Getting the measure of rubber

A new technique for testing the condition of rubber products could lead to cost and time savings for industry and improve safety.

A new technique for testing the condition of rubber products could lead to cost and time savings for industry and improve safety, by making it easier to check the likely performance life of parts in service.

Scientists from the Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO) and Monash University have developed a technique that can evaluate the condition of rubber products such as conveyor belts or vehicle tyres.

The technique uses nuclear magnetic resonance (NMR) techniques, which involves putting the sample into a magnetic field to measure the ‘health’ of the rubber.

It could lead to the development of a hand held scanning device used to check components while they are in service, eliminating the need to take samples

‘Rubber ageing results in a loss of flexibility, abrasion resistance and elasticity,’ said CSIRO’s Dr Anita Hill. ‘For many abrasive and erosive applications degradation is not a concern because the rubber will be worn away before any significant ageing effects occur.’

Rubber degradation is said to be difficult to predict because its rate depends on factors such as temperature, chemical environment, loading conditions and type of rubber.

‘Current inspection techniques for rubber condition rely on observing the subsequent effects of ageing, for example cracks or tears in the rubber — by the time these appear it can be too late to prevent failure,’ said Dr Hill.

‘Our new technique will give earlier warning if a rubber part such as a conveyor belt is degrading or losing elasticity, so that the part can be replaced well before failure occurs.’

The research has been applied to the failure analysis of rubber conveyor belts and processing tank liners, but is said to be equally applicable to other rubber products that are subjected to wear, such as vehicle tyres.

‘NMR techniques can be used to characterise the polymers in the rubber so that over time we can detect molecular symptoms of rubber ageing, such as changes in polymer chain length, crosslinking and the presence of degradation products,’ said Dr Maria Forsyth of Monash University.

‘From this we can get some idea of the likely performance life left in the rubber.’

Dr Hill said that the next step is to adapt this technique to simpler NMR equipment which is robust, portable and can show the results in a simple way.