Protocol for Studying Aqueous Foams Stabilized by Surfactant Mixtures

Even though foams have been the subject of intensive investigations over the last decades, many important questions related to their properties remain open. This concerns in particular foams which are stabilized by mixtures of surfactants. The present study deals with the fundamental question: which are the important parameters one needs to consider if one wants to characterize foams properly? We give an answer to this question by providing a measuring protocol which we apply to well‐known surfactant systems. The surfactants of choice are the two non‐ionic surfactants n‐dodecyl‐β‐d ‐maltoside (β‐C₁₂G₂) and hexaethyleneglycol monododecyl ether (C₁₂E₆) as well as their 1:1 mixture. Following the suggested protocol, we generated data which allow discussion of the influence of the surfactant structure and of the composition on the time evolution of the foam volume, the liquid fraction, the bubble size and the bubble size distribution. This paper shows that different foam properties can be assigned to different surfactant structures, which is the crucial point if one wants to tailor‐make surfactants for specific applications.     

Cobalt Oxide Electrodes-Problem and a Solution Through a Novel Approach using Cetyltrimethylammonium Bromide (CTAB)

In this article, we present a critical review of the literature on cobalt oxide modified electrodes, focusing on their cyclic voltammetric behavior. This article provides a broad survey of the field of electrochemical preparation of cobalt oxide films and their application in elecrocatalysis and electroanalysis. We discuss and analyze the complexity associated with the electrochemical behavior of cobalt oxide films, formed either through electrochemical methods or other methods. A solution is offered to the problem of complex redox couples of CoO film by introducing a novel cobalt oxide film. This is the first review paper on cobalt oxide modified electrodes. Focusing on this topic, all articles from 1922 to April 2014 are verified and the relevant articles are cited.     

A Comparative Study on the Aggregation and Thermodynamic Properties of Anionic Sodium Dodecylsulphate and Cationic Cetyltrimethylammonium Bromide in Aqueous Medium: Effect of the Co-solvent N-Methylacetamide

The effect of co‐solvent N‐methylacetamide (NMA) (0.035, 0.046, 0.127, and 0.258 mol kg^?1) on the micellization behaviour of anionic surfactant sodium dodecylsulphate (SDS) (3.21–10.35 mmol kg^?1) and cationic surfactant cetyltrimethylammonium bromide (CTAB) (0.19–3.72 mmol kg^?1) in aqueous solution was explored by employing conductivity measurements at different temperatures (298.15–313.15 K). The critical micelle concentration (CMC) values for SDS and CTAB in aqueous solutions of NMA were determined from the conductivity versus surfactant concentration plots. The variations in the CMC values of SDS with NMA concentration are in striking contrast to those observed in the case of CTAB. The various relevant thermodynamic parameters of micellization, viz. standard enthalpy change, ΔH_m^o, standard entropy change, ΔS_m^o, and standard Gibbs free energy change, ΔG_m^o, were determined using the temperature variation of the CMC values and counterion binding. The results not only relate these thermodynamic parameters to the consequences of intermolecular interactions but are also able to differentiate between SDS–water–NMA and CTAB–water–NMA systems in terms of contributions from head groups as well as alkyl chains of surfactants.     

Skin Penetration of Fatty Acids from Soap Surfactants in Cleansers Dependent on Foam Bubble Size

Skin cleansers exhibiting less irritation are required. Although most skin cleansers are applied to the skin in a foam state, the amount of surfactant penetrating into the skin is measured in the solution state. Due to the fact that surfactant penetration causes skin irritation, liquid chromatography/mass spectrometry was used in this study to investigate, from the viewpoint of surfactant penetration, the correlation between foam characteristics and the condition of skin treated with foam. Results demonstrated that as the concentration of surfactant in water drainage from the foam decreased, the composition of surfactants in water drainage shifted to contain smaller amounts of longer-chain surfactants, whereas the bubble size of the foam became smaller, notwithstanding any change in compounds. When several bubble sizes of foam were added to the skin, it was confirmed that the amount of surfactant penetrating into the skin depends on the levels in the water drainage. The amount of surfactant penetrating into the skin increased with foam bubble size. It was thought that the surfactant at the gas–liquid interface cannot act freely, and thus surfactants in the water drainage tended to penetrate the skin. These results suggest that along with the type of surfactant, both foam morphology and the actual way in which the foam is produced are also important factors that need to be considered when designing milder cleansers.     

