Bone-inspired surface strengthening of formaldehyde-free impregnated decorative paper using inorganic–organic framework protective layers

Surface strengthening of decorative materials is a crucial factor in enhancing the abrasion and scratch resistance of decorative materials, thereby extending their service life during transportation and daily use. Formaldehyde-free impregnated paper is recognized as an eco-friendly decorative material for wooden furniture. However, wood-based panels bonded with formaldehyde-free impregnated paper often suffer from insufficient surface hardness and are prone to scratching. To address this issue, improvements have been made to the surface and interfacial impregnating adhesives to enhance the performance of decorative panels. Inspired by the high hardness of bone tissue, bone derived nano-hydroxyapatite (n-HAP) was incorporated into the surface adhesive (PUA) of impregnated paper, while polyethyleneimine (PEI) and phytic acid (PA) were used for organic compounding to construct an inorganic-organic framework protective layer. The addition of PEI-PA significantly improved the dispersibility of n-HAP in the adhesive. Even after standing for 4 hours, the n-HAP-PEI-PA/PUA mixed adhesive system maintained excellent dispersion stability. Compared with the control group (pure PUA), the abrasion value of n-HAP-PEI-PA/PUA decreased from 53 mg/100r to 39 mg/100r (a reduction of 26.42%), while the surface bonding strength increased from 1.64 MPa to 2.21 MPa (an enhancement of 34.76%). Additionally, the modified adhesive exhibited a surface strengthening effect when applied to impregnated fabrics and leather. Overall, the impregnated paper modified with the inorganic-organic protective layer provides a promising strategy for manufacturing decorative panels with enhanced abrasion resistance and robust interfacial bonding.