Purpose
The surface characteristics of thermally and chemically modified wood, such as surface roughness, surface free energy (SFE) and wettability, are important properties that influence further ...manufacturing processes such as gluing and coating. The aim of this paper was to determine the influence of the surface roughness of thermally and chemically modified teak wood on their SFE, wettability and bonding quality for water-based acrylic and solvent-based alkyd varnishes. In addition, durability against subterranean termites in the field of these modified teak woods was also investigated to give a valuable information for their further application.
Design/methodology/approach
The woods tested in this study were fast-growing teak woods that were prepared in untreated and treated with furfuryl alcohol (FA), glycerol maleic anhydride (GMA) and thermal. SFE values were calculated using the Rabel method. The wettability values were measured based on the contact angle between varnish liquids and wood surfaces using the sessile drop method, and the Shi and Gardner model model was used to evaluate the wettability of the varnishes on the wood surface. The bonding quality of the varnishes was measured using a cross-cut test based on ASTM 3359-17 standard. In addition, durability against subterranean termites in the field of these modified teak woods was also investigated according to ASTM D 1758-06.
Findings
The results showed that furfurylated and GMA-thermal 220°C improved the durability of teak wood against termites. The furfurylated teak wood had the roughest surface with an arithmetic average roughness (Ra) value of 15.65 µm before aging and 27.11 µm after aging. The GMA-thermal 220°C treated teak wood was the smoothest surface with Ra value of 6.44 µm before aging and 13.75 µm after aging. Untreated teak wood had the highest SFE value of 46.90 and 57.37 mJ/m2 before and after aging, respectively. The K values of untreated and treated teak wood increased owing to the aging treatment. The K values for the water-based acrylic varnish were lower than that of the solvent-based alkyd varnish. The untreated teak wood with the highest SFE produced the highest bonding quality (grades 4–5) for both acrylic and alkyd varnishes. The solvent-based alkyd varnish was more wettable and generated better bonding quality than the water-based acrylic varnish.
Originality/value
The originality of this research work is that it provides evaluation values of the durability and SFE. The SFE value can be used to quantitatively determine the wettability of paint liquids on the surface of wood and its varnish bonding quality.
Improving the durability of short-rotation wood can be achieved through chemical and thermal modification. Chemical and thermal modification can have an impact on the physicochemical properties of ...wood, which can affect wood’s surface characteristics and its resistance to weathering. The purpose of this study was to investigate the surface characteristics and artificial weathering resistance of chemically and thermally modified short-rotation teak wood coated with linseed oil (LO)-, tung oil (TO)-, and commercial oil-based coatings consisting of a mixture of linseed oil and tung oil (LT) and commercial oil-based polyurethane resin (LB) coatings. The short-rotation teak woods were prepared in untreated and treated with furfuryl alcohol (FA), thermal treatment (HT) at 150 and 220 °C, and combination of glycerol–maleic anhydride (GMA) impregnation with thermal treatment at 150 and 220 °C. The surface characteristics measured were surface free energy, wettability, Persoz hardness, bonding quality, and color changes before and after artificial weathering exposure. The results showed that chemical and thermal modifications treatment tended to reduce total surface free energy (SFE), hardness, wettability, and bonding quality. FA and GMA at 220 °C treatments provided homogenization effect on surface characteristics, especially in total SFE and wettability. The total SFE of untreated wood ranged from 45.00 to 51.13 mN/m, and treated wood ranged from 40.58 to 50.79 mN/m. The wettability of oil-based coating according to K-value ranged from 0.20 to 0.54. TO presented better photostability than LO. Short-rotation teak wood coated with oil-based commercial coatings presented better weathering resistance compared to pure natural drying oil. Commercial oil-based coatings provided better weathering protection for the chemically and thermally modified teak wood. The application of oil-based coatings on chemically and thermally modified short-rotation teak is being considered for the development of a better wood-protection system.
