Effect of SiO2 nano-interphase on the water absorption mechanism of natural fiber reinforced composites: A multi-scale study

Natural fiber reinforced composites are emerging as a sustainable alternative to traditional materials in various industrial applications. However, their long-term performance under outdoor conditions is adversely affected by moisture absorption and interface failure. In this study, we design a SiO2 nano-interphase between the jute fibers (Jute) and polypropylene (PP) to prevent the composites (Jute-SiO2/PP composites) against the interface failure caused by water absorption under wet conditions. Combining molecular dynamic (MD) simulation, microstructure characterization and macroscopic water absorption test, we elaborate on the underlying mechanism of water absorption for Jute-SiO2/PP composites at multi-scale levels. MD simulations reveal that the SiO2/PP interface and the Jute-SiO2 interface, with their strong interlocking of molecular chains and polar interaction, respectively, effectively protect the composites from water diffusion at molecular level. Moreover, SiO2 nano-interphase with the array structure provides superior shielding against water ingress into the composites at micro level. The cooperation of the strong molecular structure and the unique microstructure for Jute-SiO2/PP interphase results in enhanced water resistance and dimensional stability of the composites. The water uptake and the thickness swelling of Jute-SiO2/PP composites are reduced by 3.6% and 3.0%, respectively. Our study offers new insights into leveraging sustainable biomaterials in moisture-prone applications.