INTRODUCI'IONThe sorption of polar liquids and vapors by proteins is considered to occur initially by hydrogen bonding at polar groups in the protein.'-l These polar sorption sites are mainly side-chain amino, carboxyl, and hydrmyl groups and peptide l i i g e s of the polypeptide ohaiins. However, there is some doubt as to whether it is side-chain polar groups or peptide links which form the main attractive sites for initial sorption.'-'There is some reported research on the.effect of side-chain masking on water sorption properties of proteins. Mellon et a1.6 found that. blocking of amino groups of casein by benzoylation decreased the sorption of water vapor. Modifications of the polar side-chains of wool results in decreased equilibrium sorption of water vapor at low or intermediate vapor pressureas-" usually without greatly affecting rate or equilibrium sorption at saturated vapor pressure. Kanagy and C a~s e l '~ found that sorption of water vapor by collagen is decreased by deamination, acetylation, and methylation.With wool, the surface scale structure can be a complicating factor in sorption studies. Although chemical and physical attack on these surface scales increases the rate of uptake of dyes1a-16 the sorption of water is unaffected. 11*18It might also be expected that physical modification of wool would produce changes in sorption behavior due to rearrangement of the polar groups and alterations in accessibility, but it has been found that severe physical changes, including supercontraction, reduction and even complete dissolution and reprecipitation, do not greatly affect the equilibrium sorption of water vapor at relative humidities up to 93%.16 Heat denaturation of egg albumin results in very little change in water-sorbing properties, but surprisingly, the sorption of ethanol is greatly This can be explained by assuming that because of their sma? size and high polarity, water molecules are sorbed extremely rapidly, attaching to polar sites with strong hydrogen bonds in such a way that even large changes in the chemical and physical properties of proteins produce little observed effect on the rate of sorption of water. By using larger and less polar molecules such as alcohols, which are sorbed much more slowly 2053

The effect of surface deposits of nylon and N -substituted nylons on the abrasion-resistance and felting shrinkage of wool has been determined. N -methoxymethyl nylons are much more effective than nylon itself, when applied from solution, in increasing the abrasion-resistance of wool fabric, but not in decreasing the felting shrinkage of the fabric. If the N -methoxymethyl nylon is first applied to the wool fabric from alcoholic solution and then hydrolyzed in situ by approximately 2N HCl, the polymer is found to confer non-felting properties on the wool. A deposit of approximately 3% by weight of polymer has been found to eliminate entirely the felting shrinkage of wool fabric under the conditions of test. The optimum degree of substitution of the nylon for the production of non-feltability is between 5% and 6% combined formaldehyde, which corresponds to between 20% and 24% —NH groups substituted.The effectiveness of these polymers in increasing abrasion-resistance and decreasing felting shrinkage is explained on the basis of their adhesion to and covering power on the wool fiber.

The use of reducing agents for setting wool has been extended to give washable non-iron effects on pure wool fabrics. Initially this was accomplished by applying the Si-Ro-Set process to garments made from shrinkproofed wool. This led to flat setting of fabrics in the mill by applying a dilute solution of a reducing agent to the fabric followed by immediate steaming on a blowing machine.When preceded by shrinkproofing, this method of setting gives excellent washable non-iron effects on pure wool fabrics. Garments made from fabric treated in this way showed satisfactory laundering and wear performance in practical trials.

When wool fibres are impregnated with a dilute solution of ferrous ammonium sulphate, dried, and then treated with a solution of methacrylic acid containing a trace of hydrogen peroxide, preferential internal polymerisation is brought about by the hydroxyl radicals formed inside the fibres when the hydrogen peroxide encounters the ferrous ions. The reaction proceeds best at low j>H values in absence of oxygen. Preferential internal polymerisation of water–insoluble monomers can also be brought about if they are emulsified with Lissolamine V, and no difficulty has been encountered in forming copolymers of methacrylic acid and methyl methaerylate, for example, within the fibres. Such internal deposits of polymer can be used to modify the properties of wool in a number of ways. When the polymer is acid, two–tone effects can be obtained by dyeing treated and untreated wool in the same dyebath, the treated wool taking a lighter shade. Conversely, when the polymer is basic, the treated wool takes a darker shade. In addition, internal deposits of polymer are capable of increasing the wear–resistance and reducing the milling shrinkage of wool fabrics. Finally, if the monomer carries reactive side–chains, e. g. methacrylamide, internal polymerisation followed by cross–linking with formaldehyde causes a striking increase in the resistance of wool fibres to extension in water. It is not yet known whethor cross–linkages are formed between the polymer and the wool, but reactions of this type should be useful in strengthening intact fibre and repairing damaged fibres.

From experiments in vitro it is found that cysteine, in the presence of certain oxidizing agents, can act as a powerful catalyst for polymerizing ethylenic monomers. This aids in explaining the reactions which occur when wool is reduced with sodium bisulphite and then treated with a monomer. Polymerization within the fibre is probably initiated by free radicals produced from reduced cystine by the action of sulphoxides or sulphones present in the wool as a result of atmospheric oxidation. Fraction (A+B) of the cystine appears to be involved as pretreatment with alkali, which converts this fraction to lanthionine, prevents polymerization from taking place. Little or no polymer can be formed in wool from the base of a staple, whereas polymer can be synthesized quite readily in the tip where oxidation products are more likely to be present. If, however, wool from the base is pretreated with a mild oxidizing agent, polymerization will then occur as readily as in the tip. The polymer is apparently chemically bound to the wool through thio-ether linkages.