Journal of Biotechnology and Biodiversity | v.8 | n.2 | 2020
Journal of Biotechnology and Biodiversity
journal homepage: https://sistemas.uft.edu.br/periodicos/index.php/JBB/index
Evaluation of the quality of surface finish of messassa wood for three types of varnishes.
Narciso Fernando Bilaa* , Rosilani Trianoskib , Andrade Fernando Egasa* , Setsuo Iwakirib , Marcio Pereira da Rocha b
a Universidade Eduardo Mondlane, Moçambique
b Universidade Federal do Paraná, Brasil
* Autor correspondente (bila.narciso@gmail.com )
I N F O A B S T R A C T
Keyworks
Brachystegia spiciformis Julbernardia globiflora furniture and frames production
lesser-used species coating products
The aim of this study was to evaluate the performance of the messassa wood Brachystegia spiciformis and Julbernardia globiflora for three types of finishing products for use in the furniture and frames in- dustries. Coating performance was assessed by adhesion strength, impact deformation resistance, abra- siveness, gloss and overall color variation tests based on technical standards. Copal painting application was higher for gloss, adhesion and lower abrasiveness compared to water based and polyurethane. The impact deformation was higher for polyurethane than water-based and copal for both species. The dark- ening of wood for Brachystegia spiciformis and a slight lightening of wood by Julbernardia globiflora characterize the overall color variation after application of the coating products. According to these re- sults, the varnishes can be used to add value to the messassa wood as a finish in solid wood furniture and frames .
R E S U M O
Palavras-chave s
Brachystegia spiciformis Julbernardia globiflora
produção de móveis e molduras
produtos de acabamento
valorização de espécies
Avaliação da qualidade de acabamento superficial da madeira de messassa para três tipos de vernizes. O objetivo deste estudo foi avaliar o desempenho da madeira das messassas Brachystegia spiciformis e Julbernardia globiflora perante três tipos de produtos de acabamento superficial para utilização na indús- tria moveleira e de molduras. Foram utilizados como acabamento o verniz Copal, verniz base de água e verniz poliuretano. O acabamento foi avaliado através de ensaios de resistência à aderência (pull-off ), impacto, abrasividade, brilho e medição de variação da cor com base em normas técnicas. As espécies apresentaram resultados satisfatórios nos ensaios para todos os vernizes. Houve variação da cor após a aplicação do acabamento caracterizada pelo escurecimento da madeira para espécie Brachystegia spici- formis e um ligeiro clareamento para madeira da Julbernardia globiflora. Conclui-se que os três vernizes podem ser utilizadas nestas espécies para agregação do valor da madeira como acabamento em móveis e molduras de madeira sólida.
Received 28 January 2020; Received in revised from 14 May 2020; Accepted 24 May 2020
© 2020 Journal of Biotechnology and Biodiversity ISSN: 2179- 4804
DOI: https://doi.org/10.20873/jbb.uft.cemaf.v8n2.bila
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INTRODUCTION
Messassa is the trade name given to the Mozam-
bican wood species Brachystegia spiciformis Benth (basic density 0.670 g/cm3) and Julbernardia glo-
biflora (Benth) Troupin. (basic density 0.680 g/cm3) (Bila et al., in press) both belonging to the
Fabaceae family. The species has the greatest com- mercial volume, which is estimated at around 360 million cubic meters, equivalent to 46% of the total existing commercial volume in the country (Magalhães, 2017). However, the messassa wood are currently used for low value applications such in civil construction as props and charcoal produc- tion in rural areas. There are several reasons that may explain this trend, such as lack of tradition in their use, technological knowledge and adequate industrial infrastructure, among others (DNTF, 2017). However, the Mozambican wood and furni- ture industry, in addition to using traditional wood species, has been exploring possibilities for the use of new and lesser-used ones, including activities to improve the quality of traded products for better fit into the increasingly competitive market.
