(II)/g of polymer] were conjugated on the microspheres by changing the initial concentration of Zn(II) ions and pH. Bovine serum albumin (BSA) adsorption on these microspheres from aqueous solutions containing different amounts of BSA at different pH and ionic strengths was investigated in batch reactors. The nonspecific BSA adsorption on the plain poly(MMA-HEMA) microspheres was very low (0.7 mg of BSA/g of polymer). Congo Red derivatization significantly increased the BSA adsorption (up to 35.8 mg of BSA/g of polymer). A further increase in the adsorption capacity (up to 61.0 mg of BSA/g of polymer) was observed when Zn(II) ions were incorporated. More than 90% of the adsorbed BSA was desorbed in 1 h in the desorption medium containing 1.0M NaSCN at pH 8.0. © 1997 John Wiley & Sons, Inc.     

Cibacron Blue F3G-A Attached Poly(Vinyl Alcohol) Particles for Specific Albumin Adsorption

Abstract

Poly(vinyl alcohol) (PVAL) particles (average size: 50 μm) were prepared in the present study by chemical crosslinking of PVAL with glutaraldehyde in an organic dispersion oil phase. Cibacron Blue F3G-A was attached to these hydrophilic PVAL particles. Bovine serum albumin (BSA) adsorption onto these dye-attached PVAL particles from aqueous solutions containing different amounts of BSA in three different salts (i.e., NaCl, CaCl₂, and NaSCN) at different pH and ionic strengths was investigated in batch reactors. The maximum adsorption capacity (about 35 mg BSA/g dye-attached PVAL) was observed around pH 6.0 in a medium containing NaCl with an ionic strength of 0.01. Nonspecific BSA adsorption on plain PVAL particles was almost zero. About 90% of the adsorbed BSA was desorbed by using a 0.5 M NaSCN desorption medium for 1 hour.     

Synthesis of 5-(4-methacrylamidophenyl)-10,15,20-triphenylporphyrin,its copolymerization with acrylamide and EDMA,use of this copolymer in the adsorption of bovine serum albumin

A rigid and porous polymeric adsorbent was prepared from monomers 5-(4-methacrylamidophenyl)-10,15,20-triphenylporphyrin (1%), acrylamide (39%), and cross-linking agent ethylene glycol dimethacrylate (60%) using suspension polymerization technique. The adsorption behavior of bovine serum albumin (BSA) on this adsorbent was studied as a function of the initial BSA concentration (0.4–2.5 mg/mL), pH (4.0–8.0), ionic strength, and type of salt in buffered solutions under batch equilibrium conditions. The amounts of adsorbed BSA at equilibrium at pH 4.0 and 7.0 for 1.0 mg/mL initial concentration of BSA were 743 mg BSA and 412 mg BSA per gram of the adsorbent, respectively. The adsorption process was nearly irreversible.     

Controlling the dispersion of multi-wall carbon nanotubes in aqueous surfactant solution

The sonication-driven dispersion of multi-wall carbon nanotubes (MWCNTs) in aqueous surfactant solution has been monitored by UV-vis spectroscopy and transmission electron microscopy. Time dependent sonication experiments reveal that the maximum achievable dispersion of MWCNTs corresponds to the maximum UV-vis absorbance of the solution. With higher surfactant concentration the dispersion rate of MWCNTs increases and less total sonication energy is required to achieve maximum dispersion. Dispersion of higher MWCNT concentrations requires higher total sonication energy. For effective dispersion the minimum weight ratio of surfactant to MWCNTs is 1.5-1. The surfactant molecules are adsorbed on the surface of the MWCNTs and prevent re-aggregation of MWCNTs so that a colloidal stability of MWCNT dispersions could be maintained for several months. The maximum concentration of MWCNTs that can be homogeneously dispersed in aqueous solution is about 1.4 wt%.     

Optimized dispersion of nanoparticles for biological in vitro and in vivo studies

Background

The aim of this study was to establish and validate a practical method to disperse nanoparticles in physiological solutions for biological in vitro and in vivo studies.

