Abstract: Polyvinyl alcohol (PVA) became crosslinkable under gammairradiation in the presence of N, N'-methyl-bis-acrylamide (BAM). It was found that with the increase of radiation dose,the radiation effect on BAM/PVA system can be divided into three stages: (1) in the lowerdose range, the gel fraction increases with increase of radiation dose and the enhanced radia-tion crosslinking is dominant; (2) the gel fractions of the system are almost independentof the radiation dose and the radiation degradation process counteracts the enhanced radiationcrosslinking and (3) in the higher dose range, the gel fraction of irradiated system decreaseswith radiation dose and the radiation degradation of the system becomes leading proces. Therelationship beteewn sol fraction S and radiation dose D for irradiated BAM/PVA systemin the first stage can be expressed by S=[(1+1/(1-K)D_g^2-K]-D_g/(1-K)D^1-K=A-BD^1-K where D_g is the gelation dose, K, a constant correlated with BAM/PVA ratio.

Key words: polyvinyl alcohol, enhanced radiation crosslinking, methylacrylamide