Flexible Biocomposites with Enhanced Interfacial Compatibility Based on Keratin Fibers and Sulfur-Containing Poly(urea-urethane)s

Abstract

Feathers are made of keratin, a fibrous protein with high content of disulfide-crosslinks and hydrogen-bonds. Feathers have been mainly used as reinforcing fiber in the preparation of biocomposites with a wide variety of polymers, also poly(urea-urethane)s. Surface compatibility between the keratin fiber and the matrix is crucial for having homogenous, high quality composites with superior mechanical properties. Poly(urea-urethane) type polymers are convenient for this purpose due to the presence of polar functionalities capable of forming hydrogen-bonds with keratin. Here, we demonstrate that the interfacial compatibility can be further enhanced by incorporating sulfur moieties in the polymer backbone that lead to new fiber-matrix interactions. We comparatively studied two analogous thermoplastic poly(urea-urethane) elastomers prepared starting from the same isocyanate-functionalized polyurethane prepolymer and two aromatic diamine chain extenders, bis(4-aminophenyl) disulfide (TPUU-SS) and the sulfur-free counterpart bis(4-aminophenyl) methane (TPUU). Then, biocomposites with high feather loadings (40, 50, 60 and 75 wt %) were prepared in a torque rheometer and hot-compressed into flexible sheets. Mechanical characterization showed that TPUU-SS based materials underwent higher improvement in mechanical properties than biocomposites made of the reference TPUU (up to 7.5-fold higher tensile strength compared to neat polymer versus 2.3-fold). Field Emission Scanning Electron Microscope (FESEM) images also provided evidence that fibers were completely embedded in the TPUU-SS matrix. Additionally, density, thermal stability, and water absorption of the biocomposites were thoroughly characterized.

Bio-Based Composites from Industrial By-products and Wastes as Raw Materials

“…According to the literature (Belarmino et al, 2012;Ana Laura Martínez-Hernández & Carlos Velasco-Santos, 2012;Reddy & Yang, 2007;Staron et al, 2011), the high water gain of the composites with feathers compared with that of resins is mainly attributed to the high hygroscopic character of keratin from feathers. The results obtained are in agreement with the results already published (Aranberri et al, 2018(Aranberri et al, , 2017Colom, Rahalli, Cañavate, & Carrillo, 2015;Hong & Wool, 2005), in which the addition of CFP's increases significantly the water absorption in a composite irrespective of the nature of the polymeric matrix.…”

“…elongation at break from 570% for PBAT resin decreased to 2.5% for PBAT 50% /CF 50% bio-composite), but on the other way improved the lightweight and thermal-insulating of the materials converting them as a good alternative to wood-plastic composites. In another study (Aranberri et al, 2018), were developed composites with poly(urea-urethane)/chicken feather fibers (different ratios) with similar mechanical properties to those presented in this study. The Young's modulus of the composites developed by Aranberri et al (2018) is range 1.2-410 MPa in function of the polymer/CF ratio, while for the bio-materials developed in this study is from 1 MPa to 800 MPa depending on the resin or filler nature.…”

“…In another study (Aranberri et al, 2018), were developed composites with poly(urea-urethane)/chicken feather fibers (different ratios) with similar mechanical properties to those presented in this study. The Young's modulus of the composites developed by Aranberri et al (2018) is range 1.2-410 MPa in function of the polymer/CF ratio, while for the bio-materials developed in this study is from 1 MPa to 800 MPa depending on the resin or filler nature. From figure 5 we can highlight that the tensile stress values of all bio-composites were considerably improved compared to that of resins, but this improvement depends on the nature of the filler but also of the resin formulation.…”

“…The thermal stability stipulated in the literature for the chicken feathers fibers is between 220 °C and 240 °C (Bessa et al, 2017;Cheung, Ho, Lau, Cardona, & Hui, 2009). According to reported results (Aranberri, Montes, Azcune, Rekondo, & Grande, 2018Flores-Hernández et al, 2014;Pourjavaheri et al, 2017) it has been observed that the addition of chicken feathers as filler in a polymeric matrix decreases the thermal stability of the composites compared to the neat resin. Pourjavaheri et al (2017) developed by solvent-casting method new bio-composites using thermoplastic poly(ether urethane) as matrix and chicken feather fibers (CFF) as reinforcement.…”

“…These values indicate a good stability of the composites, being comparable to those already stipulated in the literature. For example, the thermal stability of the poly(urea-urethane)/chicken feathers biocomposites developed by Aranberri et al (2018) is between 205-240 °C depending on the polymer/CF ratio.…”