The Effect of Sodium Dodecyl Sulfate (SDS) and Cetyltrimethylammonium Bromide (CTAB) on the Properties of ZnO Synthesized by Hydrothermal Method

ZnO nanostructures were synthesized by hydrothermal method using different molar ratios of cetyltrimethylammonium bromide (CTAB) and Sodium dodecyl sulfate (SDS) as structure directing agents. The effect of surfactants on the morphology of the ZnO crystals was investigated by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) techniques. The results indicate that the mixture of cationic-anionic surfactants can significantly modify the shape and size of ZnO particles. Various structures such as flakes, sheets, rods, spheres, flowers and triangular-like particles sized from micro to nano were obtained. In order to examine the possible changes in other properties of ZnO, characterizations like powder X-ray diffraction (PXRD), thermogravimetric and differential thermogravimetric analysis (TGA-DTG), FTIR, surface area and porosity and UV-visible spectroscopy analysis were also studied and discussed.     

Effect of Frothers on Bubble Size and Foam Stability in Potash Ore Flotation Systems

The objective of this project was to compare the effect of a selective flotation frother (MIBC) and powerful frothers (DEMPH and DF‐1012) on bubble size and foamability in water and in brine. In water, the bubble size is clearly reduced by flotation frothers which prevent bubbles from coalescing. The present study shows that the bubbles do not coalesce in brine and, therefore, frothers do not affect the size of bubbles in brine. The dynamic foamabality index measured in brine is much lower than that in water for weak frothers (e.g. MIBC); for both tested strong frothers the foamability measurements in brine reveal formation of meta‐stable foams.     

The Effect of NaCl on the Krafft Temperature and Related Behavior of Cetyltrimethylammonium Bromide in Aqueous Solution

This paper presents the effect of NaCl on the Krafft temperature (T _K), surface adsorption and bulk micellization of cetyltrimethylammonium bromide (CTAB) in aqueous solution. The critical micelle concentration (CMC) of CTAB in the presence of NaCl increased and then decreased with increasing temperature. Thus, the CMC–temperature data can be represented by a bell-shaped curve. The micellar dissociation (fraction of counterion binding) and energetic parameters (free energy, enthalpy and entropy changes) of both adsorption and micellization were calculated. The processes were found to be both enthalpy and entropy controlled and appeared to be more and more enthalpy driven with increasing temperature. An enthalpy–entropy compensation rule was observed for both adsorption and micelle formation. The T _K of the surfactant decreased significantly in the presence of NaCl, which is a sharp contrast to the usual behavior of the effect of electrolytes on the T _K of classical ionic surfactants. The surface excess concentrations decreased with increasing temperature. However, the values were much higher in the presence of NaCl compared to the corresponding values in pure water. The solubilization behavior of a water-insoluble dye, Sudan red B (SRB), in the micellar system was studied by the UV–visible spectrophotometric technique. The molar solubilization ratio in the presence of NaCl was found to be about three times higher than that in pure water, indicating that the solubilization of SRB in the CTAB micelles significantly increases in the presence of NaCl.     

溴代十六烷基吡啶增敏测定扑热息痛

在溴代十六烷基吡啶(CPB)存在下,研究扑热息痛在乙炔黑碳糊电极上的电化学行为,建立了一种简便灵敏的电化学分析方法.结果表明:CPB能使扑热息痛的氧化峰峰电位负移140 mV,并显著提高其氧化峰峰电流.在最佳实验条件下,氧化峰峰电流与扑热息痛浓度在5.0 ×10-7～1.2×10-3 mol·L-1范围内有良好的线性关系,检测限可达1.0×10-7 mol·L-1.将该方法用于速效感冒胶囊中扑热息痛含量的测定,结果令人满意.     

Aggregation Behavior of Sodium Dodecyl Sulfate and Cetyltrimethylammonium Bromide Mixtures in Aqueous/Chitosan Solution at Various Temperatures: An Experimental and Theoretical Approach

A conductometric study of the mixed micellization behavior between cetyltrimethylammonium bromide (CTAB, a cationic surfactant) and sodium dodecyl sulfate (SDS, an anionic surfactant) was carried out in the absence/presence of various percentages of chitosan in the temperature range of 298.15–318.15 K. The deviations of critical micelle concentration (cmc) from the ideal values indicate the interaction between CTAB and SDS. The micellar mole fraction values according to different proposed models X₁^Rub (Rubingh), X₁^M (Motomura), X₁^Rod (Rodenas), and X₁^id (ideal mole fraction) were estimated and the results obtained reveal the high contribution of CTAB in the mixed micellization, which enhances with the increase of the mole fraction of CTAB. The negative magnitudes of indicate the spontaneous formation of mixed micelles between CTAB and SDS. The values of activity coefficients (f₁ and f₂) were less than unity and the values of the interaction parameter (β) are negative in all cases, which indicate the attractive interaction between CTAB and SDS. The negative values of excess free energy of micellization (ΔG_ex) signify the stability of the mixed micelles. The negative values of in the chitosan systems indicate that micellization is exothermic. The values of were found to be positive in all cases.     

