To examine the pecuriarity of sulfur vulcanizates at autoxidation, their thermal and photochemical autoxidation were carried out. Polyisoprene vulcanizates containing monosulfide crosslink or polysufide crosslink and besides peroxide vulcanizates were autoxidized at 760mmHg oxygen pressure. The amount of oxygen absorbed and crosslink scission were determined.
The following results were obtained:
I) Initial oxidation rate was considerably fast in comparison with that of peroxide vulcanizate both at thermal and photooxidation. This is due to the activation of polymer chain by sulfur atom in sulfide crosslink.
II) In thermal oxidation, auto-inhibition was observed and confirmed to be the interaction of sulfide with rubber peroxides. But, in photooxidation, auto-inhibition was not detected since that interaction decreased owing to the photolysis of polymer peroxides. Scission of S-S bond in polysulfide crosslink was remarkable.

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The characteristics of SBR/EPDM and SBR/BR/EPDM blends as treads were studied.
Results as follows:
1. Wear resistance of the test tread using SBR/EPDM blend and SBR/BR/EPDM blend were found to be comparable to the corresponding controls, SBR and SBR/BR, even if antioxdants are not compounded.
2. Different behaviors in aging and dynamic fatigue were observed between the EPDM blend compounds and the controls.
3. The test tyres using SBR/EPDM tread showed equal skid resistance and cornering characteristics to the control tyres using the SBR tread, whereas SBR/BR/EPDM tread showed better skid resistance and cornering characteristics than the control tyres using SBR/BR tread.

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Uncured blends of high cis-polybutadiene rubber and styrene-butadiene-styrene block copolymer (styrene content: ca. 25%), prepared by mill blend, were studied.
And it was found that this blend system is a microheterogeneous one and crystallization of high cis- polybutadiene rubber is observed at low temperature. But, as compared with the case of polybutadiene rubbergeneral purpose polystyrene resin blend, a mutual interaction between high cis-polybutadiene rubber and styrene-butadiene-styrene block copolymer is strong and zone sizes of dispersed polymers are small.
Different from a microheterogeneous polybutadiene rubber-general purpose polystyrene resin blend system, the curves of blend ratio dependence of compression modulus at room temperature (in logarithm) were not “S” or “reversed S” shaped and were deviated much from a theoretical curve calculated from the mechanical model of a simple two phase blend system. According to a microscopic observation, in case of the blend with 50% styrene-butadiene-styrene block copolymer content changes of mixing state during remilling (roll surface temperature: 60°C) seem to exist, but the resultant softening phenomenon was not clearly observed. And further, it was deduced that the morphological characteristics of this blend system and the mutual interaction between blend polymers might be responsible for this phenomenon.

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Uncured blends of low cis-and high cis-polybutadiene rubber, prepared by mill blend, were studied, putting emphasis on dispersion state of polymers.
And it was clarified that informations on dispersion state cannot be obtained easily from curves of blend ratio dependence of hardness and compression modulus at room temperature because of likeness between the physical properties of two polymers. But, at -40°C at which high cis-polybutadiene rubber crystallizes, curves of blend ratio dependence of hardness and compression modulus (in logarithm) are “S” shaped as in the case of low cis-polybutadiene-general purpose polystyrene resin blend, and it indicates that this blend system is a microheterogeneous one. This consideration was further confirmed by crystallization of high cis-polybutadiene rubber in the blends at low temperature which was observed by dilatometry and differential scanning calorimetry measurement.

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The purpose of the present paper is to investigate the polymerization of styrene by Hard clay (Crown clay). The results obtained were as follows: Although Hard clay was treated with high temperature (700°C), its activities of polymerization were not missing, and the degree of polymerization of styrene was not affected whether the reaction was carried out an atmosphere of nitrogen or not. The reaction between Hard clay and styrene occurred in equivalent amount, the apparent activation energies of polymerization were 0.6kcal/mole. Furthermore, the average degree of polymerization of obtained polymer was about 60-80 at 0°C. These results suggest that the polymerization of styrene by Hard clay is initiated by the acid side of its surface and the progresses as a cationic mechanism.

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“Carbon black-graftcopolymers” can be prepared conveniently by the action of vinyl monomers on the surface of carbon black in suitable solvents containing an initiator such as 2, 2′-azobisisobutyronitrile.
In this paper, acrylic acid (AA) and butyl acrylate (BA) or methacrylic acid (MAA) and butyl methacrylate (BMA) are copolymerized in the presence of oil furnace black to prepare the products in which the molar ratio of BA/AA or BMA/MAA varies from 0.6 to 15 and the weight ratio of copolymers to carbon black is 1.
The products containing homopolymers and graftcopolymers are cured in one united body with a given amount of epoxide resin and then aged by a thermal pulse current to prepare “Grafted carbon resistors” with a lowered electric resistance.
The measurements are made on these resistors to compare the changes in electric resistance with temperature. The following results are noted: The variations of resistance are sharply influenced by the molar ratio of BA/AA or BMA/MAA. However, as the molar ratio is increased, a plot of the variations against the molar ratio gives an inclination having no relation to the ratio.

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