Raw Lacquer Research Articles

Preparation of Tung Oil-Modified Raw Lacquer Films and Application for Mechanical Carving Technique

Raw lacquer, known for its superior performance as a natural liquid coating, boasts excellent physical and mechanical properties as well as durability, making it widely used in manufacturing. However, the high hardness of the lacquer film upon complete curing poses challenges for carving and mechanical engraving. Therefore, it is necessary to study the curing process of lacquer films to obtain films suitable for carving or mechanical engraving. This study involves the preparation of raw lacquer with varying amounts of tung oil added, followed by the measurement of film drying time, surface roughness, glossiness, hardness, and adhesion on substrates to determine the optimal drying conditions. Additionally, SEM analysis of the carved surfaces and FT-IR analysis were used to investigate the impact of tung oil addition on lacquer carving performance and its variation. The results indicate that tung oil, to a certain extent, contributes to a smoother lacquer film but adversely affects film hardness and adhesion to Prunus serotina. However, with an increase in the amount of refined tung oil to 15%, the film exhibits improved glossiness, smoother carving tool marks, and reduced debris, thereby validating the feasibility of mechanical carving of tung oil-modified raw lacquer to some extent.

Urushiol oligomer preparation and evaluations of their antibacterial, antioxidant, and thermal stability

There have been studies published on the composition and coating uses of raw lacquers following enzymatic oxidative polymerization. The change of urushiol’ thermal stability and biological activity following polymerization to create oligomer, however, has received little attention. This work using silica gel column chromatography to separate urushiol and urushiol oligomer from polymerized raw lacquer and assessed its antibacterial, antioxidant, and thermal stability in an effort to decrease the allergenicity of urushiol and increase its application. By using gel chromatography, the urushiol oligomer were discovered to be polymers with 2–5 degrees of polymerization. According to characterization results from techniques like UV, FT-IR, and 1H NMR, urushiol was converted into urushiol oligomer by addition reactions, and C–C coupling. The findings demonstrated that the urushiol oligomer’ IC50 values for scavenging DPPH and ABTS free radicals were 40.8 and 27.4 μg/mL, respectively, and that their minimum inhibitory concentrations against Staphylococcus aureus and Staphylococcus epidermidis were 250 and 125 μg/mL. The urushiol oligomer’s thermogravimetric differential curve peak temperature (461.8 °C) was higher than urushiol’s (239.5 °C), indicating that urushiol undergoes polymerization with enhanced thermal stability. The study’s findings establish a foundation for the use of polymerized urushiol and urushiol oligomer in applications including functional materials and additives.

In vitro propagation of triploid Toxicodendron vernicifluum (Stokes) F. A. Barkl

AbstractTriploid lacquer trees have a higher yield of raw lacquer and greater stress resistance; however, it is challenging to develop efficient and rapid seedling culture techniques because of the influence of metabolites with raw lacquer. In this study, the stem segments of a triploid lacquer tree were used to investigate the effects of explant sterilization treatment, different combinations of exogenous hormone concentrations on the induction of axillary buds, seedling development, and rooting, as well as transplanting substrate ratios. The results showed that the optimal combination of disinfection treatment for triploid Toxicodendron vernicifluum (Stokes) F. A. Barkl explants involves 75% alcohol immersion for 10 s, followed by 2.0% benzalkonium chloride treatment for 1 min and 0.1% HgCl2 treatment for 4 min. The suitable medium for axillary bud induction was Murashige and Skoog (MS) containing 0.1 mg•L−1 zeatin (ZT) and 0.1 mg•L−1 6-benzylaminopurine (6-BA), resulting in a high induction rate of 95.0%. Use of 1/2 MS supplemented with 0.5 mg•L−1 6-BA and 0.3 mg•L−1 2,4-dichlorophenoxyacetic acid (2,4-D) was the most effective for axillary bud proliferation. The combination of 1/2 MS containing 0.1 mg•L−1 6-BA, 0.5 mg•L−1 2,4-D, 0.5 mg•L−1 indole-3-butyric acid (IBA), and 0.2% activated carbon (AC) was an optimum for hardening-off. With woody plant medium (WPM) supplemented with 0.5 mg•L−1 naphthaleneacetic acid (NAA) and 0.5 mg•L−1 2,4-D and 0.5 g•L−1 AC as a rooting medium, the rooting rate was 67.8%. Also, the appropriate transplanting substrate ratio for triploid Toxicodendron vernicifluum (Stokes) F. A. Barkl was grass charcoal:laterite:humus = 1:1:1. Collectively, the results provided the technical assurance for seedling scale multiplication and propagation, facilitating its application in production.

