Spherical silicas of different specific surface area (1 to 700m²/g), of different perticle size (4 to 30μm) are prepared by sol-gel method.
Apparent densities, oil absorptions, the number of silanols, pore size distributions, and equilibrium water contents are investigated.
Bound rubbers in SBR are also studied. It is considered that bound rubber are formed in case of spherical silicas of over 400m²/g and of under 20μm. By SEM observation, theae spherical silicas disperse to submicron particles and are enterwined with SBR molecules. On the other hand, silicas of low specific surface area, low absorption of oils or large particle size are formed no or little bound rubbers.

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The reinforcing behavior of the spherical silicas (specific surface area 1-700m²/g, average particle size 4-30μm, which were prepared by means of a sol-gel method) are studied for the SBR compounds. As the result, besides the specific surface area of silica, one new parameter WAI (which is derived from its equilibrium water content at two different RH) is found as a key factor for the reinforcing behavior. For instance, it is assured that the lowering phenomena of hardness by silica of high specific surface area are estimated by WAI. On the destructive strength, oil absorption of silica is observed as a dominant parameter. The compression set value of the SBR vulcanizates by loading those fine spherical silica with the higher surface area are considerably improved than the other commercial reinforcing silica fillers.

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Relation between peel strength and addition weight of sulfur in the water aging of NR-brass adherends have been investigated about various factors. The addition weight of sulfur in NR recipes was dependant upon the water resistance of the adherends since it closely relates to the properties of adherent layer formed at the interface. Sulfenamide type accelerators which release amines during curing gave low water resistance to the adherends and thiazole type accelerators which does not release gave good water resistance. Stearic acid had bad effect on the water resistance of the adherends when is used in excess of ZnO. Cobalt salts force to shift the optimum addition weight of sulfur to high sulfur side. Unpolished brass gave the adherends with low water resistance more than polished brass. High zinc content and small crystalline in brass improved the water resistance of the adherends. From the SEM observation of peeled surface and surface analysis, it was found that the fracture of adherends after water aging peeling test was generated at brass layer. Above results, the new water aging mechanism of the adherends was proposed.

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In this paper, dynamic creeps were investigated using natural rubber NR, solution-polymerized SBR, carbon black filled SBR^* modified at the end of the solution-polymerized SBR polymer chains by funtional groups, and these blended rubbers of SBR/NR and SBR^*/NR. The amount of dynamic creep is explained by (a) a dynamic creep induced by broken physical bonds by interactions between polymer chains ε₁(t), (b) a creep induced by the transformation of filled particles structures into stable ones ε₂(t) and (c) a creep induced by phase separation of a blended structure ε₃(t).
The amount of physical bonds in the blended SBR^* system, that has functional groups at the end of SBR polymer chains, is small and the filled particles have stable oriented structures. And there is no phase separation of NR during the creep test and there is a very small amout of dynamic creep compared with the SBR blended systems.

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To develop a new field for the electrochemical application of vulcanizates, the electrochemical polymerizatoin of pyrrole on conductive vulcanizates containing Ketjen black and their electrochemical properties have been investigated. When EPDM vulcanizates containing Ketjen black more than 20phr are used as a working electrode, the polymerization of pyrrole occurred easily on them and conductive laminates consisting of vulcanizates and polypyrrole were obtained. For this, the conductivity of EPDM vulcanizates needs more than 0.1S/cm. On the electrochemical polymerization proposed, the selection of elastomers and solvents for electrochemical reaction were important, that is, the combination of EPDM and acetonitrile was best in the case of electrochemical polymerization of pyrrole. Increasing Percadox 14 decreased the conductivity of vulcanizates. Polypyrrole products on vulcanizates electrode had higher close adhesion to vulcanizates and higher density and conductivity than that on Pt electrode. The conductive laminates indicated electrochemical activites such as a doping-dedoping reaction and a charge-discharge reaction.

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