Results

TiO₂ (rutile) dispersions were prepared in distilled water, PBS, or RPMI 1640 cell culture medium. Different ultrasound energies, various dispersion stabilizers (human, bovine, and mouse serum albumin, Tween 80, and mouse serum), various concentrations of stabilizers, and different sequences of preparation steps were applied. The size distribution of dispersed nanoparticles was analyzed by dynamic light scattering and zeta potential was measured using phase analysis light scattering. Nanoparticle size was also verified by transmission electron microscopy. A specific ultrasound energy of 4.2 × 10⁵ kJ/m³ was sufficient to disaggregate TiO₂ (rutile) nanoparticles, whereas higher energy input did not further improve size reduction. The optimal sequence was first to sonicate the nanoparticles in water, then to add dispersion stabilizers, and finally to add buffered salt solution to the dispersion. The formation of coarse TiO₂ (rutile) agglomerates in PBS or RPMI was prevented by addition of 1.5 mg/ml of human, bovine or mouse serum albumin, or mouse serum. The required concentration of albumin to stabilize the nanoparticle dispersion depended on the concentration of the nanoparticles in the dispersion. TiO₂ (rutile) particle dispersions at a concentration lower than 0.2 mg/ml could be stabilized by the addition of 1.5 mg/ml albumin. TiO₂ (rutile) particle dispersions prepared by this method were stable for up to at least 1 week. This method was suitable for preparing dispersions without coarse agglomerates (average diameter < 290 nm) from nanosized TiO₂ (rutile), ZnO, Ag, SiO_x, SWNT, MWNT, and diesel SRM2975 particulate matter.

Conclusion

The optimized dispersion method presented here appears to be effective and practicable for preparing dispersions of nanoparticles in physiological solutions without creating coarse agglomerates.     

碳纳米管填料静电自组装制备及在导电塑料中的应用

为了提高碳纳米管(CNTs)在塑料中的分散性能,设计碳纳米管填料(CNTs Filler)。阳/非离子表面活性剂复配在水中分散CNTs,并赋予CNTs表面正电性。与表面负电性的炭黑或聚苯乙烯微球复合,通过静电吸附作用自组装形成均匀稳定的复合物,制备出CNTs Filler。对比了CNTs Filler、CNTs和炭黑在PS和ABS塑料中,经不同成型工艺的导电结果,证明了使用碳纳米管填料提高了碳纳米管在塑料中的分散性能,总结了碳纳米管相对炭黑作为塑料导电功能体适合压延成型加工。推荐碳纳米管用于导电片材、导电薄膜和高导电塑料等领域。     

苯乙烯-马来酸酐共聚物的酯化改性及其对炭黑的分散性能

采用异丁醇对苯乙烯-马来酸酐共聚物(SMA)进行酯化改性,研究了反应温度、时间、催化剂用量、异丁醇用量等因素对共聚物酸值的影响。红外光谱测试表明,SMA中酸酐与异丁醇发生了酯化反应。在以丁酮为反应溶剂,SMA质量占反应体系总质量的5%,异丁醇质量占反应体系总质量的12%,对甲苯磺酸质量占SMA质量的1%,反应温度80℃,反应时间4 h的条件下,SMA部分酯化物(SME)的酸值降低到了271.6 mg KOH/g。炭黑分散研究结果表明,SME对炭黑分散效率优于SMA,当SME酸值低于355.1 mg KOH/g,其用量为炭黑质量的20%,pH=9时,制备炭黑分散体平均粒径为154 nm,制备的炭黑分散体表现出良好的离心稳定性。     

