Water/moisture content

In many products, the spin-relaxation properties of the components can be different due to molecular sizes, local viscosity and interaction with other molecules. Macromolecules often exhibit rapid FID decay and short T2 relaxation time due to its large molecular weight and reduced rotational dynamics [18]. Mobile water protons, on the other hand, are often found to have long relaxation times due to their small molecular weight and rapid diffusion. As a result, relaxation properties, such as T2, have been used extensively to quantify water/moisture content, fat contents, etc. [20]. For example, oil content in seeds is determined via the spin-echo technique as described according to international standards [64]. 

The water (moisture) content can rapidly and accurately be determined in polymers such as PBT, PA6, PA4.6 and PC via coulometric titration, with detection limits of some 20 ppm. Water produced during heating of PET was determined by Karl Fischer titration [536]. The method can be used for determining very small quantities of water (10p,g-15mg). Certified water standards are available. Karl Fischer titrations are not universal. The method is not applicable in the presence of H2S, mercaptans, sulfides or appreciable amounts of hydroperoxides, and to any compound or mixture which partially reacts under the conditions of the test, to produce water [31]. Compounds that consume or release iodine under the analysis conditions interfere with the determination. 

Water (moisture) content determination Quick sample heating Microscopic sample preparation Sample incineration and melting... 

FIGURE 3-21 Hydraulic conductivity of a certain unsaturated soil as a function of water (moisture) content (0). Higher conductivity occurs when 6 is larger and the pore water is under less suction. Note that the relationship between K and 6 depends on whether the soil most recently was dried or wetted. 

FIGURE 3-23 Relationship between water (moisture) content (6) and pore water pressure (if/) in a certain unsaturated soil. Pore water suction is the negative of pore water pressure. As in the case of the K — 6 relationship (Fig. 3-21), this relationship is influenced by whether the soil most recently was wetted or dried. 

Another typical study [8] showed that in wood (aspen)-plastic (polypropylene) composite the increase in wood fraction—0, 30, 40, 50, and 60%—led to the increase in water absorption as 0,2,5,7,9, and 11%, respectively, after 10 weeks of submersion under water. Moisture content at 90% relative humidity had increased in the same direction. 

ASTM. D4643. Standard Test Method for Determination of Water (Moisture) Content of Soil by the Microwave Oven Method. American Society for Testing and Materials, Philadelphia, PA, p. 7. 

ASTM. D2216. Standard Test Method for Laboratory Determination of Water (Moisture) Content of Soil, Rock, and Soil-Aggregate Mixtures. American Society for Testing and Materials, Philadelphia, PA, p. 2. ASTM. D4648. Standard Test Method for Laboratory Miniature Vane Shear Test for Saturated Fine-Grained Clayey Soil. American Society for Testing and Materials, Philadelphia, PA, p. 7. 

ASTM D 4643. 2008. Standard test method for determination of water (moisture) content of soil by microwave oven heating. West Conshohocken, PA ASTM International. 

The endothermic peak temperature of 66-67 °C was independent of the CS concentration (mass fraction 16.5-60%). The height of the main endothermic peak increased steeply with increasing CS concentration (mass fraction 16.5-40%). However, in CS containing <55% water, the height of the main endothermic peak decreased steeply with increasing CS concentration (40-60%). The second peak area increased and the second peak temperature shifted to the higher temperature side. Powders of CS alone (without added water, moisture content 12.5%) showed a small endothermic peak at about 150 °C. 

PrinciptJly three types of water provide the soil moisture free ground water, gravitational water, and capillary water. They have significant influence on the metal/environmental characteristics and determination of the corrosion rate. The amount of moisture in a soil can be determined by the method described in ASTM Test Method for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass (D 2216). 

Test Method for Laboratory Determination of Water (Moisture) Content of Soil and Rock. 

The water (moisture) content in a wet material may be reduced to an acceptable level by the use of a vented machine this will reduce not only the water content but will remove other substances which are gases (volatiles) at injection molding temperatures and will also give very efficient color compoimding. 

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