Valorization of not soluble byproducts deriving from green keratin extraction from poultry feathers as filler for biocomposites

The valorization of poultry feathers wastes is very important to reduce the environmental pollution deriving from their disposal. In this frame, we present the production process of completely natural, biodegradable, biocompatible, and eco-friendly composites made by not soluble keratin (NSK) and poly(lactic acid) (PLA). NSK has been obtained as a byproduct of a microwave-assisted keratin extraction from poultry feathers and it has been added to PLA pellets without adding any additional compatibilizers or plasticizers, unlike from the other works reported in the literature until now. The mixture has been used to obtain homogeneous NSK-based PLA filaments by means of hot-melt extrusion technology. The filaments have been subsequently 3D printed to explore applications in the additive manufacturing field. All the samples have unaltered thermal stability, but reduced toughness with respect to neat PLA. Other tested parameters (water adsorption, glass transition, and crystallinity) are dependent on NSK content and fabrication technology. Besides, Fourier Transform Infrared Spectroscopy highlights the differences in the structure of the NSK-based PLA filaments and 3D printed samples.