Effect of radiation on the structure of natural rubber

The effects of radiation-induced crosslinking on the physical arrangement of macromolecules in molten state natural rubber (NR) were examined. Three NR samples with doses of 0, 300, and 550 Mrad were studied based on differential radial distribution function (DRDF) curves derived from wide-angle x-ray scattering data. The resultant DRDF curves for all samples show the presence of intermolecular peaks at ∽5, 10, and 15 å. The appearance of such periodic intermolecular peaks suggests the presence of locally aligned chain segments, to the extent of ∽15å, in both uncrosslinked and crosslinked NR. The 5-å periodicity observed is the average chain-to-chain distance between more or less parallel molecules. The high-energy radiation causes a decrease in the area of these DRDF peaks for NR irradiated to higher than 300 Mrad. This result suggests a corresponding radiation-induced destruction of the intermolecular organization.