oa Civil Engineer in South Africa - Compounding to polysulphide sealants for resistance to biodegradation : technical paper



In the early seventies the well established use of polysulphide sealants in water-retaining structures was brought into question by the biological deterioration of a sealant in the Dunkeld Reservoir in Johannesburg. As a result, comprehensive studies were undertaken in South Africa and the UK on the mechanism of the degradation and the factors that influenced it. An accelerated biodegradation test was devised and used to determine the best combination of compounding ingredients for polysulphide sealants that are to be immersed in water. As a result of this work it is now possible to give firm guidelines for the polymer content, curative type and other ingredients to ensure the longevity of polysulphide sealants in any water environment. These recommendations are being confirmed by field trials. Nine years ago a polysulphide sealant designed according to these guidelines was installed in the same Dunkeld Reservoir in Johannesburg. A recent inspection indicated that it is still in perfect condition.


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