Effect Of Ionic Liquid And Protease Treatment On Wool Surface Behaviors

With the development of biotechnology, enzymatic treatment has received much attention as an eco-friendly method in cuticle scales removal. However, the outer surface of the scales is hydrophobic and highly cross linked, it is in practice hardly substrate for protease. To make enzymatic treatment effective, the outer scale has to be modified prior to incubation. Furthermore, pretreatment methods play an important role in protease processing. An efficient and environmentally friendly pretreatment method will undoubtedly make a very active effect for protease treatment.Ionic liquid used to be a green solvent in materials processing, was employed for wool surface modification prior to incubation. Ionic liquids are often considered as a unique type of solvents due to their excellent properties, such as negligible volatility, high thermal stability, easy recycle and high solubility for many substances. In the paper, the properties of wool treated by ionic liquid and protease was first dissected, and then the promotional effect of ionic liquid modification on protease incubation was also studied. The major findings are as follows:1. Among the three kinds of ionic liquids [BMIM]Cl, [BMIM]BF4 and [BMIM]PF6, [BMIM]Cl treatment showed the best modification results for wool fibers.The weight loss of wool fiber can be rasied 53.3% by protease processing when pretreated by [BMIM]Cl at 100℃for 10 min. Further studies on the conditions of [BMIM]Cl treatment showed that the weight loss increased with the treatment temperature and elongation of treatment duration. Compared with the treatment duration, the temperature played a much more important role in [BMIM]Cl modification. However, the degree of damage to wool fibers also increased with the treatment temperature. The alkaline solubility of wool fibers treated by [BMIM]Cl at 100℃was no more than 14.3%, but it would reach 23.3% when treated at 120℃.2. The wettability of wool can be significantly improved after ionic liquid and protease treatment.Protease treatment had little improvement on the wettability of wool fabric. The wetting time of wool fabric treated by protease was more than 1800 seconds, and water contact angle more than 110o. Whereas the wetting time and water contact angle of wool fabric decreased to 1418s and 106.4o after ionic liquid treatment, which indicated that ionic liquid treatment made an efficient impact on wool wettability. However, the water uptake of wool fibers treated by ionic liquid was smaller than the protease treated. After the ionic liquid and protease treatment, the wetting time and water contact angle of wool fabric decreased to 520s and 99.7o, and the water uptake was increased to 0.591g/g from 0.574g/g. The wettability of wool sample was fully improved.XPS analysis showed that the elemental composition of wool surface was remarkably changed by ionic liquid and protease treatment. The content of C-C/C-H groups decreased from 64.9% to 47.8%, while the hydropholic groups such as O-C=O/N-C=O increased to 35.3% from 23.3% after ionic liquid and protease treatment. At the same time, the S(VI) content of wool fiber was also increased to 27.9% from 22.2%. These increases of hydropholic groups were helpful for the surface hydrophilicity.3. The dyeing properties of wool were greatly changed after ionic liquid and protease treatment.Compared with the slightly improvement in the initial dyeing rate of protease-treated wool fibers, it was quickly increased after ionic liquid and protease treatment. The dyeing rate was also high even dyed at 80oC. Otherwise, with the increase of treatment temperature and elongation of treatment duration, the dyeing rate and final dye exhaustion was both improved. Dyeing dynamics showed that the diffusion coefficient increased by about 1.12 times and diffusion active energy of wool fibers decreased to 19.43 KJ/mol from 34.39 KJ/mol after ionic liquid treatment.The K/S value of wool fabric increased to 19.78 from 17.61 after the combined treatment, which indicated that ionic liquid treatment was help to improve the color depth. However, there was about half grade decrease in the washing fastness and wet rubbing fastness after the combination treatment.4. The mechanical properties of wool were remarkably changed by ionic liquid and protease treatment.When wool fibers were pretreated by [BMIM]Cl at 100℃for 10 min, the directional friction effect can be reduced to 3.5% from 7.09% of the untreated, and respectively, the felting shrinkage was reduced to 18.84% from 30.58% .Ionic liquid and protease treatment could lead to the decrease of tensile strength and breaking elongation. The loss of tenislie strength reached 10.1%, and 31.8% for breaking elongation after ionic liquid and protease treatment. But the breaking elongation of yarn was a bit to upgrade for the heat shrinkage.Fabric manner tests results showed that the compression and bending properties of wool fabric decreased after ionic liquid treatment, but the followed protease treatment was helpful to recover them. For the whiteness, ionic liquid treatment at 120℃could induce the wool yellowing, but the whiteness was significantly improved after protease treatment.5. Ionic liquid treatment can significantly change the fiber's surface morphology and chemical composition and thus profoundly affecte the hydrolysis of wool by protease.SEM photos of ionic liquid-treated wool fibers revealed visible deterioration to scales compared with the untreated. Although the scales treated with ionic liquid were still clearly visible, the scale edges were deeply eroded by ionic liquid. The smaller Allw?rden sacs also showed the damage of wool epicutical layer by ionic liquid solubility.As shown in the infrared spectrum of ionic liquid-treated wool fibers, the stretching vibration band of N-H and O-H bonds which falls at 3300 cm-1, became wider and stronger, while the stretching vibration band of C-H bond, which falls at 2964 cm-1, 2935 cm-1 and 2877cm-1 became smaller. This indicated that the content of CH3 and CH2 bonds was reduced for the removal of the lipid acids, and thus made the -NH2 and -OH bonds originally under the lipid layer exposed to the surface. Otherwise, there was cysteic acid produced for the emergence of absorbance band at 1040cm-1 after ionic liquid treatment.WAXD results showed that the crystallnity index of wool fibers decreased from 60.0% to 57.9% after ionic liquid treatment. These changes could be attributed to the swollen effect of ionic liquid.According to the amino acids analysis results, the content of most amino acids in ionic liquid and protease treated wool fiber such as Glu, Tyr and Ser decreased much more than that treated merely by protease. In the incubation solution, the content of some amino acids such as Ser, Thr, Phe and Cys increased quickly after ionic liquid pretreatment. Especially, the content of Ser, the active center of Savinase, increased by about 10 times. This inducated that ionic liquid treatment improved the hydrolysis of the high-sulfur protein in wool scales.With the removal of lipid acids, the broken of disulfide bonds and the derease of crystallnity of wool, ionic liquid treatment not only improved the hydrolysis rate of wool keratin, but enhanced the hydrolysis of wool scales.