Osmanthus fragrance polyurethane/silk fibroin-based double-shell microcapsules for aromatic leather with sustained release fragrance

The leather with the long-lasting fragrance is critical for functional leather commodities but limited by poor temperature durability, low loading capacity and inferior flexural resistance. Herein, we develop a novel double-shell fragrance release system via both interfacial polymerization and freeze inducement. Osmanthus fragrance (OF) was encapsulated with polyurethane (PU) and silk fibroin (SF), the double-shell microcapsules with remarkable stability and enhanced sustained release property can be prepared. The OF@PU/SF microcapsules had well-defined spherical shape with an average diameter of 5.21 μm measured by Scanning Electron Microscopy (SEM), which was larger than the single-shell microcapsules (OF@SF) with the size of 1.70 μm. The thermogravimetric analysis (TGA) indicated that the OF loading capacity (LC) of OF@PU/SF microcapsules was 51.7%. Furthermore, the sustained release measurements by UV–vis absorption spectra clarified that 22.9% OF released from OF@PU/SF microcapsules during 30 days, lower than 36.7% of OF@SF microcapsules, much less than nearly 100% of free OF. Finally, the OF@PU/SF microcapsules were applied in leather finishing to efficiently improve the odour of the leather. The aromatic leather possessed sustained aroma with great stability enabling high temperature durability and flexural resistance property.