聚合物光老化、光稳定机理与光稳定剂(下)

大多数聚合物材料,包括塑料、橡胶、纤维、涂料等,在户外使用时会发生光老化而使使用寿命缩短。为有效防止聚合物材料的光劣化,人们已对聚合物的光老化和光稳定机理进行了广泛的研究并先后研发出了几个类型的光稳定剂。但由于户外应用范围不断扩大和环境不断恶化正使聚合物的光老化变得越来越复杂而光防护难度也日益加大,因此国内外有关聚合物光老化、光稳定机理的研究和光稳定剂的研发一直十分活跃。本文下篇阐述光稳定剂的作用机理并综述光稳定剂的研发进展。     

受阻胺光稳定剂

本文介绍第4代光稳定剂——受阻胺光稳定剂的结构、合成、效率和其光稳定化作用机理,并介绍受阻胺光稳定剂的未来发展.本文可供从事高分子工业的科研、生产、助剂合成及高分子材料的老化与防老化的研究工作者参考.     

聚合物光老化、光稳定机理与光稳定剂(上)

大多数聚合物材料,包括塑料、橡胶、纤维、涂料等,在户外使用时会发生光老化而使使用寿命缩短。为有效防止聚合物材料的光劣化,人们已对聚合物的光老化和光稳定机理进行了广泛的研究并先后研发出了几个类型的光稳定剂。但由于户外应用范围不断扩大和环境不断恶化正使聚合物的光老化变得越来越复杂而光防护难度也日益加大,因此国内外有关聚合物光老化、光稳定机理的研究和光稳定剂的研发一直十分活跃。本文上篇主要阐述聚合物的光老化机理。     

高分子光稳定剂的研究——溶解度参数与光稳定效率的关系

<正> 添加光稳定剂是阻止聚合物因光照氧化降解,延长聚合物制品的使用寿命的有效方法。显然只有当光稳定剂能最大程度地均匀分散在聚合物中才能充分地发挥它的光稳定效率,这对高分子光稳定剂来说尤为重要。 光稳定剂与被稳定的聚合物的相容性对光稳定效率的影响已有过研究。如Ambrovic等曾经报道:随着2-羟基4-烷氧基二苯甲酮中烷基的碳原子数增加,它对聚丙烯的光稳定效率提高。高分子光稳定剂本身是一个有一定分子量的聚合物,使用时它与被稳定聚合物形成了共混体系。我们研究了高分子光稳定剂的溶解度参数和它对聚丙烯的光稳定效率的关系。     

光散射在高分子溶液和聚集态研究中的应用

本文较为详细的综述了光散射在聚合物研究中某些领域内的应用，并着重介绍了光散射在聚合物凝胶领域、聚合物稀溶液中、聚合物相行为领域以及聚合物加工领域中的发展历史和研究现状。     

共轭聚合物光声造影剂的研究进展

光声成像是一种新兴医学影像成像技术。作为一种非侵入式和非电离式的成像技术,光声成像具有高分辨率、高对比度和穿透深度高的特点。这种成像技术在对组织进行诊断时需要加入造影剂与组织相结合才能产生显著的光声信号。然而,目前光声成像技术仍缺乏合适的造影剂,制约了其在生物医学领域的应用。共轭聚合物因其具有优异的光热性能和良好的生物相容性,被广泛应用于光声成像领域。本文综述了共轭聚合物作为外源性造影剂在光声成像领域的应用的研究进展,并对共轭聚合物光声造影剂的发展进行了展望。     

某些高分子受阻胺对聚丙烯稳定化作用的研究

众所周知,受阻胺光稳定剂对聚烯烃有良好的光稳定效率,已引起世界的注意。然而,小分子量的受阻胺易于挥发,从而影响它的效率发挥^[1,2],为了克服这个缺点,使小分子受阻胺的高分子化是近年来受阻胺光稳定剂发展的方向,本文主要是研究三种商品化高分子受阻胺光稳定剂对聚丙烯的稳定化作用及其效率和机理。     

半水硫酸钙晶须稳定化研究

使用多种稳定剂对半水硫酸钙晶须进行稳定化处理,研究了稳定剂用量、稳定化处理温度和时间等对半水硫酸钙晶须稳定性的影响。通过FTIR、SEM、DSC-TG和XRD对稳定化处理后的产物进行了表征,结果表明：在油酸钠用量0.3%,稳定化处理温度100 ℃,稳定化处理时间20 min的条件下,实现了半水硫酸钙晶须的稳定;油酸钠在晶须表面的吸附既有物理吸附又有化学吸附,并通过化学吸附在晶须表面形成了油酸钙。     

聚合物抗污涂层的研究进展

构筑聚合物抗污涂层表面是解决生物污损的有效策略. 聚合物具有耐酸碱性和易于功能化及表面修饰等优点, 聚合物抗污涂层在降低生物污损对材料的影响和减少经济损失中发挥着重要作用. 本文综合评述了聚合物抗污涂层的各种研究策略和研究进展, 介绍了相关新型聚合物抗污涂层的成果, 并展望了该领域面临的挑战.     

