Effects of molecular structure on electrical conduction in molten polyethylene

The electrical conduction of various kinds of polyethylene (PE) has been studied above its melting point. PEs were characterized by the amount and types of branches, double bonds, and oxygen-containing groups. Two components of the conduction currents were found; one obeyed Ohm´s law in the low field range while 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 at a constant field. The conduction mechanism of the latter component is ascribed to space-charge-limited current (SCLC). Among the features of PE molecular structures, 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 known to act as traps in the solid state, but they bore no consistent relation to the electrical conduction in the molten state