Wool

Wool is unique among clothing fibers it is not only the oldest, it is also the only fiber to have been used continuously and universally. 

Wool is the fibrous covering from sheep (1) and is by far the most important animal fiber used in textiles. World greasy wool production was 2,688,000 tons in 1994—1995, equivalent to 1,557,000 t clean (2) (Table 1). In 1994—1995, 1000.1 x 10 sheep produced 2, 688 x 10 t of greasy wool. The average clip of 2.69 kg/sheep produces 1.56 kg/sheep of clean wool (Tables 1 and 2). 

Former Soviet Union, China, Eastern Europe 669 24.9 236 

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, and the outer skin layers. The relative importance of wool as a textile fiber has declined over the decades as synthetic fibers have increa singly been used in textile consumption. Wool is still an important fiber in the middle and upper price ranges of the textile market. It is also an extremely important export for several nations, notably AustraUa, New Zealand, South Africa, and Argentina and commands a price premium over most other fibers because of its outstanding natural properties of soft handle (the feel of the fabric), moisture absorption abiUties (and hence comfort), and superior drape (the way the fabric hangs) (see Fibers Textiles). Table 2 shows wool production and sheep numbers in the world s principal wool-producing countries. 

The principal characteristics of clean wool types ate average diameter, measured in micrometers, and average length, measured in millimeters (Table 3). 

Wool is a natural highly crimped protein hair fiber derived from sheep. The fineness and the structure and properties of the wool will depend on the variety of sheep fiom which it was derived. Major varieties of wool come from Merino, Lincoln, Leicester, Sussex, Cheviot, and other breeds of sheep. Worsted wool fabrics are made fiom highly twisted yarns 

The exposure of wool keratin to sunlight results in a number of physical and chemical changes [166, 1576]. 

Wool and hair fibres consist mainly of keratin, which consists of polypetide chains bound by salt Unkages between the functional groups of the amino acids (4.127) and by cystine (S—S) linkages (4.128)  

The amino acid composition of wool fibres is given in Table 4.10. For different animal fibres, the cystine content of the keratin varies, but it is higher than in any other protein. There are differences in the structural positions of the amino acids in the keratin between the hair from different animal species, and also along the fibres. 

The absorption spectrum of wood (Fig. 4.23) depends very much on its origin, i.e. the composition of different amino acids. The absorption at 250-300 nm is due essentially to the presence of the amino acids tyrosine (4.129) and tryptophan (4.130), with minor contributions from cystine (4.131) and phenylalanine (4.132) [1576, 1578]. 

Under UV and even solar radiation wool becomes yellow. The degree of yellowing very much depends on the wavelength of radiation used [1287, 1324]. Much more extensive yellowing occurs in summer than in the winter months. 

Department of Chemical Engineering, University of Delaware, Newark, DE 19716-3110, USA 

The development of the relation between interface structure and strength is suggested to proceed as follows  

Step I. The time dependent structure of the interface is determined. Relevant properties may be characterized by a general function H(t), which for the ca.se of polymer melts can usually be described in terms of the static and dynamic properties of the polymer chains. For example, with symmetric (A = B) amorphous melt interfaces, H(t) describes the average molecular properties developed at the interface by the interdiffusion of random coil chains as [ 1,6J 

The interface properties can usually be independently measured by a number of spectroscopic and surface analysis techniques such as secondary ion mass spectroscopy (SIMS), X-ray photoelectron spectroscopy (XPS), specular neutron reflection (SNR), forward recoil spectroscopy (FRES), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), infrared (IR) and several other methods. Theoretical and computer simulation methods can also be used to evaluate H t). Thus, we assume for each interface that we have the ability to measure H t) at different times and that the function is well defined in terms of microscopic properties. 

Step 2. After a contact time t, the material is fractured or fatigued and the mechanical properties determined. The measured properties will be a function of the test configuration, rate of testing, temperature, etc., and include the critical strain energy release rate Gic, the critical stress intensity factor K[c, the critical 

The protein chains formed by hair growth in the prekeratin zone are, at this stage, soluble in aqueous urea solution. Only when the hair is pushed out do the SH groups in the keratinous zone oxidize to S—bridges. 

These bridges are partly between the protofibrils and partly intracatenary. The relative ratio of these types of disulfide bridges is not known. These across-the-board cross-links make wool insoluble. This unusual characteristic is imitated commercially when permanent pleats are incorporated into textiles. By treatment with alkali pK of cysteine at 5), thiols are formed, which subsequently convert to S—bridges (thiol-catalyzed disulfide exchange)  

The reaction is favored by drawing (elongation). A brief steaming frees only covalent bonds (S—S bridges) or few van der Waals bonds. Only on longer pressing do the bonds snap into the new position, and the fibers retain the elongation ( set ). 

The bleaching of wool must be carried out with care since cystine residues can be oxidized to cysteric acid, which leads to scission of peptide bonds  

Wool is chlorinated on the surface by treatment with gaseous chlorine while the interior of the fiber is chlorinated by aqueous chlorine due to swelling. Chlorination causes the felting tendency to decrease. 

