Vietnamese lacquers collected every month from June to March of next year were characterized. Composition analysis showed that lacquer collected in rainy season contained much water, while those collected in dry season contained more lipid component. Although hardness of lacquer films is not very hard, lacquers tapped in all seasons can reach hard dry (HD) within 48 hours. Refining lacquer can accelerate drying time but the water concentration should be maintained around 10 wt% for laccase activity.
Lacquer is sap collected from lacquer tree, which belongs to Anacardiaceae and
In South Asia, especially in Vietnam, lacquer is collected from
In the lacquer market, Vietnamese lacquer has relatively poor reputation because of its slow drying and soft film. It has been said that Vietnamese lacquer collected throughout the year is combined in one barrel. This practice may be one reason it has a reputation for low quality in international lacquer market. In order to better understand the real quality and characteristics of Vietnamese lacquer, Vietnamese lacquer saps collected every month from June of 2012 to March of 2013 were analyzed. The composition, drying time, laccase activity, and infrared absorption of lacquer film collected during those months were determined; the characteristics of Vietnamese lacquer are discussed. In addition, development of fast drying lacquer was also carried out by refining (
Lacquer sap was tapped from
Lacquer viscosity was determined at room temperature using a Brookfield Engineering Laboratories programmable DV-II viscometer with a CPE-51 spindle. The rotation speed was 5–20 rpm, and the measurement volume was 0.5 mL.
Drying time was carried out using an automatic drying time recorder (Tai Yu Equipment, Osaka, Japan), and the thickness of the tested lacquer films on the glass plate was 76
The hardness and color change of lacquer film were measured by pencil hardness tester (Yoshimituseiki, Japan) and Color-Guide instrument (BYK-Gardner, Germany), respectively. ATR-IR spectra of lacquer films were measured using JASCO FT-IR410 spectrophotometer.
Laccase activity was determined using 0.216 mmol/L syringaldazine/methanol as substrate in 0.1 mmol/L sodium phosphate buffer (pH 6.5) and measured by monitoring the increase in UV absorbance at 525 nm at 30°C. One unit of enzyme was equal to an increase of 0.001 absorbance unit per min per mg of acetone powder (AP).
The
Molecular weight distribution and average molecular weight were determined at 40°C by gel permeation chromatography (GPC, TSK-gel columns
After measuring the viscosities, lacquer samples were separated with acetone to obtain lipid component and acetone powder (AP). The separation results and viscosities are summarized in Table
Compositions of season Vietnamese lacquer.
Samples | Area | Month | Lipid (%) | AP (%) | Water (%) | Viscosity (mPas) |
---|---|---|---|---|---|---|
T6 | Tho Van | 6 | 43.22 | 21.38 | 35.39 | 4447 |
T7 | 7 | 43.85 | 21.23 | 34.92 | 3113 | |
T8 | 8 | 62.40 | 14.17 | 23.43 | 549 | |
T9 | 9 | 55.56 | 15.74 | 28.70 | 1088 | |
T10 | 10 | 61.32 | 13.11 | 25.57 | 726 | |
T11 | 11 | 62.17 | 13.15 | 24.68 | 778 | |
T12 | 12 | 59.35 | 13.91 | 26.74 | 713 | |
T1 | 1 | 62.26 | 13.58 | 24.16 | 818 | |
T2 | 2 | 29.43 | 24.71 | 45.86 | 8865 | |
T3 | 3 | 29.84 | 24.22 | 45.94 | 7525 | |
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D6 | Di Nau | 6 | 70.42 | 11.12 | 18.47 | 1012 |
D7 | 7 | 39.23 | 23.43 | 37.34 | 3659 | |
D8 | 8 | 37.42 | 25.20 | 37.38 | 7387 | |
D9 | 9 | 46.49 | 20.21 | 33.30 | 1779 | |
D10 | 10 | 61.34 | 13.84 | 24.82 | 811 | |
D11 | 11 | 66.13 | 13.85 | 20.02 | 713 | |
D12 | 12 | 38.87 | 24.49 | 36.64 | 2195 | |
D1 | 1 | 59.03 | 16.87 | 24.10 | 726 | |
D2 | 2 | 49.73 | 20.30 | 29.97 | 1300 | |
D3 | 3 | 44.52 | 21.37 | 34.10 | 1884 |
The lacquers collected from June to September (T6–T9, D6–D9) had higher water concentration compared with those collected from October to January (T10–T1, D10–D1). May to October is rainy and November to March is dry season in Vietnam. Obviously, the water concentration in lacquer is related to climate, and this phenomenon affected lacquer collected from
Ratio of water to AP.