The varnishes can add value to low valued woods or lesser used in the market giving them a desired aesthetic appearance. On the other hand, Bulian and Graystone (2009) state that with finish- ing application improves the aesthetics of a ma- chined wood, provides a clean surface and protects it over time. However, the final quality of the finish depends on several elements including the applica- tion of the coating method, substrate characteristics such as porosity, chemical structure and interaction between the coating and the substrate (Ozdemir; Hiziroglu, 2007). In addition, Moura and Hernan- dez (2006) point out that sanding is the most com- monly used operation for surface preparation be- fore finishing, since it’s function is to leveling the natural differences of wood surface, providing a ho- mogeneous cover. Products commonly used in wood finishing are varnishes (natural or synthetic), sealers and paints. However, it is noteworthy that among the various possibilities, the most suitable type of finish for wood depends on the intended use of the final product and/or consumer preference
(Watai, 1995). The evaluation of the finishing qual- ity applied to the wood surface is made by tests of adhesion resistance (pull-off), impact, abrasiveness and gloss (Guedes, 2011; Silva et al., 2010; Désor et al., 1999).
Wood color is also an important component of its appearance and crucial in the consumer's final decision as well as being one of the physical param- eters of quality assessment (Jankowskya and Oza- kiewicz, 2014; Barcik et al., 2015; Dzurenda, 2018). This property should be incorporated into the planning, aiming at the technological character- ization of wood (Mori et al., 2005). Additionally, among the organoleptic properties, color is the characteristic that presents the highest subjectivity, as it is directly related to the psychophysical sens i- tivity of the observer (Zenid and Ceccantini, 2007). Therefore, depending on the specifications of the finishing product, natural wood color variation may occur, influencing the preference of the furniture or frames by the consumer.
Considering that no surface finishing studies were found in messassas wood, this work aims to generate information regarding the behavior of these species when submitted to surface finishing products, such as varnishes seeking to enhance and promote them in the furniture and frame industry.
MATERIAL E MÉTODOS
The wood species used in this study comes from the Miombo forest, located in Zambezia province, central Mozambique at coordinates WSG84 17° 18'
22” S, 37° 38' 26” W. From randomly selected heartwood pieces previously used in machining tests (planing, shaping, milling, tearing and boring) and with a moisture content of 12 ± 2%, 18 samples free of defects such as knots, rot and cracks were produced for finishing application. The samples had dimensions of 230 mm in length, 10 mm in thickness and width ranging from 100 to 120 mm. Three types of varnishes were used for finishing (Table 1) and acquired in the local market. Excep- tionally for PU varnish, the manufacturer recom- mends first applying the bottom (sealer) before the varnish and the brushing in a crosswise direction.
Table 1 - Specifications of used coating product by the manufacturer
Propertie/coating Water based Copal Polyurethane Sealer
Manufacturer Sayerlack BASF/Suvenil Sayerlack Sayerlack
Density g.cm-3 1.03 ± 0.02 0.86 – 0.90 1.00 ±0.02 1.02 ± 0. 02
Solid content (%) 32.0 ± 2 33 - 37 43.86 ± 2 60.8 ± 2
Viscosity (Cp.s) 20 ± 2 s CF4 - 28.2 s CF4 60 ± 5s CF6
Where: CF – ford cup; Cp - Centipoise
© 2020 Journal of Biotechnology and Biodiversity ISSN: 2179- 4804
DOI: https://doi.org/10.20873/jbb.uft.cemaf.v8n2.bila
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Surface Preparation and Finishing Application
The preparation and application of the varnishes complied with the manufacturer's requirements. It is noteworthy that prior to application of the finish- ing product, the lumber for sample production were subjected to sequential sanding (in the grain direc- tion) with 100, 150 and 180 grit size sandpapers in industrial production line. For this purpose a band
sander was used at a feed speed of 8 m.min-1 and surface pressure 0.03 MPa. Three passes were per- formed at a cutting thickness of 0.5 mm each.
