Compatibilization of coir fiber and elastomeric polyurethane by green modification routes

Tuning the chemical functionality of lignocellulosic fiber plays a key role in the development of mechanically strong composites to overcome the lack of compatibility between composite phases, which is a major challenge in multidimensional applications of eco-composites. Herein, coir fiber (CF) surfaces were enriched through four kinds of modification routes – namely, mercerization, amino-functional silane treatment, bio-based epoxy resin sizing and isocyanate treatment – to enhance their interfacial adhesion to a thermoplastic polyurethane (TPU) matrix. The tensile strength and Shore hardness parameters of composites were improved by surface-modified CF inclusions. The thermomechanical response of TPU was optimized after CF loadings regardless of treatment type. The composite with silane-modified CF exhibited the lowest water uptake due to the hydrophobic behavior of the silane layer. The increase in interfacial interaction between the TPU matrix and modified CF was confirmed by scanning electron microscopy investigations. The chemically enriched surface of CF improves the performance of composites, thanks to improved adhesion in the TPU–CF interface.