Viscosity of lacquer sap.
The drying time and hardness of lacquer films are summarized in Table
Compositions of season Vietnamese lacquer.
Samples | Drying time1 (h) | Hardness2 for drying days | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
DF | TF | HD | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 14 | 21 | |
T6 | 4.3 | 5.4 | 8.0 | <6B | <6B | <6B | <6B | <6B | <6B | <6B | <6B | 4B |
T7 | 3.8 | 4.8 | 8.8 | <6B | <6B | <6B | <6B | <6B | <6B | <6B | <6B | 5B |
T8 | 2.6 | 3.2 | 6.0 | <6B | <6B | <6B | <6B | <6B | <6B | <6B | <6B | 4B |
T9 | 6.5 | 7.5 | 15.0 | <6B | <6B | <6B | <6B | <6B | <6B | <6B | 5B | 5B |
T10 | 2.8 | 3.5 | 6.5 | <6B | <6B | 5B | 5B | 5B | 5B | 5B | 3B | 3B |
T11 | 4.0 | 5.0 | 8.5 | <6B | <6B | <6B | 6B | 5B | 5B | 5B | 3B | 3B |
T12 | 4.0 | 4.7 | 8.5 | <6B | <6B | <6B | 6B | 5B | 5B | 5B | 3B | 3B |
T1 | 7.8 | 8.5 | 16.0 | <6B | <6B | <6B | <6B | <6B | <6B | <6B | 4B | 4B |
T2 | 2.8 | 3.5 | 6.0 | <6B | <6B | <6B | <6B | <6B | <6B | 4B | 4B | 4B |
T3 | 2.0 | 3.0 | 4.5 | <6B | <6B | <6B | <6B | <6B | <6B | 4B | 4B | 3B |
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D6 | 14.0 | 15.5 | <48 | — | <6B | <6B | <6B | <6B | <6B | <6B | <6B | <6B |
D7 | 6.0 | 8.2 | <48 | — | <6B | <6B | <6B | <6B | <6B | <6B | <6B | 4B |
D8 | 3.8 | 5.5 | <48 | — | <6B | <6B | <6B | <6B | <6B | <6B | <6B | <6B |
D9 | 2.7 | 3.2 | 4.5 | <6B | <6B | 6B | 5B | 5B | 5B | 5B | 3B | 3B |
D10 | 2.5 | 3.0 | 5.0 | <6B | <6B | <6B | 5B | 5B | 5B | 5B | 4B | 4B |
D11 | 6.7 | 7.0 | 15.0 | <6B | <6B | <6B | 5B | 5B | 5B | 5B | 4B | 4B |
D12 | 3.0 | 4.0 | 5.5 | <6B | <6B | <6B | <6B | <6B | <6B | <6B | 4B | 4B |
D1 | 3.8 | 4.3 | 8.0 | <6B | <6B | <6B | <6B | <6B | <6B | <6B | 4B | 4B |
D2 | 1.5 | 2.0 | 3.5 | <6B | <6B | <6B | <6B | <6B | <6B | <6B | 4B | 3B |
D3 | 1.5 | 2.0 | 3.0 | <6B | <6B | <6B | <6B | <6B | <6B | 4B | 4B | 3B |
1Drying condition: 25°C, 80%RH, and wet thickness 76
2Based on pencil hardness test method.
Lacquer laccase activities.
