Study on properties of radiata pine wood treated with furfuryl alcohol as fretboard materials for string instruments

The commercial applications of endangered wood species (e.g., ebony, Indian rosewood, and African blackwood) for string instrument fretboards have been limited due to their low yield, long growth cycle, and tight trade restrictions. However, the physical and mechanical properties of radiata pine modified by furfuryl alcohol (FA) are comparable to the tropical hardwood species that are commonly used for fretboards. Therefore, this study proposes performance indicators of fretboard material selection to evaluate the physical and mechanical properties of modified wood samples with different FA concentrations. The concentration of FA was optimized to make the modified wood satisfy the performance requirements of fretboards. The density of fretboard wood needs to be greater than 800 kg/m³, and have good dimensional stability. The surface color of the wood needs to be dark brown or jet black. The hardness of fretboard wood needs to be greater than 6.0 kN, and it should have superior abrasion resistance (the friction coefficient is about 0.72, and width and depth of the wear scars are 0.8 mm and 25.0 μm, respectively). The E' and \({G}_{LT}^{^{\prime}}\) of the fretboard wood were greater than 9.32 GPa and 1.21 GPa, respectively. The fretboard wood had higher tanδ values and lower \(\upsilon\) and R values. The results indicated that the density of the 70% FA modified wood was 850 kg/m³, and it had good dimensional stability, which met the physical performance requirements of fretboard selection materials. Only the 70% FA modified wood met the requirements of the main evaluation indicators for the mechanical and sound vibration properties of the wood for fretboards. However, the furfurylated wood had the drawbacks of high brittleness and low bending strength, which needs to be addressed in the future research through FA modification combined with other modification technologies to perfectly replace the fretboard wood species.