Surface functionalization of wool using 172 nm UV excimer lamp

摘要

Wool is an important natural fiber having a complex surface structure which makes it difficult to dye and process it. It has a hydrophobic surface due to the presence of disulphide cystine crosslinks and a layer of fatty acids on the fiber surface. Conventional chemical treatments used to improve the hydrophilicity of wool often have an adverse effect on the feel and handle of this fiber. In this study, effect of monochromatic UV excimer radiation of 172 nm on the performance properties such as wetting, surface chemistry and surface morphology of wool has been studied. Irradiation reduces the wetting time of wool nearly by a factor of 10, even after a short exposure time of 1 minute, irrespective of the atmosphere used. Wetting time continues to decrease with increasing time of exposure and at 15 min of exposure, the absorption becomes instant. However, no significant change was observed in the ATR spectra of treated and untreated samples. SEM images show ablation and etching of the surface. The well defined scaly contour is not seen and there are deep striations on the surface of samples treated in nitrogen atmosphere. In case of samples exposed in O_2 atmosphere, micropores can be seen on the surface. Samples treated in nitrogen atmosphere for 15 min show nearly 100% exhaustion of acid dye as compared to 73% for untreated samples after 20 min of dyeing. Treated wool shows increased saturation dye uptake as well as improved rate of dyeing. Since these changes are restricted to surface and do not affect the bulk properties, these findings can have a significant effect on the commercial dyeing and finishing procedures used for wool and can be used to design cleaner and more efficient processes in future.