Wool, water absorption

In the early fifties, when synthetic fibers such as nylon and the acrylics were first coming onto the consumer market, Fourt et al. [56] and Coplan [57] compared the water absorption and drying properties of these "miracle" fibers with those of conventional wool and cotton. Forty-five years latter, the water absorption and drying properties of synthetics were compared with natural fibers and it was found that all fabrics pick up water, and the time they take to dry is proportional to the amount of water they initially pick up [58,59],... 

Unraveling the molecular mechanism of water binding by keratins (e.g., wool, hair, nails, etc.) has interested chemists for half a century ()L). Essentially, two types of models have been suggested for explaining water absorption isotherms of keratins one that postulates the binding of water mol-... 

You ll notice this when you dip a soap pad into water containing dishwashing detergent. Such detergents are anionics, and, as the manufacturer of SOS pads confirms, steel wool pads infused with soap use cationic surfactants. Why they use cationics, which are generally less effective cleaners, isn t clear, but it likely has to do with steel wool s absorption capabilities. 

For the system wool-water a theory of this kind has been developed by Cassie and in a particularly interesting paper by Hailwood and Horrobin The latter postulated formation of a monohydrate, i. e., binding of one water molecule by each monomeric residue of the fibre portion taking part in absorption. For the isotherm they gave the equation ... 

When applied to the systems wool-water and cellulose-water the values of M deduced from the experiment are larger than that of the actual monomeric residue (162 in the case of cellulose). In the sense of the theory this means that a certain fraction of the monomeric residues M — R)jM does not take part in absorption, where R is the actual molecular weight of the residue. In other words the percentage of crystalline substance can be deduced from the observations. This leads to the following figures Wool 44—48%, natural silk 80%, native cotton 68%, regenerated cellulose 35%. The last two figures are well in line with those independently arrived at from other data. 

Wool belongs to a family of proteins, the keratins, that also includes hair and other types of animal protective tissues such as horn, nails, feathers, beaks, and outer skin layers. The relative importance of wool as a textile fiber has declined over the past decades with the increasing use of synthetic fibers for textile products. Wool, however, is still an important fiber in the middle and upper price ranges of the textile market. It is also an extremely important export commodity for several nations, notably Australia, New Zealand, South Africa, and Argentina, and commands a price premium over most other fibers because of its outstanding natural properties. These include soft handle (the feel of the fabric), water absorption (and hence comfort), and superior drape (the way the fabric hangs). Table 2 shows wool production and sheep niunbers in the world s principal wool-producing countries. 

Many other properties have to be considered, especially for apparel fibres, e.g. moisture absorption, dyeability, drape, texture, weaving characteristics, etc. Many of the properties are strongly influenced by cross-sectional shape cotton is a round hollow fibre, whereas silk has a triangular shape giving it a fine lustre and rustle. Wool has a scaly surface and appears to be made up of two components which have different water absorption characteristics. This gives wool its crimpability and bulk. From studies like these, synthetic fibres can minimic natural fibres and can, in some cases, be more versatile. For example ... 

Y-Phenylbutyric acid. Prepare amalgamated zinc from 120 g. of zinc wool contained in a 1-litre rovmd-bottomed flask (Section 111,50, IS), decant the liquid as completely as possible, and add in the following order 75 ml. of water, 180 ml. of concentrated hydrochloric acid, 100 ml. of pure toluene (1) and 50 g. of p benzoylpropionic acid. Fit the flask with a reflux condenser connected to a gas absorption device (Fig. II, 8, l,c), and boil the reaction mixture vigorously for 30 hours add three or four 50 ml. portions of concentrated hydrochloric acid at approximately six hour intervals during the refluxing period in order to maintain the concentration of the acid. Allow to cool to room temperature and separate the two layers. Dilute the aqueous portion with about 200 ml. of water and extract with three 75 ml. portions of ether. Combine the toluene layer with the ether extracts, wash with water, and dry over anhydrous magnesium or calcium sulphate. Remove the solvents by distillation under diminished pressure on a water bath (compare Fig. II, 37, 1), transfer the residue to a Claisen flask, and distil imder reduced pressure (Fig. II, 19, 1). Collect the y-phenylbutyric acid at 178-181°/19 mm. this solidifies on coohng to a colourless sohd (40 g.) and melts at 47-48°. 

Wool Resists rapid penetration of direct splashes (more effective than cotton) Resists penetration of dust High absorption and porosity absorbs perspiration Not resistant to hot splashes Takes up water and dirt Difficult to wash ... 

Thionyl chloride method. Mix 100 g. of pure p-nitrobenzoic acid and 126 g. (77 ml.) (1) of redistilled thionyl chloride in a 500 ml. round-bottomed flask. Fit the flask with a double surface reflux condenser carrying a calcium chloride (or cottou wool) guard tube and connect the latter to an absorption device e.g., Fig. II, 8, 1. c). Heat the flask on a water bath with occasional shaking for 1 hour or until the evolution of hydrogen chloride and sulphur dioxide ahnost ceases. Allow the reaction mixture to cool, transfer it cautiously to a Claisen flask connected with a water-cooled condenser and a receiver (compare Fig. II, 13, 1). Distil off the excess of thionyl chloride (b.p. 77°) slowly and continue the distillation until the temperature rises rapidly to about 120° this will ensure that all the thionyl chloride is remov. Allow to cool, and distil the residual p-nitrobenzoyl chloride under diminished pressure as detailed in the Phosphorus Pentachloride Method. The resulting p-nitrobenzoyl chloride (a yellow crystalline solid) weighs 107 g. and melts at 72-73°. 

Electrolytes are used to promote the exhaustion of direct or reactive dyes on cellulosic fibres they may also be similarly used with vat or sulphur dyes in their leuco forms. In the case of anionic dyes on wool or nylon, however, their role is different as they are used to facilitate levelling rather than exhaustion. In these cases, addition of electrolyte decreases dye uptake due to the competitive absorption of inorganic anions by the fibre and a decrease in ionic attraction between dye and fibre. In most discussions of the effect of electrolyte on dye sorption, attention is given only to the ionic aspects of interaction. In most cases, this does not create a problem and so most adsorption isotherms of water-soluble dyes are interpreted on the basis of Langmuir or Donnan ionic interactions only. There are, however, some observed cases of apparently anomalous behaviour of dyes with respect to electrolytes that cannot be explained by ionic interactions alone. 

Before finally assembling the apparatus, the various units are charged as follows A is one-third filled with water to serve as a bubble counter. Generator B is about one-quarter filled with dry arsenious oxide, pea size or powdered. Drying towers G and H are filled with anhydrous calcium chloride. (It is well to place a wad of glass wool in front of the entrance and exit tubes.) In each of the two absorption bottles J and K is placed 200 g. of ethyl malonate. Dish L is filled with an ice-salt freezing mixture. 

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