Formation mechanism of wood rotary welding interface by various additives

Abstract

Abstract In order to improve the interfacial properties of rotary welding of wood, additive pre-treatments for wooden tenons were conducted as follows: immersion in oleic acid-modified calcium carbonate whiskers (group CA), no treatment (group DZ), immersion in CuSO4 and Na2SO3 for a duration of 8 hours (group CN), and addition of calcium carbonate in the pre-drilled holes (group L). The scanning electron microscopy (SEM), mechanical properties tests, Fourier infrared spectroscopy (FTIR), X-ray diffraction (XRD), and pyrolysis gas chromatography-mass spectrometry tests (Py-GC/MS) were performed to evaluate the properties of the welded interfaces. After additive treatment, the welded interface exhibits a layered structure resembling grout, with an increased relative content of cellulose and lignin on the interface, indicating enhanced intramolecular cohesion. The generation of high molecular weight aromatic methoxy groups confirms the intermolecular connection. As a result, the mechanical properties and water resistance of the rotational welded interface are significantly improved. With the exception of the CN group, all specimens meet the strength requirement (≥ 0.7 MPa) specified in GB/T 14018 − 2009 "Test Method for Wood Nail Grip Strength"(in China), and the CA group exhibits the most exceptional welding interface performance.