Urushi

A new crosslinkable polymer was synthesized by the SBP-catalyzed polymerization of cardanol. When HRP was used as catalyst for the cardanol polymerization, the reaction took place in the presence of a redox mediator (phe-nothiazine derivative) to give the polymer. Fe-salen efficiently catalyzed the polymerization of cardanol in organic solvents (Scheme 29). " The polymerization proceeded in 1,4-dioxane to give the soluble polymer with molecular weight of several thousands in good yields. The curing of the polymer took place in the presence of cobalt naphthenate catalyst at room temperature or thermal treatment (150°C for 30 min) to form yellowish transparent films ( artificial urushi ... 

Urushi, a natural lacquer, has been used on the ISFET surface [89] to make, amongst other devices, a chloride sensor. The natural lacquer has a long curing time (10 days) but this can be shortened to 2-3 days with the use of formaldehyde as a crosslinking agent [90] and has been successfully used in the production of a nitrate sensor. 

It has been shown by Kharasch and Foy22 and confirmed by Urushi-bara and Takebayashi28 that the presence of peroxides markedly accelerates the heterogeneous Cannizzaro reaction. Highly purified benzaldehyde undergoes dismutation to the extent of only 2-4% under conditions which result in 25-80% reaotion with ordinary benzaldehyde. 5-Bromofurfural dismutates only slowly with 30% sodium hydroxide in ether, but the reaotion is accelerated markedly by the addition of a trace of hydrogen peroxide.24 Variousjexplanations have been advanced to account for the effect of peroxides,26 260 but the problem is still obscure-. 

Sodium ion-selective field-effect transistors (Na+ ISFETs) were prepared by using three different types of polymeric matrix materials, such as polyvinyl chloride, bio-compatible polymer (polyurethane) and Urushi (natural oriental lacquer). Their electrochemical characteristics were discussed in connection with their characteristics of polymeric matrix membranes. 

Preparation of sodium Urushi/ISFET. A mixture of 5 wt. % of ETH 227, 45 wt. % of di-2-ethylhexylphthalate (DOP Kishida Chemical Co. Ltd.) containing 0.5 wt. % of potassium tetrakis(4-chlorophenyl)borate (Dojin Research Laboratories Co. Ltd.) and 50 wt. % of Urushi (Saito Urushi Co. Ltd.) was coated on the FET devices and then the resulting Na+ Urushi membranes were hardened for 10 days at 30 °C and 90% relative humidity. The thickness of the membrane was approximately 0.1 mm. The surface of the Urushi matrix membrane was lustrous, smooth and adhesive to the gate of the device. The hardening mechanisms were discussed in detail elsewhere (6). 

The response times of the three kinds of Na+ ISFETs are also within seconds of one another. The above-mentioned characteristics, such as linear response range, sensitivity and response time ate almost the same in PVC, Urushi and KP-13 matrix ISFETs. 

Matrix mechanisms of sodium Urushi and PVC/ISFETs. The electrochemical characteristics, such as linear response range, sensitivity, selectivity and response time of the Urushi matrix ISFETs are similar to those of the PVC matrix ISFETs. The reason of the same characteristics is discussed from the standpoint of matrix mechanisms as follows. The obtained results indicate that these characteristics are mainly determined not by polymeric matrix materials but by sodium-sensing materials, including the membrane solvent (NPOE etc.). Therefore, it is considered that the polymeric matrix materials, such as PVC and Urushi only act as a hydrophobic support polymer and that the major part of surface of the matrix membrane should be covered with the membrane solvent containing the Na ionophore. 

In the Urushi matrix membrane, it is supposed that the solvent at the surface would be supplied from the porous bulk phase of the mechanically hard Urushi matrix membrane by capillary action, which was discussed in detail elsewhere (6), while in the PVC matrix membrane, the solvent of the surface would be supplied by the leaching process from the mechanically soft PVC matrix membrane, because the electron micrograph of the PVC matrix membrane indicates structural damage ( ). 

Stability of sodium ISFETs. The PVC and KP-13 matrix ISFETs have some drift characteristics of a few mV per hour. The lifetimes of the both ISFETs are about 1 week. It is considered that the drift and durability is caused by the poor membrane adhesion to the ISFET device (9). The Urushi matrix ISFETs exhibited a drift <0.1 mV per hour and durability > 1 month because of the strong adhesion of the Na+ sensing membrane to the ISFET device. 