Cu–Ethanolamine Nanozymes Promote Urushiol Oxidation of Lacquer

In order to control the production cost of lacquer products, Cu–ethanolamine nanozymes were synthesized to simulate laccase to catalyze the oxidation and polymerization of urushiol. First-principles calculation results indicate that the D-band center of Cu center in the nanozymes was closer to the Fermi level than that of laccase, so Cu–ethanolamine was more conducive to the adsorption of substrate. The activation energy of Cu-ethanolamine catalyzed the oxidation of urushiol was significantly lower than that of laccase. Therefore, we inferred that the synthesized Cu–ethanolamine had a better catalytic effect on urushiol and was more conducive to paint film drying. By comprehensive comparison, the drying characteristics of the Cu–ethanolamine and raw lacquer with a 1:20 ratio are found to be closest to those of the raw lacquer, and the drying time is significantly shortened. The reaction results of the drying process performance test on the sample indicate that the composite lacquer can achieve the market-desired effect and performance requirements of the paint process.

Comparative Chloroplast Genome Analysis of Chinese Lacquer Tree (Toxicodendron vernicifluum, Anacardiaceae): East-West Divergence within Its Range in China

Chinese lacquer tree (Toxicodendron vernicifluum) is an important commercial arbor species known for the production of raw lacquer. Here, we investigated the intraspecific chloroplast (cp) genome variability of T. vernicifluum using two available and five newly sequenced cp genomes. We found that each of the seven cp genomes encoded 87 protein-coding genes, 37 tRNA genes, and eight rRNA genes. Phylogenetic analyses based on protein-coding genes indicated that the four individuals from western China formed a monophyletic group sister to the cluster containing the three individuals from eastern China. The cp genomes from western China exhibited a larger genome length and longer large single-copy (LSC), small single-copy (SSC), and inverted repeat (IR) regions than those from eastern China. A total of 466 single nucleotide polymorphisms (SNPs) and 141 insertion-deletion mutations were detected among the seven cp genomes, most of which were found between the eastern and western lineages. The two groups exhibited a similar number of microsatellites, long repeats, and tandem repeats. Notably, complementary repeat sequences were only found in the IRs of the individuals from eastern China, while reverse repeat sequences were only detected in the LSC of the individuals from western China. Eight intraspecific mutational hotspots were also identified, including six intergenic regions (trnF-ndhJ, rpl32-trnL, ccsA-ndhD, trnH-psbA, psbC-trnS, and trnL-trnF) and two gene regions (rpl32 and rps19). The genomic resources presented in this study will be useful for further studies on evolutionary patterns and resource protection of T. vernicifluum.

