The presented investigations concern the distribution and characterization of keratin waste, derived from the processes of cattle skins, and its use as a filler for carboxylated acrylonitrile-butadiene rubber XNBR. The recovered keratin improves mechanical proprieties such as tensile strength, hardness, resistance to fuel and oil. The addition of keratin in a quantity of five parts per hundred rubber (XNBR) increases the crosslinking density of composites, as testified by the formed ion nodes and the existing mono and disulphide bonds. Electric conductance and water absorption increased with time for elastomers filled with protein. Therefore these composites are biodegradable after their period of use. As a result hydrophilic-hydrophobic protein-elastomeric composites will have usable properties.

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The effects of leather powders, chrome tanned leather powders and keratin were studied on properties of the synthetic isoprene rubber IR and the microbiological decomposition of the resulting proteinous-elastomeric composites. The proteins were obtained from the waste of the leather industry. The incorporation of proteins into the mixes of synthetic 1,4-cis-polyisoprene provides increased recaptivities to microbiological decomposition.

The purpose of this work was to prepare new biodegradable starch-cellulose composites, with starch, using casein and gelatin as natural nutrients. The physico-chemical properties of the starch films and cellulose fabrics with starch coatings were studied by Fourier transformation infrared analysis, laser confocal scanning microscopy (LCSM), scanning electron microscopy (SEM), UV-Vis spectroscopy, swelling tests, mechanical tests, thermal analysis thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The susceptibility of the starch films to biodegradation was investigated, together with their resistance to thermo-oxidative aging. As a result of the formation of the starch films, both the casein and gelatin macromolecules were able to interact directly with the starch matrix and the fractions of unbranched amylose and branched amylopectin it contained. This interaction was visible as changes in the absorption bands of the polar groups, as revealed by infrared analysis. Spectral analysis of the cellulose fabrics coated with starch films suggests that hydrogen bridges formed between the micelles of long cellulose filaments and the micro and macro-fibers of the starch pectins. An applicative test revealed that when used as a covering for bean cultivation the cellulose-starch composites act as a fertilizing component, contributing to significantly improved growth of Phaseolus vulgaris in comparison to the use of unmodified cellulose.

This article presents the test results of thermal properties and flammability of crosslinked nitrile rubber in the presence of zinc oxide or nano-zinc oxide containing waste keratin, using the test results obtained by means of a derivatograph, DSC, and oxygen index. The influence of modified montmorillonite (NanoBent) on selected properties of investigated elastomer-protein composites has also been studied. The composites' thermal stability and flammability depend on the method of composite preparation and the quantity of added keratin. The addition of waste keratin reduces the flammability of NBR-keratin composites.