Understanding the physical and chemical properties of keratin films

Abstract

Hair is seen as a waste material to be discarded after a haircut. However this waste material can be reused as a biomaterial for greater applications such as wound dressing applications or skin reconstruction. Hair is made up predominantly of keratin, which is a biopolymer that is biocompatible and biodegradable. It is also found as keratinocytes on skin forming a protective layer to inhibit passage of environmental contaminants or pathogens. Hence, keratin is a promising biopolymer to be explored.

Keratin is extracted as solution from a homogenous mix of hair using reducing agent sodium sulphide in an oven at 40oC, for 4 hours. As native keratin films that are cast are brittle, plasticizers are needed to improve the films’ flexibility and elasticity. In this project, glycerol is chosen as a plasticizer to be added to keratin solution and casted into films at 60oC for 21 hours.

Glycerol is added to keratin solution at four different concentrations and cast into films. These films were characterized by Scanning Electron Microscopy (SEM), Fourier Transform InfraRed Spectroscopy (FTIR), Thermogravimetric analysis (TGA), Mechanical Testing using Instron 5567, Ultraviolet-Visible light (UV-Vis) Spectroscopy and Elcometer 456. These characterization tests are carried out to understand the physical and chemical properties of keratin films.

From the SEM images, the morphology of the film with least glycerol seems the smoothest while the one with the most glycerol shows folding and creasing. Secondly, FTIR showed the presence of glycerol and native keratin in all the films and TGA proved that the films are thermally stable up to a high temperature of approximately 170oC. Mechanical testing showed that the film with least glycerol has the highest strength but lowest elongation and UV-Vis Spectroscopy revealed that all the films absorb in the UV region due to melanin found in hair. Lastly, Elcometer measures the thickness of the films showing a trend of decreasing thickness from the film with highest glycerol content to the one with lowest glycerol content. Upon understanding the physical and chemical properties of keratin films, no one film can be said to give the best set of properties as different applications will require different sets of properties of the films. Based on the requirements of these applications, the ideal film can be chosen and used.