The spread rate in all finishing products was 180 g.m-2 estimated by an analytical scale. Two coats were applied to each varnish by a non-sanding foam roller between the coats. After application of the varnish, the samples remained at room temperature (20 ± 2) oC and relative humidity of (65 ± 5) % fo r a period of 7 days for total cure of the varnish.
Performance of tests
After curing the varnish, the gloss, adhesion, abrasiveness, impact deformation and overall color variation tests were performed. The brightness test consisted of reading the values of light intensity
range provided by the Glossmeter device at 60o an- gle. Ten (10) readings per sample were taken for each varnish and specie parallel to the grain, a pro- cedure suggested by ABNT 14535 (2008).
The pull-off test (adhesion) was performed ac- cording to ASTM D 4541 - 17 (2017) method E. Iron cylinder of 20 mm in diameter were glued to the coated sample by transparent two- component epoxy adhesive and cure time of 48 hours. After curing of adhesive, a circular groove was made around the cylinder to prevent the spread of faults outside the test area. The pull-off test involves withdrawal of cylinders upwards vertically in the opposite direction from the position of the sample
at a rate of 0.20 MPa.s-1. Three measurements were taken per sample for each varnish. This method in- volves measuring of the maximum adhesion strength of a coating that leads to the detachement of cylinder from the coated surface. The adhesion strength of each sample reached at rupture was rec- orded on the equipment display in MPa.
The abrasiveness test was performed using a Texcontrol TC 110 abrasimeter. The equipment consisted of CS-17 wheels, 1000 g adjustment load and 60 rpm (revolutions per minute). The wear rate was determined by the ratio of mass loss difference (milligrams) before and after abrasion of the fin-
ished surface to the number of abrasion cycles per- formed until the wood substrate was reached, i.e., until visually verified along the entire circle worn by the wheels the complete removal of the coating. Samples were weighed on an analytical scale of 0.0001 g precision. The samples (three per varnish and specie) were dimensioned at 100 x 100 mm in each varnish based on ABNT 14535 (2008) stand- ard.
The impact strength test of the film was carried out by dropping a 19 mm diameter steel ball at a height of 2 meters over the sample. Then, the dam- age caused to the finishing film was evaluated in a 10x magnifying glass according to the grading scale contained in NBR 14535 (2008), which ranges from 5 to 1. The degree of impact with value 5 (five) corresponds to the absence of impact, that is, no cracking or cracking on the coated wood sur- face. In turn, the impact degree with a value of 1 (one) is assigned when more than 25% of the fin- ishing film is removed from the impact area. Six (6) samples per varnish and specie were used with three repetitions for each sample. This test simu- lates the impact of small objects falling on the fin- ishing film.
Color variation analysis were performed using the CIELAB method 1976 (Commission Interna- tional de L'Eclairage) before and after application of the coating with the aid of the 10° observation angle color spectrophotometer and standard illumi- nant D65. The color measurement was made at three
(different) points of the coated surface of each sam- ple. Eighteen (18) measurements were performed by varnish. The colorimetric parameters obtained were L* (luminosity), a* (red-green axis coordi- nate) and b* (blue-yellow axis coordinate). The color variation (ΔE) due the coating was deter- mined by the following e quation:
= √( ∗)2 +( ∗)2 +( ∗) 2
Where: ΔE - is the total color variation on the sam- ple surface; ΔL*, Δa* and Δb* - average variation of the L*, a* and b* coordinates on the sample sur- face before and after finishing application (exam-
ple: ΔL* = L* uncoated - L* coated ).
The classification of the overall color variation (∆E) on the coated surface was based on assess- ment guidelines by Cividini et al. (2007) (Table 2).
