Ion-beam irradiation effects for some polymers

We have investigated that the ion-beam irradiation effects for some polymers are different from those of the γ-rays or electron beams. Heavy ion has higher stopping power than that of electron or γ-ray. Moreover, the stopping power of heavy ion is different along the trace as well-known as the Bragg curve. In present work, we present the heavy ion irradiation effects for polyethylene (PE) and polypropylene (PP), comparing with low stopping power effects. In low density PE, the transformations are occurred in the trans-vinylene, end-vinyl, vinylidine and crosslink on irradiation in vacuum. The transformation for these species depends on the stopping power of ion. In low density PE, the trans-vinylene shows the remarkable transformation, the depth profile of which resembles the Bragg curve. The vinylidine decays by ion-beam irradiation which is similar to the effect on γ-rays or electron beam irradiation. On the other hand, the irradiation effect of the end-vinyl shows the complex stopping power dependence, in which the stopping power threshold was found to be 80 keV/μm to 100 keV/μm. The end-vinyl decreases on irradiation by stopping power lower than the threshold, but increases on higher stopping power than that. On the other hand, when irradiation was carried out in air, the carbonyl groups were found other than the species transformed on vacuum irradiation. The transformation of the isotactic polypropylene (iso-PP) irradiated with various ion-beams in air was investigated. The transformations by ion-beam irradiation were found for vinylidine, end-vinyl and trans-vinylene and carbonyl groups. But the ion beam dependences of these species were different from that of PE described above. In iso-PP, the transformation of the trans-vinylene was found to be a little, compared with that of PE. On the other hand, the vinylidine group increases by irradiation. This is much different from the irradiation effect of PE. These different effects between PE and iso-PP in ion-beam irradiation depend on initial reaction processes based on the structure of both polymers. (authors)