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Magnets take heat out of sticky problem

MATERIALS Cutting Edge

WAITING for adhesives to harden has to be one of the more tedious tasks on a building site, beaten into second place only by watching paint dry.

And with today's modern super-stick adhesives it is virtually impossible to de-bond materials once they have been set down.

But now scientists at the Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research in Bremen, Germany, have developed a glue that can harden and be debonded at the f lick of a switch. The research team joined forces with chemical company Degussa to study the use of magnetic particles to help glue harden.

Normally adhesives are hardened by heat but this can prove a challenge to heat sensitive plastics that are unable to withstand high temperatures, so two-part adhesives which harden without heat over a long period of time are often used.

According to Dr Andreas Hartwig at the institute, adhesives containing the magnetic particles harden quickly without developing high temperatures.

He said: 'The adhesives contain the MagSilica filler, which can be stimulated with high frequencies. In the high frequency field the adhesive hardens immediately without any exposure to external heat sources.'

The particles of iron oxide, embedded in silicon dioxide granules, also enable the bond to be dissolved when it is exposed to an ultra-high frequency magnetic field, ensuring that materials can be easily reused.