The mechanism of photoprotection of polystyrene film by some ultraviolet absorbers

The efficiency of three commercial ultraviolet absorbers, a 2-hydroxy benzophenone, a 2-hydroxy benzotriazole, and a nickel chelate, in preventing the photo-oxidation of polystyrene films has been measured. When compared with the calculated screening and phosphorescence quenching efficiency, it is found that (i) the nickel chelate protects the substrate by UV screening alone and is a poor photoprotector, and (ii) the 2-hydroxy benzophenone and 2-hydroxy benzotriazole are more efficient photoprotectors and protect by triplet energy transfer from excited polymer carbonyl impurity groups in addition to UV screening.     

Photoprotective agents for wool. Synergism between UV absorbers and antioxidants

Several antioxidants alone, and in combination with sulfonated UV absorbers, have been evaluated as photoprotective agents for wool. Mixtures of phenolic antioxidants and sulfonated UV absorbers of the 2-hydroxyphenylbenzotriazole class were found to exhibit synergistic behavior; the most effective UV absorber also gave the strongest synergistic effect with the antioxidants. Of the systems studied, the hindered phenol, calcium bis ((ethyl-(3,5-di-t-butyl-4-hydroxybenzyl)-phosphonate)) (Irganox 1425), when used in conjunction with a sterically hindered benzotriazolesulphonate, afforded wool the best protection against photoyellowing and phototendering in sunlight, behind window glass. Sulfonated derivatives of hindered phenols acted synergistically with UV absorbers when treated fabrics were exposed to an artificial light source, but not when fabrics were exposed to sunlight through glass.     

The permanence of UV absorbers in a rubber-modified acrylic film by UV/visible spectrophotometry

A new analysis technique for UV/visible spectrophotometry is described. This technique is used to accurately determine the retention of several UV absorbers (UVAs) in a rubbermodified acrylic film during xenon arc accelerated weathering. The effects of reflectance, light scattering, and matrix absorbance are deconvoluted from the total apparent absorbance, resulting in an absorbance spectrum due to the UVA alone. All of the UVAs studied exhibit significant losses upon xenon arc exposure, which has important implications for the longterm durability of polymers that utilize these stabilizers. © 1994 John Wiley & Sons, Inc.     

Mechanism of photoprotection of wool with formaldehyde and thiol derivatives

The application of thiourea and formaldehyde offers significant reductions in photoyellowing for natural, bleached and fluorescent‐brightened wools. We have examined the use of alternative thiol derivates to thiourea and shown that a mixture of N‐acetylcysteine and formaldehyde is similarly effective. Photo‐induced chemiluminescence studies on treated wool fabrics show that the intensity of chemiluminescence following a brief exposure to ultraviolet A radiation is reduced for wool treated with thiourea and formaldehyde, N‐acetylcysteine–formaldehyde and thiourea dioxide–formaldehyde, but not for formaldehyde alone. This demonstrates that a lower population of free radicals is formed in irradiated thiol‐derivative formaldehyde‐treated wools because of free radical scavenging by the sulphur‐containing species. This free radical scavenging results in reduced photoyellowing. The effect of thiourea and formaldehyde treatment on the intrinsic fluorescence of wool is significantly different to N‐acetylcysteine–formaldehyde. Thiourea and formaldehyde quenches tryptophan fluorescence relative to untreated wool, whereas N‐acetylcysteine–formaldehyde treatment results in an increase in intensity probably because of a reduction in disulphide quenching.     

Graft-copolymerization of PVC with polymerizable UV absorbers

Summary Polyvlnyl chloride has been grafted with two different monofunctional polymerizable ultraviolet (UV) absorbers, 4-methacryloyloxy-2-hydroxybenzophenone and 2(2-hydroxy-4-methacryloyloxyphenyl) 2H-5-methoxy-benzotriazole. PVC was activated by dehydrochlorinating it in pyridine and subsequently grafted with the monomeric UV absorbers in tetrahydrofuran by free radical polymerization. The molar masses of the resulting grafted polymers and the distribution of the UV absorber moleties along different molar mass fractions were determined by GPC. It was shown that in addition to the grafting reaction, recombination of the DHPVC and homopolymerization of the UV absorber molecules take place.     

