The effect of heat and ammonia treatment on colour response of oak wood (Quercus robur) and comparison of some physical and mechanical properties

Abstract

In this paper the effect of heat and ammonia treatment on the change in colour of oak wood (Quercus robur) and comparison of physical and mechanical properties were investigated. Wood specimens were made from heartwood and sapwood in dimensions 30×30×30 mm 3 . The specimens were subjected to heat treatment at 180ºC and 230ºC for 2 and 4 hours, others were treated by ammonia for 24 hours. After these processes, CIELAB colour, hardness, EMC, density and MOE of wood were tested in comparison with untreated samples. The results show that the heat treatment contributed to darkening of sapwood and heartwood and the total colour change increased up to 38.47 units (CIELAB) in the radial direction and 37.75 units (CIELAB) in the tangential direction. Previous research into ammonia treatment shows that the most significant changes were noticed after 1 day. The colour changes between sapwood and heartwood were more noticeable in ammonia treatment than in the case of heat treatment. All other observed properties were decreased in the case of heat treatment. Ammonia treatment does not have a significant influence on the other observed properties. The results proved that ammonia treatment is a modification that improves the decorative value but has a minimal effect on technologically relevant properties of solid wood. Nevertheless, the heat treatment can be used as comparable process for colour change of wood.

Physical and Mechanical Properties of Ammonia-Treated Black Locust Wood

“…In Table 2, the average values and standard deviation of the main mechanical properties of control and treated samples are presented. The similar percentile changes were obtained by Weigl et al [6], Čermák and Dejmal [10], who considered the reduction of mechanical properties values not significant. On the other hand, Rousek et al [17] studied the possibilities of mechanical properties improvement in case of beech wood modification with ammonia gas, reporting a tendency to increase the mechanical properties of beech wood treated with ammonia, especially the MOR to compression.…”

“…The most significant chemical modification is related to the reaction of ammonia with carboxylate groups from wood with formation of ammonium salt, the reaction with aldehyde and ketonic groups resulting imines and the reaction with ester functional groups leading to formation of amides [9]. In [10], the authors studied the density profile and thermal properties of untreated beech wood and treated with ammonia and compressed beech wood. Many researchers investigated the effect of ammonia treatment on oak wood, both from colour modification and mechanical properties points of view [6,7,9,10].…”

“…In [10], the authors studied the density profile and thermal properties of untreated beech wood and treated with ammonia and compressed beech wood. Many researchers investigated the effect of ammonia treatment on oak wood, both from colour modification and mechanical properties points of view [6,7,9,10]. The uneven colour of the natural black locust wood is an aesthetic disadvantage of this species and therefore, the steaming of the black locust wood and fuming with ammonia gas for the uniformity of the colour, is a widespread practice in some countries.…”

Surface Properties of Beech Wood after CO2 Laser Engraving

“…Each type of wood surface treatment (mechanic, heat-hydro-mechanic, CO 2 laser, and other) induces changes to the wood chemical and anatomical structure and consequently causes changes in these material properties. The absorbed energy-induced chemical changes to the main wood constituents are responded by the changes in the wood surface color, morphology, and also to its hydrophilic/hydrophobic performance [1][2][3][4][5][6][7][8][9][10][11][12][13].…”

Colour changes and morphological performance of impregnated jabon wood using polymerised merbau extractives

“…To create a darkened effect in wood, many studies have been carried out by means of various methods, either physical or chemical treatment. Most studies that have been undertaken and applied to industrial production including heat treatment (Sundqvist 2004, Hill 2006, Esteves et al 2008, Pena and Hale 2009a, Pena and Hale 2009b, Dubey et al 2010, Esteves and Pereira 2009, Dubey et al 2012, Cermák and Dejmal 2013, Garcia et al 2014, Kamperidou and Barmpoutis 2015, Tuong and Li 2010. Hill (2006) stated that a darkening of the wood occurs with the colour change being related to the temperature and time of treatment.…”