Environmental drivers of the current and future distribution of high-yielding lacquer trees (Toxicodendron vernicifluum (stokes) F. A. Barkley)

Abstract Lacquer trees (Toxicodendron vernicifluum (Stokes) F.A. Barkley) are an important natural resource with significant economic and cultural value in East Asia. The main product, raw lacquer, is in high demand due to its commercially valuable characteristics. This study analyzed environmental drivers of the current and future distribution of lacquer trees in high-yielding locations using a machine-learning algorithm and Maxent models. Results identified suitable value ranges for four key environmental variables and their relative contribution to environmentally suitable areas (shown as percentages in parentheses): solar radiation, 12 000–13 000 kJ m−2 day−1 (43.1 per cent); min temperature of the coldest month, −3.5 to 3°C (18.7 per cent); annual precipitation, 900–1400 mm (13.9 per cent) and water vapour pressure, 1.2–1.6 KPa (5.1 per cent). Overall, projected climate change until 2100 will reduce the extent of environments suitable for high-yielding lacquer trees in China and the Republic of Korea, although these areas will expand in Japan. In addition to the three East Asian countries in which lacquer trees and production are currently important, the study identified environmentally suitable areas for growing lacquer trees in other countries worldwide under future climate conditions. The study’s methodology, which divided high-yielding records from other occurrence records and modeled them separately, was applicable in analyzing environmental drivers and modelling suitable areas for lacquer trees. This approach may also be beneficial to study the distributions of other plants, especially economically important crops and trees. In future studies, additional data sets capturing anthropogenic drivers and information on single tree level could further improve models exploring the productivity and sustainability of lacquer trees under future climates.

Raw Lacquer Extract from Toxicodendron vernicifluum in Combination with ONC201 Enhances the Inhibitory Effects on Colorectal Cancer Cell Activity.

The purpose of the present research was to explore the therapeutic impact of raw lacquer extract from Toxicodendron vernicifluum on colorectal cancer cells and to investigate the outcome of raw lacquer extract and ONC201 co-treatment on the activity of colorectal cancer cells. The cells of HCT116 were treated with raw lacquer extract, ONC201, or co-treatment. Subsequently, MTT, trypan blue staining, colony formation, annexin V/propidium iodide staining, wound healing, and transwell assays were performed to assess the effects of raw lacquer extract, ONC201 and the synthesis effect of co-treatment on cell activity, survival, proliferation, apoptosis, migration, and invasion in HCT116 cells. Western blotting and immunostaining assay were also performed to detect the expressions of tumor necrosis factor-related apoptosis-inducing ligand, death receptor-5, cleaved caspase-8, p-mTOR/mTOR, and p-S6K/S6K in cells. The results showed that ONC201 and raw lacquer extract had effective anti-cancer effects on HCT116 cells. ONC201 and raw lacquer extract treatment on colorectal cancer cells inhibited cell viability and growth, as well as induced cell apoptosis and cell death of HCT116. The migration and invasion of HCT116 cells were also inhibited. Significantly, raw lacquer extract and ONC201 cotreatment further enhanced the anti-colorectal cancer cell activity in HCT116 cells. Western blotting and immunostaining assay showed that raw lacquer extract in combination with ONC201 induced tumor necrosis factor-related apoptosis-inducing ligand/death receptor-5 expression activation, inhibited the expression of cleaved caspase-8/procaspase-8, and reduced the expression of p-mTOR/mTOR and p-S6K/S6K. These results indicated that raw lacquer extract in combination with ONC201 enhanced the inhibitory effects on colorectal cancer cell activity.

Chloroplast genome sequence of triploid Toxicodendron vernicifluum and comparative analyses with other lacquer chloroplast genomes

