Phosphorylated chitosan as a bio-based modifier for urea formaldehyde adhesives in wood composite applications

This study employs chitosan (CS) derived from chitin (CT) isolated from shrimp shell waste (SSW) and its phosphorylated form as sustainable bio-based modifiers for urea-formaldehyde (UF) adhesives, with the aim of improving the mechanical and physical performances of particleboard (PB) panels and reducing formaldehyde emissions (FE). CS and phosphorylated chitosan (P-CS) were prepared and characterized using SEM, XRD, ATR-FTIR, and TGA-DTG analyses. PBs were manufactured using varying proportions of CS and P-CS (4–10 wt%) and compared to a commercial UF adhesive (0:100). Mechanical and physical properties were evaluated to assess performance. The results revealed that the optimal addition of 8 wt% P-CS significantly improved mechanical properties. The dry internal bond (0.65 ± 0.03 MPa), modulus of elasticity (3659 ± 14 MPa), modulus of rupture (28 ± 0.70 MPa), and surface soundness (1.88 ± 0.04 MPa) increased by 44.44 %, 43.26 %, 75 %, and 19.74 %, respectively, compared to the control UF resin. Additionally, FE values decreased by approximately 34.63 % with the UF:P-CS (92:8; w/w) formulation. In terms of physical performance, the thickness swelling (TS) and water absorption (WA) values of the optimal adhesives, UF:CS /P-CS (92:8; w/w), were significantly lower than those of the control UF:CS /P-CS (100/0; w/w). TS values were 8.06 ± 0.09 % and 10.99 ± 0.27 %, while WA values were 39.33 ± 1.84 % and 90.01 ± 2.02 % after 2 and 24 h, respectively. These findings demonstrate the potential of P-CS as a sustainable additive for improving UF adhesives in PB manufacturing.