Garments to which the odour of perspiration tends to cling stubbornly are a problem for wearers, manufacturers and the detergent and washing machine industry in equal measure. Scientists at the Hohenstein Institute in Bönnigheim have been investigating why these odour molecules prove to be particularly tenacious in association with certain textile materials, in some cases even after washing.
The team of experts led by Prof. Dirk Höfer has developed two test methods for measuring the number of perspiration molecules that are trapped in textiles. Thanks to this work, the tendency of textiles to absorb perspiration odour can be examined even at the design stage, and then influenced in the right direction. Prof. Höfer sees a need for improvement in this regard not only for sportswear and business clothing but, especially, for upholstery textiles used on public transport and in the automotive and aviation industries. However,thanks to these Hohenstein developments, the manufacturers of detergents and washing machines will also be able to ensure in future that their products reliably reduce perspiration odour during the washing process, especially in the case of innovative combinations of textile materials.
The main factor which means that preventing unpleasant perspiration odour in textiles and removing it, is no trivial task is its complex composition, for it is made up of all kinds of different chemical substances. Among these, specific carboxylic acids are responsible for the typical (unpleasant) odour of perspiration. In their investigation, the scientists at Hohenstein “inject” different textile materials with a defined quantity of carboxylic acid which has first been treated with a radioactive marker. To ensure that the results are fully comparable, the same textile construction (knitted, crocheted etc.) and mass per unit area (g/m2) are used — only the basic fibre type (cotton, polyester etc.) is different. After a soaking time (incubation) of 24 hours, the number of radioactively marked carboxylic acids is measured and compared.
In their second test scenario, the Hohenstein experts use a synthetic sweat solution(simulated perspiration odour) which contains several of the main ingredients of perspiration odour in defined proportions, and can therefore be reproduced at any time.The textile samples are dosed with a specified amount of the synthetic sweat and kept in the same climatic conditions. At the end of the incubation time, the intensity of the odour in the textiles is assessed by specially trained testers (“sniffers”) in what is called panellist testing.
This is the only institution in the world to combine instrumental analysis and panellist testing in this way. As a result of their interdisciplinary cooperation with researchers from different specialist fields, the experts at the Hohenstein Institute ensure that they not only track down the reasons why odour adheres to textiles but also, by working with the industry, are able to develop solutions for eliminating the problem.