Thermoanalytical characterisation of modified keratin fibres

Production and thermomechanical characterization of wool–geopolymer composites

“…Moreover, from DSC curves it is possible to further evaluate the behavior of wool–geopolymer composites upon temperature and identify possible interactions between fibers and matrix. In previous works it was found that unprocessed wool fibers mainly show three endothermic events in the range 70°C–350°C, all related to transformations in the keratin structure of the wool (glass transition, changes in the crystalline phases, and rupture of disulfide and peptide bonds). The onset temperature of each reaction and the amplitude of the peaks which identify these transformations in the raw wool and in the composites can thus provide information on how the wool is eventually affected by the highly alkaline environment of the matrix.…”

“…The first, up to about 150°C, is relative to evaporation of water from wool and loss of unbound water from the geopolymer matrix . The second and the third ones are instead related to the denaturation and degradation of the wool fiber fraction and occur at different temperature ranges in raw wool fibers and wool–geopolymer composite samples.…”

“…A second single heat‐absorbing peak appeared in the wool sample around 245°C, corresponding to the denaturation process of wool keratin through crystallite cleavage and unfolding of the α‐helix structure of keratin to the β‐sheet conformation. The area under this peak is usually referred to as a measure of the α‐helix material and is indicative of the structural modification caused by any chemical/thermal modifications operated on the fibers . Even considering the low relative contribution of the wool decomposition in the composite, it is worth to note that in wool–geopolymer composites this peak was not detected, except for a barely hinted hump in G23WF15, suggesting that the alkaline environment conditions of the matrix were enough to disrupt the disulfide bonds and to produce the almost complete transition from α to β form in keratin.…”

Mechanical and biological properties of oxidized horn keratin

“…Moreover, this temperature range is usually overlapped with the peak of water evaporation in a DSC curve [36]. The endothermic peak at 236°C is ascribed to the denaturation of the α-keratin crystallites and the area under the curve can be used to measure the α-helix content; and the endothermic peak at 312°C corresponds to the destruction of crosslinks, such as disulfide bonds, hydrogen bonds, and salt links [37,38]. However, the peaks of oxidized samples are different from those of horn keratin, suggesting that the microstructure of the oxidized samples changed during the process of oxidation.…”

Characterisation of keratin biomass from butchery and wool industry wastes

“…Infrared spectroscopy was extensively used in the molecular conformation study of keratin fibres [22][23][24]; in fact, the Amide I absorption, that originates principally from C@O stretching vibration, is sensitive to the secondary structure of the proteins. Before the acquisition of the spectra, samples were dried at 105°C for 2 h in order to eliminate the water absorption band (1600-1650 cm À1 ) that interferes with the Amide I [25].…”