Moisture absorption/desorption

Moisture Absorption/desorption +/- Delay in proceeding Moisture in atmosphere Protect sample from atmosphere Proceed quickly correct for dry mass... 

Of equal interest is the hysteresis in the moisture absorption-desorption curves. At any given relative humidity between 0 and 100%, human hair contains less water when absorbed from the dry state versus when it undergoes desorption from the wet state (see Table 8-15). Chamberlain and Speakman [28] observed this same phenomenon earlier for human hair and Speakman [29] observed it for wool fiber (see Table 8-16). 

Tensile strength is not the most important element of a textile fiber. Important it is, but there are other factors of equal importance, such as flexibility, handle, dye-uptake, and moisture absorption/desorption. In fact, in many cases, even though the material specification is designed with a high emphasis on tensile properties, quite often the rigours of use come nowhere near the product s tensile capabilities. 

Phase change process in the textile material. It is an approach allowing the heat and moisture transfer in a coupled way, including moisture condensation/evaporation in the fabric air void volume, moisture absorption/desorption of fibers, and micro-encapsulated phase change materials ... 

The moisture absorption/desorption capability of the solid fiber depends on the relative humidity of the enclosed air in the microclimate around the fiber and the type of fiber material. When fibers absorb moisture, heat is generated and released. Consequently, the temperature of fiber will rise and thus results in an increase of dry heat flow and a decrease in latent heat flow across the fabric [11]. The absorbed/desorbed moisture of fibers and the water vapor in the enclosed microclimate in textiles compose the water content of the textile material, which can originate from the... 

The first model describing the transient heat and moisture transfer process in porous textile material was developed by Henry (1939) in terms of two differential equations respectively for mass and heat governing formulation [13], as listed in the following. A simple linearity assumption was made in this model to describe the moisture absorption/desorption of fibers to obtain analytical solution. This modeling work established a basic framework of modeling the complicated coupled process of heat and moisture transfer through the textiles material. 

Chl-Hung Shen and George S. Springer, Moisture Absorption and Desorption of Composite Materials, Journal of Composite Materials, January 1976, pp. 2-20. 

During the last lew years, important research has gone into the addition of multiple humectants and water to food systems. Studies have shown that a hysteresis effect may occur with certain humectants. i.e, a different rate of moisture absorption than the rate for moisture desorption. Multiple humectants tend to compensate these hysteresis effects, giving uniform rates in both directions. 

Corveleyn, S., De Smedt, S., Remon, J.P. Moisture absorption and desorption of different rubber lyophilization closures. Int. J. Pharm. 159, 57-65,1997... 

Wood has many properties that make it superior to other materials in everyday use. For example, it has beautiful grain and color, comfortable touch, moisture absorptive and desorptive properties, high specific mechanical strength, and so on. These characteristic properties result in part from its cellular structure. Ideally, chemical modification of wood should improve properties in which wood is deficient without compromising those that give it its appeal. 

Shen C, Springer GS. Moisture absorption and desorption of composite materials. J Comp Mater 1976 10 2-20. 

Table 8-16 also shows that moisture loss (desorption) and regains (absorption) for human hair and wool fiber are virtually identical. It has been suggested [22] that the moisture regains of human hair and wool fiber are virtually identical up to about 90% RFl, where they diverge—wool to... 

Moisture absorption in uncured and cured adhesives is important for reliable adhesive bonding. Absorbed moisture in adhesives, particularly those used in surface-mounted parts, may result in voids in the bond hne due to moisture desorption or entrapment. Absorption of moisture after cure also affects reliability. Popcoming, the cracking of plastic parts during solder reflow, is due to the rapid vaporization and expulsion of moisture retained by the die-attach adhesive or the plastic encapsulant. 

Sericin biopolymer, an amorphous glue-like substance, is made up of 18 amino acids most of which 70% have a polar terminal functional group, such as -OH, -COOH, and -NH2 groups, which are responsible for its solubility as well as water absorption and desorption [72, 143]. Biocompatibility, blodegradablllty, excellent antimicrobial activity, resistance to UV radiation, and moisture absorption ability inherent properties along with its availability have facilitated its potential applications in different fields, including textiles [72, 77,143]. 

Conventionally, the moisture sorption characteristics of fibers are depicted by absorption-desorption isotherms. In practice, it is difficult to compare isotherms of different fibers over the whole range of RH and temperature values. It is often sufficient to compare their regains at the standard conditions of 65% RH and 21°C (70°F). Table 8.9 gives absorption regains for a few fibers, together with the difference between absorption and desorption regains. 

Figure 3.1 Typical Fickian moisture diffusion curve for an equilibrated resin casting of a bismaleimide modified epoxy resin which had previously been subject to thermally enhanced moisture absorption, followed by desorption prior to reabsorption. The sorption shown does not begin at zero because of a small residual quantity of absorbed moisture from the first conditioning cycle (4).

Figure 3.1 shows an example of a Fickian diffusion curve [4]. In this case, the resin had been previously conditioned and subjected to moisture absorption at 50°C and 96% RH, followed by desorption in vacuum at 50°C, prior to resorption [4]. One-dimensional diffusion can therefore be described by the following characteristics of the M, versus curve ... 

The coefficient A lies between 0.005 and 0.01 per kelvin for relative humidities between 0.1 and 0.9 for such materials as natural and synthetic fibers, wood, and potatoes. A could be taken to increase linearly with ijf. So for = 0.5 there is a 0.75% fall in moisture content for each degree kelvin rise in temperature. The extent of absorption-desorption hysteresis becomes smaller with increasing temperature. 

Moisture Regain of Fibers for Moisture Absorption and Desorption at 21 °C... 

First number is for moisture absorption and second number is for moisture desorption. 

G.W. Springer and C.H. Shen, "Moisture Absorption and Desorption of Composite Materials", AFML-TR-76-102, June 1976. 

S Caorvele5m, S De SmedL JP Remon. Moisture absorption and desorption of different rubber lyophihsation closures. Int J Pharm 159 57 5, 1997. 

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