CHAIN SCISSION AND CROSS-LINKING IN THE RADIATION DEGRADATION OF POLYMERS - LIMITATIONS ON THE UTILIZATION OF THEORETICAL EXPRESSIONS AND EXPERIMENTAL RESULTS IN THE PREGEL REGION

An appraisal is made of current methods of determining radiation-chemical yields for main-chain scission and cross-linking of a polymer from measurements of molecular size distributions and average molar masses after high-energy radiation doses D below the gel dose Dg. Calculation of molecular size distributions by a single cycle of successive scission and cross-linking is shown to give significant errors. A multicycle procedure that uses iterative, numerical solutions of the fundamental scission and cross-linking equations is developed and shown to be superior. On the basis of theoretical calculations of likely experimental errors in measurements of Mw and Mz it is recommended that radiation doses be restricted to the region D < 0.4Dg for evaluation of scission and cross-linking yields from the dose dependence of average molar masses. © 1979, American Chemical Society. All rights reserved.