Dielectric Loss in 66 Nylon (Polyhexamethylene Adipamide)

The dielectric loss in 66 nylon (polyhexamethylene adipamide) has been studied over a range of temperatures (—40 to 100°C) and frequencies (50 cps—70 Mc). The effects of radiation induced crosslinking and hydrogen bonding solutes were studied. The principal dipole orientation absorption is similar to that in amorphous polar polymers in that it involves long chain segment rearrangements in the amorphous regions. However no temperature range was found in which the distribution of relaxation times is independent of temperature, thus there is no time-temperature superposition. The effect of crosslinking allows a semiquantitative estimate of the segment length of about 15 amide groups to be made. The plasticizing effect of the solutes and their effect on the activation energy for dielectric absorption and the relaxation time distribution is discussed. The static dielectric constant associated with the long chain segment rearrangement mechanism is derived. From its temperature and solute dependence, the equilibrium disappearance of this mechanism at low temperatures is inferred. This disappearance seems to be associated with increased interchain coupling. The solute dependence also shows the presence of tightly bound solute molecules at the amide groups. A weak absorption occurring at lower temperatures (—10°C and 100 cps) is also observed. Comparison of the dielectric absorption with mechanical absorption is made.