Wool, enzymatic treatment

Physicochemical Changes on Wool Surface after an Enzymatic Treatment... 

The amount of the individual amino acids released during the enzymatic treatment of wool was monitored by the HPLC method. Moreover, an XPS analysis of enzymatic-modified wool fabric samples and contact angle measurements were performed. The data obtained by the XPS method allowed comparison of the changes in the elemental concentration on the wool surface after enzymatic treatment. The results of the contact angle measurements demonstrated an increase in the wettability of the modified wool surfaces. 

Electrokinetic measurements Enzymatic treatment Surface properties Wool... 

Figure 3 presents SEM pictures of untreated, enzyme-treated, and wool fibres after enzymatic treatment and chitosan deposition. The characteristic scaly structure of the... 

Fig. 3 SEM micrographs a blank wool fibre - magnification 3000 x b wool fibre after enzymatic treatment - 4% o.w.f. of Perizym LAN, 30 min - magnification 3000 x c wool fibre after enzymatic treatment - 4% o.w.f. of Perizym LAN, 30 min and 1.7% o.w.f. of chitosan deposition - magnification 2000 x...

Figure 4 shows an increase in the electronegative PCD potential, both for the enzymatic bath (from —70 mV to about —310 mV) and the wool fabric sample (from — 180 mV to —670 mV), as a function of the time of enzymatic treatment. This increase in PCD potential can be ascribed to an increased wool surface acidity, which occurs... 

Fig. 4 Changes in the PCD potential during the enzymatic treatment of wool (4% o.w.f. of Perizym LAN)...

The results of the PCD measurements confirm the acidic character of wool surface and an enzymatic bath and demonstrate that the optimum time of enzymatic treatment amounts to about 35-45 min. After that period a plateau in the PCD potential for wool fibres can be seen. 

Also, the enzymatic treatment causes a change in the isoelectric point (IEP) value of wool, as demonstrated by the electrokinetic measurements (Fig. 5). With an increase in enzyme concentration the IEP value shifts in the direction of more acidic pH (from 3.8 for untreated wool to 3.7 for wool after 1% enzymatic treatment, and 3.45 for wool... 

Untreated wool Binding energy [eV] FWHM [eV] Elemental concentration [%] Share of line [%] Wool after enzymatic treatment Binding FWHM Elemental energy [eV] concentration [eV] [%] Share of line [%]... 

Most likely the changes in IEP value, as well as in PCD potential, during the enzymatic treatment of wool are the result of enzyme-initiated oxidation reactions. As can be seen from the XPS results specified below (Table 1), a slight increase in SO2, SO3, SO4 groups concentration, from 0.248% (0.248%= 11.8% of 2.1% of total elemental concentration) for untreated sample to 0.314% (0.314% = 19.6% of 1.6% of total elemental concentration) can be observed. 

The data obtained by the XPS method (Table 1, Fig. 7) show the changes in the elemental concentration of C, N, S, and 0 on the wool surface after enzymatic treatment, as compared to untreated wool. The increase in the atomic concentration of carbon, from 78.6% for untreated wool to 79.4% for wool after enzymatic treatment, and the decrease in the atomic concentration of nitrogen from 6.5% for untreated wool to 5.3% for wool after enzymatic... 

The increase in the atomic concentration of oxygen (Table 1) suggests an increased amount of hydrophilic groups on the wool surface. This fact can be confirmed by the results of the contact angle measurements (Table 2). Following enzymatic treatment the contact angle is distinctly decreased, from 122.5° for untreated wool to 108° and even 102°, but the wool fabric surface is still hydrophobic (0 > 90°). The contact angle value obtained for wool after an intensive treatment (4% o.w.f. of enzyme) equals the one for wool samples with chitosan deposited. 

Changes in the topography of wool fibres, confirmed by SEM micrographs, can be observed as a result of the enzymatic treatment of wool fabric. 

An enzymatic treatment causes the release of a significant amount of amino acids containing sulphur (methionine and cysteine) as well as an aspartic acid from the wool surface. 

As a consequence of enzymatic treatment, an increase can be observed in the acidity of the wool surface, which is demonstrated by a distinct increase in the electronegative PCD potential of wool fabric, the reduction of IEP value, and by XPS results. 

Moreover, an enzymatic treatment of wool causes an increase in the amount of hydrophilic groups at the surface. This is proved by the increase in the elemental concentration of oxygen, as obtained by XPS, and the increase in the wettability of enzyme-modified wool surfaces. 

Shen, J., 2010. Enzymatic treatment of wool and silk fibers. In Nierstrasz, V.A., Cavaco-Paulo, A. (Eds.), Advances in Textile Biotechnology. Woodhead Publishing Ltd, Cambridge, UK, pp. 171-192. 

The results of treating wool with proteolytic enzymes will be unpredictable in the absence of detailed knowledge of (a) the processing history of the substrate and (b) how specific process conditions affect subsequent enzymatic treatments. To elucidate this point, the effects of adsorbed ionic species on enzyme/substrate adsorption and reaction kinetics were studied. ... 

An average size of continuous treatment plant for antifelt treatment of wool releases approximately 140 g/hour AOX. As an optimization of the process is possible only within certain limits, alternative processes for an antifelt treatment have to be chosen to substitute the chlorination process, for example, enzymatic processes, oxidative processes (KMn04, persulfate), or corona or plasma treatment. In many cases combinations with resin treatments are proposed. 

Enzymatic pre-treatments to protein fibres are generally concentrated on wool and silk. It is possible to remove skin residues, skin grease and vegetable matter ol wool by enzymatic degradation method. Furthermore, the wool surface can be modified, and felt free finishing with simultaneous improvement of lustre and handle of woollen fabric is possible by enzyme treatment. 

Pretreated (enzymatic and enzymatic-I-hydrogen peroxide) knitted wool fabrics were treated with argon and atmospheric air plasma to improve adsorption capacity (Demir et al., 2010). After plasma treatment, a chitosan solution was appUed for antimicrobial effect. The treated fabrics were evaluated in terms of washing stabiUty as well as antimicrobial activity. The surface morphology was characterized by SEM images and Fourier transform infrared (FilR) analysis. The results indicate that the atmospheric plasma treatment had an etching effect and increased the fiinctionahty of wool surface. Atmospheric plasma treatment also enhanced the adhesion of chitosan to the surface and improved the antimicrobial activity. 

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