Relations between crystalline structure and dielectric properties of polyethylene

Slightly oxidized polyethylenes show dielectric loss factor–frequency curves exhibiting three maxima. The magnitude of the α‐maximum at low frequencies is proportional to the oxygen content and to the weight of crystalline material per cc. The frequency of this maximum is in general higher as the degree of branching of the polyethylene increases. The frequency of the α maximum of solutions of n ‐ketones in polyethylenes decreases with the length of the ketone and increases with the degree of branching of the polyethylene. A theory was developed which quantitatively describes the frequency of this α maximum as a function of the temperature, the chain length of the ketone, the average crystalline density of the polyethylene, and a quantity which is related to the twist energy per unit length of the chain. This theory can be experimentally used in to find a value for the length of the molecules participating in the α process in oxidized polyethylenes. The values found are about equal to the crystallite lengths, or the lamella thicknesses, of the polyethylenes.