Samples | Activities (unit/mg AP) | Samples | Activities (unit/mg AP) |
---|---|---|---|
T6 | 555 | D6 | 693 |
T7 | 556 | D7 | 416 |
T8 | 750 | D8 | 538 |
T9 | 552 | D9 | 455 |
T10 | 669 | D10 | 710 |
T11 | 645 | D11 | 528 |
T12 | 697 | D12 | 329 |
T1 | 614 | D1 | 746 |
T2 | 570 | D2 | 534 |
T3 | 617 | D3 | 447 |
The laccase activity contained in AP was measured using syringaldazine as substrate, and the results are summarized in Table
Because components are rather different depending on the collection season and lacquer dries by evaporation of water, we hypothesized that dry lacquer films have different properties. In order to reveal the reason, we analyzed the contact angle of drying lacquer films, T3, T7, and T11, and the results are summarized in Table
Composition percentage, lipid/AP, and contact angle of lacquer films.
Samples | Composition percentage (wt%) | Lipid/AP | Contact angle (degree) | ||
---|---|---|---|---|---|
Lipid | AP | Water | |||
T3 | 29.8 | 24.2 | 45.9 | 1.23 | 67.0 |
T7 | 43.8 | 21.2 | 34.9 | 2.07 | 72.5 |
T11 | 62.2 | 13.2 | 24.7 | 4.73 | 77.0 |
ATR-IR spectra of lacquer film.
From the above analyses, it can be concluded that although selecting the best season to collect high quality Vietnamese lacquer sap is difficult, sap collected in dry season (from September to December) has a higher percentage of lipid that gives the film high hardness, and the sap collected in other seasons has a higher percentage of water and AP that makes the film more hydrophilic.
In order to improve the performance of Vietnamese lacquer, we performed differential
Data results of kneaded lacquers.
Kneading speed (rpm) | Kneading time (min) | Water (%) | Viscosities (mPas) | MW distribution (%)1 | Drying time2 (h) | ||||
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Monomer | Oligomer | Polymer | DF | TF | HD | ||||
— | — | 35.4 | 1203 | 86.8 | 13.0 | 0.2 | 7.8 | 8.1 | 12.5 |
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60 | 15 | 26.4 | 1400 | 73.8 | 25.6 | 0.6 | 12.2 | 13.8 | 31.5 |
60 | 30 | 20.4 | 2442 | 56.5 | 41.8 | 1.7 | 6.6 | 7.2 | 11.8 |
60 | 45 | 13.6 | 2694 | 50.1 | 48.1 | 1.8 | 2.8 | 3.3 | 5.5 |
60 | 60 | 12.5 | 4639 | 44.8 | 52.8 | 2.4 | 2.2 | 2.7 | 5.2 |
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120 | 15 | 27.1 | 3192 | 66.9 | 32.6 | 0.5 | 15.8 | 19.0 | 96 |
120 | 30 | 16.6 | 2747 | 54.1 | 45.0 | 1.0 | 3.8 | 4.5 | 7.5 |
120 | 45 | 8.1 | 3558 | 51.3 | 45.3 | 1.6 | 3.0 | 3.4 | 4.5 |
120 | 60 | 5.2 | 3625 | 50.2 | 47.4 | 2.4 | 3.4 | 3.8 | 6.0 |
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180 | 15 | 21.5 | 1936 | 67.4 | 32.0 | 0.6 | 16.2 | 18.5 | 72 |
180 | 30 | 9.0 | 2250 | 56.1 | 42.7 | 1.1 | 1.7 | 2.8 | 6.0 |
180 | 45 | 5.2 | 2389 | 55.7 | 42.7 | 1.6 | 3.3 | 3.6 | 7.0 |
180 | 60 | 4.3 | 3322 | 52.3 | 45.8 | 1.9 | 3.1 | 3.7 | 6.0 |
1Determined by GPC. Monomer: MW = 320; oligomer: 10000 > MW > 600; polymer: MW > 10000.
2Drying condition: 25°C, 80%RH, and wet thickness 76
Gloss,
Lightness, gloss, and coloration of kneaded lacquer films1.
