Technological characterisation of wood from Australian red cedar after first thinning of a plantation at five years

Abstract

Australian red cedar (Toona ciliata M. Roem.) is a forest species planted in Brazil especially for lumber production. This study aimed to evaluate technological properties of the wood after selective first thinning of a plantation 5 years after planting. The technological properties evaluated were: (i) physical – apparent specific mass at 12% moisture content and shrinkage; (ii) mechanical – modulus of elasticity (E), modulus of rupture (σ), and brittleness; (iii) weathering; (iv) surface macrostructure – colour and roughness; (v) chemical – soluble and insoluble lignins, and holocellulose and ash contents; and vi) thermal – thermogravimetric analysis and calorific value. Apparent specific mass was 380 g m−3; the calculated shrinkage anisotropy of 1.04 and swelling anisotropy of 1.14 fit the classification ‘excellent quality’; the elasticity modulus was calculated as 4 700 MPa, and strength to flexion was 45 MPa. The mechanical properties other than brittleness were not compromised with weathering exposure. However, the accelerated weathering testing as a simulation of natural weathering showed modified colour of the wood and reduction of the mechanical properties. The calorific value of the wood (4 634.03 Kcal g−1) was similar to that reported for other fast-growing woods at even more advanced planting ages. Thermal stability of the wood was comparable to other fast-growing species used for energy purposes, owing especially to high holocellulose content.

Keywords: accelerated weathering; calorific value; holocellulose; thermal stability; wood characteristics