The base rubber, wether natural or synthetic, needs to be mixed with a number of different chemicals/ingredients to actually give a rubber compound that can be processed and made into a finished product.
A recipe for making a rubber compound includes, except for the rubber, approximately 10 -15 different chemicals. The different chemicals are divided into groups, depending on their function, and one of the most important chemicals is the vulcanization agents which crosslinks the rubber molecules into a three dimensional network, giving the rubber its unique properties.
Group | Chemical | Function in the rubber compound |
Filler | Carbon black | Stronger, harder |
Filler | Titanium oxide | Stronger, harder |
Filler | Clay | Harder, cheaper |
Softener | Oil, parrafin | Softer |
Pigments | Iron oxide, | Colour |
Antioxidants | Amines | Ageing resistance |
Antiozonants | Phenols | Ozon and ageing resistance |
Flame retardants | Aluminium hydroxide, | Burning resistance |
Vulcanizing agent | Sulphur, peroxides | Crosslinks the rubber molecules |
Vulcanizing activator | Starts vulcanizing | |
Vulcanizing accelerator | Speeds vulcanizing | |
Vulcanizing retarder | Slows vulcanizing |