Scouring resistance

Moore, W.L., Masch, F.D., Jr. (1962). Experiments on the scour resistance of cohesive sediments. Journal of Geophysical Research 67(4) 1437-1446. 

The use of dopamelanin or its precursors as an additive of a cement mixture substitutes the capillary water proportion in the cement mixture (51). The use of dopamelanin in an aqueous solution, in less than 3%, as a concrete setting and curing agent significantly increases the ductility and scouring resistance of the cement mixture. 

Solvent Resistance. Elastomeric fibers tend to swell in certain organic solvents mbber fibers swell in hydrocarbon solvents such as hexane. Spandex fibers become highly swollen in chlorinated solvents such as tetrachloroethylene [127-18-4] (Perclene). Although the physical properties of spandex fibers return to normal after the solvent evaporates, considerable amounts of its stabilizers may have been extracted. Therefore, the development of stabilizers that are more resistant to solvent extraction has become important as solvent scouring during mill processing replaces aqueous scouring at many mills, especially in Europe (26). 

Textiles. Sorbitol sequesters iron and copper ions in strongly alkaline textile bleaching or scouring solutions (see Textiles). In compositions for conferring permanent wash-and-wear properties on cotton fabrics, sorbitol is a scavenger for unreacted formaldehyde (252) and a plasticizer in sod-resistant and sod-release finishes (253). 

Preparation for Dyeing. A hot alkaline scour with a synthetic surfactant and with 1% soda ash or caustic soda is used to remove size, lubricants, and oils. Sodium hypochlorite is sometimes included in the alkaline scouring bath when bleaching is requked. After bleaching, the polyester fabric is given a bisulfite rinse and, when requked, a further scouring in a formulated oxahc acid bath to remove mst stains and mill dkt which is resistant to alkaline scouring. 

Cellulose Triacetate. Cellulose acetate having 92% or more of the hydroxyl groups acetylated is referred to as triacetate. This fiber is characteristically more resistant to alkaU than the usual acetate and may be scoured, generally, in openwidth, with aqueous solutions of a synthetic surfactant and soda ash. 

Additionally, the surfactant properties of filmers reduce the potential for stagnant, heat-transfer-resisting films, which typically develop in a filmwise condensation process, by promoting the formation of condensate drops (dropwise condensation process) that reach critical mass and fall away to leave a bare metal surface (see Figure 11.2). This function, together with the well-known scouring effect on unwanted deposits keeps internal surfaces clean and thus improves heat-transfer efficiencies (often by 5-10%). 

The second approach assigns thermal resistance to a gaseous boundary layer at the heat transfer surface. The enhancement of heat transfer found in fluidized beds is then attributed to the scouring action of solid particles on the gas film, decreasing the effective film thickness. The early works of Leva et al. (1949), Dow and Jacob (1951), and Levenspiel and Walton (1954) utilized this approach. Models following this approach generally attempt to correlate a heat transfer Nusselt number in terms of the fluid Prandtl number and a modified Reynolds number with either the particle diameter or the tube diameter as the characteristic length scale. Examples are ... 

Scorch resistance, in vulcanization, 22 811 Scorch time, in vulcanization, 22 803 SCORE cleaning system, 24 22 Scotch-Marine boiler, 22 319 Scouring, 9 171, 183, 189, 192, 197 of fibers, 22 180 in wool processing, 26 384-385 Scoville Heat test, 23 159 Scrap... 

Cellulose Triacetate. Cellulose acetate having 92% or more of the hydroxyl groups acetylated is referred to as triacetate. This fiber is characteristically more resistant to alkali than the usual acetate and may be scoured, generally, in open-width, with aqueous solulions of a synthetic surfactant and soda ash. Triacetate is a hydrophobic liber, as compared to secondary acetate, and consequently does not dye rapidly. It is necessary to increase the rate of diffusion of the disperse dye into the fiber by increasing the dyeing temperature to 110— 130CC or using a dye accelerant or carrier, or both. 

A third approach to the application of insect resist finishes is to combine the finish with spinning lubricants and then to apply the combination to loose wool prior to spinning. This method of finish application produces yams with only a superficial treatment with much lower fastness than applications made during dyeing or scouring. 

Venn obtained very little levoglucosan from the pyrolysis of raw cotton, whereas washing with water increased the yield to 28 %, and further prepurification by treatment with dilute alkali and acid provided a yield of 38%. Holmes and Shaw found that a cotton fabric purified by scouring and bleaching provided more tar and less char on vacuum pyrolysis than the reference materials. A Russian patent" claims that the heat resistance of cellulose is greatly increased by lowering the content of alkali metals to 0.03 — 0.05%. 

Mild alkalis have less effect, but again temperature and concentration are important factors. Sodium carbonate is used in wool scouring and small quantities of ammonia are sometimes added to a dyebath. Slight damage caused by an alkali in scouring can render the fibre less resistant to subsequent processes. Ammonia, ammonium carbonate, borax, sodium hexa-metaphosphate, tetrasodium pyrophosphate, and sodium triphosphate can be used at temperatures up to 60 to 70°C (140° to 158°F) with safety. 

Many endeavours have been made to specify a satisfactory test for detergent power, but none is infallible, partly because, in practice, there is so much variation in the conditions under which scouring is carried out. There are differences in the ratio of liquor to goods, the nature of the mechanical agitation, the composition of the impurities to be removed, and the resistance of different fibres to alkali and temperature which have to be taken into account in practice. 

---