Fractional free volume dependence of neutron-irradiated polystyrene (PS)‎ measured by positron method

Abstract EN

The fractional free volume (Fh) in polystyrene (PS) as a function of neutron -irradiation dose has been measured, using positron annihilation lifetime (PAL) method.

The results show that Fh values decreased with increasing n-irradiation dose up to a total dose of 501.03× 10-2 Gy.

A percentage reduction of 2.14 in Fh values is noticed after the initial n-dose corresponding to a percentage reduction in the free volume equal to 42.14/Gy.

The total n-dose induces a percentage reduction of 7.26, corresponding to a percentage reduction of 1.45/Gy.

These results indicate that cross -linking is the predominant process induced by n-irradiation.

The results suggest that n-irradiation induces structure changes in PS, causing cross-linking in PS chains, whereas the presence of oxygen during irradiation causes retardness of cross-linking yield, which consequently affects the values of the above mentioned parameter with respect to their values in case the irradiation is performed in vacuum.