Ultrahigh molecular weight polyethylene free volume hole structure studiedby positron annihilation lifetime technique

The positron annihilation lifetime technique has been used to study the str ucture of three types of ultrahigh molecular weight polyethylene, obtained via different supported catalyst systems and hence having different molecul ar weights and degree of crystallinity. Pores with two different mean radii , about 1.8 Angstrom and 3.3 Angstrom, were observed in the studied samples . A comparison between positron annihilation and wide angle X-ray scatterin g and microhardness measurements has been made. There are evidences that cr ystalline phase contributes to o-Ps formation. The existence of a shorter l ong-lived component tau (3) is explained by the latter fact.