Product Development Manager
Sulphur also makes a valuable contribution in our coloured materials. We use ultramarine powder to give a blue colour to some products. Although the original ultramarine pigment was powdered lapis lazuli, modern ultramarine is made by heating powdered sulphur, sodium sulphate and sodium carbonate in the presence of iron-free clay and a reducing agent such as coal or pitch. The beautiful blue colour arises because of the S8 groups caught in the aluminosilicate cage.
An area of adhesive technology exploiting sulphur’s chemistry is in crosslinking epoxies. Although the epoxy link will cross-link with amine, this reaction generally requires high temperature for initiation. A mercaptan group in the mix catalyses the reaction by reacting with the amine to form a mercaptide ion, which readily opens the epoxy link. The low activation energy for this process means the reaction can occur at room temperature, allowing epoxy technology to be used on heat-sensitive substrates.