BackgroundToxicodendron vernicifluum, belonging to the family Anacardiaceae, is an important commercial arbor species, which can provide us with the raw lacquer, an excellent adhesive and painting material used to make lacquer ware. Compared with diploid, triploid lacquer tree has a higher yield of raw lacquer and stronger resistance to stress. Triploid T. vernicifluum was a newly discovered natural triploid lacquer tree. However, the taxonomy of triploid T. vernicifluum has remained uncertain. Here, we sequenced and analyzed the complete chloroplast (cp) genome of triploid T. vernicifluum and compared it with related species of Toxicodendron genus based on chloroplast genome and SSR markers.ResultsThe plastome of triploid T. vernicifluum is 158,221 bp in length, including a pair of inverted repeats (IRs) of 26,462 bp, separated by a large single-copy region of 86,951 bp and a small single-copy region of 18,346 bp. In total, 132 genes including 87 protein-coding genes, 37 tRNA genes and 8 rRNA genes were identified in the triploid T. vernicifluum. Among these, 16 genes were duplicated in the IR regions, 14 genes contain one intron, while three genes contain two introns. After nucleotide substitutions, seven small inversions were analyzed in the chloroplast genomes, eight hotspot regions were found, which could be useful molecular genetic markers for future population genetics. Phylogenetic analyses showed that triploid T. vernicifluum was a sister to T. vernicifluum cv. Dahongpao and T. vernicifluum cv. Hongpigaobachi. Moreover, phylogenetic clustering based on the SSR markers showed that all the samples of triploid T. vernicifluum, T. vernicifluum cv. Dahongpao and T. vernicifluum cv. Hongpigaobachi in one group, while the samples of T. vernicifluum and T. succedaneum in another group, which is consistent with the cp genome and morphological analysis.ConclusionsThe current genomic datasets provide pivotal genetic resources to determine the phylogenetic relationships, variety identification, breeding and resource exploitation, and future genetic diversity-related studies of T. vernicifluum.

Kinetics of thermal degradation of raw lacquer enhanced by formaldehyde urea prepolymer

In this study, formaldehyde-urea prepolymer (FUP) were synthesized, which were used to modify the raw lacquer (RL) and this composition named LF, while the basic properties of the RL were tested. Thermal gravimetric (TG) analysis and scanning electron microscopy (SEM) were used to analyze the degradative characteristics and the surface morphology of RL before and after modification. The result indicated that FUP can significantly improve the performance of RL. The drying time of the LF is significantly shortened, the gloss, the pencil hardness, and the impact performance are significantly enhanced at the same time. TG analysis and thermal decomposition kinetics analysis illustrated that the thermal stability and the activation energy of LF2 were stronger than that of RL. In addition, SEM analysis illustrated that the surface smoothness of RL were also improved.

Preparation and Properties of Chinese Lacquer Modified by Methylolureas

In this study, different molar of methylolureas (MMU) were used to improve the properties and drying speed of the raw lacquer (RL). The drying time, gloss, pencil hardness and impact resistance of the lacquer film were tested. The thermal behaviors and chemical structures of the lacquer membrane were also discussed by thermal gravimetric analysis (TGA), fourier infrared spectrometer (FT-IR) and nuclear magnetic resonance (NMR) analysis, respectively. The results demonstrated that lower molar ratio MMU can significantly improve the properties of lacquer. The TGA analysis showed that the modified lacquer had high thermal stability than that of the control. The FT-IR and 13C NMR analysis revealed that the structures of the modified lacquer were significantly improved by cross-linking with the hydroxymethyl groups and methylene methyl ethers of MMU. In addition, through scanning electron microscopy (SEM) characterization, it was found that the introduction of MMU can effectively improve the surface smoothness of the lacquer film.

Research Progress on Modification and Application of Raw Lacquer

AbstractRaw lacquer is a kind of natural polymer coating with excellent performance. The lacquer film formed after drying of pure natural raw lacquer has the advantages of hard quality, heat resistance and corrosion resistance. However, natural raw lacquer also has some disadvantages. For example, it must be dried at a specific temperature and humidity to form a film, difficult to spray, dark color, poor alkali resistance, easy to cause human skin allergy and so on. Due to urushiol is the main film‐forming material in raw lacquer, its performance and drying film‐forming process will directly affect the properties of the lacquer film. Taking advantage of the particularity of its structure, urushiol can be modified in its drying film‐forming process, so as to speed up its drying film‐forming process or obtain a modified lacquer film with excellent performance. Thus, the research on raw lacquer and its modification mainly focuses on the modification of urushiol, the main film‐forming substance of the raw lacquer. This paper reviews the modification and combined methods of the natural urushiol by researchers in recent years, mainly including urushiol polymerization catalyzed by proton acid, urushiol polymerization initiated by UV irradiation, copolymerized with other polymer materials, reacted with metal compounds to form urushiol metal polymers, and formed composite coatings with multi‐wall carbon nanotubes, graphene oxide, nano‐TiO2 and so on. The modified lacquer has shown excellent performance in some aspects, such as the gloss and hardness of the lacquer film have been significantly improved, the heat resistance, acid and alkali resistance have been enhanced, the ageing resistance and solvent resistance have been improved, the impact strength and toughness have been enhanced, the curing time of the lacquer film has been greatly shortened and so on. Then the application fields and development trends of the modified raw lacquer are discussed, hoping to provide a theoretical basis for the further development and utilization of raw lacquer.

