Wool keratin-polypropylene composites: properties and thermal degradation

Wool fibres were submitted to green hydrolysis with superheated water in a microwave reactor, in view of potential valorisation of keratin-based wastes. The keratin hydrolysates containing free amino acids, peptides and low molecular weight proteins, were exploited as a biofiller in preparing polypropylene matrix composites. Maleic anhydride grafted polypropylene was used as a compatibilizer to promote dispersion of keratin. The thermal and mechanical properties were investigated in dependence of keratin and compatibilizer loadings, and related to morphological characteristics. The presence of keratin preserved the molecular weight of the polymer matrix during the processing and gave good overall mechanical properties to the compatibilized composites. The keratin hydrolysates strongly interfered on the crystallization behaviour and thermo-oxidative degradation of the polypropylene. The increase of polypropylene crystallization rate and the enhancement of thermal stability were observed as a function of the keratin amount in the compatibilized composites.