Keratins extracted from Merino wool and Brown Alpaca fibres as potential fillers for PLLA-based biocomposites

Abstract

This paper reports on the promising per- spectives of using keratins extracted by sulphitolysis reaction from Merino wool (KM) and Brown Alpaca fibres (KA) in poly (L-lactide) (PLLA)-based biomateri- als. Both types of keratin were dispersed in chloroform (CHCl3) and tetrahydrofuran (THF), and optimisation of dispersion methods and parameters using the two selec- ted solvents was considered. The extraction yield, as well as supermolecular structures, morphology and ther- mal behaviour of the two proteins before and after the regeneration in CHCl3 was investigated. The results indicated that the supermolecular structures and thermal behaviour of the two proteins were affected by the interaction with CHCl3, producing decrease of the amount of a-helix structures in KM and an increase for KA, a slight decrease of b-sheet structures and a reduced thermal stability of a-crystallites for both keratins. Biocomposite films based on PLLA polymer matrix and two different contents of Merino wool and Brown Alpaca keratins (1 % and 5 % wt) were successfully developed by solvent casting in chloroform and the resulting morphologies after incorporation of different keratins (as a function of content and source) give evi- dence of different surface topographies, with a random distribution of keratin in flask-like structure. PLLA/5KA and PLLA/5KM samples with 1 % and 5 % wt of ker- atins show a specific pore-like surface microstructure, induced by solvent evaporation.