Investigations of Palladium Catalysts on Different Carbon Supports

Pd-catalysts (5 wt%) were prepared on various supports: powdered and pelletized activated carbon derived from pine wood or beech wood, carbon black, and graphitized carbon black. The supports were palladized in the original condition or after HCl-treatment. The catalysts were characterized with CO-chemisorption, transmission electron micrographs, and X-ray photoelectron spectrometry. The precious metal dispersion and the catalytic activity are improved by the acid treatment of activated carbon as well as carbon black supports. A selection of samples were also characterized by means of inelastic neutron scattering (INS) to study the hydrogen-related features of the acid modification of the carbon supports. Indications for different sensitivities of the final Pd/C-catalysts to catalytically driven hydrogasification effects of the supports and the impact of these effects on the precious metal dispersion and the formation of Pd-hydrides were obtained. The formation of molecular-like polyaromatic structures was observed especially on HCl-treated activated carbon due to enhanced spillover of active hydrogen from the Pd-particles to adjacent sites on the support. The generation and accessability of these sites on the support seems to be promoted by the removal of ash and adsorbed species.     

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 influence of single-walled carbon nanotube functionalization on the electronic properties of their polyaniline composites

The “in situ” preparation and characterization of composites of polyaniline (PANI) and single-walled carbon nanotubes (SWCNTs) are reported. To improve the dispersion and compatibility with the polymer matrix the raw SWCNTs were modified following different routes. SWCNTs oxidized by chemical or thermal treatments (nitric acid and air oxidation, respectively) were subjected to covalent functionalization with octadecylamine (ODA). SWCNT/PANI composites were prepared either from just oxidized SWCNTs, or from ODA functionalized SWCNTs. Temperature-programmed desorption, elemental analyses, ultraviolet-visible (UV-vis), UV-vis with near infrared and Raman spectroscopy, X-ray diffraction, scanning and transmission electron microscopy and conductivity measurements were used to characterize the functionalized SWCNT materials, dispersions and composites. The PANI composite prepared from air oxidized SWCNTs showed the best electrical conductivity indicating a better interaction with polyaniline than ODA functionalised SWCNTs. The improvement of conductivity is attributed to the doping effect or charge transfer of quinoide rings from PANI to SWCNTs.     

Adsorption behaviour of carbon black/latex by cationised cotton fabrics

A carbon black/latex dispersion was prepared by mini‐emulsion polymerisation, and its absorption behaviour towards cationised cotton fabric was investigated. The results indicated that the prepared carbon black/latex dispersion had excellent freeze–thaw stability. Cotton fabric that was cationised with 3 g/l of 3‐chloro‐2‐hydroxypropyltrimethyl ammonium chloride at a liquor ratio of 30:1 can be optimally dyed with 4% owf carbon black/latex under the conditions of pH 7.2, 60 °C, and 1 h. The adsorption behaviour of the carbon black/latex towards cationised cotton fabric followed the Langmuir adsorption isotherm, with a lower dyeing rate and a better colour levelness than the ordinary carbon black dispersion with binder.     

中性墨水用碳黑色浆的分散稳定性

通过分散剂的筛选,研制了配置中性笔墨水的水性碳黑色浆. 提出了用于表征碳黑色浆分散稳定性的离心分离-吸光光度方法,并初步实验验证了其可行性. 优化了分散剂的用量,并研究了砂磨时间对色浆存储稳定性的影响. 结果表明,具有芳环结构的高分子嵌段共聚物是制备碳黑水性色浆的优良分散剂. 以碳黑颜料为基准,当苯乙烯-马来酸酐树脂铵盐溶液分散剂用量为20%、砂磨2 h时,得到平均粒径为117.1 nm的碳黑色浆,放置15 d后平均粒径为160.0 nm,具有较优的存储稳定性,以此色浆制备的中性墨水具有良好的存储稳定性和书写性能.     