The encapsulation effect of UV molecular absorbers into biocompatible lipid nanoparticles

The efficiency of a cosmetic product depends not only on the active ingredients, but also on the carrier system devoted to improve its bioavailability. This article aims to encapsulate two couples of UV molecular absorbers, with a blocking action on both UV-A and UV-B domains, into efficient lipid nanoparticles. The effect of encapsulation on the specific properties such as sun protection factor and photostability behaviour has been demonstrated. The lipid nanoparticles with size range 30-350 nm and a polydispersity index between 0.217 and 0.244 are obtained using a modified high shear homogenisation method. The nanoparticles had spherical shapes with a single crystallisation form of lipid matrices characteristic for the least ordered crystal structure (α-form). The in vitro determination of photoprotection has led to high SPF ratings, with values of about 20, which assure a good photoprotection and filtering about 95% of UV radiation. The photoprotection effect after irradiation stage was observed to be increased more than twice compared to initial samples as a result of isomerisation phenomena. All the results have shown that good photoprotection effect and improved photostability could be obtained using such sunscreen couples, thus demonstrating that UV absorbers-solid lipid nanoparticles are promising carriers for cosmetic formulations.     

化妆品防晒剂的研究进展及其安全性问题(续前)

一类重要的且光稳定的UVA紫外线吸收剂是苯三唑邻位羟基取代的化合物。这类紫外线吸收剂主要吸收长波段的紫外线UVA,但其吸收效率或称摩尔消光系数要比二苯甲酰甲烷类化合物如Avobenzone低。由于这类苯三唑化合物中形成的氮-氢(N-H)     

New class of ultraviolet light absorbers

The DNA bases are found to be effective ultraviolet light absorbers in high‐density polyethylene (HDPE) and poly(vinyl chloride) PVC. J. Vinyl Addit. Technol. 10:41–43, 2004. © 2004 Society of Plastics Engineers.     

Enhancing the performance of exterior waterborne coatings for wood by inorganic nanosized UV absorbers

Enhancing the durability of the architectural wood coatings is essential for a successful commercialization of the forest products. Therefore, this paper is focused on UV resistant waterborne nanocomposites coatings for exterior uses of wood, which were improved with inorganic UV absorbers such as zinc oxide and titanium dioxide nanoparticles. The performance of such nanocomposites coatings applied on black spruce boards was demonstrated trough accelerated weathering. Artificial aging behavior of the coatings was followed by color, gloss and thickness changes. Scanning electron microscopy and transmission electron microscopy was used to investigate nanoparticles dispersion in nanocomposite dry films. Fourier Transform Infrared Spectroscopy was used to characterize the chemical modification of the weathered coatings surface. The results have shown significant improvement in UV-shielding of the nanocomposites coatings. Depending of aging criteria, a selection of the best nanocomposite coatings formulations for exterior wood could be done.     

Photodegradation of UV absorbers: Kinetics and structural effects

When poly(methyl methacrylate) films containing UV absorbers are exposed to UV light, the absorbers undergo photodegradation resulting in loss of absorbance. If the data extend for less than one half-life, both zero and first order kinetic treatment give fairly linear fits, but the rate constants so derived are dependent on the initial absorbance of the films. When the zero order rate constants are corrected to account for the higher rate of degradation near the surface compared with the bulk that occurs in highly absorbing films, consistent “infinite absorption” zero order rate constants are derived. The inhomogeneous degradation is due to only the highly absorbed, higher energy light contributing significantly to the degradation. For the benzophenone and benzotriazole classes of absorber, at least 65% of the degradation is due to light with wavelengths < 350 nm. Structural variations generally caused only small differences in the rates of degradation of these classes of absorbers unless the substitutions disrupted the intramolecular hydrogen bonds that are critical for stability. If the hydrogen bond is weakened, the absorber is less stable.     

Effect of phase transitions on the volatility of UV absorbers from polypropylene

The volatility of 2-hydroxy-4-methoxybenzophenone and 2-(2′-hydroxy-5′-methylphenyl) benzotriazole from isotactic polypropylene was studied by thermal methods in the temperature range that included the melting point of one of the stabilizers and the fusion of the polymer. The process proceeds according to the first order of kinetics. The rate constants of the stabilizers' volatility were calculated and the Arrhenius plots were constructed. The observed discontinuities in the Arrhenius dependences are interpreted as the result of the phase transitions of the polymer (melting) and the stabilizer. The activation energies for all zones were calculated. © 1993 John Wiley & Sons, Inc.     

