Abstract: Aiming to address the problems of slow retraction， small retraction force， and poor safety and reliability of common peroxide crosslinked polyethylene （PE-Xa） memory ring， a novel nano-silica （SiO2） modified PE-Xa memory ring was prepared， and the effect of crosslinking degree on the performance of the memory ring was investigated. The results indicated that the retraction speed and retraction force of the memory rings increased with an increase in crosslinking degree. The effect of surface treatment and addition of nano-SiO2 on the performance of the memory rings were investigated. The results indicated that nano-SiO2 was well dispersed due to the surface treatment with a silane coupling agent KH-570 as well as the mixing process at an ultra-high speed with a linear speed above 1 km/min. The addition of 1.5 % surface-treated nano-SiO2 could improve the retraction speed， retraction force and creep resistance of the memory ring greatly. The performance investigation indicated that the retraction speed and retraction force of the memory ring were better than those of the commercially available memory ring， and it passed the thermal stability test under the hydrostatic pressure specified in the standard of XLPE pipe as well as the hydrostatic pressure test specified in the system applicability.

Key words: peroxide crosslinked polyethylene memory ring, crosslinking degree, nano silica, retraction performance, creep resistance