The polymerization of ε-caprolactam in rubber was studied.
Usually ε-caprolactam was well known to be easy to polymerize in the presence of catalysts (water, acid, base, amine, etc.) at high temperatures about 200°C. The behaviors of various polymers in the temperature range of 180-240°C and the compatibility of these polymers with the melted ε-caprolactam at about 200°C were examined.
The possibility of grafting a polymer of ε-caprolactam on the carboxylic polybutadiene rubber was confirmed by chemical analysis.
Moreover, the effect of the addition of liquid carboxylated polybutadiene rubber on the polymerization of ε-caprolactam in the presence of sodium catalyst was studied.

View full abstract

The graft polymerization of ε-caprolactam on SBR was studied. It was found that ε-caprolactam could be grafted on SBR even in the absence of catalyst, but the reaction would be accelerated by adding the catalystic agents, and that triethanolamine and phosphoric acid were the most effective in catalytic action among the several agents tested in this work.
With an increase in the amount of catalyst and ε-caprolactam, the amount of ε-caprolactam grafted on the rubber increased. The grafted rubber had better physical properties.

View full abstract

Tensile stress relaxation behavior at large deformations were further investigated for seventeen samples of raw, oil-extended and filler-loaded rubbers. The temperature range and the strain range tested were 35135°C and 0.15.0, respectively.
All of the samples were found to be thermorheologically simple irrespective of the magnitude of strain. Thus
S(t)=S₀ (t/a_T),
where S(t) and S₀ (t) are the relaxation stress (true) at an arbitrarily chosen and a reference temperatures, respectively, and a_T, shift factor, appeared to be little affected by the change in strain.
Time dependences of relaxation stress, S (t), in all samples were found to be expressed in the form,
S(t)=f(γ)∫∞-∞He^-t/θd(lnθ)
where H represents the relaxation spectra which is a function of relaxation time, θ.
f(γ), the non-linear factor, is a function of strain, γ, and the following empirical equation was obtained.
f(γ) =aln[1+(γ/a)].
Here a is a factor independent of γ. The value of a appeared to be equal to unity for raw and oil-extended rubbers but smaller than unity in filler-loaded rubbers.

View full abstract

Polysulfide rubber has a special ability to set at room temperature; thereby lead peroxide is commonly used as its oxidizing agent. In this study, increases in its viscosity after the additions of various oxidizing agents are measured, in order to investigate the condensing abilities of the agents from the standpoint of molecular weights. Potassium permanganate is found to display a prominent curing ability.
Furthermore, infrared spectrum absorption measurement is made to observe the decrease of thiol terminals (SH) during reaction, and by means of calculating the approximate values of reaction degree and also poly-condensation degree, the following results are obtained :
1) In the case of employing either 4% mixture of lead peroxide and permanganate or 4% of lead peroxide only, the degree of condensation is 3 to 6.
2) In the case of employing 4% of potassium permanganate, the degree of condensation is about 17, 40 minutes after the beginning of the reaction at the temperature of 35°C.
Comparison between these two cases leads to the recognition that potassium permanganate displays a more prominent condensing ability, which coincides with the result obtained from the investigation on the viscosity.

View full abstract

Polysulfide rubbers produced by employing metal oxides as various oxidizing agents have been tested on rigidity-temperature curve under a free torsion pendulum method, stress relaxation, stress-strain curve and solubility.
Judging from the fact that the polysulfide rubbers thus produced have a wide range of “plateau” from 0° to 130°C as well as the elasticity of about 1× 10⁷ dyne/cm² and that their low molecular components are dissolved in the solubility test, the polysulfide rubbers are concluded to have very long molecular structures, with comparatively loose cross-link among molecules.

View full abstract

There has been no simpler method of canalizing vulcanized rubber, but we could canalize it by adopting the process of the attenuated total reflection of the infrared spectrum (ATR process). Two kinds of rubber were blended in various weight ratios and were vulcanized. From the chart of the attenuated total reflection of the infrared spectrum of these samples the strength of key band of rubbers was measured. We calculated the relation between the key band of rubber and the blended rubber weights. The results of the quantitative analysis were very satisfactory. The error in these measurements was about 2%.

View full abstract

Polymerization of styrene was carried out in cyclohexane solution of chlorinated butyl rubber with stannic chloride in a sealed tube, and the rate of polymerization of styrene was discussed. It was determined in terms of an increase in the weight of solid.
It was found that the rate was in proportion to the concentrations of styrene, chlorinated butyl rubber and stannic chloride, respectively.

View full abstract

Grafting copolymerization of styrene onto chlorinated butyl rubber was carried out with stannic chloride in cyclohexane and grafting percentage and grafting efficiency were discussed.
The reaction product, after drying, was extracted by boiling acetone to determine the weight of grafted polystyrene. Grafting was confirmed by fractional dissolution and IR spectra.
Grafting percentage increased with an increase in the concentrations of styrene and stannic chloride, but remained constant with chlorinated butyl rubber. It also increased with time and with an increase in halogen content in backbone polymer. The addition of a polar solvent such as nitrobenzene promoted grafting reaction very much, and grafting percentage amounted to 200%.

View full abstract