Control of Bubble Size and Location in Nano‐/Microscale Cellular Poly(propylene)/Rubber Blend Foams

Plastic foam with nano‐/micro‐scale cellular structures was prepared from a poly(propylene) (PP)/propylene‐ethylene copolymer (PER) blend by controlling bubble nucleation sites and bubble growth in disperse PER domains. Batch foaming experiments using a CO₂ pressure quench method were conducted at room temperature. The bubble size and location were highly controlled in disperse PER domains by exploiting the differences in CO₂ solubility and viscoelasticity between the PER domains and the PP matrix. The average cell diameter of PP/PER blend foams can be controlled within 0.5–2 µm by the PP/PER ratio, depressurization rate, and foaming temperature.

     

Theoretical prediction of flow regime transition in bubble columns by the population balance model

Theoretical prediction of flow regime transition in bubble columns was studied based on the bubble size distribution by the population balance model (PBM). Models for bubble coalescence and breakup due to different mechanisms, including coalescence due to turbulent eddies, coalescence due to different bubble rise velocities, coalescence due to bubble wake entrainment, breakup due to eddy collision and breakup due to large bubble instability, were proposed. Simulation results showed that at relatively low superficial gas velocities, bubble coalescence and breakup were relatively weak and the bubble size was small and had a narrow distribution; with an increase in the superficial gas velocity, large bubbles began to form due to bubble coalescence, resulting in a much wider bubble size distribution. The regime transition was predicted to occur when the volume fraction of small bubbles sharply decreased. The predicted transition superficial gas velocity was about 4 cm/s for the air-water system, in accordance with the values obtained from experimental approaches.     

填料粒径分布及其对填充PP性能的影响

本文用分形理论分析填充料粒径分布,揭示其分形特性,把一定总量下,小于某一当量直径r的填料质量份数W(r)与孔径r之间的指数关系定义为粒径分布的分形维数—分数维,即InW(r)=D_fInr K,D_f即为粒径分布的分数维。分数维值适中时,复合材料的力学性能最佳。     

超临界CO2下AOT/CTAB混合反胶团体系萃取乳酸钙中蛋白质的研究

研究了超临界CO2下AOT/CTAB混合反胶团体系萃取乳酸钙中影响产品品质的杂蛋白质.并且分析了萃取压力P、温度T、AOT用量VAOT及 AOT/CTAB摩尔混合比nAOT / nCTAB、水量VH2O、pH值等各因素对于该体系中蛋白质的萃取率的影响.通过正交试验得出最佳操作条件 P = 25 MPa,T = 45℃,VAOT =0.15 mL·(g乳酸钙)-1,nAOT/nCTAB = 3001, VH2O = 1.6mL水·(g乳酸钙)-1,pH =4.在此操作条件下,蛋白质的去除率可达70%.     

The Effect of Methanol on the Micellar Properties of Dodecyltrimethylammonium Bromide (DTAB) in Aqueous Medium at Different Temperatures

The micellar properties of dodecyltrimethylammonium bromide (DTAB) in water and methanol water mixtures at different temperatures have been studied by conductivity and surface tension measurements. The critical micelle concentrations (CMC), degree of ionization (α), standard Gibbs free energy of micellization (), standard enthalpy of micellization (), standard entropy of micellization () and free energy of transfer () were evaluated from conductivity data. The CMC, maximum excess surface concentration ( ), area occupied per surfactant molecule ( ), surface pressure at the CMC ( ), packing parameter (P) and standard free energy interfacial adsorption ) were estimated from surface tension measurements. The CMC of DTAB was found to increase with increasing volume fraction of methanol and increasing temperature. Thermodynamic parameters and surface properties revealed that the addition of methanol changes the relevant physicochemical properties which affect the process of micellization.     

