Mastication of Elastomers I. Natural Rubber in Nitrogen

In accordance with theoretical expectation, the mastication of acetone extracted natural rubber in the absence of radical acceptors leads to gel formation. Unextracted rubbers undergo no gelation. The extent of gelation is determined almost entirely by the initial molecular weight of the rubber: under the conditions studied here rubbers of initial molecular weight less than ca. 3×105 do not gel on mastication. Only very small quantities of radical acceptors are required to repress gelation suggesting that acetone extracted rubber still contains appreciable quantities of such materials.