Contents 1 Moisture

Moisture plays a vital role in all aspects of general handling of powders - it is, therefore, appropriate that this guide should also 

Moisture content (also water content ) is in principle very simple to measure it is the quantity of water in a unit mass of bulk powder, as a percentage or fraction by mass (or weight). The confusion arises whether the mass of bulk powder includes moisture or not. The moisture content may, therefore, be either on a dry basis (i.e. per unit mass of dry powder) or on a wet basis, the former being more frequently used such as in soil mechanics for example16. 

At one extreme, the sample can be dried under ambient conditions (which may be specified), by natural air, and the result is the air-dried moisture content which, obviously, does not include all of the moisture in the powder (inherent moisture). 

In order to prevent the sample absorbing moisture from the atmosphere when taken out of the oven, it is best to cool the 

Besides the above mentioned gravimetric methods, there are many, more sophisticated commercial instruments for measuring moisture, some suitable for on-line applications and monitoring. Those are based on backscatter radiation, electrical conductance, near-infrared absorption or reflection photometry and most require prior calibration. 

Moisture present in the coal is known to influence spontaneous heating in a stockpile insofar as the moisture affects ventilation (air flow) and pyrite reactivity. 

The effect of moisture on the self-ignition is twofold on the one hand, the vaporization of moisture consumes energy and hence the ignition process is impeded. On the other hand, a promotion of self-ignition by the wetting of materials prone to this has been observed (Gray, 1990). 

In addition to the heat of wetting moisture simply blocks the access of oxygen through the coal pores. The water vapor diffusing outward through the pores reduces the oxygen partial pressure and hence lowers the rate of the reaction or the polar water molecules attach to the reactive sites in coal (Jones, 1998). 

Moisture which is lost on aii -dryiiig is called Surface, Adsorbed or Free Moisture. Amount of free moisture is widely variable and depe on factors like the treatment given to the coal, the extent of subsequent drying, the size of the coal lump, rank of the coal and the nature of its surface. Free moisture is disadvantageous to the extent that 

However, coals containing 5 to 10% evenly distributed free, moisture have been reported to 

Inherent Moisture is the moisture that is retained by an air-dried coal. It decreases with increasing rank and is a rough indicator of the maturity (age or degree of coalification) of coal. Coals with high inherent moisture are easily oxidised in air and therefore are liable to spontaneous combustion. 

1 in diameter) with aluminium cover or a platinum crucible (previously heated, 

Weight of capsule (or crucible) + sample, before drying = Bg Weight of capsule (or crucible) + residue, after drying = Cg 

The total moisture in coal is the determination of the moisture (in all forms except water of crystallization of the mineral matter) that resides within the coal matrix. In fact, moisture (or water) is the most elusive constituent of coal to be measured in the laboratory. The moisture in coal ranges from 2 to 15% by weight in bituminous coal to nearly 45% by weight in lignite. 

The standard methods of determining the amount of moisture in coal include a variety of test methods designed to differentiate between the various types of 

TABLE 3.1 Composition and Property Ranges for Various Ranks of Coal 

Moisture loss can (and often does) occur during grinding and/or pulverization and is believed to be related to the types and amounts of banded (maceral) ingredients in the coal. Losses are least for vitrain and increase in order of vapor pressures for moisture (e.g., vitrain clarain durain fusain). 

The role of water in coal and the quantitative measurement of water are complicated because water is present within the coal matrix in more than one form (Allardice and Evans, 1978). Thus, the total moisture includes both the surface moisture and the residual moisture remaining in the sample after determining the air-dry loss (ASTM D-3302). Thus, 

Moisture (water) content of soil (u ), often referred to as natural moisture, is defined as the ratio of the water mass contained in the soil (M ) to the mass of solids (M ) and is expressed as a percentage by mass of solids. The equation used is simply 

The natural moisture of the soil is a crucial factor for the highway engineer, since the bearing capacity of the pavement s foundation layer depends directly from it. 

More information regarding the determination of water content can be found in AASHTO T 265 (2012), ASTM D 4959 (2007), ASTM D 4643 (2008) and CENISO/TS 17892-1/AC (2005). 

