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Sunday, 22 September 2019
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Raw materials & technologies, Applications

Clear separation: New adhesive for better recycling

Wednesday, 17 October 2018

A thermolabile and reversible adhesive developed at the Karlsruhe Institute of Technology (KIT) makes it possible to clearly take high-tech products such as mobile phones apart into their raw materials.

Being able to dismantle electrical scrap back into its raw materials during recycling saves resources. Source: Amadeus Bramsiepe/KIT.

Being able to dismantle electrical scrap back into its raw materials during recycling saves resources. Source: Amadeus Bramsiepe/KIT.

With increasing recycling rates, the European Union is promoting a recycling economy that preserves products, materials and resources for as long as possible. The aim is not only to further reduce waste, but also to manufacture products that can be repaired, reused and recycled. At the same time, the service life of electrical appliances, for example, is decreasing. Today, a smartphone is phased out after one to two years. However, recycling it professionally and without residues remains a challenge.

In industrial joining, adhesive bonding is increasingly replacing welding, riveting or screwing. Adhesives reduce the total weight and fulfil additional functions such as insulation or damping. The disadvantage is that once they have cured, the connections can only be loosened again with a great deal of time or energy. If a bonded product is dismantled for repair or recycling, this often results in the damage or destruction of individual components.

Installation of predetermined breaking points in the network of long-chain polymer molecules

The new thermolabile adhesive developed by Professor Christopher Barner-Kowollik and his research team at KIT can solve this problem. It is stable at room temperature, but can be degraded precisely, quickly and at comparatively low temperatures. Once the process is finished, this is immediately apparent because the corresponding spot is colored. For this "debonding on demand" (DoD), the experts have built predetermined breaking points into the network of long-chain polymer molecules that make up a typical adhesive. At these points, even at moderate temperatures below 100 degrees Celsius, the chemical compounds open again and the adhesive dissolves. Its composition and the exact temperature required for the release can be adapted to the individual application.

Possible use in production and on construction sites

The clever adhesive, which the experts originally developed for dental technology and which is to be used there to gently remove bonded crowns or clasps, has now opened up to a wide range of applications. In addition to electronics, applications in production are conceivable, for example to temporarily fix materials on a workbench or on construction sites, for example to remove industrial dowels. The thermolabile adhesive is patented and will now be further developed in cooperation with partners from various industrial sectors.

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