cis‐trans Isomerization in polyisoprenes. Part III. Reduction in the rate of crystallization of natural rubber at low temperatures by treatment with sulfur dioxide

The explanation given previously for the low rates of crystallization of natural rubber at moderately low temperatures after treatment by thiol acids leads to the prediction that treatment of rubber with sulfur dioxide above the ceiling temperature will give modified rubbers of low crystallization rates. This prediction is confirmed. Butadiene sulfone addition to rubber and heating to a convenient rate of its decomposition also gives rubber of low rate of crystallization. The cis‐trans mechanism of reaction is briefly discussed.