The dielectric properties of polymers are very important to investigate the molecular structure of polymers
In this paper the dielectric absorptions of pure rubber vulcanizates were measured in the frequency range of 30cps to 1Mc at temperatures from -60°C to +20°C.
The temperature T_max of dielectric loss maximum ε"_max depends greatly on the segmental motion of rubber chains. The temperature T_max of vulcanizates increases as follows, BR, NR, SBR and IIR. This order corresponds with the low temperature properties of these polymers. T_max increases as the crosslink density of rubber increases but type of accelerators, that is, guanidine, thiazole and thiuram, sulfur content and vulcanization times give different effect on T_max and ε"max, even if the crosslink densities are equal.
The softeners commonly used as process oil, for example, pine tar, spindle oil and Komorex A give only a slight effect on the segmental motion of rubber chains but DIOA (diisooctyl adipate) lowers T_max greatly and improves much better the low temperature properties of vulcanizates.

View full abstract

On the curing of thick rubber specimens, the thermal diffusivities of rubber compounds are important.
In order to find a way to define these thermal diffusivities easily, we studied the additive property of the thermal diffusivities in SBR compounds.
It was showed that the thermal diffusivities of SBR compounds were able to be calculated approximately by means of applying the values of the thermal diffusivities of the compounding materials in them.
Then, by applying these thermal diffusivities we derived a formula which gave proper curetime of thick rubber slabs, and checked this formula on comparison with vulcanization-curves for the surface and the center of thick specimens which were actualy vulcanized.

View full abstract