High-strength and water resistant lignocelluloses based composites (LC) were fabricated using branched polyethylenimine (PEI) as the main bonding agent combined with glutaraldehyde cross-linking reaction and grinding pre-treatment. Physical and mechanical properties of different composites prepared were measured and investigated. It is evident that PEI was efficient in endowing LC with high strength and excellent water resistance. The obtained physical and mechanical properties of LC were complied with the requirement of the Chinese national standard for medium-density fiberboard (MDF). Most notably, the glutaraldehyde cross-linking and grinding pre-treatment could further improve these properties. When 5% PEI and 2.5% glutaraldehyde were incorporated, together with 2-hour grinding treatment, the LC prepared exhibited the optimum modulus of rupture (MOR) 58.1 MPa, modulus of elasticity (MOE) 5077 MPa, internal bonding strength (IB) 2.14 MPa, and thickness swell (TS) 30.2%. The excellent properties obtained could be attributed to the cross-linking effect and Schiff's base addition reaction among lignocelluloses, PEI and glutaraldehyde, which were confirmed by the Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) analysis. The high-strength LC prepared in this study is expected to be used as load-bearing material in structural application.
Keywords: Cross-linking; High strength; Lignocelluloses based composites; Polyethylenimine; Schiff's base addition reaction; Water resistance.
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