Comparison of the effects of gamma and ultraviolet radiation on wool keratin

Abstract

The effects of γ‐radiation (60Co) on some chemical and physical properties of wool keratin are compared and contrasted with the effects of ultraviolet radiation in the UVC (200–280 nm) region. The effect of UVC doses up to 25 J/cm2 (equivalent to 20 min exposure to a bank of high intensity lowpressure mercury arcs) on fabric strength is small (≤5%), whereas γ‐irradiated wool experiences strength reductions of ≥15% at doses over 100 kGy. Colour changes following UVC and γ‐irradiation are quite different: UVC wool is initially green changing to yellow under ambient conditions, γ‐treated wool becomes pink‐red at doses 25–250 kGy, and yellow at higher doses. The chromophores produced by UVC are easily removed by oxidative bleaching with hydrogen peroxide, whereas γ‐treated wool remains yellow even at relatively low doses (25–50 kGy). This has implications for the use of γ‐radiation as a means of sterilising wool for compliance with quarantine regulations. The effects of the two forms of radiation on the natural fluorescence of wool, permanent setting, printing properties and the epicuticle layer are also described.

Effect of Radiation on Textile Dyeing

“…The colour changes i.e. green followed by yellow in wool keratin due to UV radiation have been observed also (Millington, 2000).There are several processes to reduce the pilling yet no process can guarantee the zero pilling in wear. But Millington reported that it is only UV radiation which can reduce the pilling through siro flash technology followed by oxidation with hydrogen peroxide in germicidal UV Tubes.…”

“…The irradiation of fabric is also another factor which affects the colour strength of the fabric. Previous studies show that UV irradiation adds value to colouration and also increases the dye uptake ability of the cotton fabrics through oxidation of surface fibers of cellulose (Millington , 2000;Javed et al ., 2008). The colourants from Methanol solubilized extract reach the vicinities of fibres and upon investigation of colour strength using spectraflash SF 650, dark yellow shade was observed.…”

“…Upon irradiation the cross linking changes the crystal structure of the cellulose, which can add value in colouration process and causes photo modification of surface fibers. The irradiated modified fabrics can allow: more dye or pigment to become fixed, producing deeper shades, more rapid fixation of dyes at low temperature and increases wet ability of hydrophobic fibers to improve depth of shade in printing and dyeing (Millington, 2000). The influence of gamma radiation on the colour strength values of the fabric dyed with natural dyes extracted from eucalyptus bark has been shown in Fig.…”

Photoyellowing of wool. Part 1: Factors affecting photoyellowing and experimental techniques

“…Colour changes also occur when wool is exposed to high‐energy radiation such as X‐ and γ ‐rays. Wool exposed to γ ‐rays from a 60 Co source turned pink‐red, and the depth of shade increased with γ doses up to 250 kGy [50]. After 500 kGy, the pink‐red coloration had changed to yellow, presumably because of the instability of the pink chromophores to higher γ doses.…”

“…The distinct colour change at low γ doses poses a problem for the use of ionising radiation (normally ∼50 kGy) required by some quarantine authorities for the sterilisation of any seeds present in imported bales of raw wool. Also the chromophores formed by γ ‐exposure of wool are not fully removed after bleaching with hydrogen peroxide [50].…”