Moisture equilibration

Drzal et al. 90) have investigated the effect of interphase modification on interfacial moisture absorption. The fibers used were a surface treated and a surface treated and finished type A carbon fiber in the same epoxy matrix studied previously. Three equilibrium exposure conditions were investigated. 20 °C, 70 °C and 120 °C were selected for moisture equilibration of single fiber samples and for the neat epoxy resin. The interfacial shear strength was measured both in the saturated and the dehydrated cases and compared to the initial dry values. 

From the TGA of the moisture-equilibrated samples, the amount of water adsorbed onto the surface of titanium-substituted mesostructured silica materials was measured as the wt. % loss around 100°C (Figure 3), obviously the presence of organic groups resulted in a significant decrease in the amount of adsorbed water. 

Copolymers. There are two forms of copolymers, block and random. A nylon block copolymer can be made by combining two or more homopolymers in the melt, by reaction of a preformed polymer with diacid or diamine monomer by reaction of a complex molecule, eg, a bisoxazolone, with a diamine to produce a wide range of multiple amide sequences along the chain and by reaction of a diisocyanate and a dicarboxylic acid (193). In all routes, the composition of the melt is a function of temperature and more so of time. Two homopolyamides in a moisture-equilibrated molten state undeigo amide interchange where amine ends react with the amide groups. 

In order to determine the endpoint of the process, many procedures have been suggested, including pressure rise measurement, the Karl Fischer method, weight curves, vapor tension, moisture equilibration, nuclear magnetic resonance, and dielectric measurement. 

An important part of the dehulling process is to precondition the seed before dehulling. Moisture should be adjusted, usually by drying and, in the traditional method, the seed should be left to temper for a few days. As the moisture equilibrates between the freshly dried surface and the harder-to-reach interior, stresses develop, which help to loosen the hull from the kernel, thereby improving dehuller performance. Drying has normally been done in steam-jacketed vessels, either with the jackets on the walls or with a steam tube assembly revolving within the vessel. However, there are alternative ways of drying. 

Since moisture equilibration, i.e. "conditioning of wood is a slow process that may require a week or longer depending on product thickness, and since temperature adaptation lags by at least an hour, the emission from wood products is not always at equilibrium. This fact has caused non-technicaI people to incorrectly distrust product performance. However, it has been found that the emission directly reflects the daily temperature cycles of outside wails (52). Thus, mobile home placed in a warm climate, indoor air levels may change by a factor of 6 or more during a This is shown in Figure 1. 

For adsorption isotherms, pear cubes (10 mm X 10 mm) were frozen at — 40°C and freeze-dried (Telstar Lioalfa-6 lyophyliser) at 10 Pa. Afterwards, samples were placed in chambers with controlled relative humidity (RH) up to equilibrium was reached. Desorption isotherms were obtained in pear slices with skin (with approximately 8 cm diameter and 10 mm thickness), partially dehydrated in a conventional dryer at 45°C for different times to ensure different final water contents in the samples. After the drying treatment, samples were kept in plastic bags under refrigeration to ensure the internal moisture equilibration and then their water activity was measured. Experiments were carried out in triplicate for each sample. 

Using standardized phytotoxicity test methods, Rocheleau et al. [40] investigated the effects of TNT, TNB, 2,4-DNT, and 2,6-DNT freshly amended (following a 24-h moisture equilibration period) or weathered and aged (13 weeks) in SSL soil. Tests... 

Fatigue crack propagation tests were performed on 73-nmi x 73-mm (2.9 in. x 2.9 in.) compact-tension specimens that had been machined from the plaques and then precracked. An electrohydrau-lic closed-loop test machine was used to produce a constant-amplitude, 10-Hz sinusoidal load. Host of the tests were performed in duplicate at room temperature in laboratory air at an average ambient RH of A0%. In view of the slow rate of moisture equilibration in air at room temperature (15), the difference between the ambient RH and that of the nylon being tested was presumed to be unimportant within the time period of the test (3-5 hr). 

C for 1-2 days and then held at room temperature for 2-3 days to allow for moisture equilibration. 

Leistner (1987) stated that the number of Gram-positive bacteria in the raw meat should be moderate. The a must be decreased to <0.92 within 12 hr and to <0.90 by 36 hr. This can be achieved by drying for 36 hr at 48°C and 65% relative humidity. If drying is not carried out over charcoal, it should be lightly smoked at 48°C and 65% relative humidity. The product should be held at 20-25°C and 75% relative humidity for 3 days to allow for moisture equilibration or until an a of <0.80 is achieved. The sausage should then be vacuum-packaged, since this improves the flavor and inhibits mold growth. 

For the prediction of the time required for moisture equilibration of a structure, the diffusion constant, D, for each material is required, but their measurement is time-consuming because the equilibrium moisture content (A/00) has to be determined in long-term tests. Therefore, accelerated tests are used. As with other... 

Compared with heat transfer, the process of moisture transport is slower by a factor of approximately 10. For example, moisture equilibration of a 12 mm thick composite, at 350 K, can take 13 years whereas thermal equilibration only takes 15 s. Fick adapted the heat conduction equation of Fourier, and his (Pick s) second law is generally considered to be applicable to the moisture diffusion problem. The one-dimensional Fickian diffusion law, which describes transport through the thickness, and assumes that the moisture flux is proportional to the concentration gradient, is ... 

In the case of determination of the dry weight concentration, the water content can be determined in the regular way by weighing and drying. Before analysis, the powder has to be moisture-equilibrated with the laboratory room. 

Grape (V ifis vinifera) of the Azal white winemaking cultivar, washed and dried with paper cloth. Moisture equilibration was carried out over saturated salt solutions (aw 0.12-0.90) for 15 days at room temperature. 

Commercially available enriched syrups are those from maltotriose, maltotetraose and maltohexaose. They are used in the production of diagnostic materials for testing amylase enzyme patterns as well as for their antiputritive activity in the human intestine as components in nutritive and dietetical formulations. Future industrial significance in nonfood applications may result from their moisture-equilibrating and - retrogradation-retarding properties. 

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