Abstract
This paper describes an attempt to soften vulcanized rubber by chemical reactions with use of atmospheric oxygen and various chemicals. Experimental results showed that ferrous chloride-phenylhydrazine system was the most effective softening reagent examined. Individual use of the two chemicals was much less effective. The ferrous chloride-phenylhydrazine system considerably softened pulverized scrap tire mainly composed of natural rubber during several hours under the atmospheric pressure at the temperature up to 120°C The softened rubber easily twined on the roll and showed good properties for processing. The softened rubber was revulcanized by press at140°C with use of sulfur and vulcanization accelerator. Tensile strength and elongation at break of the revulcanized rubber were about 60 kg/cm2 and about 300%, respectively. The use ofappropriate modifier increased the tensile strength of revulcanized rubber to 100 kg/cm2, which is superior to that of the corresponding revulcanizates of commercially reclaimed rubber. The use of ferrous chloride was found to show no bad influence upon the thermal stability of the revulcanized rubber, since the rubber was more stable than the corresponding vulcanizates of commercially reclaimed rubber. This new chemically reclaiming process for vulcanized rubber was found to be applicable to waste tire of passenger cars mainly composed of SBR, reclamation of the latter rubber has been very difficult.
