This work is focused on the development of renewable and biodegradable films by the valorisation of wastes from food processing industries, with the aim of contributing to the development of more sustainable films. In this context, different contents of blueberry pomace (BP) were incorporated into cassava starch (CS) film forming solutions and the functional properties of the films prepared by solution casting were investigated, specifically, thermal, optical and physicochemical properties. BP-incorporated films showed good barrier properties against light, indicating their beneficial effect to prevent food deterioration caused by UV radiation when these films are used for food packaging applications. These results were related to the presence of aromatic compounds in BP, which can absorb light at wavelengths below 300nm. Furthermore, all films maintained their structural integrity after immersion in water (24h) and the maximum swelling displayed was lower than 300%. Additionally, the release of active compounds from BP into food simulants (after 10days) showed higher migration into the acetic acid medium in comparison with the ethanol medium. Therefore, the incorporation of BP into CS film forming solution resulted in the improvement of film performance, suggesting the potential application of these films as active packaging.
The study of the effect of the diisocyanate structure on the microstructure and macroscopic properties of polyurethanes was the main aim of this work. Biodegradable segmented thermoplastic elastomeric polyurethanes based on a poly(hexamethylene carbonate-cocaprolactone)diol (PHM-co-PCL) as soft segment were synthesized using 1,4-butanediol (BD) as chain extender and both 4,4 0 0 -diphenylmethane diisocyanate (MDI) and 1,6-hexamethylene diisocyanate (HDI) as components of the hard segment by the two shoot synthesis procedure. Microphase structure and properties were analyzed using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) as complementary techniques, used to characterize thermal transitions of the polyurethanes and to assign them to determinate functional groups interactions. Gaussian deconvolution technique was used to decompose carbonyl region in four peaks and to study the hydrogen bonding within the different polyurethanes. Both DSC and FTIR showed that MDI-based biodegradable polyurethanes were less phase segregated than to those based on HDI, and thus that diisocyanate structure has an important role on microdomain composition and polyurethanes properties. Macroscopic properties as hardness and water-polymer contact angles are related to polyurethanes microphase compositions.
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