Surface modification of keratin from agro-industrial products treated by green processes to generate sustainable materials

Natural fibers have attracted increasing interest for diverse purposes, driven by their environmental sustainability, favorable mechanical properties, and potential for the development of various innovative materials. Keratin fibers (feathers and angora rabbit) obtained from agroindustrial processes have recently gained significant attention in fields such as environmental treatments and materials science. This study introduces a eco-friendly methodology for treating fibers without using chemical reagents, providing a sustainable alternative. Fourier Transform Infrared Spectroscopy revealed that the integrity of the main keratin structure after treatments was maintained and only slight changes in secondary structure were found where the band related to hydrogen bonds rearrangement, the shifts related to amide I in barbs, rachis and angora fibers are found from 1629 cm⁻¹ to 1631 cm⁻¹ and 1642 to 1627, 1629 and 1641 respectively. Thermal behavior was observed through Differential Scanning Calorimetry and Thermogravimetric Analysis showed that despite treatments with heat and pressure, generating disruption of disulfide bonds, the thermal stability was unaltered, and even thermal stability is improved for instance from 276 °C (barbs), 322 °C (rachis) and 320 °C (angora) in untreated fibers to the ranges of 277–284 °C (barbs), 336–339 °C (rachis) and 323–330 °C (angora). The hydrophobic characteristic behavior of keratin fibers was studied, and results showed it remains favorable. Scanning Electron Microscopy showed subtle surface modifications and severe damage was not observed. XRD analysis show slight changes in crystal arrangement and corroborate FTIR results with the hydrogen bonds modification producing α-helix and β-sheet secondary structure transitions due to eco-friendly treatments. Thus, these chemical-free approaches not only offer a sustainable option for fiber treatment but also holds the potential to replace chemical treatments due to the achieved surface modifications. Moreover, it focuses on the imperative need to explore reutilization options for fibers derived from agro-industrial processes, contributing substantially to environmental conservation. This dual effect positions the methodology as a promising opportunity for sustainable material processing. Thus, the study provides alternatives to avoid chemical reagents in fiber treatments, producing rugosity and surface changes in fibers, these characteristics are useful in polymers reinforced with natural fibers but preserving their intrinsic physical properties.