To evaluate the groove cracking resistance of the tire tread compound in the laboratory, A. S. T. M. D-813 or its modified methods, in general, have been employed.
But it is said that the laboratory test results are poorly reproducible and rarely agree with practical experience.
In order to improve the correlation between the laboratory data and the actual road test results, we carried out the experiment, using the modified W. Kern method.
By applying this new method to the tread compounds including N. R, SBR, Polybutadiene, and Cis 1.4 Polyisoprene respectively, we obtained laboratory results better reproducible and agreeable with road service performance than by A. S. T. M. method.
Next, the research for testing the effect of ozone, ambient temperature and flexing speed on the groove cracking resistance of variable polymer was carried out, using three typical method, i. e. crack initiation, cut growth, and crack formation (W. Kern′s) methods. Increase of flexing speed from 300r.p.m to 600r.p.m led to slight decrease of the rate of crack growth and formation.
Finally, the experiment for testing the effect of typical antioxidants and antiozonants in the natural rubber tread compounds with three method was carried out.

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Some kinds of binders of non-wovens were graded, being based on the bonding power. The author represented the bonding power of binders with the standard strength-pick up gradient coefficient Ku and tried to check the properties of binders.
Though the same binders were used, the standard gradient coefficient Ku has remarkably changed with the fibers in non-woven fabrics.
Therefore, we can estimate the affinity of binders for the fibers. It became clear that acrylic polymers are more suitable binders for nylon, tetron, and cotton in non-wovens.
The author has also studied the variation of Ku depending upon the melamine content in binders.

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For the purpose of adaptability to softness of nonwoven fabrics, we inspected in detail the Peirce′s method, which has been fairly succeeded in the evaluation of textiles flexibility. From this results, we knew that the Peirce′s method was sufficiently applicable to non-woven fabrics, with only the modification of his parameter contained in the Peirce′s approximate equation. And then, with this modified equation, we measured the values of flexural rigidity for the samples which were prepared with several different binders. It was proved that the differences of thickness between products resulting from the sorts of binder, influenced remarkably upon the flexural rigidity.

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The combustion method used for the determination of carbon black contents in the black rubber, is based on distilling the test sample in a stream of carbon dioxide and removing rubber fraction. But actually it is impossible to calculate the amount of raw black in the test sample by the formula specified in ASTM, because of the existence of the residual ash, the residues formed by the carbonization of polymer, and the removal of volatile matters in the raw black. We have determined corrective factors for these items and proposed a formula to determine the amount of raw black. Furthermore, ASTM specifies the use of the standard sample to correct the aberration resulting from the interaction between the polymer and the black, but we have determined previously the corrective factor for this interaction by using the standard sample, and developed new procedure, by which the amount of black in the test sample can be calculated directly. On numerous test runs for the latex-black masterbatches on our pilot plant, it has been found that the difference between the calculated values from the material balance and the analytical results by our new procedure, is negligibly small.

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In studies on manufacturing of foam rubbers, it was found that gelling of SBR-latices is accelerated by adding water-soluble salts of amino acid such as gelatine, glue and sodium glutaminate to latices.
It was considered that gelling of SBR-latices is accelerated due to the creaming action to latex in the case of gelatine and glue, and due to zinc ions that is induced by the reaction with zinc oxide in the case of sodium glutaminate.
In this case, the quantity of induced zinc ions differs by pH and temperature of compounded latices, and also by the chemicals added.

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Now available are few data of rubber vulcanizates for mechanical and acoustic uses at audiofrequencies. In this paper mechanical and acoustic properties of various pure gum stocks are measured at frequency range from 100cps to 2, 000cps by means of longitudinal wave resonance method.
Dynamic moduli and propagation velocities in elastomers increase slightly with increasing frequencies, and mechanical loss factors and acoustic attenuations increase more rapidly. Elastomers, here tested, are classified in three groups as follows:
(Group 1); IIR, NBR and Hypalon whose properties show considerable dependency on frequencies.
(Group 2); NR, SBR, BR and Silicone are less dependent on frequencies.
(Group 3); CR, EPR and polyurethane are between (Group 1) and (Group 2).

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Some common amine antioxidants were estimated quantitatively by photoelectric colorimetry. The colors were formed for three naphtylamine class antioxidants by coupling with diazonium salt of sulfanilic acid, and for phenylenediamine class antioxidants by oxidation with benzoylperoxide.
Results obtained from acetone extracts of stocks containing known amounts of antioxidants coincided fairly well with calculated values except for the stocks containing aldol-α-naphtylamine. It was assumed that some parts of compounded aldol-α-naphtylamine were changed chemically during vulcanization and acetone extraction.
Possibliity of estimation of each component of mixed antioxidants of naphtylamine and diphenylamine were also investigated.

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