Moisture absorbing capacity

The incidence of the amide linkage in the polyamide chain is considerably lower than in Nylon 6 and 6-6, and this increased hydrocarbonlike character of the material is shown in a lower moisture-absorbing capacity as well as a little lower dyeing affinity. 

The moisture-absorbing capacity of certain surfactants may enhance the activation of water-soluble compounds the capacity to do so appears to depend upon surfactant chemical class, E content, and ambient relative humidity. Hydrophilic surfactants of high E content are the most hygroscopic, and under field conditions they may act as condensation nuclei just below water vapor saturation. Under these circumstances, a water droplet may re-form over the original droplet, thus enhancing uptake of the a.i. 

Moisture absorbents or desiccants are required. These are spread on trays and distributed throughout the boiler, so that circulating air passes over them. Quick lime (CaO) is used at 8 to 10 lb for every 1,000 lb/hr of steaming capacity. Alternatively, silica gel is used at 4 to 6 lb per 1,000 lb of steaming capacity. 

A moisture-absorbing pad may be tested with this protocol. In principle such a pad will absorb the meat drip into its fibres or in a cross-linked polymer. Due to the absorption capacity the migration of the absorber s constituents is not likely. However, in case the absorber starts to become saturated, migration is more likely. To simulate this, an absorber should first be saturated with water to approximately 80% of its capacity before migration testing. 

Cellulose fibers and an adhesive binder characterize the fibrous composition of most wipes. Often, special applications involve the depositing of cellulose fibers with the assistance of an electrostatic field to promote the properties of moisture absorbency and bulkiness with high absorption capacity. High-quality premoistened wipes are usually marketed in converted quarter-folded or flat-pack forms within a resealable plastic container. 

The moisture-holding capacities, and percentage of this that is available for plant use, are also given in Table 30.1 for the peats, soils and mixtures. It will be seen (column 5) that the values range between 75.5 and 93.5. The value for moss peat is similar to that for the sandy soil and actually 8% higher than for the clay loam. The colloidal reed peat held the water most tenaciously. Evidently the water absorbed by peats, especially the more fibrous types, is not as unavailable for plant use as many have believed. 

Research [8] has found that MVT at equilibrium bears no relationship to the moisture absorption capacity of a rubber formulation. This was a critical determination because, previously, it was assumed that MVT rate was the only real characteristic of concern in relationship to a rubber closure and its use for lyophilization. Table 3 lists both MVT and percentage weight gain for several rubber formulations. Weight gain can be used to understand the capacity of an individual stopper to absorb moisture after an autoclave cycle or some other environmental conditioning. 

Water absorbing capacity was determined gravimetrically using a modification of the method described by Elizalde et al (//), with some modification. Briefly, all samples were equilibrated in a 10% relative humidity (RH) chamber for 48 hours. Then, samples were transferred into a 98% RH chamber and exposed to moisture for 5 min. The dry matter and the absolute amount of absorbed water were determined. All measurements were made in triplicate. The results were expressed as the mean SD in mg water absorbed by per gram of psyllium per minute. 

Storage. For receiving glycerol from standard 30.3-m (8000-gal) tank cars (36.3-t), a storage tank of 38—45-m ((10-12) x 10 — gal) capacity should be employed. Preferably it should be of stainless steel (304 or 316), of stainless- or nickel-clad steel, or of aluminum. Certain resin linings such as Lithcote have also been used. Glycerol does not seriously corrode steel tanks at room temperature but gradually absorbed moisture may have an effect. Therefore, tanks should be sealed with an air-breather trap. 

Hot lay-up is most suited for standby and for short outages for minor repairs. Here, the metal surfaces are maintained at 170 °F (77 °C) or higher by an auxiliary heat source, such as a gas air heater, to deter moisture. Typically, magnesium-based treatments are employed at the rate of 1 lb per 1,000 lb/hr of steaming capacity to absorb and neutralize sulfuric acid vapor. These products are blown through the fireside using the FD fan. 

Plant uptake is one of several routes by which an organic contaminant can enter man s food chain. The amount of uptake depends on plant species, concentration, depth of placement, soil type, temperature, moisture, and many other parameters. Translocation of the absorbed material into various plant parts will determine the degree of man s exposure—i.e., whether the material moves to an edible portion of the plant. Past experience with nonpolar chlorinated pesticides suggested optimal uptake conditions are achieved when the chemical is placed in a soil with low adsorptive capacity e.g., a sand), evenly distributed throughout the soil profile, and with oil producing plants. Plant experiments were conducted with one set of parameters that would be optimal for uptake and translocation. The uptake of two dioxins and one phenol (2,4-dichlorophenol (DCP)) from one soil was measured in soybean and oats (7). The application rates were DCP = 0.07 ppm, DCDD 0.10 ppm, and TCDD = 0.06 ppm. The specific activity of the com-... 

Texturization is not measured directly but is inferred from the degree of denaturation or decrease of solubility of proteins. The quantities are determined by the difference in rates of moisture uptake between the native protein and the texturized protein (Kilara, 1984), or by a dyebinding assay (Bradford, 1976). Protein denaturation may be measured by determining changes in heat capacity, but it is more practical to measure the amount of insoluble fractions and differences in solubility after physical treatment (Kilara, 1984). The different rates of water absorption are presumed to relate to the degree of texturization as texturized proteins absorb water at different rates. The insolubility test for denaturation is therefore sometimes used as substitute for direct measurement of texturization. Protein solubility is affected by surface hydrophobicity, which is directly related to the extent of protein-protein interactions, an intrinsic property of the denatured state of the proteins (Damodaran, 1989 Vojdani, 1996). 

It is obvious that acid hydrolysis methods leave a number of unsolved problems and many minor disagreements to be ironed out. In general, however, the available results suggest that the natural celluloses consist chiefly of crystalline material which is only slowly eroded by acids. The non-crystalline fraction appears to be relatively more susceptible to hydrolysis than the crystalline fraction and to have a greater capacity to absorb moisture. In other words, the non-crystalline fraction is probably more reactive than the crystalline material, as Mark14 has suggested. In this connection the fact should not be overlooked that the surface layer of the crystallites is probably amorphous and hence relatively more reactive than the underlying layers. 

This type of equation, used in Volume 1 for the rate of vaporisation into an air stream, simply states that the rate of transfer is equal to the transfer coefficient multiplied by the driving force. It may be noted, however, that (Ps — Pw) is not only a driving force, but it is also related to the capacity of the air stream to absorb moisture. 

As indicated in Table I, most properties of polyamide derivatives of BA, nylons 13, and 13/13, are predictable from properties of commercial engineering plastics such as nylon-11 and nylon-6/10 -- the BA based nylons are have lower moduli and most physical properties are unexceptional.[9,10] However, the BA based nylons have one exceptional property -- their very low capacity to absorb moisture. This property suggests that these materials may be less affected by water plasticization than other nylons, and it has attracted interest in developing BA-based nylons commercially. Development has been impeded by the fact that BA is not produced on a sufficient scale to make it cost-competitive, and apparently the attractive markets are not large enough to justify investment in development of BA processes, creating a chicken-or-egg" problem. 

---