Physical properties and structural features of common walnut (Juglans regia L.) wood: A case-study / Physikalische Eigenschaften und strukturelle Charakteristika des Holzes der Walnuß (Juglans regia L.): Eine Fallstudie

Abstract

We assessed wood quality in common walnut using a combination of physical properties and structural features. Five common walnut trees were selected and processed in order to produce wood samples for further analyses. The results showed a wide spread of values of structural features and of wood water content. The color indices were strongly grouped around the averages. All experimental distributions were stratified following at least one of the analyzed factors (tree and its structural directions i.e. longitudinal, radial, and tangential). The radial anisotropy was the most pronounced. The longitudinal stability of density and water content, the inter-tree stability of color saturation as well as the homogeneity of all color indices on the girth were noticed. The heartwood covered up to 12.5% of transverse section and included 1-10 growth rings. The annual rate of bio-accumulation allowed the separation of stages of radial development of the structure using the width of growth rings: juvenile wood, composed of the first 8-9 rings from the pith; a transition zone to the mature wood (10 rings); and mature wood under way to be formed. Wood density was not a reliable criterion for differentiating the sapwood from heartwood but brightness, redness and hue's color could be used for this purpose. ZusammenfassungEine Kombination unterschiedlicher physikalischer und struktureller Holzkennwerte wurde eingesetzt, um Walnußholz zu untersuchen. Hierzu wurden fünf Probebäume ausgesucht, bearbeitet und definierte Holzproben hergestellt. Die Ergebnis zeigten eine weite Streuung bei den Werten der strukturellen Kennwerte sowie des Wassergehaltes. Die Farbkennwerte waren streng um die Mittelwerte gruppiert. Alle experimentellen Verteilungen wurden an mindestens einem der analysierten Faktoren stratifiziert (der Baum und sein strukureller Aufbau, d.h. longitudinal, radial und tangential). Die radiale Anisotropie war dabei besonders ausgeprägt. Die Stabilität von Dichte und Wassergehalt in longitudinaler Richtung, eine Stabilität der Farbsättigung zwischen den Probebäumen sowie eine Homogenität aller Farbindices im Randbereich konne festgestellt werden. Das Kernholz deckte bis zu 12,5 % des transversalen Abschnittes ab und umfaßte 1-10 Ringe. Die jährliche Bioakkumulationsrate erlaubte eine Trennung von Stadien der radialen Strukturetwicklung auf Basis der Breite der Zuwachsringe: juveniles Holz, die ersten 8-9 Ringe um das Mark umfassend, eine Übergangszone zum reifen Holz (10 Jahrringe) und reifes Holz in Entstehung. Die Holzdichte war kein zuverlässiges Kriterium um Splintholz von Kernholz zu unterscheiden, jedoch konnten Helligkeit, Rötung und hue's Farbe zu diesem Zweck erfolgreich eingesetzt werden.

Development and Characterization of Environmentally Friendly Wood Plastic Composites from Biobased Polyethylene and Short Natural Fibers Processed by Injection Moulding

“…In fact, the incorporation of the fibers provides positive values for the colour coordinates a* and b*, which corroborates that their addition generates a series of materials with reddish-like colours with brown tones. The colour coordinates of the obtained BioHDPE composites are similar to some typical woods such as pine, oak, birch, walnut, or teak, among others, thus opening new potential applications for these materials as wood substitutes as reported by Liminana et al [ 83 ] in polybutylene succinate (PBS) composites with almond shell flour, and other natural woods [ 84 , 85 ]. This fact can be interesting from an aesthetic point of view in packaging elements, such as trays, decoration elements for gardens and interiors or substitute elements of different woods [ 8 ].…”

The Effect of Varying Almond Shell Flour (ASF) Loading in Composites with Poly(Butylene Succinate (PBS) Matrix Compatibilized with Maleinized Linseed Oil (MLO)

“…In particular, both the a* and b* coordinates decrease as the ASF loading increases. Figure 2b also shows the colour coordinates (a*b*) of several commercial woods [56,57]. Poly(butylene succinate)/ASF/MLO composites with 10 wt % show similar colour coordinates to those of eucalypt [58] and teak woods [59].…”

Upgrading Recycled Polypropylene from Textile Wastes in Wood Plastic Composites with Short Hemp Fiber

“…Figure 7a shows the obtained materials, and it is evident that the visual aspect significantly changed acquiring wood aspect. As can be seen in Figure 7b, the incorporation of SHF modified the color coordinates so that they acquired the appearance of woods like teak or eucalyptus [72,[76][77][78]. In this instance, rPP-H30-M took an appearance very similar to oak wood.…”