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Pour Point Depressants
Published in Leslie R. Rudnick, Lubricant Additives, 2017
Mineral oils are commonly understood to be Newtonian fluids, meaning that they behave according to the following equation: Shear stress=Shear rate×Viscosity Experiments show that this equation holds for mineral oils as long as the temperature is above the cloud point of that oil. The cloud point is the temperature at which some of the waxy components of a mineral oil start to crystallize and precipitate from solution, leading to a hazy appearance. This visual evidence of the onset of wax crystals can be tested using American Society for Testing and Materials (ASTM) D2500 [1]. A plot of viscosity versus temperature is shown in Figure 14.1. Above the cloud point, denoted by the data point in Figure 14.1, the viscosity decreases proportionally with temperature. At temperatures below the cloud point, the viscosity increases steeply as the temperature decreases. Proper selection of a PPD will improve the viscosity of a fluid below the cloud point allowing fluid viscosities that approach that fluid’s theoretical best viscosity temperature line, the dotted line in Figure 14.1. Below the cloud point, it is not uncommon to observe one of the two non-Newtonian behaviors in these otherwise Newtonian fluids: Bingham fluid behavior or unpredictably high viscosity.
Colorimetric Determination of Uranium
Published in Alexandra C. Miller, Depleted Uranium, 2006
John F. Kalinich, David E. McClain
Two postcomplexation concentration techniques are being tested by us: cloud-point extraction and concentration of the Br-PADAP/uranium complex by adsorption to microcrystalline naphthalene. The technique of cloud point extraction attempts to capitalize on the solubility characteristics of Br-PADAP [36]. The solubility of many nonionic surfactants/detergents in aqueous systems is greatly reduced above a well-defined temperature called the cloud point. By forming the Br-PADAP/uranium complex, adding a nonionic surfactant, heating it, then letting it cool, the mixture should separate into an aqueous layer and a smaller surfactant layer. The Br-PADAP/uranium complex, due to its limited solubility, should be concentrated in the surfactant layer. This layer then can be resuspended in an appropriate solvent and the uranium concentration determined by measuring the absorbance at 578 nm. The microcrystalline naphthalene technique uses the affinity of pyridylazo compounds for tetraphenylborate-treated microcrystalline naphthalene in order to concentrate uranium from dilute solutions [37]. In this procedure, the Br-PADAP/uranium complex will be formed in the test sample. This, then, will be reacted with a small amount of a slurry of tetraphenylborate and microcrystalline naphthalene. The Br-PADAP/uranium should bind to the naphthalene mixture. After filtration, the precipitate will be dissolved in an appropriate organic solvent, and the uranium levels determined by measuring the absorbance at 578 nm.
Polymer/Surfactant Interaction in Applied Systems
Published in E. Desmond Goddard, James V. Gruber, Principles of Polymer Science and Technology in Cosmetics and Personal Care, 1999
E. Desmond Goddard, James V. Gruber
It is well known that many soluble polymers have an inverse solubility/temperature relationship, and their solutions exhibit a “cloud point” or lower consolute temperature. Examples are polymers based on polyalkylene oxides and those with multiple amide groups, or multiple ether/hydroxyl groups—as in several water-soluble, cellulose-based materials. While the phenomenon, in general terms, is explained as being due to “dehydration” of polar groups such as ether, amide, hydroxyl, and so forth, it is well known that it can often be offset by the addition of ionic surfactants, which can result in increases in cloud point of several degrees. This phenomenon seems to be a clear case of polymer/surfactant interaction with the formation of complexes of increased intrinsic solubility. Practically speaking, prevention of clouding in formulations can be important for maintaining viscosity and the stability of matter in suspension.
Effect of organic solvents and acidic catalysts on biodiesel yields from primary sewage sludge, and characterization of fuel properties
Published in Biofuels, 2021
Mohamed A. Gomaa, Nicolas Gombocz, Dominik Schild, Farouq S. Mjalli, Ahmed Al-Harrasi, Raeid M.M. Abed
The biodiesel cloud point was measured according to the ASTM D 2500 method, where the samples were gradually cooled from room temperature until the first sign of a cloud forming at the bottom of the sample was observed. Cloud point is the temperature at which the first wax crystals appear when a liquid is cooled. The pour point is the lowest temperature at which the fuel can still flow or be pumped. The pour point was measured according to ASTM D 97, where the samples were first cooled to freezing and then gradually heated until the lowest temperature at which movement was observed. For further analysis of the produced biodiesel, Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H-NMR) were performed to confirm the presence of FAME. FTIR was performed using a Perkin Elmer STA 6000 with a spectrum observing the range of 4000–400 cm−1. For 1H-NMR analysis, a Bruker Avance III HD spectrometer operating at 700 MHz was used with CDCl3 as a solvent. The 1H-NMR spectrum obtained was used to calculate the conversion efficiency of primary sludge to FAME according to the following equation [28]: where C% is the conversion efficiency to FAME (as a percentage), and AME and Aα-CH2 are the areas of methoxy and methylene protons, respectively.
Production and characterization of biodiesel from Jatropha (Jatropha curcas) seed oil available in Bangladesh
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Anik Prodhan, Md. Ikramul Hasan, Shah Mohammad Asaduzzaman Sujan, Mosharof Hossain, Md. Abdul Quaiyyum, Mohammad Ismail
Pour point, one of the primary parameters helps to understand fuel behavior at low temperatures, and this is closely related to cloud point. Cloud point is the temperature at which the first lump of crystal appears in fuel during the cooling process, whereas, pour point is the temperature where crystals are enough to form a gel and the fuel loses its fluidity below this temperature. Fuels that have lower pour points are more suitable for application in cold regions. Usually, biodiesels show a higher pour point which limits its utilization in low-temperature regions. However, the pour point of JCOME was found relatively lower (−10 °C) compared to other biodiesels, e.g. Calophylluminophyllum (4.3 °C), Heveabrasiliensis (−8 °C), and Madhucaindica (6 °C). However, it is still higher than that of commercial diesel (−2 °C).
Feedstocks for biodiesel production: Brazilian and global perspectives
Published in Biofuels, 2018
Simone P. Souza, Joaquim E. A. Seabra, Luiz A. Horta Nogueira
The higher the fatty acid saturation, the higher the cloud point and pour point values. These values depend on the feedstock used for biodiesel production and are affected by the type of alcohol (methanol or ethanol) used in the transesterification process [220]. Cloud and pour points are important properties as they may negatively affect the fuel injection system and the fuel filter, especially in cold temperatures. Cloud point is the temperature at which the liquid oil, originally translucent, becomes cloudy as a consequence of the formation of crystals and solidification of saturates [215]. Castor oil and macaw oil are great alternatives for cold temperatures as they present low cloud point, while palm oil, wild radish, and animal fat may be partially solid at room temperature, limiting its use, especially when pure, to tropical regions (Table 5). The solid formation increases as the temperature decreases, approaching the lowest temperature at which the material still flows, the so-called pour point [215].