Microcellular Crosslinked Silicone Rubber Foams: Influence of Nucleation Agent (Polyhedral Oligomeric Silsesquioxane) on the Rheological,Vulcanizing, Cell Morphological Properties

A series of microcellular silicone rubber/silica/polyhedral oligomeric silsesquioxane (POSS) foams were prepared by supercritical carbon dioxide. The effect of POSS particles on the rheological behavior, vulcanizing, and cellular morphology of the composites was investigated. The results showed that the POSS grafted carboxylic acid group can improve the matrix strength of silicone rubber. POSS grafted carboxylic acid group act as inhibiting agent in the vulcanizing process. POSS particles play an important role in the microcellular structure formation. When the POSS content was 2.0?wt%, the cell size and cell density can reach to 3.77?µm and 7.99?×?10⁹ cell/cm³, respectively.     

The Effect of Sodium Dodecyl Benzene Sulfonate on Particle Size in Suspension Polymerization of Styrene: A New Investigation

It is well known that inorganic solids can be used for droplet stabilization in suspension polymerization. This work investigates the effect of tricalcium phosphate (TCP) as an inorganic stabilizer and sodium dodecyl benzene sulfonate (SDBS) as a surface active agent for suspension polymerization of styrene. The results show that when large amounts of TCP is used, the amount of SDBS has no effect on particle size. The effect of concentration of SDBS will be very important if a small amount of TCP is used. Scanning electron microscopy analysis shows that TCP is adsorbed on the surface of monomer droplets and also the coalescence factor changes with concentration of SDBS in the solution.     

炸药自由基的检测及钝感机理探讨(简报)

以顺磁共振为手段获得了冲击下RDX炸药的自由基信号,并以获得的自由基谱线为依据,用顺磁共振等分析仪器测定吸气剂（getter)捕获自由基的能力,评价炸药的低易损性,提出了以自由基理论为基础的钝感机理来指导设计低易损炸药的思想。     

Investigation of the Physical and Tribological Properties of Iso-Oleic Acid

Oleic acid was isomerized into iso-oleic acid using a modified ferrite zeolite catalyst. The isomerization produced a mixture of iso-oleic acid isomers, with a methyl branching at the double bond, whose position has been randomly distributed along the fatty-acid chain. The effect of isomerization on the physical and tribological properties of iso-oleic acid relative to oleic acid was investigated. The neat fatty acids and their blends in polyalphaolefin (PAO-6) and high-oleic sunflower oil (HOSuO) base oils were used in the investigations. Relative to neat oleic acid, neat iso-oleic acid displayed: higher kinematic viscosity but lower viscosity index (VI) and acid number; lower pour point (PP) and cloud point (CP); better oxidation stability; similar four-ball (4-ball) antiwear friction and wear; and similar 4-ball extreme pressure weld point. Blends (0–10%, w/w) of iso-oleic and oleic acid in PAO-6 displayed the following similar trends with increasing concentration: mildly decreasing kinematic viscosity at 40 and 100 °C; increasing VI; lower coefficient of friction; and no change in wear. Blends (0–10%, w/w) of iso-oleic and oleic acid in HOSuO displayed the following similar trends: decreasing oxidation stability with increasing concentration; constant PP and CP with increasing concentration.     

聚丁二酸丁二醇酯/淀粉复合材料制备与性能研究

采用熔融共混法制备了聚丁二酸丁二醇(酯PBS)/淀粉复合材料。用扫描电镜、宽角X-射线衍射、差示扫描量热、热重分析等方法研究了复合材料的力学性能、微观形貌、结晶性能和热稳定性。结果表明:复合材料的拉伸强度、断裂伸长率和冲击强度随淀粉含量的增加而降低,而硬度、拉伸模量和弯曲模量则随淀粉含量的增加而提高;PBS和淀粉间的界面明显,断裂面上存在淀粉脱落的痕迹;淀粉的加入并未影响PBS的晶型;随着淀粉含量的增加,PBS的结晶和熔融温度均向低温方向移动;PBS和淀粉在各自的温度区域产生了热降解,随着淀粉含量的增加复,合材料的热稳定性逐渐降低。     

无卤阻燃增强聚对苯二甲酰癸二胺(PA10T)阻燃性能研究

采用一种次膦酸金属盐阻燃剂(FRP)对增强聚对苯二甲酰癸二胺(PA10T)进行阻燃改性。通过垂直燃烧法考察了不同阻燃剂含量下体系的阻燃性,运用极限氧指数仪测试了不同阻燃剂含量下体系的极限氧指数(LOI),并对体系燃烧后的残炭进行扫描电镜分析。结果表明,随着FRP添加量的增加,体系燃烧后的残炭量增加,炭层也变得更加致密,越容易通过UL94阻燃性测试。