Synthesis and photochromic property of nanoparticles with spiropyran moieties via one-step miniemulsion polymerization

Summary  Photochromic nanoparticles with spiropyran moieties were prepared by a facile one-step miniemulsion polymerization. The nanoparticle dispersion was obtained by mixing the monomers, spiropyran-containing molecules and hydrophobe, dispersing them into an aqueous solution with surfactant, subjecting the dispersion to ultrasonification and polymerizing the monomers by using a water soluble initiator. The shape and size of the nanoparticles was determined with the atomic force microscope (AFM) and dynamic light scattering (DLS), and the determined average diameter of the nanoparticles ranges from 30 nm to 60 nm. The absorption and fluorescence spectra for the nanoparticles dispersions reveal that the spiropyran molecules were successfully incorporated in the polymer nanoparticles. Moreover, the nanoparticle dispersions were found to exhibit enhanced photo-reversibility, photo-stability and relatively fast photo-responsive property compare to the same species in aqueous solution.     

Dispersibility of carbon black by polyvinyl alcohol solutions

The dispersibility of carbon black by eight types of polyvinyl alcohol solution has been studied which differed in their degree of hydrolysis (i.e. amount of free acetate groups) and molecular weight. The degree of hydrolysis varied from 80 to 100% and the molecular weight (viscosity average) from 6000 to 40,000. Adsorption isotherms of the polyvinyl alcohol on to the carbon black and contact angles of water on carbon black on to which polyvinyl alcohol had been previously adsorbed were measured. These results are related to the concentration at which dispersion occurs. It is shown that dispersion occurs when the contact angle falls below 90° but that this does not correspond to monolayer coverage of the polyvinyl alcohol on the carbon black. In fact, dispersion occurs at very low levels of adsorption, suggesting that only a low surface coverage is necessary to produce a hydrophilic surface.     

The chemical anchoring of noble metal amine precursors to silica

The effect of pretreatment on the dispersion of supported noble metal Catalyst prepared from amine precursors in basic solution have been studied. The following metal precursors were used: Pt(NH₃)₄(NO₃)₂, Pd(NH₃)₄(NO₃)₂, Ru(NH₃)₆Cl₃ and [Rh(NH₃)₅Cl]Cl₂ Pretreatment in oxygen, prior to reduction in H₂ at 400C, resulted in poor dispersions for Ru and Rh, moderate dispersions for Pd and high dispersions for Pt. Pretreatment in H₂ resulted in poor dispersions for Pd and Pt and high dispersions for Ru and Rh. Decomposition of the adsorbed Pt and Pd precursors in argon resulted in very high dispersions.     

Einfluß von Lösungsmitteln auf den Partikeldurchmesser von Dispersionen anionischer Polyurethanionomerer

Aqueous dispersions of anionic polyurethanes were prepared by reaction of polyethers, 1,6-hexamethylene diisocyanate, 1,2,4-benzenetricarboxylic acid anhydride and triethyl amine. Formation of the dispersion was achieved by phase reversal or by precipitation. Phase reversal occurred when the solution or the melt of the polymer was treated with water, while precipitation took place when the solution was stirred into water. The amount of acetone used has an effect on the mean particle diameter, D?_T, obtained by turbidity measurements. There was an optimal acetone concentration at which D?_T reached a minimum. A similar effect was observed when tetrahydrofuran, 2-butanone or acetonitrile were used as solvents instead of acetone. When the dispersion was formed by precipitation, only adequately diluted acetonic solutions formed colloidal dispersions, while concentrated solutions gave dispersions with a broad particle size distribution.     

炭黑-SiO2双相纳米填料的制备、结构及其填充溶聚丁苯橡胶的性能

分析了炭黑-SiO2双相纳米填料(CSDF)的制备工艺条件、相态结构及其组成,并研究了CSDF填充溶聚丁苯橡胶(SSBR)体系的相态结构及性能。结果表明,采用凝胶-相容复合法,控制硅凝胶溶液的pH值为7,加入表面活性剂十六烷基三甲基溴化铵和炭黑,经24h陈化后可制备纳米掺杂的CSDF1;CSDF1在填充SSBR体系中分散均匀,体系的拉伸强度、扯断伸长率及撕裂强度明显高于炭黑填充SSBR体系,滞后损失低于炭黑填充SSBR体系,且CSDF1填充SSBR体系的性能也优于凝胶-复合法和物理掺混法分别制备的CSDF2、CSDF3填充SSBR体系。     

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。