Some Observations with Ultra-Accelerators

Abstract

ALTHOUGH much has been done on accelerators, in such a vast field there is always room for additional work, particularly if, as Whitby predicts, ultra-accelerators will be the main class used in course of time. This investigation was started with the following points in view: (1) to prepare several thiuramdisulfides and related compounds; (2) to note their relative behavior when used as accelerators; and, if possible, deduce some explanation for the mode of action of the class or for the behavior of some particular compound, or gain additional evidence for any existing theories. The relative inactivity of thiurams derived from primary amines has been mentioned but no explanation published. Evidence is presented to show that decomposition of the compound into hydrogen sulfide and a mustard oil takes place so quickly at the temperatures used that there is not time for the generation of much active accelerator. It was found that tetramethylthiurammonosulfide plus sulfur equivalent to the difference in sulfur content between it and the disulfide gave a cure in a rubber-zinc oxide mix practically equivalent to that given by the disulfide alone. This indicates that zinc dimethyldithiocarbamate may be the active accelerating agent.