The infrared spectra of rubber-filler system are important for the investigation of the effect of filler for rubber. Although the infrared spectra of rubbers and elastomers have been investigated by several authers, the literature contains no extensive collection of infrared spectra of fillers. In the present work the spectra of 33 practical fillers are given. These spectra are useful for the identification of fillers.

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The conventional techniques for the infrared analysis are not available for the cured rubber compounded with filler. In the present work, a microtome of freezing type is used for the preparation of thin section of cured rubber compounded with filler as the sample for infrared analysis. The microtome technique herein have been applied as a rubber analysis, and, at the same time, this makes it possible to identify the filler contained in rubber. Several examples of infrared spectra of those thin sections, such as natural rubber and SBR-filler systems, are shown.

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Time dependent mechanical data were obtained for different kinds of raw rubber, both synthetic and natural, by using a conventional Mooney Viscometer at a fixed temperature of 100°C. For the data obtained by rotating the rotor at a constant rate of rotation, it was found that the shearing stress in Mooney Unit, ML, could be expressed approximately by the equation;
ML=ML₀e^-t/τ+ML_∞,
irrespective of the species of rubber. Here ML₀, ML_∞, and τ are constants independent of time t. Stress-relaxation following a sudden cessation of the rotation of the rotor at any given rotation period appeared in all cases to be linear with a slope of -1/2 in the shorter time region on a log-log graph. For this region we have
ML^*=AL•t^*-1/2.
Here the asterisk specifies those obtained in the stress-relaxation experiment. AL is a constant independent of time t^*. It approaches a constant value, AL_∞, when the rotation period is long enough so that a stationary state is reached in the constant rate of rotation experiment.
The dependence of the value of AL on the previous rotation period of the rotor could be written in the form,
(ML-ML_∞)/(AL-AL_∞)/AL_∞=XL,
where XL is a proportionality constant which is independent both of t and t^*.

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The crosslinkage of butylacrylate-acrylonitrile (87/13) copolymer, cured with triethylentetramine-sulfur, was investigated and the following results was obtained.
1) From the swelling measurements of the vulcanizates, the interaction constant of the polymer-solvent (μ) were estimated for various solvents and the cohesive energy densities of the copolymer was given as 8.58 (cal/cc)1/2 from these μ values.
2) From the relation between the amount of crosslinks and of combined sulfur, it was found that the aminolysis of ester groups was main reaction in the crosslinking, because the ultimate number of crosslinks were more dependent on the amine concentration than the combined sulfur. It may be considered that sulfur evolves H₂S during cure and partly combines with NH groups in the crosslinkage of polyamine and the products accelerate aminolysis.

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Two samples of polychloroprene which were made by the emulsion polymerization at 10°C and 40°C respectively have been fractionated by the succesive precipitation method from the dilute solution of benzene using methanol as the precipitant.
The fractions examined both osmotically and viscometrically in toluene solutions at 30°C.
The relationship of Mark-Houwink equations were obtained as respectively.
10°C [η]=5.64×10^-4Mn^0.63
40°C [η]=9.73×10^-5Mn^0.77
It was found that the width of distribution function decreased with the increase of polymerization temperature. The parameter for the representation of average width of distribution function were discussed.

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Rubber-acrylonitrile graft polymer (nitrogen content of 1-20%) was prepared by polymerizing acrylonitrile in rubber solution, under different conditions of polymerization. Rubbers used here were masticated smoked sheet, gutta percha and hydrochlorinated rubber.
The physic chemical properties of graft polymers with different acrylonitrile contents were determined.

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Following the previous paper1), some new active calcium carbonates were studied for reinforcement of styrene-butadiene rubber. These active calcium carbonates were prepared by means of several ways whereby carbon dioxide gas was introduced to calcium hydroxide solution in the presence of chemical reagent as activator.
These reagents used for this purpose can be classified into two groups. That is (1) organic compounds having group such as amine, mercaptan or hydroxide besides carboxylacid, for example, sodium glutaminate, hystidine, lysine, arginine, phenylalanine, p-aminobenzoic acid, lactic acid, p-hydroxybenzoic acid, gallic acid, thioglycolic acid, thiosalicilic acid, sulfanic acid, serine, tyrosine and cysteine, and (2) sodium sulfide and/or polysulfide, and calcium sulfide and/or polysulfide.
After two or three parts by weight (based on hundred parts of calcium oxide) of these reagents were reacted with calcium hydroxide solution, active calcium carbonate were obtained by introducing of carbon dioxide.
SBR vulcanizates loaded with these active fillers indicated good physical properties. As the results, tensile strength at break of some of them were three or five times as high as that of vulcanizate loaded with conv- entional calcium carbonate.
It was shown that the excellent activators were sodium glutaminate, lysine, gallic acid, sodium sulfide and/or polyscelfide, and calcium sulfide and/or polysulfide.
By means of electromicroscorpe, diameters of active calcium carbonate particle activated with sodium glutaminate were found to be about 0.03μ and the dispersion of the above filler as well as that activated with sodium sulfide and/or polysulfide were both fairly good.
1) J. Furukawa, T. Kotani, S. Yamashita: J. Soc. Rubb. Ind. Japan, 34, (1961) 89

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