In contrast to the degradation of polyolefinic insulations stressed by "pure" electrical, inhomogeneous fields of sufficient intensity ("electrical treeing") the growth of "water-trees" (which require the presence of water in addition to the electrical load) has been found in some cases to be dependent on the morphology and the state of the resin. This state may be influenced by annealing.Water-treeing is accompanied by local accumulation of water requiring an enlargement of free volumes within the amorphous regions of the semicrystalline polymer.The results of our investigations may be interpreted by assuming annealing dependent variations of free volume size-distribution as well as annealing dependent resistance against deformations within the interior of the polymer which allow the growth of waterclusters.

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