UV curatives

A further alternative for cutting down on solvents is to work with radiation curing of wire enamel systems [176-178]. A characteristic property of UV-cur-ing systems is their very low energy requirement for the curing process, but the thermal stability of the obtained films requires improvement. The handicap is the double bonds, acrylic or olefinic, necessary for the curing reaction, which... 

Other uses include the production of flexographic printing plates from UV-cur-able materials. An interesting application is three-dimensional modeling (stereolithography) in which a solid part is made from a vat of UV-curable liquor by the use of UV lasers controlled by computers using CAD/CAM software. 

Uses Slip agent, leveling agent, antiblocking agent for metal coatings and wood finishes, ind. UV-cur polyesters EFKAitd033 [EFKAAdditivesBV]... 

Uses Prod, of solv.-resistant elastomers, polyacrylate rubbers UV-cur-able reactive diluent soft contact lenses PVC impact modifier fabric coatings barrier coatings for polyethylene textile coalings plasticizer softener... 

The potential advantages far outweigh the disadvantages, and the development work is continuing in laboratories at many universities and some companies. To the best of our knowledge, there is no large-scale production system in use today for UV-cur-able tape casting. 

Water-soluble vitamins (vitamin Bi, vitamin Bg, vitamin B12, and vitamin C) in Kombucha drink (a curative liquor) were separated by TLC on silica gel plates with water as the solvent. The plates were visually examined under UV light at 254- and 366-nm wave-g lengths. The four vitamins were identified and determinec by comparing the Rf values with the reference values (vitamin Bi, 0.21 vitamin Bg, 0.73 vitamin B12,0.34 anc vitamin C, 0.96). ... 

Fig. 36 UV-VIS and CD spectra of CUR-N" [1.3mM (monomer unit)], poly(C) [0.24 mM (monomer unit)] and poly(C)/CUR-N [1.3 mM (monomer unit), 0.24 mM (monomer unit)] in 1.0 mM tris-HCl buffer (pH 8.0) at 5°C with a 1.0 cm cell (CUR-N" + poly(C) in absorption spectra corresponds to the sum of the individual spectra). Reprinted with permission from [192]...

Fig. 37 A UV-VIS, fluorescence (Xex = 290 nm) and CD spectra of PMDS/CUR-N composite ([CUR-N+] = 3.0 X 10" M (monomer unit)), [PMDS] = 2.5 x 10 M (monomer unit) in an aqueous solution at ambient temperature and B The TEM image of PMDS/CUR-N" composite after treatment with phosphotungstic acid. Reprinted with permission from [192]...

Various veterinary residues can be found in food, particularly antibacterial agents used as curative or prophylactic treatments in livestock. A concern with the presence of residual levels of these antibacterial drugs in foods is the increase in antimicrobial resistance. CE methods have been applied to the determination of drug residues in fish and chicken muscle. The quantitative analysis of oxolinic acid fish muscle can be achieved using CZE with a basic phosphate buffer (pH 9) after solid-phase extraction. Enroflox-acin and its metabolite ciproflaxin are detectable in chicken muscle using LIE detection after separation by CZE in an acidic phosphate buffer (pH 2.2). Oxolinic acid and flumequine can be simultaneously determined in chicken by using a basic phosphate buffer (pH 8.02) and UV-visible diode array detection. 

Subsequent investigations showed that D vitamins were involved, and eventually it became known that one of several D vitamins, called vitamin D3, is the curative factor. Vitamin D3 is formed in the skin from 7-dehydrocholesterol by two reactions. In the first reaction (below), ultraviolet light in the UV-B range (280-320 nm, which can penetrate the epidermal layer) brings about a 6-electron conrotatory electrocyclic reaction (see Special Topic H, WileyPLUS) to produce pre-vitamin D3. Following this event, a spontaneous isomerization (by way of a [1,7] sigmatropic hydride shift) produces vitamin D3 itself. 

One technique for dealing with this low temperature cure/reactivity dilemma is to use a two component powder system. The resin and other binder components comprise one component and the curative and other nonreactive binder ingredients, the other (80). In the case of uv curable powders, an imsaturated polyester resin is one of the major binder components but more reactive binder components such as oligomers with high allyl functionality (81) or vinylether/ester groups (82) must also be present. Crystalline resins with reactive methacrylyl groups have also been disclosed (83). A review of photoinitiators, additives, and other components of uv-curable powders are given in References 84 and 85. 

Applications . Due to the nature of fillers, UV and visible speetroseopy is not the most popular method of testing, but there is some useful information which can be obtained from these methods. The following information can be found in the cur-... 

Some pyrethroids are especially useful for wood preservation due to their physico-chemical parameters, e.g. very low vapor pressure, high UV-resistance and very low water solubility, resulting in a long-term protection of technical material. Today the active ingredients Permethrin, Cypermethrin, Cyfluthrin, Deltamethrin and Bifenthrin (Figure 18 and 19) are used in wood protection. Due to their long-term protection and their fast action these compounds can be used in preservative and curative applications. Table 7 summarizes the efficacy in tests according to European standards EN 21 and EN 47. 

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