© 2020 Journal of Biotechnology and Biodiversity ISSN: 2179- 4804
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Table 2 - The criteria to assess the overall color var- iation (∆E) on Brachystegia spiciformis and Jul- bernardia globiflora wood
0.2 < ∆E Invisible change
0.2 < ∆E < 2 Small changes
2 < ∆E < 3 Changes visible by high quality filter 3 < ∆E < 6 Changes visible by medium quality
filter
6 < ∆E< 12 Distinct color changes
RESULTS AND DISCUSSION
Gloss
The average gloss obtained from the coated sam- ples of B. spiciformis and J. globiflora were mostly classified as semi-gloss. Exceptionally samples fin- ished with copal varnish for species B. spiciformis this property was classified as bright, witnessed by
∆E > 12
Date analysis
A different color
the highest average value (Table 3). This exception may have been caused by the intrinsic characteristic of the wood in presenting light color associated
The data were submitted to Bartlett test to verify the homogeneity of the variances. Then, an analysis of variance (ANOVA) and determination of aver- age values of each property were performed. The Tukey test were used to compare the average values of finishing products and t-student test for compar- isons between the species both at 5% significance level in order to verify the best performance of the applied finishing product and the species.
with the inherent gloss characteristics of the copal product when compared to water based and polyu- rethane varnishes. In addition, according to the manufacturer water-based and polyurethane var- nishes are satin-like with semi-glossy characteris- tics while the copal is glossy which justifies the (statistically significant) difference in gloss be- tween the finishing products as well as between species.
Table 3 - Average gloss of the varnishes applied to the wood of Brachystegia spiciformis and Julbernardia globiflora
Species
Water based
Varnish gloss (GU) Copal
Polyurethane
B. spiciformis
34.92 Ca (4.5)
73.85 Aa (2.7)
45.18 Bb (6.7)
J. globiflora
32.27 Cb (4.3)
66.68 Ab (5.0)
52.85 Ba (4.8)
Means followed by the same lowercase letter in the column (t-student test) and uppercase in the row (Tukey test) do not differ statisti- cally at 5% significance level; Value in parentheses is the coefficient of variation in percentage; GU – gloss unit .
The average gloss for both species had a decreas- ing trend in the order copal coating, followed by polyurethane and lastly water based (Table 3). Namikata (2016) also reported similar results to this observed trend in the present study in the eval- uation of the brightness in Cryptomeria japo nica wood. Differently, studies comparing the gloss of the water based with synthetic and nitrocellulose coating (Çakicier et al., 2011) and polyurethane (Budakçi and Sonmez, 2010) found a higher gloss value than that of water based, caused by the for- mulation of the varnishes used. It is noted that the varnishes are formulated in order to obtain the de- sired gloss for the consumer's preference, and for each type of varnish (whether water based, polyu- rethane or copal), a variant of matte gloss can be found, satin, semi-gloss or even glossy.
When comparing the performance of each spe- cies (Table 3), it is noticeable that B. spiciformis
showed greater brightness in the wood when apply- ing water based and copal varnish, while the appli- cation of polyurethane varnish was the one that pro- vided higher brightness in relation to J. globiflora species.
Adhesion strength
The results of the finish adherence test showed a range of variation from 2.60 to 5.97 MPa between varnishes as well as between species (Table 4). In turn, it is also observed that both in the species B. spiciformis and J. globiflora, copal and polyure- thane varnishes had average values statistically equal and superior to water-based varnish. This re- sult is associated with the specifications of each fin- ishing product used, in which the water based var- nish compared to the others, had a lower solids con- tent and viscosity as shown in Table 1.
© 2020 Journal of Biotechnology and Biodiversity ISSN: 2179- 4804
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Tabela 4 - Average of adhesion strength in adhesion tests of the surface finish on wood of Brachystegia spic- iformis and Julbernardia globiflora, under three types of varnishes.
