Electrical conductivity of polypropylene

Abstract

The steady‐state (d.c.) electrical conductivity of polypropylene has been measured as a function of temperature (25–150°C.) and field strength (0–94 kv./cm.). The temperature coefficient of the conductivity is 34.6 kcal./mole expressed as an activation energy. This is much larger than the activation energy for diffusion of small molecules in the same polymer. Thus, ionization rather than diffusion appears to be the primary activation process. The conductivity is nonohmic; the conductance quotient is a linear function of field strength but is larger than predicted by Onsager's theory. The ion “jump distance” as evaluated from the isothermal field dependence, is the same order of magnitude as the diffusional mean free path estimated from diffusion studies in other polymers. The conductivity, conduction activation energy, and field dependence appear to be relatively insensitive to polymer crystallinity.

Hopping conduction in “pure” polypropylene

“…using eqs. ( 3 ) and (51, of our HDPE theory, and the symbols are experimental points. Different hopping distances X were required at different temperatures to obtain good agreement between theory and experiment.…”

Electrical Conduction in Polymers

“…Figure 5 shows a typical glass cell used to study powders (Gray, 1969). The nature of the specific sample frequently dictates the type of sample holder to be used.…”

“…There are well-known methods for deciding which elements and structures will be useful for lowering ionization potentials and increasing the electron affinity of the donor and acceptor (Turner, 1966;Briegleb, 1964). There are well-known methods for deciding which elements and structures will be useful for lowering ionization potentials and increasing the electron affinity of the donor and acceptor (Turner, 1966;Briegleb, 1964).…”

“…Thus, for such materials, the existence of narrow bands similar to those of molecu lar crystals would be expected. Fox and Turner (1966) have calculated that a dipole of 1.65 D is capable of binding an electron (with the additional effect of dielectric relaxation around the trapped charge carrier). In general, even highly crys talline polymers do not show greater than 90% bulk crystallinity and even the crystalline regions are likely to be disordered.…”

Photoelectric Effects in Polyethylene‐iii Physical Models

“…(9) The theoretical tunnelling characteristic follows the Fowler-Nordheim relation rather well for a number of different barrier geometries,c4) so we may write where q is the electronic charge, V, the barrier voltage, I the current, A the area, m* the effective mass of the carrier, S* the tunnel length, 4 the barrier height and 7 the Fermi energy in the emission region. The value of V , was found from the relation VT= E+ V,,-Z(R+S) (7) and the value of the constant C1 which appears in V,, was adjusted to give the best fit to equation (6). It is seen in Fig.…”