Physical Properties Of Wool Fibers Research Articles

Modification of wool protein fiber with plasma and dendrimer: Effects on dyeing with cochineal

In this study, plasma treatment and a poly(propylene imine) dendrimer were employed to improve the dyeability of wool fibers with cochineal natural dye. FESEM, EDX, AFM and FTIR techniques were employed to investigate the effects of these treatments on chemical and physical properties of wool fibers. The etching of the surface layer of wool fibers and increased roughness after plasma treatment was confirmed by FESEM and AFM images. EDX and FTIR analyses confirmed the creation of oxygen-containing groups and attachment of dendrimer molecules on wool fibers after plasma and dendrimer treatments respectively. The effects of different dyeing parameters on dye absorption and the applicability of different isotherm and kinetic models on the dyeing process were investigated. The results showed that the kinetics of absorption of cochineal on raw, plasma-treated and dendrimer-treated fibers was best fitted with the pseudo-second-order model and the isotherms of the dyeing processes followed the Freundlich model.

Pilling properties of wool single jersey made of compact and conventional ring yarns after anti-felting treatment

This work studied the differences between wool single jersey made from compact and conventional ring-spun yarns composed of surface-modified fibers with different anti-felting treatments. Wool yarns (100%), produced from the fibers modified by two commercial chemical treatments, Basolan®88 and Kroy-resin, were spun according to compact and conventional ring-spinning systems in two different twist factors of spun yarn. The surface morphology and physical properties of wool fibers and conventional and compact ring yarns and the pilling properties of these fabrics were examined and compared with each other before and after the chemical treatment. The breaking strength of modified fibers decreased if compared with the control. Results indicated that the surface morphology of wool fiber changed by Basolan®88 and Kroy-resin treatment, and a lower friction coefficient increased with the differential frictional effect value. The hairiness index ( S3) of compact yarn was a reduction by 60% and the strength and elongation percentages were higher compared with conventional ring yarn. The fiber packing density of compact yarn was 30% higher from the fiber distribution pattern in the yarn cross-section. Another important finding was that the fabric produced with compact yarn showed better anti-pilling property and more mass loss.

Effects of Atmospheric Pressure Plasma Treatments on Some Physical Properties of Wool Fibers

Knitted wool fabrics were treated with argon and air atmospheric plasma. Pilling, bursting strength, thermal resistance, thermal conductivity, air permeability, water vapor permeability and friction properties were investigated. The surfaces of untreated and plasma-treated wool fabrics were analyzed by scanning electron microscopy to compare the morphological changes. The outcomes showed that atmospheric plasma treatments affected the physical properties of wool fabrics such as thermal properties, water vapor permeability, air permeability and friction properties. While there was an increase in thermal resistance, water vapor permeability and friction properties; pilling tendency, bursting strength, thermal conductivity and air permeability values decreased.

Physical properties of wool fibers modified with isocyanate compounds

AbstractWool fibers were chemically modified with various kinds of isocyanates and diisocyanates. The reactivity of these modifying agents was examined as a function of the reaction solvent, temperature, time, and isocyanate chemistry. The use of dimethyl sulfoxide as the solvent, aliphatic mono and bifunctional isocyanates, such as dodecyl isocyanates and hexamethylene diisocyanate, and a temperature of 75°C resulted in higher weight gains. The moisture content of wool fibers tended to decrease with increasing the weight gain, the extent of which depended on the isocyanate used. Monofunctional isocyanates caused a sharp drop of tensile strength and an increase of elongation at break, while bifunctional isocyanates preserved the intrinsic tensile properties of wool. The FTIR spectra showed changes in the amide I, II, and III ranges, in the CO stretching range at 1750–1700 cm−1, and in the CH stretching and bending regions at 3000–2800 and 1500–1350 cm−1, respectively, attributable to the incorporation of the modifying agent. DSC measurements highlighted remarkable changes in the thermal behavior of acylated wool fibers. The bimodal melting endotherm at 230–240°C shifted to lower temperature, and the relative intensity of the constituent peaks changed as a function of the weight gain. Foreign deposits adhering to the surface of chemically modified wool fibers were detected by SEM analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1390–1396, 2003

Physical Properties of Wool Fibers in Electrolyte Solutions

The tensile modulus of Lincoln wool fibers immersed in a range of neutral salt solutions has been investigated as a function of time and solution concentration. Salt solutions with high water activity, reduced ionic strength, and low viscosity will lead to favorable conditions for the penetration of ions into the fibers. The reduction in tensile modulus when salts penetrate wool fibers can be fully accounted for by the increased regain and associated swelling of the fibers. It appears unlikely that the breaking of salt links or destabilization of the α-helices plays a significant role in reducing the tensile properties of wool fibers in neutral salt solutions.

Physical Properties of Wool Fibers at Various Regains

In previous work on recovery from longitudinal cohesive set, the setting extension was produced when the fibers were in water. This paper presents a comparison between recovery of fibers set in this way (a), and when the extension is done at the relative humidity of recovery (b). There is a qualitative similarity in the results, but for the same period of setting and relative humidity of recovery, set is lost more rapidly in case (b). At fixed RH there is a direct correlation between the force at the instant of release and the rate of subsequent recovery. In work up to the present time, the most important parameters in recovery from cohesive set have been duration of setting, RH during deformation, and RH during recovery.

Physical Properties of Wool Fibers at Various Regains

Length recovery vs time curves were obtained after release of wool fibers that had been held at 20% extension for various times, at various relative humidities, and at temperatures in the range 20° to 50° C. The forces in the fibers at all times prior to release were also measured. All changes in treatment prior to release led to changes in recovery, but many of the effects were small. Relative humidity remains the most important parameter. The activation energy of recovery was found to be approximately 650 cal mole.

