An α or β crystalline phase will appear primarily during the improvement of polypropylene materials. To study the influences of crystalline phase on conduction current and space charge in isotactic polypropylene（iPP）

α and β nucleating agents are adopted separately to prepare iPP samples with different crystalline phases

denoted as iPP–pure

iPP–α

and iPP–β

for the study of conduction current

space charge

and DC breakdown characteristics at 25 ℃. The results show that iPP–β possesses the maximum breakdown strength under both positive and negative DC voltages

while iPP–α is the minimum. The magnitude of conduction current is: iPP–α > iPP–pure > iPP–β

and the transition voltage of space charge limited current is: iPP–α > iPP–β> iPP–pure. Both positive and negative space charges can be accumulated in three groups of iPP samples after 30 minutes polarization under-20 MV/m at 25 ℃. During the depolarization process

the amount of space charge accumulated in iPP–pure is the largest

while iPP–α is the smallest. Analyses reveal that the crystalline morphologies of α crystalline phase and β crystalline phase can result in the formation of shallow traps in iPP–α and deep traps in iPP–β

respectively

which will lead to a larger carrier mobility in iPP–α accompanying the Anger effect and capture space charge near the surface of iPP–β sample.