Different methods of dew point measurement can be used to determine low moisture contents. For measurements in the parts per million range, the condensation temperature is very low and the precipitated quantities of liquid are small. The actual measurement can be difficult to determine, especially as the condensation points of other components of a gas are approached. Dew points of -18 to -34°C (0° to -30°F) can be measured readily on a conventional dew-pointer, whose operational principle is the condensation of moisture on a mirror. 

An indirect method for moisture content determination uses a capacitor with an aluminium oxide dielectric, designed in such a manner that moisture can easily migrate into and out of the dielectric. The amount of wa- 

A third measurement process uses an electrolytic cell in which the moisture is absorbed and electrolyzed. The electrolytic current constitutes a measure of the moisture content of the gas. 

In all moisture content measurement, it is important that the entire measuring system, including the detector, be made of metallic materials. Plastics and rubber may not be used. 

Because water can be adsorbed so readily by most surfaces—especially if they are rough, contaminated, or corroded—long purging times are necessary, and low-dew-point gas ( 3 ppm) must be used. The moisture content of gas from a container will vary, therefore, depending on the container pressure. As the container pressure decreases, more and more adsorbed water is released from the walls and the moisture con- 

The presence of any appreciable amount of moisture in solvents used in a two-component polyurethane system can react with isocyanate crosslinkers and thus impair crosslinking efficiency. Therefore, moisture content is one of the important properties of solvents such as ketones and esters, which are used in two-component polyurethane coatings. Moisture content is normally determined by the Karl-Fischer titration method. 

Wood is an orthotropic material, that is, its physical properties are unique and independent in three mutually perpendicular directions longitudinal, radial, and tangential. Moreover, the physical properties of wood strongly depend on its moisture content (i.e., mass fraction of water). Owing to this strong dependence of properties on moisture content, it is advisable when using timber in some particular applications (e.g., marine, chemical process industry, or foodstuffs) to take figures at maximum moisture content when data are available. 

When carbon fiber is compounded with a thermoplastic to produce a carbon fiber reinforced thermoplastic moulding compound, the most important property to control is the 

Weighing in combination with drying using an IR, halogen or microwave source. 

Only the Karl Fischer method will permit accurate measurements of low moisture 

The TVI test can be used for unreinforced polycarbonate, but will only distinguish between inadequately and adequately dried material. The temperature of the test hotplate is set to the requisite temperature for a given polymer (e.g. 270 5°C for polyearbonate) and a few granules of the test material inserted between two glass slides, which are plaeed on the hot plate until the material is molten. After a further one minute, the two slides are pressed firmly together until the granules have been flattened to about 10 mm diameter. The slide sandwich is removed from the hotplate, allowed to cool and examined, when the absence of bubbles indicates adequate drying. 

ASTM D 3641 covers the practice of mold design for the injection molding of test specimens from thermoplastic molding compounds and a design option with the mold join on the diagonal is preferred. 

Reinforcement depends on two features the number of interactions at the interface between polymer and filler (which is mainly controlled by the low primary particle size in conjunction with the surface activity) and the hydrodynamic effects of particle aggregation and agglomeration (which are linked with shear modulus and hysteresis during dynamic or static deformation). 

Methods currently used to determine this require the filler to be comminuted by means of ultrasound - but this causes severe degradation of the agglomerates in carbon blacks, and also distorts the distribution of silicas. An alternative method has been developed using transmission electronic microscopy, in which the filler morphology retained is similar to that obtained in the incorporation process. 

Anisometry and fractal dimension are also used as parameters for characterizing fillers, the former to predict various mechanical properties of filled compounds and vulcanizates and the latter to investigate the surface structure. Anisometry, which is always subject to distribution, is found to widen with the fillers investigated, with an increase in the dimensions of the objects detected. 

Modern compounding, especially for technical or engineering plastics, may require the addition of a complex range of materials, each with its own characteristics. The sequence in which these are introduced into the compounder (and the position down the screw) is fundamentally Important. Fillers, with their weight and volume, are usually brought in first, but the latest technology, in which polymerization or cross-linking takes place in the extruder, may alter the sequence. 

