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The native structure of the keratin macromolecules was partially modified upon extraction as revealed by the decrease of the \u03b2-sheet to \u03b1-helices\/coils ratio but high molecular weight fractions (31, 22 and 13 KDa) was retained permitting film formation and plastic behaviour of films. Keratin films were plasticised with glycerol and sodium dodecyl sulphonic acid (SDS), which provided different hydrophobic character to bioplastics. Water content in the films depend on the relative humidity (RH), being able to absorb up to 35\u2009wt% H<jats:sub>2<\/jats:sub>O at an ambient of 80% RH. Films were mechanically, thermally and optically analysed. The spectroscopic analyses revelled that these bioplastic films absorb UV light, what is interesting for packaging applications. Thermogravimetric and thermomechanical analysis revealed high stability of keratin macromolecules up to 200\u2009\u00b0C with no inherent thermal transitions. Tough bioplastics (19\u2009\u00b1\u20094 MJ\u2219 m<jats:sup>\u22123<\/jats:sup>) were obtained after thermal cross-linking with glycerol and formaldehyde outperforming mechanical properties previously reported for protein films.<\/jats:p>","DOI":"10.1038\/s41598-019-51393-5","type":"journal-article","created":{"date-parts":[[2019,10,15]],"date-time":"2019-10-15T11:22:28Z","timestamp":1571138548000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":78,"title":["Tough and Functional Cross-linked Bioplastics from Sheep Wool Keratin"],"prefix":"10.1038","volume":"9","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5209-5089","authenticated-orcid":false,"given":"Borja","family":"Fern\u00e1ndez-d\u2019Arlas","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2019,10,15]]},"reference":[{"key":"51393_CR1","unstructured":"Ashby, M.F. 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