Summary of using ftir with respect to water activity
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| Jenifer Brown Summary of using FTIR with respect to water activity Article: -“Application of FTIR spectroscopy to determine transport properties and water–polymer interactions in polypropylene (PP)/poly(ethylene-co-vinyl alcohol) (EVOH) blend films: Effect of poly(ethylene-co-vinyl alcohol) content and water activity” -Aurora Lasagabáster, Maria Jose Abad, Luis Barral, Ana Ares, and Rebeca Bouza -Departamento de Química Orgánica I, Escuela de Optica, Universidad Complutense de Madrid (UCM), Arcos de Jalón s/n, 28037 Madrid, Spain -Grupo de Polímeros, Departamento de Física, E.U.P. Ferrol, Universidad de A Coruña, Avda. 19 febrero s/n, 15405 Ferrol, Spain Link to article In this experiment, researchers measured water sorption and diffusion through polypropylene (PP)/ethylene alcohol vinyl (EVOH) blends with increasing EVOH content using FTIR spectroscopy. Blends of EVOH and PP are used in food packaging, so knowledge of the water activities is important to ensure freshness. The researchers used beakers of salt slushes with varying water activities (0.26 - 0.98) and placed PP/EVOH films containing varying amounts of EVOH over them. After allowing the films to sit for a period of time, FTIR spectroscopy was performed; “The amount of sorbed moisture was detected as the difference between the hydrated spectrum and the spectrum of anhydrous specimen.” After the analysis of the data, researchers found that at low water activities the different blends of PP/EVOH have little difference in their water uptake. At high water activities water uptake increases in a linear fashion with EVOH content. In the FTIR analysis, researchers also found that there were water molecules that bonded to the EVOH polymer with differing hydrogen bond strengths depending on hydration time and water activity. “Regardless of the EVOH content, the molecules more strongly associated by hydrogen bonding are dominant at low sorption levels, whereas those less hydrogen bonded prevail at high sorption levels.” |