Lactic acid (LA), citric acid (CA), and glycerol (G) are renewable and environmentally friendly chemicals that could improve the qualities of short-rotation teak (SRT) woods. This study investigated ...the effect of thermal and chemical modification using 20% aqueous solutions (w/w) of LA, CA, and G and their mixtures in the same composition on physical and mechanical properties of SRT teak wood. The impregnation process was initiated by vacuum process for 1 h and pressure (12.2 bar) for 2 h, followed by thermal (150 °C) treatment for 6 h on the SRT wood samples after being removed from the vacuum-pressure tube. Retention (R), weight percent gain (WPG), density (D), anti-swelling efficiency (ASE), leachability (WL), modulus of elasticity (MOE), and modulus of rupture (MOR) were measured. FTIR spectrometry and SEM analyses were performed. The wood impregnated with a mixture of 10% LA + 10% CA provided the highest ASE values of 50.1%, and the lowest leaching resistance of 1.54%. Based on wood strengths (MOE and MOR) and physical properties, as well as supported by FTIR and SEM analysis, the use of 10% LA + 10% CA is the most prospective as an impregnant formula for SRT wood modification of this research.
Short rotation teak wood has been produced to overcome the scarcity of long rotation teak. The short rotation teak has low quality, especially in dimensional stability and durability. Glycerol-maleic ...anhydride (GMA) treatment as non-biocidal wood preservation system was applied to improve technological properties, especially dimensional stability and durability. Impregnation with 10% w/w aqueous solution of GMA followed by thermal modification at 150 and 220 °C under inert conditions was investigated on short rotation teak sapwood. The following technological properties were studied: chemical compound; mass alteration; density; leachability; dimensional stability (volumetric swelling, anti-swelling efficiency (ASE), and water uptake; modulus of elasticity; modulus of rupture; decay resistance; and termite resistance. The results show that chemical modification with 10% GMA combined with thermal modification increased ASE by 62.31% and 73.22% for 150 and 220 °C, respectively, indicating improved dimensional stability. Decay resistances of GMA-thermal treated teak wood against fungal decay of
Coriolus versicolor
,
Pycnoporus sanguineus
, and
Coniophora puteana
were categorized to be class 1 (very durable). Weight loss of GMA-thermal at 220 °C against termite attacks was 0.19%, which presented excellent durability (rating 10) against subterranean termites. Fourier transform infrared and carbon 13 nuclear magnetic resonance analyses indicate that the presence of reaction between GMA polymer with lignin occurred after thermal treatment at 220 °C. Thermogravimetric analysis shows that GMA-thermal treatment also presented better thermal stability than untreated wood. GMA-thermal treatment gave a significant improvement in dimensional stability and resistance to wood-decaying fungi and termite.
Acacia mangium requires the addition of a finishing material to increase its resistance to weathering. Herein, the effectiveness of a nanocoating containing titanium dioxide nanoparticles (TiO2-NPs) ...as a finishing material for mangium wood was investigated. The coating material formulations used were oil-based (V1) and water-based (V2) varnishes with TiO2-NP concentrations of 1% (CT1), 5% (CT5), and 10% (CT10) (w/v). The uncoated and coated samples were subjected to weathering periods of 0, 2, and 4 months. The results showed that the addition of TiO2 nanoparticles to the V1 and V2 varnishes resulted in more gradual colour changes after the weathering period. The surface of the mangium wood also became smoother after being coated. However, the surface roughness increased with the duration of the weathering period. The wettability (K-value) of the sample decreased after coating, indicating that the coated sample was more hydrophobic than the uncoated sample. The results of a photocatalyst test, which analysed the effectiveness of the coatings, showed that the best coating material formulas were V1-CT10 and V2-CT10, as they degraded 75.21% and 71.03% of methylene blue content, respectively. Fourier transform infrared analysis showed that mangium wood did not undergo rapid weathering after the nanocoating treatment, as indicated by an insignificant decrease in the peak absorption intensity of the main structural functional groups of wood.
Short rotation teak (SRT) has a diameter of around 30 cm at the age of 15 years; however, the wood still has low quality, especially in dimensional stability and biological durability. The objective ...of this study was to improve dimensional stability and biological durability of SRT through modification treatment using non-biocide chemicals, citric acid (CA) and benzophenone tetracarboxylic acid (BPTCA). SRT sapwood was impregnated by 20% and 40% of CA or BPTCA followed by heating in the oven at 150 °C for 2 h. Dimensional stability, strength, surface characteristics and durability against termite attacks of the modified woods were evaluated. Results show that dimensional stability as anti-swelling efficiency (ASE) increased by an average of 46% (CA) and 50% (BPTCA) after treatments. Durability against termites showed that the modified woods were categorized to be class 1 (very durable). Fourier Transform Infrared (FTIR) and X-ray Diffraction observations indicated a possible chemical reaction between the wood components with CA and BPTCA. The water-based acrylic and oil-based alkyd contact angle values of the modified woods were lower than 90°, indicating their high wetting ability against the varnish liquids. The treatment can be applied to improve the quality of SRT for high-quality wood product utilization.
