Influence of the glycerol concentration on some physical properties of feather keratin films

The influence of glycerol concentration on some physical properties such as the thermal, mechanical, water solubility, hydrophilicity and water barrier properties of feather keratin films was studied. Feather keratin was extracted with an aqueous solution of urea, 2-mercaptoethanol and sodium dodecyl sulphate (SDS) at 50°C and pH 9.0. Film-forming solutions were prepared with 7 g keratin/100 ml, adding glycerol at level concentrations of 0.01, 0.03, 0.05, 0.07 and 0.09 g glycerol/g keratin. The films tensile strength decreased from 16.6±5.5 to 2.0±0.2 MPa and the elongation at break increased from 1.7±0.7% to 31.9±4.5%, while the water vapor permeability of keratin films increased from 5.19×10−8 to about 10−6 g m/m2 h Pa for samples without plasticizer and prepared with 0.09 g glycerol/g keratin, respectively. Films solubility was also increased from 0.307 to 0.507 g/g of initial dry matter when 0.09 g glycerol/g keratin was added. The use of the hydrophilicity concept was very useful to understand the phenomena controlling the water vapor barrier offered by the film, and can be useful as a procedure to investigate this phenomenon in other situations.