The degradation of cellulose by ionizing radiation

When subjected to the effect of ionizing radiation, such as atomic pile radiation or gamma radiation, cellulose is rapidly degraded into a powdery material. A theoretical treatment shows that if the effect of radiation is to cause fracture at random in the main chain, the relation between intrinsic viscosity [η] and radiation dose R should be of the form: where R0 is a “virtual” radiation dose needed to produce the initial number-average molecular weight from a chain of infinite molecular weight. The published data of Saeman, Millett, and Lawton have been used to verify this formula, which leads to a relationship between [η] in cupriethylenediamine and viscosity-average molecular weight Mv: with α = 0.71. The constant K has been evaluated by comparison with data given by Gralen, but is less accurately known. It is deduced that one million roentgen results in fracture of 0.16% of the monomer units in the main chain. The decomposition of carbohydrates under radiation, which occurs at the same time as main chain fracture, can be explained on the assumption that approximately one monomer unit is decomposed per main chain fracture. The study of intrinsic viscosity of irradiated polymers appears to offer an accurate means of evaluating α in the usual formula for intrinsic viscosity [η] = KMα.