Jana Braniša

The uptake and release of humidity by wool irradiated with electron beam

In this work, wool samples a) degreased and stored in desiccator (WD), b) degreased and stored freely (WF), c) cleaned in water and stored freely (WW) were irradiated by accelerated electron beam with doses within the range (0-400) kGy in air. Content of S-sulphonate as primary oxidation product was determined in WD using FTIR spectra inverted in the second-order derivative spectra. The uptake of humidity by all the samples at room temperature and 97% relative humidity was examined gravimetrically. As expected, the highest humidity uptake was observed for WD and the smallest one for WW. Development of the humidity uptake showed some fluctuation for all samples and, for WD the fluctuation corresponded with generated S-sulphonate, presumably due to formation of numerous H-bonds. The increasing uptake of humidity for WD and WW was observed up to 40 kGy dose while for WF, the uptake decreased below the initial level already from 16 kGy. Surface tension was measured using sink-float method combining stalagmometry. The initial surface tension of WW was higher than for WD and WF but, grew equally for all samples from 25 kGy. From 100 kGy dose the surface tension showed stabilized level. The humidity release by WD was measured using thermogravimetry. Variation of the rate humidity release around 100 °C, adequate for desorption of weakly bound water, and the mass residue of the heated wool for 120 °C corresponding to release of total water, showed an inverse dependence. It was concluded that content of S-sulphonate is responsible for variability of the sorption properties. The more S-sulphonate formed, the higher uptake of humidity and the lower rate of humidity release that can be observed. It is suggested that, within a certain range, a properly chosen dose can affect humidity uptake.

Sorption properties of sheep wool irradiated by accelerated electron beam

Electron beam (EB) irradiated wool was examined for sorption of chromic ions. Sorption increased with the adsorbed dose non-monotonously, which is a result of the generation of S-oxidized groups, secondary structure variation, and the breaking of the keratin backbone. For a dose of 400 kGy, an increase by 120 % was observed at the cystine dioxide and cysteine acid amounts. Examining sorption of unexposed wool and that irradiated with doses of 25 kGy and 40 kGy for basic, methylene blue (MB), or acidic, pyrogallol red (PR) dyes revealed that such low doses have no effect on the carboxylic or amino groups of keratin. Sorption of MB is independent of the EB treatment and is identical for both samples due to the interaction of MB amino groups with the carboxylic groups of wool; however, the sorption capacity for PR is a function of the EB treatment. The sample irradiated with the dose of 25 kGy showed higher PR sorption than that with the EB dose of 40 kGy, which was equal to that of unexposed wool. While the 25 kGy sample provided more active sites for PR interaction compared with the unexposed one, the 40 kGy sample contained already enough active sites to generate intra- and intermolecular interactions inside wool. Thus, PR adherence to the 40 kGy sample was restricted and comparable to the level of unexposed wool.