Structural characterization and thermal behaviour of wool keratin hydrolizates-polypropylene composites

Innovative polypropylene composites were prepared using as a biofiller, wool keratin hydrolizates obtained by a green process with superheated water in a microwave reactor. To promote the affinity between the hydrophobic polymer and the biofiller, maleic anhydride grafted polypropylene was used as a compatibilizer. The composites showed a homogeneous dispersion of the keratin particles in the polymer matrix. The thermal properties and the structure of the composites were investigated in dependence of keratin loading and crystallization conditions. The keratin particles had a heterogeneous nucleating action on polypropylene crystallization that increased the overall crystallization rate. The nucleation density increased as a function of the keratin amount in the composites. The crystallinity, the crystal dimension and the long period of the polypropylene were found to be dependent on the crystallization condition and the composite composition. In the crystallized composites, the keratin component, having dimension in the nano- and micro-scale length, was relegated to the intraspherulitic and/or interspherulitic polypropylene regions.