Influence of polyethylene oxide (PEO) on the performance of Chinese lacquer films

The Chinese lacquer composite films were prepared by modifying raw lacquer with polyethylene oxide. The film was characterized via Fourier-transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. The infrared spectra confirmed the interaction between the polyethylene oxide and urushiol. The heat-resistance of the film was found to have decreased due to the presence of polyethylene oxide via thermogravimetric analysis. Additional pores and wrinkles were observed in the scanning electron microscopy image of polyethylene oxide modified lacquer films. The mechanical properties were tested according to the national standard. The results indicated that the gloss and flexibility of the modified film was enhanced by the presence of polyethylene oxide. When the ratio of polyethylene oxide was 3%, the gloss was increased from 59.8 to 81.6 and the flexibility changed from 15 mm to 1 mm. The alkaline-resistance, hardness, and adhesion were also increased via the modification of polyethylene oxide.

Electrospinning PVP/Urushiol/Ag nanofilms: Use as wrapper of stainless steel yarns

In this study, ethanol rotary steaming is used to extract urushiol from raw lacquer. Polyvinylpyrrolidone (PVP) and urushiol are mixed at different ratios, after which the blends are made into PVP/Urushiol nanofilms by means of the electrospinning process. The test results show that PVP/Urushiol nanofilms are insoluble in water, improving the water contact angle. In addition, with a PVP/Urushiol rate being 4/5, the resulting nanofilms retain an impact structure when being immersed in an H2SO4 solution with a concentration being 60%, 80%, or 100%. This result indicates that the combination of urushiol helps improving the downsides of PVP films (i.e., the water-soluble feature and low acid resistance). Furthermore, PVP/Urushiol nanofilms are tested for antibacterial efficacy, which is proven that the antibacterial efficacy is only 15% regardless of whether it is Staphylococcus aureus (S. aureus) or Escherichia coli (E. coli). In order to improve the antibacterial efficacy, a PVP/Urushiol ratio being 4/5 and a nano Ag antibacterial agent are formulated to form the electrospinning mixture that is subsequently electrospun into nanofilms that wrap 0.08 mm-diameter stainless steel yarns, thereby produces acid resistant, antibacterial PVP/Urushiol/Ag-cladded stainless steel yarns. The urushiol is acid resistant, instead of alkali resistant, which enables the application of the PVP/Urushiol/Ag-cladded stainless steel yarns in detecting the pH value of the surroundings, or serving as conduction lines or flexible smart wearable devices in an acid environment.

Synthesis of a Compound Phosphorus-Nitrogen Intumescent Flame Retardant for Applications to Raw Lacquer.

