Wool keratin-polypropylene composites: properties and thermal degradation

Wool fibres were submitted to green hydrolysis with superheated water in a microwave reactor, in viewof 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 polypropylenematrix composites. Maleic anhydride grafted polypropylene was used as a compatibilizer to promotedispersion of keratin. The thermal and mechanical properties were investigated in dependence of keratinand compatibilizer loadings, and related to morphological characteristics. The presence of keratin preservedthe molecular weight of the polymer matrix during the processing and gave good overall mechanicalproperties to the compatibilized composites. The keratin hydrolysates strongly interfered on thecrystallization behaviour and thermo-oxidative degradation of the polypropylene. The increase ofpolypropylene crystallization rate and the enhancement of thermal stability were observed as a functionof the keratin amount in the compatibilized composites.