用正电子湮没研究γ辐照和压力驰豫对聚苯乙烯自由体积特性的影响

Effects of γ-radiation and pressure relaxation on the free-volume properties of polystyrene studied by positron annihilation

在γ辐照０～４０Ｍｒａｄ的范围内测量了高强度聚苯乙烯（ｈｉｇｈｉｍｐａｃｔｐｏｌｙｓｔｙｒｅｎｅ，ＨＩＰＳ）的正电子湮没寿命谱，发现随着辐照剂量的增加，ｏ－Ｐｓ寿命τ３基本不变（约为１．９８ｎｓ），而ｏ－Ｐｓ强度Ⅰ３下降；当辐照剂量由２０Ｍｒａｄ上升到４０Ｍｒａｄ时，自由体积孔洞的半径分布宽度变窄；此外，还测量了在压力驰豫期间ＨＩＰＳ的正电子湮没寿命谱，施加的静态压力为０，２５，５０ＭＰａ，发现τ３不随驰豫时间ｔ变化（约为２．０ｎｓ），但Ⅰ３随时间下降。

The positron annihilation lifetline spectra of high-impact polystyrene(HDS) as a func-tion of γ-radiation dose in the range of 0～40Mrad have been measured. It is observed that the o-Ps lifetune τ_3 is basically constant(≈1. 98ns)and Ⅰ3 decreases with the increase in radiation dose,Moreover,the width of hole- size distribution is dramatically reduced when the radiation doseincreases ftom 20 to 40 Mrad; We also measured the PAL spectra of HIPS during the pressure re-laxation at initial static pressures P=0,25 and 50 MPa.We found τ_3 remains constant (～20ns) with the relaxation time t ,but Ⅰ_3 decreases with t at P=0,25 and 50 MPa。