Smelly Adhesives? — Chromatography Can Help

There is no getting away from the impact that adhesives have on our lives. From the humble sticking plaster to car windscreens. Mobile phones to shoes. We are stuck with using adhesives. But anyone who has ever tried to fix their mum’s favourite ornament after a game of balloon tennis knows — sometimes adhesives smell.

Sometimes it is the carrier solvent that smells, but even when the adhesive is solvent free it can sometimes whiff a little. What causes those smells and should we be worried about them? Researchers at Fraunhofer in Germany have been finding out.

Smelly stuff at the Fraunhofer Institute

Surprisingly, it seems little research has so far been carried out into the origin of smells in adhesives and what effect they might have in the humans. So, the Department of Sensory Analytics at the Fraunhofer Institute for Process Engineering decided to investigate the topic.

The institute is Europe’s largest application-oriented research organization and carries out research in many varied fields including energy, health, security and environment. Employing over 24,000 staff, scientists and engineers in over 65 institutions — much of its work is as a contract partner with industrial partners.

Developing a nose

Scientists at the Institute undergo sensory training sessions to develop their ‘nose’ as odour experts — but technology is not forgotten as the institute also uses high resolution gas chromatography olfactometry (HRGC-O) and HRGC-O with mass spectrometry (HRGC-MS/O) to help analyse odours in all kinds of products. And it was the combination of HRGC-O and HRGC-MS/O that was used to help the team analyse the odours in acrylic adhesives.

The researchers analysed the volatile components of the adhesives — it is the volatiles that reach your nose and cause the odour — using an extraction technique before the chromatography took over. Chromatography is an ideal tool to use for analysing volatiles as discussed in the article, A New Method for Fast Residual Solvents Analysis and Untargeted Unknown Identification. Faster Sample Throughput and Shorter GC Runtimes Using GC-VUV and Static Headspace.

What’s that smell?

The researchers identified 27 odorous substances in the analysis reported in the International Journal of Analysis and Adhesives. They included phenols imparting leather-like odours, acrylates with mouldy/fruit like smells and esters with honey-like odours.

Since these substances can be considered hazardous, the team suggest that adhesive manufacturers should look to optimize the product development of adhesives to eliminate hazardous substances. In a press release from the Fraunhofer Institute — Professor Buttner who led the work — said:

Our analysis shows that a series of substances we found ought to be eliminated, and not just in terms of odour emissions. Strong odours can most definitely cause headaches and dizziness. We should be asking why adhesives smell.