Swollen Diameter Test for Natural Rubber Latex Compounds

Manufacturer: We are using "Swollen Diameter Test" for assessing the cure state of natural rubber film by recording the percentage swell of the film. Can you please help us to correlate this result with the degree of vulcanization? 

John Woon (Senior Latex Consultant): The variation in percentage swelling with crosslink density using toluene is as follows:

160% Swell   = unvulcanized
100 - 160%    = lightly vulcanized
80 - 100%      = moderately vulcanized
75%               = fully vulcanized

Latex compounds are best used while they are at "moderately vulcanized" stage. Do not use the latex compound once it has reached "fully vulcanized" stage otherwise you would encounter cracking or tearing of the rubber films.