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Bronze-filled DuPont

Du Pont Engineering Polymers : 20 October, 2004  (Company News)
In a prize-winning innovation, Chemplast Marc Etter (Pty) Ltd., of Elandsfontein, South Africa, has developed diamond
Used in the monitoring and control of the separation process whereby valuable diamonds are recovered from mining gravel, the ‘dummies’ simulate the properties of real diamonds during so-called grease diamond recovery. To date, no satisfactory method existed for monitoring this process, leading to incomplete recovery and the loss of valuable diamonds.

This development, which depends on the hydrophobic (non-wettable) and oleophilic (oil attracting) properties of Teflon® PTFE, won first prize for Chemplast Marc Etter (Pty) Ltd. in the Europe/Middle East/Africa section of the global DuPont Plunkett Awards 2004 competition for innovation with DuPont™ Teflon® and Tefzel® fluoropolymer resins. This was the ninth competition in the series established in 1988 to mark the 50th anniversary of the discovery of Teflon® PTFE fluoropolymer resin by DuPont scientist Dr. Roy J. Plunkett.

Diamond crystals, the hardest of all natural substances, are retrieved from mining gravel through various methods including grease recovery, a system that relies on the unique non-wettability (hydrophobicity) property of a newly exposed diamond surface. Diamonds are also ‘oleophilic’ i.e. attracted to oil or grease. Thus, when the gravel is washed over an inclined grease belt with water, the ‘wet’ ore does not stick to grease, while the ‘dry’ diamond does. However, variances in diamond, grease and water quality can result in diamonds being lost if settings are not accurately controlled.

Teflon® PTFE was chosen as a base material in Chemplast Marc Etter’s new process because its hydrophobic and oleophilic properties closely resemble those of diamonds. Bronze filler is added to increase the density to 3.50 g/cm3, matching that of diamond. Since some diamonds carry surface contaminants and do not behave totally hydrophobically, Chemplast has etched the surface of the bronze-filled Teflon® PTFE 'dummies to increase the hydrophobicity of the PTFE.

The result, according to the company, is significantly better monitoring of grease diamond recovery, and a reduced risk of diamond loss during the process.

For further information visit the DuPont company website at, and the Chemplast Marc Etter website at

Chemplast Marc Etter is a specialist fluorocarbon processor, chemical equipment supplier, and projects group, operating worldwide. The company is a majority owned subsidiary of Poly Hi Solidur Incorporated of the Menasha Corporation USA. Chemplast Equipment (Pty) Ltd was registered in 1972 and in 1984 was merged with Marc Etter (Pty) Ltd.
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