New adhesive could aid recycling

A new adhesive, which detaches itself at high temperatures and can then re-bond at lower temperatures, could be used to aid recycling, as well as making component repair and upgrading easier and cheaper.

The new technology, developed by scientists at the US Department of Energy’s Sandia National Laboratories, is an epoxy adhesive which works by using reversible chemistry. The bonding ability of the new adhesive breaks down at 90 to 130°C (roughly 190 to 260°F), depending on the formulation, requiring minimal force to separate to attached objects. The adhesive can then be re-bonded at 20-60°C. Currently, there is no other adhesive available which has these characteristics, say scientists at Sandia.

“Our approach to a removable adhesive relies on the use of a reversible chemistry that breaks apart the adhesive at elevated temperatures, resulting in low adhesive molecular weight and low bond strength,” said research team leader Jim Aubert.

The unheated adhesive has a rubber-band like texture, and can be prepared in any size and thickness, and can be cut to match objects being attached. The adhesive has been successfully applied to a number of metals and also some foams and polymers. Aubert notes, however, that the adhesive only has the ability to bond and un-bond a limited number of times, and at some point will become nonremovable.

The new adhesive has a number of potential applications, including upgrading of components should new technology become available, and re-building if defects are discovered after deployment. Coatings can also be applied to circuit boards to provide protection from the environment, mainly moisture, debris and chemicals, say the researchers. Currently, traditional, almost indestructible epoxy adhesives mean that recycling of circuit boards is not possible (see related story).

“Normally, no thought is given to disassembly after bonding parts with an epoxy,” said Aubert. “Yet disassembly is becoming an increasingly important aspect of manufacturing as we become more concerned with the cradle-to-grave aspect of materials for environmental and economic reasons.”

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