The chemical reclamation of crushed waste tires was carried out in swelling solvents containing small amounts of the crosslink-scission reagents such as thiol and amine compounds.
It was found that the tensile properties of reclaimed rubber vulcanizates obtained by this process were inferior to those obtained by the mechano-chemical one. From various reclaiming model experiments, these results may be interpreted as a phase separation between carbon gel and sol fraction with a branched structure which came from the scission of crosslinking under the swelling conditions.

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Improvement of comminuted vulcanizates from mechanically ground used passenger car tires has been achieved by the addition of sulfur, accelerator, and milling of the powder by an open roll. The rubber powder was mixed with rubber and then vulcanized. The vulcanization rate and the crosslink density of the rubber matrix for the composite has been studied.
The addition of sulfur and accelerator to the rubber powder increased the vulcanization rate of the rubber matrix in the composite. On the other hand, milling of the rubber powder by an open roll increased the crosslink density of the rubber matrix and decreased the size of the rubber powder in the composite. The physical properties of the composite is shown to be improved considerably by the above treatment.
The tensile strength of the composite is improved by the increased vulcanization rate and crosslink density of the matrix rubber. However, the tearing energy of the composite is contrary to the above behavior. The main reason is estimated to be due to the crosslink density of the matrix rubber.

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Inhomogeneous crosslink density distribution is formed in vulcanizate containing comminuted vulcanizates due to dissolution, diffusion, and reaction of vulcanizing agents. In this report, diffusion and reaction of vulcanizing agents in comminuted vulcanizates with various types of crosslink has been investigated during vulcanization of the composite. The vulcanization reaction have been found to be influenced by the type of crosslinks in comminuted vulcanizates.
The discontinuity of crosslink density between comminuted vulcanizates and rubber matrix, and the change of crosslink density in the comminuted vulcanieates during vulcanization of the composite have been small for the rubber powder with less polysulfidic crosslinks. The strength of the composite and the improvement of rubber powder by mechanical treatment are also influenced by the type of crosslinks in the rubber powder.

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