The Influence of Weathering on Some Chemical and Physical Properties of Wool Fibers, with Particular Reference to Felting

The influence of weathering on the chemical and physical properties of wool fibers has been investigated. The weathered fiber tips are modified to a great extent by weather ing; this is shown in changes in solubilities and in the amino acid composition. As a result of photochemical degradation, fibers show a decrease in tenacity and extension as well as in compressional resistance. Weathered fiber tips showed, in spite of removal of a great number of scales, a better feltability than the fiber roots. On the basis of these results a theory of felting is presented and discussed.

The Physical Properties of Wool Fibers at Various Regains

Each water molecule in the keratin-water system is considered to have four asso ciations, each of which may be either an association directly with the keratin structure or an association with another water molecule. By assuming, as a first approximation, that the energy of binding of a water-keratin association is a fixed value above that of a water-water association, and using available data on the differential heats of wetting of keratin, the change in the proportion of keratin-water and water-water associations with change of regain may be calculated. From this, the proportion of water molecules with four, three; two, one, or no associations with keratin at any regain may be estimated. If the water not associated at all with' the keratin structure is considered "free" or "liquid" water, and the associated water "bound" or "localized" water, then reasonable agreement is found with the corresponding water fractions estimated by Cassie. Experi mental data are presented which appear to indicate that these two fractions have a definite physical Significance Nuclear magnetic resonance results are also discussed, to show where disagreement exists with the earlier concept of water sorption. The model presented is shown to be compatible with. these results and with other evidence from experiments on the drying of wool from saturation and from intermediate relative humidities.

The Physical Properties of Wool Fibers at Various Regains

At relative humidities ( p/p0) between 5% and 90% the force ft at time t acting on a a wool fiber at fixed extension in the yield region is given by ft = [a - b ( p/p0)]ϕ ( t). Here a and b are quantities independent of humidity and time, while ϕ( t) is a function of time only and approximately linear with the logarithm of time. A model consisting of a network of bonds with various energy barriers to breakdown is proposed to explain the above relationship between force and time. Further, this model is applied to explain the mechanism of recovery from cohesive set. The role of water in bond breakdown and the effect of the mobility of the water are discussed with reference to the mechanisms of relaxation and recovery.

The Physical Properties of Wool Fibers at Various Regains

Watt and Kennett [11] have shown that water may be incorporated into the keratin structure by long exposure at relative humidities between 5% and 80%. This incor porated water is not removed on drying in vacuo and results in an increase of the "dry" weight of the wool fibers. Mechanical tests carried out on fibers containing incorporated water show an increased stiffness for relative humidities less than 60-70% over stiff ness measured at the same humidities after the incorporated water had been removed by saturation in liquid water. It is proposed that the water which is incorporated into the keratin structure and produces the "dry" weight increase becomes immobilized at intermediate relative humidities by increased strength of bonding of the water directly with the keratin structure. Saturation in liquid water reduces the amount of associa tion between any one molecule and the keratin structure. Drying rapidly from this state hence lowers the possibility of formation of strong, direct bonds between water and keratin.

Physical Properties of Wool Fibers at Various Regains-

Both direct absorption curves and derivative curves due to proton magnetic resonance absorption in wool have been obtained. Peak heights and widths of the absorption lines were measured for wool samples equilibrated at a number of relative humidities in the range 0 to 90%. All water protons in wool appear to be less firmly bound than the keratin protons, but less mobile than liquid water. It seems clear that an increment of absorbed water changes the binding energies of previously absorbed water. No evi dence was obtained of a subdivision of water in wool into two or three fractions with different binding energies which are successively bound as the equilibrium regain is increased.

An Effect of Ionizing Radiations on the Hydrogen Bonds in Wool

Irradiation with 15-Mev electrons changes certain physical properties of wool fibers profoundly, even after doses of as little as 5 x 10/sup 6/ rads. Lithium bromide solutions disorientate the crystalline areas of wool which consist of polypeptide chains held together by hydrogen bonds. Irradiation increases the disorientation prcduced by lithium bromide and renders it irreversible. In sodium bisuifite solutions, wool contracts by breaking the disulfide bonds in the matrix in which the micelles are held. This effect is increased by irradiation, but the influence of radiation is less far-reaching than in the lithium bromide test. These radioinduced changes can be stimulated, in part at least, by chemical treatments that break disulfide or peptide bonds. But the number of bonds that have to be broken is many times as great as the number that are destroyed by a dose of radiation that gives a comparable effect. It is concluded that the relevant changes produced by radiation reside in the hydrogen bonding of the micelles and that radiochemical chanas involving covalent bonds are not principally responsible. The changes studied were essentially independent of moisture content of the wool fibers and of the presence of oxygen. (auth)

Physical Properties of Wool Fibers at Various Regains

The paper reports determinations of stress changes which take place in wool fibers held at constant extension of 1.5 or 10% and subjected to various relative humidity changes. Stresses may be very different according as equilibrium at a given relative humidity is approached by absorption or desorption of water by the fiber. At 1.5% strain, when approach was by absorption, for all relative humidities used the stress fell to a level lower than when the fiber was in water and then increased. A qualitative explanation is given in terms of changes analogous to sol-gel transformations.

Physical Properties of Wool Fibers at Various Regains

Under all conditions of extension and relative humidity which were used, length re covery took place in two stages: an early, rapid recovery was followed by a slow recovery which was, in most circumstances, linear with log (time). The amount of rapid recovery depends on the stress in the fiber at the instant of release. Recovery from 20% strain is greatly accelerated as relative humidity increases above 60%o this is probably due to a sharp increase in the amount of "free" water in the wool fiber. Recovery from 1.5% strain is different in character, and the reason may be that t recovery from low strain contains a large elastic component.