Johnson et al. reported adhesion studies of some polymeric matrix membrane by using PVC, Urushi and copolymer (vinylchloride/vinyl alcohol copolymer matrix membrane with treatment of tetrachlorosilane) by using an ultrasonic bath (10). They also reported the use of Urushi gives improved adhesion lasting over 5 hours and that in some cases the membrane lasted for over 20 hours. The stability of the Urushi matrix ISFETs was discussed in detail elsewhere (6). 

Besides the membrane materials described above, several other membrane materials have been investigated. Aminated [44,45] and carboxylated [46,47] PVC membranes were used for covalent attachment of ionophore to the matrix and showed to have improved adhesion to the gate oxide. These membranes were also used in ion-selective electrodes and showed to be ion-sensitive up to about 50 days, but had the disadvantage of being pH dependent. Membrane adhesion to the gate oxide can also be enhanced by using Urushi latex as membrane material. Urushi latex mainly consists of Urushiol which is a mixture of 3-substituted pyrocatechol derivatives... 

Technical examination of objects coated with a protective covering derived from the sap of a shrubby tree produces information that can be used to determine the materials and methods of manufacture. This information sometimes indicates when and where the piece was made. This chapter is intended to present a brief review of the raw material urushi, and the history and study of its use. Analytical techniques have included atomic absorption spectroscopy, thin layer chromatography, differential thermal analysis, emission spectroscopy, x-ray radiography, and optical and scanning electron microscopy these methods and results are reviewed. In addition, new methods are reported, including the use of energy dispensive x-ray fluorescence, scanning photoacoustical microscopy, laser microprobe and nondestructive IR spectrophotometry. 

Raw lacquer is called urushi. For our knowledge of the composition of urushi and the complex hardening process of the thin film layers, we now rely primarily on the recent work of Kumanotani and his coworkers (1-7). The sap of the Japanese lacquer tree is a latex containing 20-25% water, 65-70% urushic acid (urushiol), approximately 10% gummy sub-... 

Urushi, although it forms a thin film in an oxidation process, is unique in that it hardens in the presence of a high relative humidity. Hardening is actually accelerated with an increase in the amount of moisture present. Lacquer will not harden perfectly at normal room temperature and humidity conditions a good film is only possible in a damp enclosure between 20 and 28 °C. 

Many grades of urushi are used, depending on the different applications or decorative effects desired. (A detailed description of materials and methods may be found in Reference 8.) The sap, after removal of some water and careful filtration and cleaning, is most often coated onto a prepared core. This core is usually made of wood, but examples of leather, basketry, cloth, paper, metal, pottery, shell, horn, and fish skin may be found. Normally, many lacquer layers are built up on the core, with polishing occurring after each layer has hardened. 

Over the past hundred years numerous experimental methods have been used for the study of urushi and the finished lacquer ware. The first recorded reports on chemical experiments are those of Ishimatsu (14), Yoshida (13) and Korschelt and Yoshida (15). Miyama gave the name urushiol to urushic acid (16), and he and Majima and coworkers (17-26) further explored the composition of urushi. Work by Sunthanker, Dawson, and Symmes (27,28) helped to determine that it contained three substituted catechol derivatives containing various diflFerent side chains. The previously mentioned reports by Kumanotani and coworkers (1-7) have allowed us to understand more of the details of the raw urushi, the complex mechanism of film hardening, and some properties of the hardened layers. 

Figure 1. Dynamic viscoelasticity of artificial urushi from urushiol analogue having a linolenic acid group.

Fast drying hybrid urushi was developed [97]. Kurome urushi was reacted with silane-coupling agents possessing an amino, epoxy or isocyanate group, resulting... 

Although the production of lacs from Rhus vernicifera and relatives is a smaller volume industry on account of the fact that the product is solely the latex, the current production of urushi is probably more than 3,000 tonnes in China and less in Japan and other Far Eastern countries. The industry is of great antiquity and has probably been in operation for the past 40,000 years. In more recent years the production oiAnacardium occidentale has been introduced in Hainan the only warm enough region in that country suitable for its cultivation. 

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