Space charge distributions formed in commercially available low-density polyethylene (LDPE), modified LDPE with carbonyl groups (LDPE/spl alpha/), and sandwiched LDPE between two LDPE/spl alpha/ layers (LDPE/spl alpha/-LDPE-LDPE/spl alpha/) were observed by means of the pulsed electroacoustic method. LDPE-/spl alpha/, in which no space charges were observed up to an applied electric field of 40 kV/mm, was used as the suppression layer in the sandwiched sample for blocking the charge injection. In this sample, hetero space charges were observed in the central LDPE layer. On the other hand, apparent homo space charges were observed in LDPE. The amounts of charges actually injected into LDPE were estimated by subtracting the amount of heterocharges formed in the sandwiched LDPE sample from the homocharges formed in the LDPE sample.
展开▼
