Melting water content

There are no generally accepted specifications manufacturers set their own specifications for hydroxyl number range, melt viscosity, water content, etc. Typical properties of Du Pont Terathane PTMEG are Hsted in Table 2, and selected thermal properties are given in Table 3 (260). For all grades, water content is <0.015 wt % ash, <0.001 wt % iron, <1 ppm peroxide, <5 ppm as H2O2 and flash point TOC is >163°C. 

Sodium acetate [127-09-3] M 82.0, m 324°, d 1.53. Crystd from acetic acid and pumped under vacuum for lOh at 120°. Alternatively, crystd from aqueous EtOH, as the trihydrate. This material can be converted to the anhydrous salt by heating slowly in a porcelain, nickel or iron dish, so that the salt liquefies. Steam is evolved and the mass again solidifies. Heating is now increased so that the salt melts again. (NB if it is heated too strongly, the salt chars.) After several minutes, the salt is allowed to solidify and cooled to a convenient temperature before being powdered and bottled (water content should now less than 0.02%). 

Figure 2.19 Intrinsic viscosity of the polymer melt as a function of extruder residence time and temperature for an initial water content of 3 ppm...

Harrison T.M. and Watson E.B. (1983) Kinetics of zircon dissolution and zirconium diffusion in granitic melts of variable water content. Contrib. Mineral. Petrol. 84, 66-72. 

Hurwitz S. and Navon O. (1994) Bubble nucleation in rhyolitic melts experiments at high pressure, temperature, and water content. Earth Planet. Sci. Lett. 122, 267-280. 

Thomas R. (2000) Determination of water contents of granite melt inclusions by confocal laser Raman microprobe spectroscopy. Am. Mineral. 85, 868-872. 

Microencapsulation using extrusion is mainly described for glassy carbohydrate matrices [14-16, 28-29]. The glassy carbohydrates, such as starch and maltodextrins, are melted at elevated temperature and low water contents and are intensively mixed with the active in the extrusion barrel. Extrusion has been used for volatile and unstable flavours. The shelf life of flavour oils could be extended from several months to 5 years, compared with 1 year for spray-dried materials. The main drawbacks of the technology are the high investments costs and the formation of rather large particles (500-1,000 pm). 

The procedure is designed to maintain the proper amount of water in the crystallization mixture so that the monohydrate 1 is obtained. It has the highest melting point and is the least hydroscopic. Other hydrated forms, such as the dihydrate (m.p. 35-60°) and mixed hydrates, may be isolated. A Karl Fischer assay of the water content is not necessary if the obtained material melts within the range given. 

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