Varnish
Minimum
Adhesion strength (MPa) Average
Maximum
CV (%)
B. spiciformis Water based
2.60
2.83 b
3.47
13.10
Copal 3.68 4.16 a 4.58 7.32
Polyurethane 3.46 3.86 a 4.33 9.80
J. globiflora Water based
3.90
3.41 b
4.50
4.63
Copal 3.47 4.17 a 5.72 19.61
Polyurethane 3.11 4.16 a 5.97 9.17
Averages followed by the same letter between varnishes within the specie do not differ statistically from each other by Tukey test at 5% of significance level; CV - coefficient of variation.
In a similar study, Souza et al. (2011) reported in solid wood a better adhesion of solvent based coat- ing compared to water based, having also stated that it was the result of the type of varnish and the specificity of it’s formulations. In contrast, Hazir and Koc (2019) reported for MDFpanels better per- formance of water based varnish compared to sol- vent based with adhesion strength values ranging from 2.98 to 3.47 MPa and 2.06 to 2 , 31 MPa, re- spectively. It is important to emphasize that the dif- ference in results between different studies might be due to the intrinsic characteristics of the wood and/or derived products evaluated, the incompati- bility of the wood with the product or the applica- tion or final assessment methodology, among oth- ers.
Comparison of species performance under coa t- ing products shows statistically equal adhesion strength only when finished with the copal (Figure 1).
Where: Averages followed by the same letter between species within the varnish do not differ statistically from each other by t-student test at 5% of significance level.
Figure 1 - Adhesion strength variation of the coat- ings on Brachystegia spiciformis (Bs) and Julber- nardia globiflora (Js) wood.
In turn, (based on Figure 1) it is observed that the species J. globiflora had higher adhesion strength compared to the species B. spiciformis when fin- ished with water-based and polyurethane varnishes. This result may probably be due to the anatomy of the wood species as a whole but also to the high content of extractives (in particular) of the species B. spiciformis (19,63 %) in relation to J. globiflora (16,66 %) as reported by Bila et al. (2019, in press). Ghofrani et al. (2016) state that the effect of the ex- tractives content in the case of the application of finishing products, is the reduction of the compati- bility and the adhesion strength of the varnishes. In this respect, considering the relevance of the film adhesion test in the evaluation of the pe rfor- mance of finishing products, studies that also eval- uate wood samples of the species B. spiciformis and
J. globiflora coated with the three types of var- nishes and exposed to weather conditions in order to provide more comprehensive information about
their adhesion strengths are demanded. Abrasiveness
Results of the abrasion strength test are pre- sented in Table 5. The wear rate ranged from 0.1432 to 0.3635 mg / 1000 cycles and was statisti- cally equal across species for all varnishes. Com- paring the varnishes in each species, there is a ten- dency of higher wear rate in the water-based, fol- lowed by the polyurethane and lastly the copal. However, it is found that the abrasion strength oc- curred in the opposite direction being higher in the polyurethane, followed by the copal and water based coating, witnessed by the larger number of abrasion cycles required to remove the film from
the coated surface.
The greatest resistance to polyurethane varnish
may have been due to its higher thickness of the finishing film layer. Bulian and Graystone (2009)
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point out that polyurethane varnish has some ad- vantages such as flexibility, abrasion resistance, chemical resistance, good adhesion and fast cure when compared to water based, nitrocellulosic and copal varnishes, and for this reason they are most used in the furniture industry.
There was no statistically significant difference
in the wear rate between water-based varnish and polyurethane in both species (Table 5). It is note- worthy that the abrasion resistance test assesses the gradual wear of the surface of the finish by abrasive action that can be caused by shoes, transport and movement of materials on a floor, sand, dirt, among others (Moreschi, 2005; Silva et al., 2010).
Table 5 - Abrasion strength of the varnishes applied to Brachystegia spiciformis and Julbernardia globiflora wood.
