Simultaneously enhancing strength and toughness of coir fiber through NaOH and sodium alginate treatment
Coir fibers are commonly subjected to alkali treatment to eliminate impurities and tune their mechanical properties. However, this process can damage the fibers’ microstructures, posing a challenge in significantly enhancing both strength and toughness simultaneously. Herein, we successfully enhanced both strength and toughness of coir fibers through a combined treatment with NaOH and sodium alginate aqueous solution. Coir fibers treated with 5 wt% NaOH solution, followed by 0.5 wt% sodium alginate solution, exhibit a tensile modulus of 2475.0 MPa, a tensile strength of 126.4 MPa, and a toughness of 30.7 MJ/m³, representing improvements of 57.1 %, 72.7 %, and 116.2 %, respectively, compared to the raw fibers. Mechanistic studies revealed that NaOH treatment effectively removes pectin, hemicellulose and lignin from coir fibers but introduces numerous defects. Sodium alginate can repair these defects by forming hydrogen bonds with the rich oxygen-containing group of coir fibers. The combined treatment also increases the crystallinity of coir fibers from 30.3 % for the raw fibers to 44.1 % by removing a large number of amorphous substances. Additionally, the combined treatment reduces the microfibril angle from ∼63.6° to ∼46.6° by elongating the helix structure and filling the gaps between helical fibers. Our cost-effective strategy not only promotes the applications of coir fibers but also provides guidance for the modification of other natural plant fibers.
危险品化学品经营许可证（带存储）