The probe to the influent factors of the electric breakdown

In a long period of the cauldron-type intermittent direct casting sheet process for producing PET films it often happens that the electric breakdown strength is too unstable to meet the technical requirements. In order to probe the factors that play a role here, the authors investigated the relations between the breakdown strength and the contents of DEG carboxyl in the PET body, and the melting point of PET. The natural characteristic of PET, the contents of DEG and carboxyl, and the melting point of PET are the main factors influencing the electric breakdown strength of the PET film. The electric breakdown strength will largely decline if the content of DEG in PET natural characteristic is high. A suitable additive can promote the enhancement of the electric breakdown strengths