When poly (ethylene terephthalate) fibers were irradiated by gamma radiation in air
macromolecular peroxides were formed
which could be decomposed into macromole-cular radicals by hydrazine cupric ion catalytic system. These radicals thus formed can initiate in situ graft copolymerization of acrylic acid in its aqueous solution. The oxygen in the reaction medium has no effect on the graft yield. There is a optimal concentration range of the hydazine for the graft reaction pertinent to the graft condition. The graft yield increases with cupric ion concentration within the range of 0---2.5×10-3mole/l.