The state of filler dispersion in rubbers has been, in general, observed by means of a transmission electron microscopy (TEM). In the case of silicone rubber, however, TEM has seldom been applicable to such an observation, which may be attributable to the fact that the ultramicrotome method is difficult to apply for preparation of the specimens for reasons of its very low glass transition point.
In this paper, the specimens of silica-dispersed silicone rubber were prepared by the modified well-known freeze fracture, and a scanning electron microscopy (SEM) was successfully applied to observation of the despersion of silidca. The aggregates of silica with the diameter of over 10μm were observed clearly in shape. Further, it was found that the rubber areas with no silica filler existed around the aggregate in case of the surface-untreated silica dispersed, while such areas could not be noticed in case of the surface-treated silica dispersed.

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Continuous devulcanization by shear flow stage reaction control technology for vulcanized rubber has been developed. Screw geometry and alignment, screw rotation, reaction temperature, internal pressure, and addition of process oil and devulcanizing agent are the most important factors for this process. This process can be applied to sulfur vulcanized rubbers such as EPDM, NR, SBR and IIR. This paper described the results of the devulcanization of EPDM rubber. The obtained devulcanized rubber was found to be even mixture of two components; one is linear chain which is soluble in toluene and whose average molecular weight is nearly equal to that of the original raw rubber, and the other is very loosely crosslinking network whose effective network chain density is about one twentieth of that of the virgin vulcanized rubber. The devulcanized rubber can be revulcanized by conventional curing process with sulfur-accelerator vulcanizing system. The revulcanized rubber exhibited excellent mechanical properties and formability nearly equal to virgin vulcanized one.

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Continuous devulcanization by shear flow stage reaction control technology has been developed. In this technology, it is very effective to give high shear strain to vulcanized rubber under high internal pressure. Using adequate screw geometry and alignment based on this concept, devulcanization can proceed continuously. Properties of devulcanized rubber depend on reaction temperature, screw rotation and addition of devulcanizing agent and process oil. Under adequate reaction temperature and screw rotation, devulcanization can proceed without devulcanizing agent and process oil. Revulcanized rubber obtained by this condition shows excellent mechanical properties nearly equal to virgin ones. Furthermore, mechanical properties of revulcanized rubber can be controlled by addition of devulcanizing agent and process oil.

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