Surface morphology of prevulcanized natural rubber latex films by atomic force microscopy: New insight into the prevulcanization mechanism

Prevulcanization of natural rubber latex was investigated as a function of maturation duration. The morphology of the film formed from these latexes w as monitored using atomic force microscopy (AFM) as the film aged. The morp hology is correlated with the cross-link density of the rubber molecules. F ilm formed from prevulcanized latex was further postvulcanized, and their f ilm morphologies were compared. Inhomogeneous latex particles cross-linked on the surface with an unvulcanized core were obtained during prevulcanizat ion. This gives rise to the characteristic indentation structure when these hard shell-soft core latex particles coalesce to form film. Basically the prevulcanization mechanism is controlled by the relative rates of the diffu sion of vulcanizing reagents and the cross-linking reaction within the late x particles. It is clear that the partially vulcanized particles have a pro found influence on the film-forming property of the prevulcanized latex.