With the progress of polymer chemistry in recent years, polypropylene and polyethylene of crystalline polymers have been used as the insulating materials, as a power cable and a power condenser owing to the high performance of electric insulation. But the spherulites are formed on the process of cooling these polymer materials after being melted. It has been said that there might be some relations between this spherulite and treeing degradation.
We made the specimens with different degrees of spherulites on the various colling conditions and we made tree occur by applying an alternating current high voltage to every specimens. In this paper, we examined about tree growth in a spherulite by means of an image processing technique.
The main results obtained are as follows:
(1) The shape of spherulite was clear after about 6.7 seconds when the nucleus occurred.
(2) It was possible to stop the growth of spherulite when the specimen was cooled in the water of 0°C immediately after it was melted in homoiothermal box and taken out.
(3) There were differences in tree shape and growth according to the positions of a needle point of electrode.
(4) Relations between the spherulite and tree became more distinct by using a pseudo color processing.
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