Varnish
B. spiciformis
Nr. of Cycles WR (mg/1000 cycles)
Nr. of Cy- cles
J. globiflora
WR (mg/1000 cycles)
Water based
169 b (13.25)
0.3635 Aa (19.9)
265 b (17.2)
0.3535 Aa (19.3)
Copal
195 ab (5.63)
0.2159 Ab (45.2)
435 a (9.6)
0.1432 Ab (8.2)
Polyurethane
221 a (14.7)
0.3538 Aa (17.4)
443 a (18.0)
0.2733 Aa (24.99)
Means followed by the same lowercase letter in the column (Tukey test) and uppercase in the row (t-student test) do not differ statisti- cally at 5% of significance level; WR - wear rate; Value in parentheses is the coefficient of variation, Nr. - Number.
Impact deformation resistance
The results of the impact test demonstrate that there was no significant difference between water
based and copal varnish as well as between species in all varnishes. In turn, the polyurethane varnish had lower average impact values compared to the other varnishes in both species (Table 6).
Table 6 - Average impact strength of varnishes on wood of Brachystegia spiciformis and Julbernardia globi- flora
Specie
Water based
Varnish Copal
Polyurethane
B. spiciformis
5.0 Aa (0.0)
5.0 Aa (0.0)
4.1 Ba (8.4)
J. globiflora
4.9 Aa (2.3)
5.0 Aa (0.0)
3.8 Ba (4.6)
Means followed by the same lowercase letter in the column (t-Student test) and uppercase in the row (Tukey test) do not differ statisti- cally at 5% of significance level
According to ABNT 14535 (2008) standard, the impact grade values is inversely proportional to the presence of cracks in the area impacted by the sphere. The polyurethane were attributed the lower average grade (4) in both species (Table 6) com- pared to the other finishing products varnish, which means that, this varnish presented cracks around the impact area. This result is owing to the thick film layer that the polyurethane varnish presents due to its higher solids content, associated with the appli- cation of the sealing bottom, as illustrated in Table 1. Namikata (2016) also reported less resistance to
impact on the polyurethane varnish in relation to ni- trocellulosic varnishes, water-based and copal on the wood of Cryptomeria japonica. In turn, Erdinler (2019) analyzing the performance of two MDF panel finishing products obtained greater re- sistance to the impact on polyurethane varnish (4 and 5) when compared to cellulosic varnish (grades 2 and 3). It is noteworthy that, the variation in the results among different studies may occur depend- ing on the composition of the finishing product, substrate and even the application method.
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Color variation
The colorimetry parameters of uncoated and coated wood surface of B. spiciformis and J. globi- flora showed a wide range of variation of the basic parameters L*, a*, b* and ∆E (Table 7). It is ob- served that with the application of the varnishes on B. spiciformis wood the brightness value (L*) was decreasing significantly compared to the uncoated wood and therefore the varnishes caused a darken- ing in the natural color of the wood whose ranged from 39.64 to 46.14. Copal varnish resulted in
greatest darkening of the wood. There is no stati- cally significant difference between the effect of water based and polyurethane varnish in the bright- ness. The luminosity value L* (53.92) of uncoated wood of the species B. spiciformis is within the light range of thirty tropical wood species repo rted by Silva et al. (2017). It is noticeable that the value of the parameter L* has a direct proportionality with the clarity of a particular material and/or sub- strate to be evaluated. According to Camargos and Gonçalez (2001), wood is considered dark if the L* value is less than or equal to 56.
Table 7 - Evaluation of overall color variation for coated and uncoated wood of Brachystegia spiciformis and Julbernardia globiflora .
Specie
Varnishes
L *
Color coordenates a *
b *
Total color variation ΔE Evaluation
Brachystegia spic- iformis
Uncoated Water based
Copal Polyurethane
53.92 a 43.28 ab 39.64 c
46.14 ab
12.01 bc 17.16 a 17.91 a
15.29 ab
20.46 c 25.89 ab 27.81 a
27.57 a
-
13.0 17.1
11.0
-
Different color Different color Distinct color changes
Julbernardia globiflora
Uncoated Water based
Copal Polyurethane
38.38 c 44.61 ab 40.92 ab 37.45 c
10.06 d 11.37 c 11.49 c 11.66 c
19.01 d 20.47 c 21.90 bc 22.01 bc
-
5.7
3.8
3.1
-
Changes visible by medium quality filter
Means followed by the same letter within the same column per specie do not differ statistically by Tukey test at 5% of significance level.
