Water treeing in polyethylene at low temperature region (-196 /spl deg/C /spl sim/ -10 /spl deg/C)

The properties of water treeing at low temperatures below 0 /spl deg/C are very important in clarification of the water tree initiation mechanisms. We investigated the properties of water treeing in polyethylene (PE) in the temperature region (-196 /spl deg/C /spl sim/ -10 /spl deg/C). We found that water tree is formed even at -65 /spl deg/C, and the initiation rate and the length of water tree increase with temperature above -65 /spl deg/C. Water tree is not formed below -100 /spl deg/C. We consider that at below -100 /spl deg/C PE is in the glass state and that the movement of water molecules and ions in PE is very restricted.