Performance improvement of radiata pine wood by combining impregnation of furfuryl alcohol resin and densification for making fretboard materials

The fast-growing plantation radiata pine wood has undesirable intrinsic properties, which cannot meet the physical and mechanical performance requirements of string instrument fretboard materials. In this study, the synergistic modification technology of FA impregnation treatment and densification treatment was proposed to improve the density, dimensional stability, and mechanical properties. In addition, its surface color of radiata pine wood was deepened to imitate precious tropical hardwood (e.g., ebony, Indian rosewood, and African blackwood) that are commonly used in the fretboards of string instruments. This technology combined the characteristics of the wood densification and FA impregnation treatment, that is, the densification treatment can improve the mechanical strength of low-quality wood and FA can fix the deformation of the densified wood, preventing treated wood from spring back. The performance differences between the fretboard wood and FA-densified-wood with compression rates (CRs) of 17 %, 33 %, and 50 % were analyzed, and the optimal CR was determined. The fretboard wood has high density (> 800 kg/m3), dimensionally stable, and red brown or jet-black surface color. The modulus of rupture (MOR), modulus of elasticity (MOE), compression strength (CS), Brinell hardness (BH), and impact bending strength (IBS) of the fretboard wood are higher than 140.0 MPa, 13.0 GPa, 120 MPa, 7.9 N/m2, and 17 kJ/m2, respectively. The fretboard wood also has good abrasion resistance. The FA-modified wood with a CR of 50 % had a high density (> 1000 kg/m3), superior dimensional stability, excellent mechanical properties, and its surface color was jet black, which was the same as those of the fretboard wood. The FA-modified wood with a CR of 50 % met the performance requirements of wood for fretboards, and has the potential to replace the fretboard wood for string instrument fretboard manufacturing. It breaks through the restriction that fast-growing plantation wood cannot be used for musical instruments, alleviating the shortage of the resources of commonly used tropical hardwood for fretboards and providing new insights for the high-value utilization of plantation radiata pine wood.