The parameters a* and b* increased significantly with the application of the varnishes meaning thereby increasing the influence of the red- green and blue-yellow axis respectively. The increase in the red pigmentation (a*) may also explain the wood darkening after applying the varnishes. In dif- ferent circumstances, Paula et al. (2020) reported that the combination between the high values of L* coordinate and the low values of coordinate a* may still be indicative of the low percentage of extrac- tives present in the wood. However, for the species under study whose extractive contents are high, typical of tropical wood, perhaps a more in- depth chemical analysis could help to understand the fact. For the species J. globiflora, the luminance value L* had a statically significant increase only in the water-based (44.61) and copal (40.92) varnishes lightening the wood to a certain extent in relation to its natural color. The application of polyurethane coating caused a statistically non- significant change in surface brightness (Table 6). The param- eters a* and b* show similar behavior and are in- creasing with the application of the varnishes as ob- served in B. spiciformis wood.
The overall color variation (ΔE) parameter
showed that B. spiciformis wood had a considerable color change. In turn, for J. globiflora wood the color variation is visible with the medium quality filter (Table 6) which assumes that the natural color of this wood has had a subtle changed with the ap- plication of the varnishes. Also based on Table 6, it is noted that J. globiflora has a dark natural color (L* = 38.38) compared to B. spiciformis (L* = 53.92).
Figure 2 shows the overall color variation (ΔE) for the three types of coating products. The total color variation of wood after coating is character- ized by darkening for B. spiciformis and a slight lightening of wood for J. globiflora. This color shade difference may have been influenced by the intrinsic anatomy of the species as well as the char- acteristics of the finish products in interaction with wood chemical components (Yamamoto et a l. 2007).
From figure 2, the polyurethane coating caused the lowest color variation of the wood for both spe- cie. The water based coating had an intermediate color variation value in species B. spiciformis. For J. globiflora species the intermediate color v aria- tion was verified in the copal coating. It may be
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noted that, the effects of these finishing products on the quality of the wood of the messassas will be in- ferred in the end by the consumer since it is based on the color that it is classified aesthetically as ac- ceptable or not.
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Bila NF, Trianoski R, Egas AF, Iwakiri S, Mussana AF, Ro- cha MP. Bonding quality of Brachystegia spiciformis and Jubernardia globiflora, lesser-used wood species from Mozambique. In press.
Budakçi M, Sonmez A. Determining adhesion strength of some wood varnishes on different wood surfaces. Journal
0
Water base Bs Jg
3,82 Copal Varnish type
3,12 Polyurethane
of the Faculty of Engineering and Architecture of Gazi University, v.25, n.1, p.111-118, 2010.
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Figure 2 - Overall color variation (ΔE) of coated surface of B. spiciformis (Bs) and J. globiflora (Jg) wood.
CONCLUSIONS
From the results obtained, it is concluded that:
• The gloss of the surface finished with the water based and polyurethane varnish used in the wood of B. spiciformis and J. globiflora were classified as semi-gloss. The copal varnish resulted in bright gloss;
• The impact resistance was equal for water based and copal varnish as well as between species. Polyurethane varnish was the lesser resistant to impact;
• Copal and polyurethane varnishes presented equal adhesion strength in both species. The water based varnish had the lowest adhesion;
• Polyurethane varnish showed the highest wear resistance;
• The used coating products induce a considerable color variation mainly for B. spiciformis in relation to J. globiflora ;
• The performance of the three varnishes was satisfactory and can be used in the species studied to add value to the wood as a finish on furniture and solid wood frames.
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