Fig. 1. Hierarchical structure of hair and wool (not to scale).
Wool farming in Australia is a viable industry delivering textile fibre mostly from Marino sheep to the textile industry. Being the leading producer of wool with 25% of the global market share, the revenue generated from Australian wool is estimated at $2 billion.1 The quality of the wool is based on a number of factors with the diameter of the fibre being the most important, followed by crimp, colour, strength and yield. Wool with fibre diameter less than 25 microns can be used in garments while that with a diameter greater than 36 microns can be used in outerwear and rugs. However not all wool is suitable for use in the textile industry (including kemp which cannot be spun) and not all sheep farms harvest wool. Certainly the rising costs of shearing sheep have offset the income from selling the fleece and this is especially true in small farms.2 Developing applications for waste wool is important in reducing this bio-waste and offers exciting possibilities for developing benign processes and products for the future economies.
Keratin-rich material such as hair and wool consist of three main components: an outer layer, (i) composed of scale edges, which point in the direction of the fibre tip such that there is no resistance when rubbing a fibre from follicle to tip; (ii) the core, composed of a central medulla; and (iii) a surrounding cortex. Cortical cells can be removed by treatment with the proteolytic enzyme, trypsin,3 or the reagent o-chlorophenol. The nucleus of the cortical cells is surrounded by macrofibrils,4 and, in general, only the thicker cortical cells from hair have a medulla. The medulla cells can be separated by dissolving the cuticle layer in the presence of KOH.5 Macrofibrils within the cortical cells are made up of smaller components known as microfibrils which are approximately 6 nm thick in hair,4 Fig. 1.
Fig. 2. Green minimal waste processing
We have developed a novel technologythat uses a cheap and benign ionic liquid composite of choline chloride/urea6, 7, 8 in a 2:1 ratio, as a eutectic melt of the two components to disassemble the fibrous structure of such materials, without generating waste, with appraisal of the components for applications as natural sunscreens and hair products, obtaining mass quantities of high value amino acids and peptide supplements, drug delivery and novel gels, and forensic applications. It is worth mentioning that the residual material is an ideal chicken feedstock noting choline chloride and urea are supplements in the diet of animal in the poultry industry, Fig. 2.
If you want to find out more, watch this space! Publication coming out soon!
By Ramiz Boulos, Supervisor Colin Raston
1. T. Morris, Too soon to think of discarding shears yet, www.theustralian.com.au/business/wealth/too-soon-to-think-of-discarding-shears-yet/story-e6frgac6-1226000467049.
2. Hair sheep production and marketing, www.sheepandgoat.com/articles/hairsheepprodmktg.html.
3. V. G. Kulkarni and J. H. Bradbury, Aust. J. Biol. Sci., 1974, 27, 383-396.
4. B. Bhushan, Prog. Mater. Sci., 2008, 23, 585-710.
5. C. R. Robbins, Chemical and physical behavior of human hair, Springer, New York, 2002.
6. A. P. Abbott, G. Capper, D. L. Davies, R. K. Rasheed and V. Tambyrajah, Chem. Comm., 2003, 0, 70-71.
7. A. Biswas, R. L. Shogren, D. G. Stevenson, J. L. Willett and P. K. Bhowmik, Carbohydrate polym., 2006, 66, 546-550.
8. R. A. Boulos, E. Eroglu, X. Chen, A. Scaffidi, B. Edwards, J. Toster and C. L. Raston, Green Chem., 2013.