Effects of molecular structure on electrical conduction in low-density polyethylene above its melting point

The electrical conduction of various kinds of low-density polyethylene (LDPE) has been studied above the melting point. LDPEs are characterized by the amount and types of branches, double bonds, and oxygen-containing groups. Two components of conduction currents were found: one obeyed Ohm´s law in the low field range and the other was proportional to the square of the field at lower temperatures in the high field range, and was also inversely proportional to sample thickness for a constant field. The conduction mechanism of the latter component is ascribed to space charge limited current (SCLC). Among the features of the LDPE molecular structure, only the oxygen-containing groups were well correlated with the SCLC. In fact, the oxygen-containing groups reduced the SCLC, suggesting that they act as traps even in the molten state. Branches and double bonds are also known to act as traps in the solid state, but they bore no consistent relation to the electrical conduction in the molten state