Raw lacquer (RL) is a natural polymer compound with highly promising applications; however, its inflammable attribute restricts the industrial applications. In this study, melamine is used to formulate tri (1-melamine-2-propanol) phosphate (FR-1), after which it is synthesized with ammonium phosphate (FR-2) and diatomite to form a compound phosphorus-nitrogen intumescent flame retardant (IFR). Next, IFR is used as the filling agent that then cross-links with RL, and as such RL/IFR membranes are formed after the curing. The limiting oxygen index (LOI) measurement, the vertical combustion test (UL-94), the microshape calorimetric analysis (CCT), and the thermal gravimetric analysis (TGA) are conducted to examine the combustion resistance and thermal stability of the membranes. Fourier transform infrared spectroscopy (FT-IR) and electron scanning microscope (SEM) are performed to separately characterize the structure and compatibility; the mechanical properties of the membranes are also evaluated. The vertical combustion test results confirm that with 30 wt% of IFR, RL/IFR membranes acquire 12.3% higher LOI and a vertically combustion of V-0 level. The TGA indicates that RL/IFR membranes demonstrate a greater adhesion level, a higher rigidity, and better luster than pure RL membranes.

Anticorrosive coating of polymer composites: A review

This paper provides an overview of the research done in the anticorrosive coating of polymer composites mainly of Urushiol Formaldehyde Polymer (UFP). UFP which is obtained from the raw lacquer is used to do coating of products with admirable physicomechanical properties. The procedures to obtain graphene oxide (GO) and various other techniques to obtain graphene-based anticorrosive coatings have been discussed. The methods used for the preparation of GO/UFP composite coatings have also been discussed in detail. The effects of GO/UFP composites coating on being used with modified graphene oxide (MGO) and multi-walled carbon nanotubes (MWCNTs) in enhancing the physicomechanical properties, microstructure, and anti-corrosive properties have been highlighted.

Preparation and application of urushiol methacrylate-bonded silica liquid chromatographic stationary phase

A novel stationary phase for high performance liquid chromatography was prepared using urushiol methacrylate as the chromatographic ligand. The mixed urushiol methacrylate was prepared using urushiol and methacryloyl chloride via a substitution reaction and then coated onto the surface of spherical silica by physical adsorption. The spherical silica was chemically modified with 3-methacryloyloxypropyl trimethoxysilane. Then, the urushiol methacrylate-bonded silica stationary phase (USP) was synthesized via the surface radical polymerization of urushiol methacrylate and the pendant vinyl groups onto the surface of the spherical silica. The stationary phase was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and elemental analysis. The results revealed that the urushiol methacrylate was successfully immobilized on the spherical silica surface after the surface polymerization reaction, and that it had excellent monodispersity. The stationary phases were packed in a stainless-steel hollow column by the slurry packing method, with methanol as the slurry solvent and absolute ethanol as the propelling solvent. The chromatographic performance of the stationary phases were investigated for the separation of Gastrodia elata extract. Acetonitrile-0.05% phosphoric acid solution (3:97, v/v) was employed as the mobile phase at a flow rate of 0.4 mL/min, with the detection wavelength of 220 nm. The separation performance for Fructus evodia extract was also studied, using acetonitrile-water (50:50, v/v) as the mobile phase at a flow rate of 0.5 mL/min, and the detection wavelength was 290 nm. This column showed good separation performance for both these extracts. Out of the five peaks observed for the Gastrodia elata extract, one was attributed to gastrodin, but the other four peaks need to be further verified. Two peaks assignable to evodiamine and rutaecarpine were observed for the Fructus evodia extract. Compared with C18 column, the USP column allowed for more effective separation of the components from the Gastrodia elata extract, with baseline separation; on the other hand, the chromatographic conditions for the separation of the components of the Fructus evodia extract were more environmentally friendly and safer. Because of the low flow rates adopted for the separation of the Gastrodia elata and Fructus evodia extracts, the amount of mobile phase used could be reduced. This study provides not only a new method for the separation and purification of gastrodin and evodiamine in real samples, but also a new strategy for the preparation of chromatographic stationary phases. It expanded the application of raw lacquer in chromatographic separation materials.

A Study on the Improvement of Using Raw Lacquer and Electrospinning on Properties of PVP Nanofilms.

