Study of the electric‐field effect in polyethylene by the positron annihilation technique

摘要

AbstractThe positronium formation and the reversibility behavior of the electric field from 31.75 to 588.24 kV/cm were studied in high‐density polyethylene (HDPE) using the positron annihilation lifetime technique. The lifetime measurements were performed using the conventional fast‐fast coincidence timing system. The observedortho‐positronium life time τ3does not show significant variation from the corresponding values measured without the electric field. On the other hand, the corresponding intensityI3increases with increasing the electric field strength in the range from ∼ 100 to 588.24 kV/cm. This result indicates a strong irreversible effect of the electric field. In addition, the effect of temperature on the sample stressed at 450 kV/cm was investigated. The structural changes on the heating and cooling cycles show reversible behavior. The thermal expansion coefficient has been deduced to be 7.53 × 10−3/°C. © 1993 John Wi