Raj Pal Singh

Ozonolysis of natural rubber: A critical review

Studies of the action of ozone on diene rubbers were of fundamental importance in understanding of the structure of natural rubber. Ozonisation is still a key tool for the clarification of molecular structure and monomer sequences in the polymer and is widely used to characterise the structures of various rubbers to make telechelic oligomers. Nowadays it is routine to check the action of ozone on a rubber, because of the presence of ozone in the atmosphere as a pollutant. Priestly and Cavendish(1,2) (1875) noted that electrical sparks fired in a closed volume of air resulted in volume compression. In 1840, Schonbein repeated these experiments and concluded that the specific odour was due to a gas which he named ozone, from the Greek ozein(3). Numerous researchers since, have worked to clarify the nature and actions of ozone. Mariniak and Delarive(4) showed that it is an allotropic form of oxygen and Mulliken and Dewar clarified its molecular architecture. In the latter of the 19th century, ozone was found to oxidise a spectrum of organic compounds and to interact with double bonds. Chemists made use of these properties to study complex molecules by cleaving them into smaller fragments. Harries, by such methods, discovered the structure of natural rubber(4). The problems of ozone attack and antiozonant protection continue to be the subject of great importance. The ozone attack on the rubber causes chain scission and the formation of various decomposition products such as ozonides, polymeric peroxides, hydroperoxides, lactones, esters and aldehydes etc..