Raw lacquer (RL), ethanol being used as the solvent, was added to polyvinyl pyrrolidone (PVP) and then electrospun into RL/PVP nanofilms. Manufacturing parameters such as RL/PVP ratio, voltage, flow velocity, needle type, and the distance between syringe and the collection board were systematically investigated. A scanning electronic microscope (SEM) was used to observe the surface morphology of nanofilms; the block drop method was used to measure the water contact angle; the mechanical properties of RL/PVP nanofilms of different proportions were tested by universal material testing machine; and Fourier-transform infrared spectroscopy (FT-IR) was used to characterize the structure. Based on the water resistance and acid resistance measurements, the proposed nanofilms demonstrated to be water and acid resistant were successfully produced. The results show that PVP that melts in water becomes incompatible with water after adding raw lacquer, and the acid resistance is greatly improved. Furthermore, the smaller the fiber diameter, the better the mechanical properties of the nanofilms are under low ratio of RL/PVP. With a high proportion of RL/PVP, the inner structure of the nanofilm is denser, and the water resistance and acid resistance are better. The dense structure can protect the inner material of the nanofilms.

Inlaid materials and techniques of an ancient Chinese bronze mirror

A bronze mirror was unearthed at Xi’an, China, the capital of the Sui dynasty (581–618 AD). The utilized inlay technique is unique and no similar mirrors have been found in China. This study analyzed the structure and composition of the inlays via digital microscopy, metallography, scanning electron microscopy and energy disperse spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, X-ray fluorescence and Raman spectroscopy. The results identified the mirror as a casted high-tin bronze, and each inlaid block included four layers: a mineral base layer (clay and raw lacquer), a gold leaf layer (made of native gold), a pigment layer (malachite and minium) and a glass layer (high-lead glass and sodium-calcium glass). The soda-lime glass is a plant ash glass that likely originated from the Sassanid area. The utilized techniques involved the two crafts of gold pasting (Tie Jin) and pigment filling (Tian Cai). Pigment filling was rarely used in bronze works of the Sui dynasty. This study provides new information on the ancient Chinese bronze mirror-making technology.

Improvement on properties of Chinese lacquer by polyamidoamine

AbstractIn this study, polyamidoamine (PAMAM) was added to raw lacquer in different proportions, and the curing process and properties of lacquer film were investigated by using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT‐IR), and scanning electron microscopy (SEM). To investigate the cross‐linking state between PAMAM and urushiol, NMR was used in this study. The experiments revealed that the comprehensive mechanical properties of modified‐film, especially the impact strength, were significantly improved. In addition, the touch‐free drying time of lacquer film decreased, and its alkali resistance was improved due to the cross‐linking of PAMAM and urushiol molecules.

Materials and provenance determination of lacquerware from the Ryukyu Kingdom period by pyrolysis-gas chromatography/mass spectrometry and 87Sr/86Sr isotope ratio

Three wood chips found in a wooden coffin discovered in the Mumujyana graves of the Ryukyu Kingdom period were analyzed by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), and the 87Sr/86Sr isotope ratio of one piece was measured by multi-collector inductively coupled plasma mass spectrometry to determine the materials used to produce the lacquerware and their provenance. Results from the derivative Py-GC/MS indicate that the lacquer was produced from sap of both Toxicodendron vernicifluum, which grows in eastern Asia, and Toxicodendron succedaneum, which grows in southeastern Asia. The 87Sr/86Sr isotope ratios of the film layer and wooden base of one large chip, which is considered to be a stripped piece of the wooden coffin, were <0.710. The Sr concentration of the film layer, however, was 35.0 ppm, significantly higher than that of raw lacquer sap. It is possible that the Sr isotope ratios of the film layer reflect that of a black pigment observed by cross-section analysis. From the 87Sr/86Sr ratios of two parts of the chip, it is likely that the lacquer painting was done where the black pigment and wood were available. It is likely that the wooden coffin was constructed on the main islands of Japan. Meanwhile, the presence of a chip lacquered with Toxicodendron succedaneum demonstrates that the Ryukyu Kingdom had diverse trade relationships with surrounding countries.