Short rotation teak has been developed to overcome the limited supply of long rotation teak. The characteristics and technological properties of sapwood and heartwood of short rotation teak are not ...well studied. The purpose of this study was to evaluate the effect of sapwood and heartwood differences on technological properties for short rotation teak. The short rotation teak woods used were Plus Perhutani teak of 15 years old with a sapwood proportion of 30% and Biotrop teak of 8 years old with a sapwood proportion of 18%. The following technological properties of sapwood and heartwood were studied: extractive content, chemical composition, volumetric swelling, water-sorption isotherm, modulus of elasticity, modulus of rupture, decay resistance, termite resistance, surface roughness, surface free energy, wettability, and weathering performance. The results showed that the extractive content of heartwood was higher than sapwood. The main compounds in the extractive content of heartwood were lapachol and 9,10-anthracenedione; meanwhile the main compounds of sapwood were mostly single sugars and derivatives. The extractives present could contribute to technological properties of short rotation teak wood, particularly for improved dimensional stability, reduced water-sorption, higher decay and termite resistance, and better photostability. Sapwood presented lower quality especially in dimensional stability and durability, which could restrict its utilization for both indoor and outdoor applications. Therefore, sapwood should require certain treatments, especially for wood exposed to outdoor conditions.
Short rotation teak wood has low quality especially in dimensional stability and durability. Furfurylation treatment was applied to improve technological properties of the short rotation teak wood. ...The purpose of the study was to improve dimensional stability and durability through furfurylation treatment. Short rotation teak sapwoods (Plus Perhutani and Biotrop teaks) were treated through the impregnation process of 45% of furfuryl alcohol (FA) and 5% of tartaric acid as catalyst followed by heated in oven at 120 °C for 16 h under nitrogen atmosphere. Dimensional stability was characterized by volumetric swelling, anti-swelling efficiency (ASE), water uptake (WU), and bulking effect (BE), meanwhile decay durability was determined by the weight loss (WL). The results show that ASE increased in the average of 64%, WU decreased in the average of 59%, and BE increased in the average of 11%, which indicated the improvement of dimensional stability. Weight losses of furfurylated teak woods due to fungal decay of Coriolus versicolor (CV), Pycnoporus sanguineus (PS), and Coniophora puteana (CP) were in the average of 2%, 1%, and 1%, respectively, which categorized their durability to be class 1 (very durable). The increase of lignin content showed by Klason lignin content measurement and Fourier Transform Infrared (FTIR) and Carbon 13 Nuclear Magnetic Resonance (13C NMR) analysis indicated that the reaction of FA with lignin occurred after furfurylation treatment. Furfurylated sapwood presented also better thermic stability compared to untreated wood by Thermogravimetric Analysis (TGA). The FA treatment can be applied for improving the quality of short rotation teaks for high quality wood product utilization.
The surface free energy (SFE) of woods and their wettability are important characteristic for wood painting. No information is available regarding the SFE and wettability of Indonesian tropical ...woods. The purpose of the study was to determine the SFE and wettability of 10 Indonesian tropical woods. The woods tested in this study were fast-growing species from plantation of teak, sengon, jabon, pine, and species from natural forest of ramin, meranti, mahagony, camphor, keruing, and ebony. Surface roughness was measured by a profilometer, while wettability was determined by sessile drop method. The SFE values were calculated based on the Rabel method. Wettability was characterized by constant contact angle change rate (K) using the Shi and Gardner (S/G) model. The results showed that the mean roughness (Ra) value of fast-growing species from plantation was 13.58 μm and of species from natural forest was 10.73 μm. The SFE of woods varied from 36.00 mJ/m
2
in the Meranti to 69.68 mJ/m
2
in the Sengon. It was observed that the Meranti wood with the lowest value of SFE provided the lowest value of K (0.01) which indicated the poorest in wettability. The Sengon wood with the highest value of K (0.06) should provide the best wettability for the acrylic paint.
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