The Effect of Low Doses of Co60 Gamma Radiation on Some Physical Properties and the Structure of Wool Fibers

Abstract

It has been found that small doses of gamma radiation (0.5-10 Mrad) produce marked effects on some physical prop erties of wool. These effects are not readily detected by mechanical strength measurements on fibers, but are revealed by changes in the behavior of the wool when it is converted to the supercontracted quasi-rubbery state by treatment with LiBr solution. Kinetic studies of the initial supercontraction reaction indicate that irradiation produces a marked reduction in the activation, energy and increases the rate of the reaction. There is also a trend for the initial contractile force to increase and for the equilibrium length contraction to decrease at the higher radiation dose levels. Stress-strain measurements on supercontracted wool show that doses as low as 0.5 Mrad greatly reduce the number of effective cross links in the rubbery network, the effect being similar to that produced by complete removal of the normal disulfide cross links in wool by chemical treatments. There is also evidence of the rebuilding of stable linkages as the radiation dose is increased over a limited range, before bond breakage predominates at the higher dose levels where changes in mechanical strength properties begin to become noticeable. Measurements of the swelling of wool in formic acid give similar evidence of bond breakage and rebuilding processes in wool as it is irradiated. The results indicate that even small doses of gamma radiation break sufficient covalent bonds to make the crosslinked heptide chain structure more susceptible to the action of swelling and disordering agents. These small radiation-induced changes can be expected to affect properties of wool significant in absorption and penetration processes, such as those involved in dyeing, chemical modification, and grafting treatments of wool.