Investigating the Photo-Oxidation of Wool Using FT-Raman and FT-IR Spectroscopies

Fourier transform infrared and Fourier transform Raman spectroscopies are used in combination to investigate the photo-oxidation of wool and the protective effect of the uv absorber Cibafast W. Extended light exposure decreases the intensity of the S-S and C-S bands due to cystine and also reduces the intensity of the C-C stretching band, which is mainly attributed to the α-helix. A "new" band at 977 cm-1 in the Raman spectrum increases with exposure time, but its nature is uncertain. Exposure to light also produces changes in the chemical environment of tyrosine residues. Cibafast W decreases the rate of disulphide bond fission and cysteic acid formation, being most effective at low levels of light exposure. This effect is confirmed by measurements of the rate of photoyellowing and phototendering of wool fabrics.