Originally, rubbers are independent macromolecular chains with poor characteristics and it is essential to incorporate numerous additives into them, currently 10 to 15, using a mixing process to promote crosslinking, reinforcement, protection.
Additives: their various roles
Rubbers must have a set of properties related to:
* Vulcanisation
* Ageing
* Flexibility at room and low temperature
* Reinforcement
* Processing
* Cost
* Some specific characteristics...
A large choice of additives (see figure 1) is proposed to modify fundamental properties of the basic elastomers such as polyisoprene (natural or synthetic), SBR, nitriles, silicones, fluorinated and others.
* Combinations of sulphur, one or more accelerators and one or more activators for rubbers with reactive double bonds. Sometimes, a retarder is used to delay the beginning of the cure.
* Combinations of organic peroxides and coagents for all rubbers
* Specific ingredients such as sulphur donors, amines for fluoroelastomers, metal oxides for polychloroprene, phenolic resins for butyl rubber...