Determination cloud point

One of the main characteristics of phase separation in polymer blends is the cloudy appearance of the materials. This cloudiness is a consequence of light scattering due to the inhomogeneity of the phase-separated blend structure. Hence, a cloud-point determination method, based on the static light-scattering phenomenon, has been employed customarily to locate the position of the 

I 5 Characterization of Phase Behavior in Polymer Blends by Light Scattering 

F re 5.3 H light-scattering profile during continuing crystallization. 

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To check the validity o this approach, we considered the sur- actants that we previously evaluated in the cloud point determinations. We evaluated the HLB by taking the percent o ethylene oxide per the particular sur actant and dividing it by ive (5), which usually yields reliable HLB values, and conpar-ing those results with the results ound using the equation involving C.E.R. described above. 

The low molecular weight hydrocarbon resins have solubility parameter values in the range of 8.2 to 9.5. This might seem narrow, but the solubility behavior of the various resins is quite different and parameter values to the second decimal point are required in choosing a formulation. Usually a solubility test in specific solvents and a cloud point determination are needed for precise control. 

Watkins, J. J., V. J. Krukonis, S. Smith, M. Satkowski, B. M. Hasch, S. H. Lee, and M. A. McHugh. 1991. The effect of crystallinity on the phase behavior of LLDPE in propane A. fractionation with respect to crystallinity, B. Cloud point determination of fractions exhibiting various crystallizabilities. Paper presented at the Annual AIChE meeting, Los Angeles, CA, November. 

We found that the observed cloud points (determined by turbidity measurements at 500 nm) only depend on the molecular weights (according to a Flory-Huggins behavior) at high pH, and that the architecture of the polymer does not show a significant impact. However, at lower pH a slight modulation is observed in addition to the shift of the whole cloud point curve to elevated temperatures, the cloud points... 

There is no way to determine the solubility parameter of polymers by means of the heat of vaporization instead, swelling experiments, methods involving cloud-point determinations, and some others are used to determine it [13]. 

A first cloud point determined by lowering the temperature can also be obtained in an analogous manner to that produced by addition of precipitant. The dependence on concentration of the first cloud-point temperature is given by... 

Fig. 10.31 Phase diagram of (a) PEO/Aramid and (b) PEO/PES blend system (A) cloud point determined by optical microscopy, ( ) onset of demixing obtained by modulated differential scanning calorimetry (Dreezen et al. 2001)...

Composition-dependent cloud points ( ) determined from light scattering and glass transition temperatures Tgj (O), (A), and... 

The cloud point determination is limited only to transparent oils otherwise there may be slight variation in results due to the human error involved, since the decrease in transparency is to be visually observed. 

Noninstramental analysis of ether sulfates is complex because of the various types of organic material which must be distinguished. Puschmaim and Wickbold have described comprehensive procedures for quantitative determination of the components in alkyl ether sulfates by wet chemical methods (68,69). Nowadays, these tests are usually performed by HPLC. Cloud point determination, a measure of EO content, is described in Chapter 2 with characterization of nonionic surfactants. 

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