Bond-line strength, chemical properties and cellulose crystallinity of welded pine and itauba wood

The aim of this research was to evaluate the bond-line strength and chemical changes of pine (Pinus taeda) and itauba (Mezilaurus itauba) joints welded by rotary friction and the use of the internal standard method with Rietveld refinement for the determination of the absolute cellulose crystallinity of wood samples. The specimens were composed of itauba dowels welded in substrates made of pine and itauba wood. The shear engaged by tensile pullout of the dowels was determined by mechanical tensile tests. Furthermore, macrostructural evaluation of the specimens and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction (XRD) tests were performed. The cellulose crystallinity was determined quantitatively by the internal standard method with Rietveld refinement and compared with the Segal and the deconvolution qualitative methods. The results reveal that itauba dowels welded in itauba substrates produce stronger joints (0.81 MPa) and slighter chemical changes than in pine substrates (0.62 MPa). The welded bond-line of itauba dowel and pine substrate has greater cellulose crystallinity than that of itauba dowel and substrate. The cellulose crystallinity is qualitatively consistent for the three applied methods, however, quantitatively, there are divergences between them.