Kneading speed (rpm) | Kneading time (min) | Lightness and coloration2 | Gloss | ||
---|---|---|---|---|---|
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— | — | 22.66 | 33.27 | 22.78 | 8.9 |
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60 | 15 | 31.42 | 40.09 | 49.75 | 72.8 |
60 | 30 | 20.57 | 38.84 | 33.33 | 76.6 |
60 | 45 | 9.40 | 27.52 | 12.50 | 85.8 |
60 | 60 | 6.08 | 25.27 | 9.05 | 98.2 |
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120 | 15 | 35.87 | 37.43 | 58.74 | 98.3 |
120 | 30 | 11.78 | 30.72 | 16.53 | 92.2 |
120 | 45 | 6.22 | 25.32 | 9.26 | 96.1 |
120 | 60 | 5.03 | 21.42 | 7.18 | 96.6 |
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180 | 15 | 40.24 | 37.22 | 65.49 | 99.0 |
180 | 30 | 6.32 | 25.99 | 9.57 | 96.7 |
180 | 45 | 5.05 | 21.21 | 7.16 | 97.0 |
180 | 60 | 6.47 | 21.91 | 7.23 | 95.2 |
1Drying condition: 25°C, 80%RH, and wet thickness 76
2
In this study, we found that if the water concentration in Vietnamese lacquer is lower than 10 wt%, which was kneaded at 120 rpm for 45 and 60 min and 180 rpm for 30, 45, and 60 min (Table
Data results of repeated
Water addition | Kneading time (min) | Water (%) | Viscosities (Pas) | MW distribution (%)1 | Drying time2 (h) | ||||
---|---|---|---|---|---|---|---|---|---|
Monomer | Oligomer | Polymer | DF | TF | HD | ||||
None | 0 | 33.6 | 1.2 | 86.8 | 13.0 | 0.2 | 7.8 | 8.1 | 12.5 |
60 | 5.2 | 6.6 | 50.2 | 47.5 | 2.3 | 3.0 | 3.6 | 8.3 | |
90 | 4.3 | 9.0 | 45.9 | 51.2 | 2.8 | 4.4 | 7.4 | 8.6 | |
120 | 4.1 | 10.8 | 45.3 | 51.7 | 3.0 | 4.4 | 5.3 | 8.6 | |
180 | 4.4 | 10.6 | 45.0 | 51.6 | 3.3 | ||||
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5%/30 min | 60 | 7.1 | 6.1 | 49.3 | 48.0 | 2.7 | 2.9 | 3.3 | 8.3 |
90 | 4.5 | 7.8 | 44.6 | 52.4 | 3.1 | 3.4 | 3.8 | 5.3 | |
120 | 5.1 | 8.4 | 43.5 | 53.2 | 3.3 | 3.5 | 3.9 | 7.7 | |
180 | 3.7 | 12.6 | 39.5 | 56.3 | 4.1 | ||||
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10%/30 min | 60 | 7.8 | 4.2 | 56.1 | 41.2 | 2.7 | 3.4 | 4.2 | 8.6 |
90 | 5.9 | 6.3 | 47.1 | 49.3 | 3.6 | 3.8 | 4.3 | 8.3 | |
120 | 4.1 | 10.9 | 40.6 | 54.6 | 4.7 | 3.3 | 3.6 | 7.5 | |
180 | 3.8 | 22.4 | 35.9 | 58.2 | 5.9 | ||||
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20%/30 min | 60 | 7.3 | 5.8 | 48.2 | 47.5 | 4.2 | 3.2 | 4.5 | 8.3 |
90 | 5.5 | 11.2 | 39.6 | 54.8 | 5.6 | 5.5 | 6.4 | 9.0 | |
120 | 9.5 | 23.4 | 33.1 | 58.2 | 8.7 | 2.6 | 3.4 | 6.0 | |
150 | 12.3 | 43.5 | 30.5 | 59.4 | 10.1 |
1Determined by GPC. Monomer: MW = 320; oligomer: 10000 > MW > 600; polymer: MW > 10000.
2Drying condition: 25°C, 80%RH, and wet thickness 76
Lacquer saps collected from
The authors declare that there is no conflict of interests regarding the publication of this paper.
The authors thank United Nations Industrial Development Organization (UNIDO) of Vietnam for