A method of using a combination of multiple chemical additives to improve the performance of wood (round tenon) rotary friction welding

Abstract

The existing research mainly improves the performance of wood (round tenon) rotating welded specimens by using a single type of additive. Due to the single type of chemical additive used, the performance of welded specimens is limited. Therefore, we have found a joint pretreatment modification method that can simultaneously improve the waterproof, mechanical, and environmental adaptability of welded specimens. It mainly includes: the CA group (calcium carbonate and oleic acid treatment) and, the CN group (Na₂SO₃ and CuSO₄ oxidation sulfonation treatment). Techniques such as scanning electron microscopy, mechanical testing (Wood Nail Grip Strength testing and Water Resistance Test testing), Fourier transform infrared spectroscopy, X-ray diffraction, and pyrolysis gas chromatography–mass spectrometry were utilized to assess the welded interfaces. Methods including pyrolysis gas chromatography-mass spectrometry, Fourier transform infrared spectroscopy, mechanical testing, X-ray diffraction, and scanning electron microscopy were employed to evaluate the welded interfaces. Following the treatments, the interfaces displayed a grout-like layered structure with increased amounts of cellulose and lignin, enhancing intramolecular cohesion. Hydrogen bonding of oleic acid-stearic acid and tetrahydrofuran (THF) and high molecular weight aromatic methoxy groups were generated at the welding interface of the CA group. Consequently, this leads to a significant improvement in the mechanical properties and water resistance of the rotating welding interface, which in turn enhances the environmental adaptability of the welded specimen. Excluding the CN group, all samples met the ≥ 0.7 MPa strength criterion set by GB/T 14018–2009 “Test Method for Wood Nail Grip Strength” in China, with the CA group showing superior interface performance, In addition, the calcium carbonate whiskers in the CA group enhanced the mechanical properties of the welded specimens, but weakened the water resistance, which led to a large difference between dry and wet in the CA group. The CN group enhances the activity of lignin due to the oxidative sulfonation reaction, maintains a certain viscosity of the welding interface, and is resistant to water. Therefore, although the overall welding strength is low, there is no dry and wet difference in this group.