Surface modification and low temperature dyeing properties of wool treated by UV radiation

The surface modification and dyeing properties of wool treated by UV radiation have been investigated. Wool samples were exposed to UV radiation for 60 min and the surface modification of the wool fibre was investigated by X-ray photoelectron spectroscopy. The chemical change caused by the UV treatment was identified as surface oxidation of cystine (disulphide bonds) and thereby induced changes in the dyeing properties of the wool. The dyeability of UV-treated and untreated wool samples was determined at temperatures of 45, 50, 55 and 60 °C using CI Acid Blue 7. The UV-treated wool samples showed greater levels of dye uptake compared with those of the untreated samples. The adsorption behaviour and diffusion coefficients were also studied. The dyeing properties of wool were enhanced by UV radiation due to the increased diffusion coefficient of the dyes in the treated wool fibres.     

化妆品防晒剂的研究进展及其安全性问题(待续)

从分子结构特点、光稳定性、应用性能以及安全性等方面综述了已被欧盟化妆品及非食品科学委员会、美国食品及药品管理局、日本厚生省以及中国卫生部批淮使用的化妆品用紫外线吸收剂。对全球近期在该领域的主要研究开发方向进行了综述和分析。三嗪类及苯三唑类衍生物因其优越的光稳定性和安全性仍然是两类研究活跃的化妆品用紫外线吸收剂。尽管高分子类紫外线吸收剂无疑是将来的主力，但要通过美国食品及药品管理局的批淮仍需时日。     

Investigation into the effect of UV/ozone treatments on the dyeability and printability of wool

The effect of UV/ozone treatments on the surface and bulk properties of wool has been investigated. X–ray photoelectron spectroscopy indicates that the oxidative process causes extensive surface modification, while vibrational and electron spin resonance techniques show the formation of cysteic acid and free radical species. The beneficial effect of UV/ozone treatment on wool dyeing, printing and shrink–resist properties has been investigated.     

TiO2／UV／O2和TiO2／UV／N2体系降解水中对氯硝基苯

以商用TiO2P25为催化剂,分别在TiO2/UV/O2和TiO2/UV/N2两种体系下进行降解对氯硝基苯(pCNB)试验.采用ESR对两种体系下光催化反应形成的.OH进行测定,利用LC-MS对两种体系下反应形成的中间产物进行了定性和定量分析,最后对pCNB降解过程中氯和硝基的存在形式进行了研究.结果表明:TiO2/UV/O2体系的催化降解效果要明显优于TiO2/UV/N2体系;两种反应体系都有.OH产生,并且TiO2/UV/O2体系产生的.OH的量多于TiO2/UV/N2体系产生的.OH的量;TiO2/UV/O2体系形成的中间产物的种类要多于TiO2/UV/N2体系形成的,苯环上的氢、氯、硝基均可被.OH取代形成对硝基酚(pNP)、5-氯-2-硝基酚(5-C-2-PN)等酚类物质;两种体系下均有Cl-和NO2-存在,其中Cl-生成势与pCNB的去除势一致,只有TiO2/UV/O2体系中存在NO3-.     

Determination of wool wax in raw wool by raman spectroscopy

A Raman spectroscopic method for the determination of wool wax content in raw wool has been developed. The analyses were performed on 250-mg wool samples by using a spectral component band resolution method. The method has a moderate sample throughput rate, is non-destructive and does not require the use of solvents. Samples ranging between 0.5 and 31% (w/w) wool wax were analyzed. The results obtained were compared with those obtained by a solvent extraction method. If the nonextractable lipid content of the wool is considered, the results of the Raman spectral and extraction methods were in excellent agreement. From a practical standpoint, the minimum detection limit of the method is 3% wax. In general, the precision of the Raman spectroscopic method was better than that obtained for the extraction method.     

无机金属氧化物复合羊毛纤维的阻燃机理研究

通过热分析、剩碳率、氧指数和扫描电镜对无机金属氧化物溶胶处理后的羊毛样品的热降解行为进行了表征,并对其阻燃机理作了初步探讨。结果表明,经过阻燃处理的羊毛其氧指数、剩碳率比未处理的羊毛升高,阻燃性明显增强。