Biodegradation of natural rubber vulcanisates

Abstract

Rubber has been used to form flexible seals between pipe sections in water mains and sewers for over 100 years. During the past 30 years, instances have been found of rings showing deep pitting due to microbiological attack. The need was to devise compositions resistant to attack which were easy to manufacture and complied with standard physical requirements. By careful choice of ingredients, natural rubber vulcanisates can be prepared which have negligible weight losses under accelerated test conditions and should have a long working life. The avoidance of extractable or degradable ingredients with a generous quantity of an insoluble antioxidant and a chlorinated wax are seen to be effective. Chain scission seems to be an essential prerequisite for microbiological degradation. The capture of transition metal oxidation catalysts from the water over a long period may be a factor in the attack mechanism.