The third component is the medulla, which may be empty or may contain a group of open cell walls. The cells in medulla do not contain sulfur in their 

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It is used in the dispersed form as a dye for acetate silk, though it has no affinity for other fibres. It is also used as a starting point for alkyl- or acyl-aminoanlhraquinones which are used either as vat dyes or, after sulphona-tion, as acid wool dyes. 

Bismarck brown, Basic Brown 1 Basic azo-dyestuff, dyes wool (reddish brown), used for cotton with tannin as mordant. Used as hair dye. 

CH3 [CHJb-COOH. M.p. 31 5"C, b.p. 268-270 C. A fatty acid, occurring in wool as the potassium salt, as esters in fusel oil, and as glycerides in cows and goats milk and coconut and palm oils. 

C, obtained from the wool oil of Bulnesia sarmienti, Lorenz. On heating with sulphur it gives guaiazulene. 

C. A trilerpenoid or irimethylsierol, first found in the non-saponifiable material of wool wax. Lanosterol (4,4,14ot-trimethyl-5a-choiesta-8,24-dien-3 -ol) is the precursor in animals and fungi of other sterols such as... 

Most of the trichloroethylene produced is used for metal degreasing. Other important uses are in the scouring of wool and as an extractive solvent, e.g. for olive and soya bean oils. Minor uses are as a heat transfer medium, anaesthetic, insecticide and fumigant, paint remover and fire extinguisher. 

The reducing action of sulphurous acid and sulphites in solution leads to their use as mild bleaching agents (for example magenta and some natural dyes, such as indigo, and the yellow dye in wool and straw are bleached). They are also used as a preservative for fruit and other foodstuffs for this reason. Other uses are to remove chlorine from fabrics after bleaching and in photography. 

Fig. l.fi. The van tier Waals (vdw) surface of a molecule corresponds to the outward-facing surfaces of the van der Waak spheres of the atoms. The molecular surface is generated hy rolling a spherical probe (usually of radius 1.4 A to represent a mater molecule) on the van der Wools surface. The molecular surface is consiructed from contact and re-entrant surface elements. The centre of the probe traces out the accessible surface. 

Experiment 6. Fractional Distillation of a Mixture of Benzene and Toluene. Fractionally distil about 40 ml. of a mixture of equal volumes of benzene and toluene, using the type of fractionating column shown in Fig. ii(b), in which about 18-20 cm. of the column are actually filled with glass sections, but in which the cotton-wool lagging is not used. Distil very slowlyy so that the total distillation occupies about hours. Shield the apparatus very carefully from draughts. Collect the fractions having the b.ps (a) 80-85°, ( ) 85-107°, (c) 107-111°. A sharp separation should be obtained, e.g.y these fractions should have volumes of about 19, 2, and 17 ml. respectively. 

Chromatographic Separation of a Mixture of o- and p-Nitroaniline. Prepare a glass tube A (Fig. 24) in which the wider portion has a diameter of 3 cm. and a length of ca. 30 cm. the narrow portion at the base has a diameter of 5-7 mm. Wash the tube thoroughly (if necessary, with chromic acid, followed by distilled water and ethanol) and then dry. Insert a small plug of cotton-wool P as shown just within the narrow neck of the tube it is essential that this plug does not project into the wider portion of the tube. Clamp the tube in a vertical position. 

A i-litre measuring cylinder may be used in place of the cylinder E, but when the bung F is in position, any gap at the lip of the cylinder must be tightly plugged with cotton wool. 

The apparatus shown in Fig. 38 can also be used for fractionation by placing a secure plug of glass wool at the base of the vertical condenser and then filling it with short pieces of glass tubing. 

Lead formate separates from aqueous solution without water of crystallisation. It can therefore be used for the preparation of anhydrous formic acid. For this purpose, the powdered lead formate is placed in the inner tube of an ordinary jacketed cond ser, and there held loosely in position by plugs of glass-wool. The condenser is then clamped in an oblique position and the lower end fitted into a receiver closed with a calcium chloride tube. A current of dry hydrogen sulphide is passed down the inner tube of the condenser, whilst steam is passed through the jacket. The formic acid which is liberated... 

Potassium Hydroxide, Alcoholic. Boil under reflux a mixture of 10 g. of powdered KOH and 100 ml. of rectified spirit for 30 minutes. Cool and if solid material remains, decant through a filter of glass-wool. 

Two forms of the so called calcium chloride tubes (also termed drying tubes, straight form) are shown in (c) and (d) these are fiUed with anhydrous calcium chloride or with cotton wool (previously dried at 100°), and are attached by means of a stopper to a flask or apparatus containing substances from which moisture is to be excluded. 

Fig. 77,13, 1 illustrates a distillation unit when it is desired to protect the distillate from moisture in the atmosphere. The drying tube may be filled with anhydrous calcium chloride held in position by loose plugs of glass wool or with a loose plug of cotton wool. Fig. 77,13, 2 depicts the use of an air condenser for liquids of boiling point above 140-150°. 

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