antiozonants

[ABM Nazmul Islam]

When diene rubbers are exposed to ozone under stressed conditions, cracks develop which are perpendicular to the direction of stress. The mechanisms of ozone attack and its inhibitions are not well understood.It is believed that an antiozonant reacts with either the zwitterion (A) or the ozonide (B) to form an inert protective film. Every time this film is broken, is repaired by the formation of fresh film produced from the three reactants (rubber, ozone and antiozonant) in situ.Para phenylenediamines (PPDs) are the only class of antiozonants used in significant quantities in combating the ozone – initiated degradation.