Easily recyclable printed circuit boards designed by Kazakhstani researchers

A group of researchers from Kazakhstan have used polylactic acid (PLA) to bind together easily recyclable printed circuit boards (PCBs), allowing valuable components to be separated and reused; a discovery which could improve the recycling of e-waste in the future.

Traditionally, toxic and non-renewable thermosetting resins are used as binders, which cannot be degraded environmentally. PLA polymers have similar properties to thermosetting resins, but are biodegradable and easily recyclable.

Fibreglass and PLA printed circuit boardProfessors Dmitry Khrustalev and Azamat Yedrissov also found that tetrahydrofuran is the most efficient solvent for separating PCB components. Tetrahydrofuran is not classified as ‘hazardous’ and carries no carcinogenic effect. It is also an easily distilled solvent.

For sample recycling, the PLA-PCB was placed in a container of solvent tetrahydrofuran and placed in an ultrasonic bath. This resulted in the complete separation of the binder, copper tracks and fibreglass filler from each other. No additional processes were needed and the separation was complete in 30 minutes.

The PLA solution is then able to evaporate into dryness through the use of high temperature and a water bath, which allows for 98 per cent of the chemical to be recovered.

Fibreglass and PLA printed circuit board life cycle
Life cycle of the newly designed printed circuit boards
One of the researchers said of the finding: “The use of biodegradable and easily recyclable polymers as binders for printed circuit board manufacturing opens new perspectives for both environmental protection and resource conservation and aims to maximise the recovery of valuable materials like gold and for reuse.”

He estimates that one tonne of used PCBs contains an average of 130 kg of copper, 1.38 kg of silver, 0.35 kg of gold and 0.21 kg of palladium. The presence of these metals can account for over 80 per cent of a product’s economic value. 

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