Since the initial mixing state in the internal mixer is very complicate, to obtain the reproducible data about BIT taken as a measure of mixing operation difficulty has been regarded as difficult. As mentioned previous paper, the operating method of mixing which can obtain the reproducible data was established, so we investigated the each factor which affects BIT by using former method. Various carbon blacks, oil-extended rubber and oil were taken as a material. Rotational velocity and rotational ratio of rotor, fill factor and ram pressure were taken as a mixing condition. We attempted to investigate the effect of these factors on BIT by the new mixing theory based on the static electricity phenomena and rubber viscoelasticity.

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Remarkable reductions in the physical properties of polyurethane elastomers (PUEs) prepared from polymer with 4, 4′-diphenylmethane diisocyanate (MDI) were observed when they were subjected to high temperatures (above 105°C) for long periods of time (400hrs). These results were caused by the fact that PUEs were deteriorated by a decomposition of their left in urethane linkages which resulted from their having been attacked by triethylenediamine (TEDA) residues in the PUE.
Deteriorations were observed in the center parts of PUE samples over 1cm thickness. Associated amine degradation products were later detected. Also, urea compounds occuring from the amine degradation in samples thicker than 1cm were determined directly from degraded PUE by FT-IR. By using diethylene glycol and butane diol as chain extender, a new PUE has been developed with reduced hardness. Additionally, the mechanisms causing amine residues to degrade PUEs were discussed.

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At the part 1 of this study, using a flat-belt tire testbed and investigated causal factors in the wear of tire tread under condition of small slip angle. To ensure the success of the experiment the accuracy of the testing devices were improved and the trial conditions were kept under close control. As a measure against sticky particles of worn rubber clinging to the surfaces of the Safety-walk and tires a uniform amount of mica powder was electrostatically coated onto the tire tread surfaces. Consequently, in a comparatively short time it was possible to ascertain measurable wear rates (abraded weight per unit travelling distance) as affected by a number of factors including: warm-up running, slip angle together with lateral force and lateral force coefficient, load, internal pressure, running speed and temperature. In this part 2, the mica powder coating device was improved further more, and measured the changes of frictional coefficient and linear wear rates (abraded weight per unit slip distance) and energetic wear rates (abraded weight per unit loss energy) according to slip velocity under condition of large slip angle.

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Gelation process of polyurethane networks was studied by measurement of extent of reaction, gel fraction, viscosity, and allophanate concentration, and mechanical properties. Gel permeation chromatograms of sol fraction were also measured. The polyurethanes were prepared from poly (etylene adipate) glycol, 2, 4-tolylene diisocyanate, and 1, 4-butane diol by a prepolymer method. In initial step of curing process, chain extention reaction with formation of hard segment occurred and small amounts of allophanate linkages were also formed but gel fraction was not observed. Extent of reaction at the gel point determined by viscosity was nearly equal to that determined by gel fraction. Rubber elasticity was developed after the extent of reaction passed on the gel point.

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Radiation effect of allergic response of proteins in NR latex has been studied to evaluate the properties of radiation vulcanized NR latex by means of passive cutaneous anaphylaxis (PCA) test of the water soluble latex components in mouse-rat system, quantitative analysis and measurements of molecular weight distribution of water soluble latex components, quantitative analysis of nitrogen content in the rubber film from the latex, and measurement of molecular weight distribution of proteins in water soluble latex components by SDS-PAGE. The irradiated NR latex exhibited milder allergenic response in PCA than that of sulfur vulcanized NR latex does. The response was independent on irradiation dose. Total amount of the water soluble latex components and the nitrogen content increased by irradiation of the latex. The extraction of the nitrogen containing materials in the film by leaching with 1% ammonia solution became easy by irradiation. High molecular weigh constituents of the water soluble components increased by irradiation. Contrasting, increase in low molecular weight constituents of the proteins was observed in the irradiated latex. These results suggested that the non-rubber latex components such as proteins and carbohydrates are decomposed by irradiation of the latex and eluted to water phase. Therefore it was concluded that the radiation denatured rubber proteins can be removed from latex products by leaching under modest conditions.

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