Cloud-point measurement

Cloud point. Measures the solubility/compatibility of a resin with solvents. The value reported is the temperature at which a specific mixture of a resin and a solvent or solvents blend gives a cloudy appearance, having been cooled from a temperature at which the mixture was clear. Commonly, a test tube of a given diameter is used and the temperature is noted when the lower end of the thermometer, placed at the bottom of the tube, disappears. Resins with cloud points below 0°C are commonly regarded as soluble and cloud points greater than 10°C indicate poor solubility/compatibility. White spirit with various aromatic contents is a widely used solvent in the determination of cloud point, but other solvents or solvents mixtures are also used. 

Cloud Point Measurements Cloud points were recorded by the visual observation of aqueous solutions containing 1% W/V surfactant. The measurement defines the temperature at which the system under test shows a characteristic transitional change from a clear solution to an opalescent or cloudy state. All cloud points were recorded in both ascending and descending temperature cycles to ensure data confidence. The influence of salt and/or oils on the cloud point were systematically evaluated. 

Cloud-point measurements were also made with the block polymers even though the theta concept has little meaning in this case. With the block copolymers the cloud-point is less easily seen as the change is to a low turbidity only. Unlike the random copolymers and the homopolymers, where gross phase separation... 

The cloud point measurement is used to predict the temperature at which wax in fuel may begin causing operating problems such as filter plugging and blockage of lines in fuel systems. 

Solvent Power and Compatibility. We will consider four methods for measuring the solvent power and compatibility of a plasticizer the Flory-Huggins n value, the cohesive energy density, viscosity measurements, and cloud point measurements. 

Marszall (1988) studied the effect of electrolytes on the cloud point of mixed ionic-nonionic surfactant solutions such as SDS and Triton X-100. It was found that the cloud point of the mixed micellar solutions is drastically lowered by a variety of electrolytes at considerably lower concentrations than those affecting the cloud point of nonionic surfactants used alone. The results indicate that the factors affecting the cloud point phenomena of mixed surfactants at very low concentrations of ionic surfactants and electrolytes are primarily electrostatic in nature. The change in the original charge distribution of mixed micelles at a Lxed SDS-Triton X-100 ratio (one molecule per micelle), as indicated by the cloud point measurements as a function of electrolyte concentration, depends mostly on the valency number of the cations (counterions) and to some extent on the kind of the anion (co-ion) and is independent of the type of monovalent cation. 

This dependence suggests a spinodal temperature for the PSH/PVME system of I40°C which is in agreement with cloud point measurements. Figure 12 shows that the temperature dependence of Xpsd/pvme and Xpsh/pvme are parallel indicating that deuteration brings about a uniform shift in the spinodal temperature. This result, however, may not hold for other compositions. 

Fig. 6. Cloud point measurement in the system PMMA/SAN (8.5/91.5) at 100 bar. Heating rate lK/min. Line represents intensity averages every 10 sec.

The solubility of linear alkanes present in diesel quickly decreases with temperature. The temperature at which the first crystals appear is called the cloud point and is one of the most important specifications for fuels concerning their low temperature behaviour. The utilization of a fuel is restricted to temperatures above their cloud point. Cloud point measures the temperature at which the wax crystals form a haze. Below the cloud point, the presence of crystals in suspension impairs the flow, plugging fuel filters. Immediately below the cloud point the fluid stops flowing, reaching what is known as pom point. The CFPP test measmes the highest temperature at which wax separating out of a sample... 

Figure 11.5 The temperature-concentration phase diagram for aqueous j crystallin (MW 20 000) systems (pH = 7, /= 0.24 mol kg" ) , cloud point measurements , concentration measurements of separated phases A = critical point.

F. Fitzpatrick, H. Schagerldf, T. Anderson, S. Richardson, F. Tjemheld, K.-G. Wahlund, and B. Wittgren, NMR, Cloud-point measurements and enzymatic depolymerization Complementary tools to investigate substituent patterns in modified celluloses. Biomacromolecules, 7 (2006) 2909-2917. 

BAK Bakshi, M.S., Kaur, N., Mahajan, R.K., Singh, J., and Sing, N., Estimation of degree of counterion binding and related parameters of monomeric and dimeric cationic surfactants from cloud point measurements by using triblock polymer as probe. Coll. Polym. Sci., 284, 879, 2006. 

