Mechanical property enhancement of self-bonded natural fiber material via controlling cell wall plasticity and structure

Abstract

Self-bonded natural fiber material (SNFM) is a promising alternative for plastic and wood owing to its abundant raw material resources and low environmental impact. In this study, a high-performance SNFM was developed by the comprehensive treatments for the plasticity and structure of fiber cell walls. The cell wall structure was treated by a progressive chemical etching process for selectively removing surface lignin, internal lignin and hemicelluloses, respectively. The cell wall plasticity was tuned by controlling the fiber moisture content during compression molding process. The results showed that the increase in fiber plasticity improved the tensile strength from 38.0 to 83.5 MPa and the flexural strength from 31.2 to 73.3 MPa. The selective removal of surface lignin increased the flexural strength from 101.3 to 122.1 MPa. The functional relationships among mechanical strength, lignin content, hemicellulose content and moisture content were established. The self-bonded mechanism for natural fiber materials was also discussed. The SNFM products showed excellent mechanical performance (tensile strength: 21.5–83.5 MPa; flexural strength: 31.2–127.3 MPa), which was superior to that of natural wood (46.5–55.6 MPa; 70.7–92.4 MPa) and plastic (15.9–51.0 MPa; 21.7–73.0 MPa) (e.g., HDPE, PP, PVC, and ABS).