1972 年 14 巻 2 号 p. 64-70
In the present part, the authors in order to capture the process of the condensation reaction of polysulfide brought about by various oxidizing agents, repeatedly measured the absorption of -SH, the terminal groups of polysulfide at regular intervals, using infrared rays absorption spectrum, and recorded the series of spectrum.
The process of the condensation reaction is almost in proportion to the decrease of the intensity of absorption of -SH. So the approximate value of the degree of reaction was determined and the degree of poly-codenesation was calculated. As the result it was made clear that when 4 % of PbO2 and the mixed oxidizing agent (MnO2 and PbO2) were severally used, the degrees of condensation in both cases were only 3-6 at 20°C and 35°C. But when 4 % KMnO4 was used, it reached 17 at 35°C after 40minutes, showing a remarkably strong condensation efficiency of KMnO4, as compared with the other two oxidizing agents. This result agrees well with that of the examination viewed from viscosity.
In conclusion, the molecular weight of the product rubber having KMnO4 as oxidizing agent, used for the purpose of examination on dynamic properties of polysulfide rubber in Part 9 [6] and Part 10 [7], is more than 70, 000 when calculated from the degree of poly-condensation, which can be presumed to be high enough to make molecules 'twisted'.