BYU Byun, H.-S. and Lee, H.-Y., Cloud-point measurement of the biodegradable poly(DL-lactide-co-glycolide) solution in supercritical fluid solvents, Korean J. Chem. Eng., 23, 1003, 2006. 

For cloud point measurements the blends were prepared by solvent casting of a 5 wt% solution of total polymer at different blend ratios in tetrathydrofurane on a cover glass at room temperature. 

Cloud point measurements The films were isothermally annealed for 24 h at every temperature and the phase behavior was checked by optical microscopy and light scattering. Reversibility was usually found but could not be detected at the extreme edges of the phase diagrams. 

A newly developed thermal micro attenuated total reflection (ATR)/FTIR spectroscopic system with curve fitting program was used forthe quantitative investigation of molecular interactions in aqueous solutions of poly(N-isopropylacrylamide) (PNIPAAM). The lower critical solution temperature (LCST) in water of the PNIPAAM studied was found to be about 33C by cloud point measurement, DSC and the thermal micro ATR/FTIR spectroscopic system. The results from the new spectroscopic system with curve fitting program indicated that intermolecular interactions might predominate between PNIPAAM and water at temperatures below the LCST but above the LCST, PNIPAAM molecules in water were aggregated because of intramolecular interactions within the PNIPAAM molecules and the hydrophobic interactions in the system. 35 refs. 

Figure 9.24 Comparison of experimental and calculated phase diagram. The circles are from experimental cloud point measurements. Lines were calculated for the system with 0 = 0.27, = 600, = 1200, T = 600 K at a...

For the application of supercritical carbon dioxide as a medium for the production of polyolefins, it is important to have rehable thermodynamic data for the systems involved. Knowledge of the phase behavior of the reaction mixture is crucial to properly choose process variables such as temperature and pressure in order to achieve maximum process efficiency. For this reason, the ethylene-poly (ethylene-co-propylene) (PEP)-C02 system has been taken as a representative model system [3]. The effect of molecular weight as well as the influence of CO2 on the phase behavior has been studied experimentally by cloud-point measurements. In addition, the Statistical Associating Fluid Theory (SAFT) has been applied to predict the experimental results. 

The phase behavior of the binary system ethylene-PEP and the ternary system ethylene-PEP-C02 have been determined in an optical high-pressure cell designed for pressures up to 400 MPa and temperatures up to 450 K. Fig. 8.1 gives a schematic view of the method used for cloud-point measurements. 

The sample preparation has been carried out at ambient pressure and temperature. The properties of the PEP-polymers used for the cloud-point measurements are listed in Table 8.1, for which the molecular weights have been measured with high temperature gel permeation chromatography (GPC, dynamic viscosity). The estimated relative error in the amounts of the components in the mixtures is <2% for PEP8.7, <0.1% for PEP51 and ethylene, and <0.7% for CO2. 

Fig. 8.1 Schematic view of the Cailletet apparatus used for the cloud-point measurements, with 1. mercury,...

Fig. 8.2 Cloud-point measurements of (a) PEP51 and PEP8.7 in ethylene and (b) pressure-composition sections for PEPSl-ethyl-ene system, (a) PEPSI + iVp=0.0357 x ii/p = 0.0498 O iVp=0.0756 Q iKp=0.0989 ...

In this chapter, the possibihty of using late transition metal catalysts to synthesize polyolefins in supercritical carbon dioxide was demonstrated [43]. The multicomponent phase behavior of polyolefin systems at supercritical conditions was studied experimentally by measuring cloud-point curves as well as by modeling polymer systems at supercritical conditions. The cloud-point measurements show that CO2 acts as a strong antisolvent for the ethylene-PEP system, which implies that the polymerization concerned will involve a precipitation reaction. The model calculations prove that SAFT is able to describe the ethylene-PEP-CO2 system accurately. Solubility measurements of the Brookhart catalyst reveal that the maximum catalyst solubility is rather low (in the order of 1x10 mol L ). However, a number of strategies are given to enhance this value. 

NOZ Nozaiy, S., Modarress, H., and Eliassi, A., Cloud-point measurements for salt + poly(ethylene glycol) + water systems by viscometiy and laser beam scattering methods, J. Appl. Polym. Sci., 89, 1983, 2003. 

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