The electrical properties of some additive (allyl) polymers.

In the work described in this Thesis some attempt has been made to correlate the structures, mode of preparation and ageing of polymers with their electrical properties. The electrical properties investigated were the insulating as opposed to the dielectric properties. The electrical parameters monitored were conduction currents at temperatures from 20° - 100° C, breakdown voltages under steady fields and lastly internal discharges under alternating fields. The hardness of the polymers were determined using a modified dial indicator. The molecular structure and structural charges due to polymerisation were studied by infrared absorption spectra. Thermosetting polymers were prepared under controlled conditions. They were self polymerising diallyl esters or co-polymers with diethyl fumarate. The samples for electrical tests were prepared in specially designed jigs with the spherical electrodes preset at a known distance apart and polymerisation taking place round these electrodes. For the discharge measurements the E.R.A.discharge detector was modified from a purely visual display to one in which the discharge pulses could be extracted and analysed by use of a pulse height analyser. The results indicate that the current flow in the polymer is dependent on the conversion of monomer to polymer. The change in conductivity with both electric stress and temperature is clearly demonstrated and activation energies for electric conduction are calculated. The relation between breakdown strength and hardness is shown. Finally a mechanism of current flow is discussed