When compounding there may often be an adhesion problem between a nonpolar polymer matrix and a tiller, so it is essential to obtain perfect wetting of the particles by the matrix. Before it can do anything, a filler has to bond effectively with the polymer matrix. The size and geometry of the filler particles influence 

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When thermal or chemical energy is used to remove a volatile species, we call the method volatilization gravimetry. In determining the moisture content of food, thermal energy vaporizes the H2O. The amount of carbon in an organic compound may be determined by using the chemical energy of combustion to convert C to CO2. 

Use the molecular weight ratio to calculate the apparent extent of reaction of the caprolactam in these systems. Is the variation in p qualitatively consistent with your expectations of the effect of increased water content in the system Plot p versus moisture content and estimate by extrapolation the equilibrium moisture content of nylon-6 at 255 C. Does the apparent equilibrium moisture content of this polymer seem consistent with the value given in Sec. 5.6 for nylon-6,6 at 290°C ... 

Plywood requirements—includes wood species used, synthetic repair requirements, veneer grades, veneer layers and thicknesses, panel grades with respect to end-use, adhesive bond requirements, panel constmetion and workmanship, scarf and finger-jointed panels, dimensional tolerances, moisture content, and packaging and loading... 

A measurement of particle moisture content will normally be taken at the exit of the dryer. This allows the process operators to make such adjustments as may be needed to maintain moisture within the desired range. Various instmments are used, none of which are entirely satisfactory, and periodic hand samples are used in some mills. Considering the importance of moisture sensing and control at the dryers, it is unfortunate that a truly efficient, consistent, and accurate sensing system is not yet available to the industry. The primary reasons for the difficulty of measuring moisture at the dryer exit are the extreme and adverse conditions of heat, dust, and moisture present at this location. 

The strands move through large dmm dryers which reduce the moisture content to about 2 or 6%, the difference being whether Hquid or dry resin is to be used. Because a desired moisture level into the press is about 6—7% me, a Hquid resin adds water to the system and requires a lower flake moisture than a dry resin. 

The ABS polymer is recovered through coagulation of the ABS latex. Coagulation is usually achieved by the addition of an agent to the latex which destabilizes the emulsion. The resulting slurry can then be filtered or centrifuged to recover the ABS resin. The wet resin is dried to a low moisture content. A variety of dryers can be used for ABS, including tray, fluid bed, and rotary kiln type dryers. 

Cyanoacrylate adhesives (Super-Glues) are materials which rapidly polymerize at room temperature. The standard monomer for a cyanoacrylate adhesive is ethyl 2-cyanoacrylate [7085-85-0], which readily undergoes anionic polymerization. Very rapid cure of these materials has made them widely used in the electronics industry for speaker magnet mounting, as weU as for wire tacking and other apphcations requiring rapid assembly. Anionic polymerization of a cyanoacrylate adhesive is normally initiated by water. Therefore, atmospheric humidity or the surface moisture content must be at a certain level for polymerization to take place. These adhesives are not cross-linked as are the surface-activated acryhcs. Rather, the cyanoacrylate material is a thermoplastic, and thus, the adhesives typically have poor temperature resistance. 

Adipic acid is shipped in quantities ranging from 22.7 kg (50-lb bags) to 90.9 t (200,000-lb hopper cars). Upon long standing, the soHd material tends to cake, dependent on such factors as initial particle size and moisture content. Shipping data in the United States are "Adipic Acid," DOT-ID ALT 9077, DOT Hazard Class ORM-E. It is regulated only in packages of 2.3 t (5,000 lb) or more (hopper cars and pressure-differential cars and tmcks) (157). 

Sensible Heat Factor. The ratio of the change in sensible (constant moisture content) cooling enthalpy to the change in total cooling enthalpy. 

Pet foods are produced in canned, semimoist, and dry forms. Canned pet foods contain approximately 78 to 82% water and have a strong appeal to both pets and owners. Semimoist foods have moisture contents of 25 to 50%. Dry-type foods contain 10 to 12% moisture and supply about 90% of the nutrition consumed by dogs and 72% of the nutrition eaten by cats. 

Properties. Important properties of NSP are free acid content, as H2SO4, 1—2% moisture content, 5—8% P2O5 soluble, in neutral citrate... 

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