STUDY ON THE EB IRRADIATED VINYLESTER RESIN BY POSITRON ANNIHILATION LIFETIME SPECTROSCOPY (PALS)

The microstructure and mechanical properties of vinylester resin were studied by Positron Annihilation Lifetime Spectroscopy (PALS) The results showed that the average diameter and fraction of the free volume were decrease with increase of the irradiation dose, but the free volumes were increase under higher dose irradiation because the degradation of polymer occurred. Gel fraction analysis showed the relationship between free volume fraction and irradiation dose was quite similar to the relationship between sol fraction and irradiation dose. The influence of irradiation dose rate on the free volume characters was less than that of irradiation dose, Smaller free volume appeared for lower dose rate irradiation. DMA and mechanical properties analysis indicated the resin with smaller free volume tended to have higher T-g and storage modulus. With the increasing of free volume, the flexure strength and tensile strength of the resin decreased but the impact properties were improved.