Oxidative aging of elastomers is a very serious problem. During the aging process small amounts of oxygen are absorbed by natural or synthetic rubbers or by their vulcanizates. This causes a considerable change in their physico-mechanical properties. Consequently it is necessary to add antioxidants to rubber mixes to protect the rubber from oxidative degradation. The addition of antioxidants to any rubber mixes can prolong the service life of the rubber vulcanizates. However the efficiency of the antioxidants depends on different factors such as the type of rubber, the type of aging and the nature of the rubber ingredients in the mixes. The efficiencies of the antioxidants also greatly depend on their chemical structure. Antioxidants can generally stabilize rubbers against light and heat aging. Oxidation of polymers can lead to chain scission, crosslinking, or formation of oxygen containing functional groups in the polymer chains or their degradation products 1-3.
The majority of these compounds are derivatives of phenols, amines, organo sulfur and organo phosphorous compounds. In most rubber formulation systems, amines are more effective in preventing long-term oxidative degradation. However, amine antioxidants often discolor with ageing and may not be the system of choice for light and brightly colored rubber articles where color retention is important4,5.The molecular weights of these compounds are relatively low, often leading to surface bloom and volatilization from the compounds. One method to increase the persistence of the antioxidant in the polymer is to use high molecular weight compounds that cannot migrate to the rubber surface and are less readily lost by volatilization 6, 7. Comparative study on natural antioxidant as an aging retardant for natural rubber vulcanizates 8. Accelerated ageing of styrene-butadiene rubber nano composites stabilized by phenolic antioxidant 9. The synthesis of novel Schiff base antioxidants to promote anti-thermal aging properties of natural rubber 10. Effect of some polymeric phenolic antioxidants on the properties of SBR vulcanizates 11.
The present work aims to evaluate the efficiency of MPM that contained specific functional groups as antioxidants for rubbers (NR and SBR) to protect them from oxidative ageing through storage or use and to increase shelf life. As well as comparing their effect with the conventional antioxidants applied in the rubber industry, such as (2,2,4-trimethyl-1,2-dihydroquinoline) TMQ) .