Electrical tree growth in extruded s-polypropylene

This paper presents experimental results from examination of electrical treeing in extruded syndiotactic polypropylene (s-PP), using needle-plane electrode geometry. Two different types of electrical trees were observed, either with single or multiple branches to ground before breakdown. Two different cooling rates were used during manufacturing of samples. The effect of slow cooling was to increase the size of the spherulites. The results indicated that this had no effect on electrical tree propagation or time to breakdown. Neither the degree of crystallinity nor the elasticity modulus were affected by the cooling rate.