Direct determination of crosslinking and chain scission in polymers

Abstract

Abstract A direct method has been developed for determining G (crosslinks) for irradiated polymers using the analytical ultracentrifuge. The sedimentation velocity technique is employed to follow changes in the molecular weight of a narrow distribution polystyrene sample irradiated in vacuum with 60 Co γ‐rays. It is shown that G (crosslinks) can be determined at low doses before significant structural changes have occurred in the polymer. At about one‐fifth of the gel dose G (crosslinks) was found to be 0.019 compared to a value of 0.040 obtained from gel‐sol fraction measurements. It is concluded that G (crosslinks) may increase with dose due to processes such as the addition of radicals to double bonds formed during the irradiation.