低密度 polyethylene film을 冷延伸된 方向에 對해서 直角方向으로 延伸하면, 延伸比 1.2∼1.8 付近에서 部分放電에 의한 劣化가 顯著히 增加하고, Void發生에 의한 部分放電開始電壓이 低下한다. 延伸 film에 對해 强制振動法에 의해 求한 彈性率 빛 力學的 tan δ는 上記의 延伸比付近에서 各各 極小 및 極大를 나타내고, 上記의 電氣的特性과 密接한 關係가 있다. 더욱이 微結晶은 延伸에 의해 작은 緖晶으로 分解되는 것을 X線回折 認定할 수 있고, 또한 非晶領域의 分子鎖는, 高延伸에서 再配向하는 것을 赤外吸收에 의해 認定할 수 있다.

Deterioration induced by partial discharge was investigated for low-density polyethylene samples. Under an electrical field, a cold-drawn PE film was stretched perpendicularly to the direction of the original drawing, The starting voltage of the discharge shows a minimum at the draw ratio of 1.2 to 1.8. Around the same draw ratio, the elastic modulus and mechanical loss factor (tan δ) of the sample exhibit a minimum and a maximum, respectively. According to the X-ray analysis, the size of microcrystals decreases with increasing draw ratios. Reorientation of the molecular chains was observed above a draw ratio of 1.5 by the IR method.