Zh. Fan et N. Yoshimura, THE INFLUENCE OF CRYSTALLINE MORPHOLOGY ON THE GROWTH OF WATER TREES IN PE, IEEE transactions on dielectrics and electrical insulation, 3(6), 1996, pp. 849-858
A small amount of phenolphthalein, acting as a nucleating agent, was a
dded to low density polyethylene (LDPE) to modify the size and number
of spherulites. The crystalline morphology was observed and analyzed w
ith the aid of a chemical etching method. It was found that the growth
of water trees is faster in LDPE samples in which spherulites are lar
ger and the number of the spherulites is lower. In contrast, water tre
es grow more slowly in other LDPE samples in which spherulites are sma
ller in size and greater in number. On the other hand, three different
kinds of additives, weak electrolyte and hydrophilic or hydrophobic s
ubstances, were added to the LDPE materials to investigate the influen
ce of typical spherulite boundary regions on the growth of water trees
. It was verified experimentally that during the process of crystalliz
ation, these three different additives are rejected and finally settle
d near the spherulite boundaries. Therefore, three kinds of boundary r
egions with different characteristics are formed. It has been conclude
d that hydrophillic boundary regions can strongly inhibit the gTowth o
f water trees, while the other two boundary regions (weak electrolyte,
hydrophobic) have little influence on the water tree growth.