Identifiying odourous constituents in acrylic adhesives

It is a known fact that adhesives may smell unpleasant. However, as researchers have recently discovered, this doesn’t need to be the case. Through extensive research on acrylic adhesives they were able to identify the substances responsible for the offensive odours.

The researchers rely on a variety of analysis methods -

Most products in our surroundings contain adhesives, including acrylic adhesives which are used in many industry sectors. Some of these adhesives contain solvents that produce strong odours, but even adhesives which are produced without solvents can emit intensive or pungent odours. In the latter case, the odour may arise from monomers in the adhesive product, from manufacturing by-products or from degradation products.

Analysing methods

In the study researchers from Fraunhofer Institute for Process Engineering and Packaging IVV analysed several acrylic, methacrylic and benzyl acrylic adhesives to identify representative odourous contaminants. The volatile fraction of the products was extracted and isolated by solvent-assisted flavour evaporation (SAFE), then analysed via high-resolution gas chromatography olfactometry (HRGC-O), HRGC-mass spectrometry (HRGC-MS/O) and two-dimensional HRGC-MS/O. Aroma extract dilution analysis was carried out to determine the most prominent odourants.

27 substances identified

Using this targeted odourant-analytical approach, the scientists identified 27 odourous substances representing diverse classes of molecules, including phenols with leather-like, horse stable-like or medicinal odours, acrylates eliciting glue-like, moldy and fruity impressions, and different esters with honey-like or effervescent tablet-like smells. These results show that the odour of acrylic adhesives results from a mixture of different odourants that cannot generally be traced back to the main constituents of the product but are rather likely to stem from impurities and trace side products and other contaminants.

The study is published in: International Journal of Adhesion and Adhesives, Volume 78, October 2017, Pages 182-188

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