At this stage, up to a dozen chemicals are added, including accelerators (which help control the later vulcanisation process) and antioxidants (which prevent deterioration of the rubber molecules in the final product by heat, moisture and ozone). Accelerators (thiurams, mercaptobenzothiazole, carbamate, thioureas) are well known as Type IV allergens. Thiurams are well known as sensitising agents and many manufacturers now replace thiurams with dithiocarbamates as the accelerators of choice.
Pete Phillips <pete@smtl.co.uk>