Microstructural characterization and evaluation of certain important physical properties of thuja burl wood

S.R Shukla,D.P Kamdem

doi:10.4067/s0718-221x2018005002701

Abstract

This investigation aimed to characterize certain important anatomical, chemical and physical properties of Tetraclinis articulate (Thuja) burl wood from Morocco. Anatomical properties and constituent structure were analysed using image analysis system, environmental scanning electron microscope (ESEM) and powder x-ray diffraction techniques. A few important physical properties of Thuja burl wood such as density, specific gravity, equilibrium moisture content (EMC), total swelling and water absorption characteristics were evaluated. Real-time water absorption and swelling profiles were recorded electronically using a digital force sensor and linear variable differential transformers (LVDTs) respectively. Microscopic structure observed on fractured surfaces showed very compact and thread-like fibers. Average crystallinity index and diameter of cellulose crystallite was found to be 0.35±0.03 and 36.00±5.58 A respectively. The average values of air-dry density and the EMC of Thuja burl wood were 932.67±50.57 kg/m3 and 10.19±1.43% respectively. Swelling profile as a function of the water immersion duration followed a curvilinear variation with maximum swelling coefficient of 2.9±0.43% after 24 hour from oven-dry condition. The suitability of this wood for decorative and handicraft items is attributed mainly to its dense microstructure, higher dimensional stability, lower water absorption, random grain texture, dark brownish with intense and pleasant smell.

Highlights

Small, uncontrolled, irregular or spherical extra growths occasionally occurring on the trees near ground level are called burls
Structural and chemical characteristics using x-ray diffraction (XRD) and physical properties such as equilibrium moisture content (EMC), density, specific gravity, water absorption and swelling profiles were evaluated and Microstructural characterization..: Shukla and Kamdem analysed for numerous specimens as described below
The burl wood was commonly composed of light and dark bands of high density woody tissues with random orientation showing distinct dark brown with random grain texture

Summary

Introduction

Small, uncontrolled, irregular or spherical extra growths occasionally occurring on the trees near ground level are called burls. The structure of burl wood is generally characterized by eye-like markings surrounded by distorted soft, “velvet-like” and swirls tissues (Beals and Davis 1977). Tetraclinis articulata is an evergreen conifer tree from the Cupressaceae family with the ability to develop burls generally found under the collar of tree. Being native to North-Western Africa and endemic to SouthWestern coast of the Mediterranean Sea, this species is mostly abundant in Morocco and North Africa and commonly known as Thuja, thuya, sandarac or Arar (Ibaez et al 1989, Hatimi 1994, Moussaouiti et al 2010, Sanchez-Gomez et al 2013). Other than Thuja, such wood burls are found to occur on walnut, maple, redwood just to mention a few

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