We tried to identify various species of rubbers by the method of gas chromatography with the accuracy of 0.1-0.01%.
The dry-distilled rubbers (raw, vulcanized and blended) were dissolved in suitable solvents as homogeneous solutions.
From the amount of main constituents analysed, we can easily identify the species of rubbers.

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Various heterocyclic compounds, namely, perhydro-4, 6-dimethyl-1-phenyl-2-thio-1, 3, 5-triazine, four urazole derivatives, 2-mercapto-5-phenyl-1, 3, 4-oxadiazole and three thiadiazole derivatives were prepared with an aim at the possible vulcanization accelerator. Mooney scorch test indicated that accelerating efficiency of perhydro-4, 6-dimethyl-1-phenyl-2-thio-1, 3, 5-triazine and bis (5-phenyl-1, 3, 4-thiadiazolyl- 2) disulfide is not inferior to that of the commercial accelerators. The other compounds prepared here did not show comparable effect to the commercial accelerators by judging from Mooney test, probably owing to their high melting points near or over 200°C and to their poor solubilities in rubber.

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On the basis of the previous paper, 5-phenyl-1, 3, 4-thiadiazole-2-sulfenyl group was coupled with a moiety of the commercial accelerators to obtain unsymmetrical mono- or disulfide or sulfenamide type accelerator. Thus, dimethylaminothiocarbamyl (thiadiazolyl) sulfide, 2-benzothiazolyl (thiadiazolyl) disulfide, N-cyclohexyl thiadiazol sulfenamide and N-oxydiethyleneaminomethylthiothiadiazole were prepared.
Thiolsulfonate type accelerators, namely, 2-benzothiazolyl 2′-benzothiazolethiolsulfonate and oxydiethyleneaminothiocarbamyl 2-benzothiazolethiolsulfonate were also prepared. Mooney test indicated that both the thiadiazole derivatives and the thiolsulfonates had comparable accelerating effect to the commercial accelerators.

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Non-Newtonian flow of concentrated cyclohexanone solutions of five polymethyl methacrylate of different molecular weights have been studied. The dependence of the apparent and zero-shear viscosities on rate of shear, molecular weight and concentration is very similar to that in polyvinyl chloride solutions (see previous paper).
The log-log plot of zero-shear viscosity against concentration for polymethyl methacrylate solutions is represented by two straight lines intersecting at one point (critical concentration Cc). The slopes of the lines are 5 above Cc and 3.2 below Cc, respectively. Furthermore, the critical concentration in volume fraction of polymer, V_2c, multiplied by the chain length Z is found to range from 70 to 180. The product Ccρ√Z is (ρ: density of solution) is approximately constant and independent of the chain length as ame-as in the previous study on polyvinyl chloride.
These results do not follow the Bueche′s Theory. Many experimental results are explained reasonably by using a Equivalent Gel Sphere Model.

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In order to study more clearly friction of rubber, real contact area of the flat specimens on a glass plate was obtained by optical manner.
This area measuring apparatus consists of a light source, a total reflecting prism and two photoelectric tubes and its attachments.
When the rubber touches really to the total reflecting plain of the total reflecting prism, the intensity of the reflecting light decreases in proportion to the increase of the contact area. Therefore it is possible to determine the real contact area by measuring the decrease of the light intensity.
The real contact area of conventionally molded samples increases by loading according to the following empirical equation.
S=S₀(1-exp(-kW))
But in case of unloading, it begins to decrease and in small load range follows next equation.
S=AWⁿ n<1
The above two empirical equations showed a histeresis curve.
As the result of measuring friction force and real contact area at the same time, just as the real contact area was decreased to 40-60 percent by adding lateral force, slipping appeared, and real contact area gradually decreased as the slipping velocity was increased.
The relation among contact area, load and friction force can be shown by the following semiempirical equation.
F=αS+μW
This equation consists of two therms, the latter term is the coulomb friction and the former is correction term due to remarkable real contactarea.
So α is considered to be the adhesive force due to a molecular force and μ is a material constant which is independent to the adhesive force of surface.
This equation can be applied to metal, because the real contact area is negligible small (αS_??_μW).
The above equation can be explained by the next integral equation on the whole real contact area S.
F=∫_sfds
f is a function of temperature, slip speed and loading pressure. Under the constant condition of temp. and speed, it is shown by the following empirical equation of contact pressure p.
f=α+μp

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