有机/聚合物光探测器在医疗健康领域中的应用

有机/聚合物光探测器因其具有响应光谱大范围可调、可制备柔性化器件以及可溶液加工等优势,受到研究人员的广泛关注.随着近年来有机/聚合物光电材料体系的迅速发展,有机/聚合物光探测器的各项性能指标已经可以与商业化硅基光探测器媲美,甚至在短波红外光区的响应性能已经超越硅基光探测器,这使其显示出巨大的应用潜力.特别是在医疗健康领域中,具有轻、薄、柔性等优势的有机/聚合物光探测器受到了广泛的关注,为新型便携式健康监测设备的发展提供了新的技术可能.本文围绕有机/聚合物光探测器,综述了近年来有机/聚合物光探测器在医疗健康领域中的研究进展,并对与之相关的应用原理进行了分析与讨论,最后指出了有机/聚合物光探测器在医疗健康领域中的发展潜力,展望了其未来的发展.     

Synthesis of highly photostable blue-emitting 1,8-naphthalimides and their acrylonitrile copolymers

Two novel highly photostable blue-emitting 1,8-naphthalimides, containing active fragments of a hindered amine radical scavenger and an s-triazine UV absorber were designed as multifunctional additives capable of simultaneous fluorescent brightening and photostabilization of polymers. Their light absorption and fluorescence properties have been determined and discussed. The ability of the combined fluorescent brighteners to copolymerize with acrylonitrile was demonstrated by obtaining acrylonitrile copolymers with an intense blue fluorescence. Photodegradation of the new fluorophores and their influence on the photostability of the fluorescent copolymers have been studied and compared to other similar 1,8-naphthalimides, not containing either UV absorber or hindered amine fragment in their molecules as well as not containing both of them. Novel fluorophores showed the best photostability in both solution and polymer. A significant photostabilizing effect towards photodegradation of polyacrylonitrile was found.     

Preparation of new full UV-absorbing carbon dots from quercetin and their application in UV-absorbing systems for waterborne polyurethane coatings

In this paper, a kind of novel fully UV absorbing carbon dots (QC-CDs) were prepared as UV absorbers by a one-step hydrothermal method using quercetin as raw material. The prepared QC-CDs have high absorption efficiency (over 98%) in the whole ultraviolet region (200–400 nm), and are almost completely transmitted in the visible light region. The prepared QC-CDs have good stability and resistance to photobleaching. After the treatment with different pH and temperature, the QC-CDs maintained good absorption stability. QC-CDs have a wider UV absorption range than commercial water-soluble organic UV absorbers-BP-4. In terms of aging resistance, QC-CDs can achieve the same effect as BP-4. After subjecting QC-CDs and BP-4 to different pH values, it was found that QC-CDs remain fully UV absorbing at different pH conditions and maintain good absorption stability, but BP-4 loses its function as a UV absorber under alkaline conditions. Then, the UV absorption mechanism of QC-CDs has also been investigated and applied to the UV absorption systems of waterborne coatings PU. Finally, the QC-CDs@PU with full UV absorption properties was applied in the photodegradation prevention experiment of Rhodamine B. At present, the preparation process of QC-CDs is simple and environmentally friendly. QC-CDs have the potential to become a new generation of water-soluble UV absorbers.     

聚乙烯光引发交联过程中的表面光氧化和光稳定

通过测定凝胶含量并利用红外-光声光谱和光电子能谱对光交联聚乙烯表面氧化程度和氧化产物进行了研究.结果表明,聚乙烯光交联过程中随着光照时间的增加,表面光氧化加剧,氧化产物主要是氢过氧化物和含羰基的化合物.考察了预辐照和添加受阻胺型光稳定剂对聚乙烯光交联过程的影响,发现这两种方法都能有效地降低光交联聚乙烯(XLPE)的表面氧化,但有些光稳定剂会降低XLPE的交联度.     

Hyperbranched Polyurethane Acrylate Applied to UV Curable Flame Retardant Coatings

UV curable hyperbranched prepolymers based on amine-ester, ester-amide and ether-amide started with AB_2-type monomers have been prepared by the authors. A series of work on allyl ether maleate hyperbranched polyesters for UV curing coatings by Hult and his colleagues has been reported. However, the UV cured films from those materials are all flammable when attached to fire without addition of flame retardants. In this work, a new kind of hyperbranched polyurethane acrylate containing phosphorus     

Effect of ultraviolet light absorbers on photostabilization of azadirachtin-A in solution (part: II)

The effect of photostabilization of azadirachtin-A (Aza-A) was examined in solutions when exposed to UV radiation, in the presence of four structurally different UV absorbers namely, p-aminobenzoic acid, 2,4-dihydroxybenzophenone, 4,4'-dihydroxybenzophenone and phenyl salicylate. The percentages of Aza-A recovered from the solutions after 6 h exposed to UV radiation in the presence and absence of UV absorbers indicated that the order of stabilization of Aza-A by these absorbers was similar to that obtained in the solid phase experiments in accordance with our previous observations. It is observed that the addition of phenyl salicylate in Aza-A (in 1:1 mole ratio) provides the excellent photostabilization of Aza-A molecule in solid phase as well as in solution among the four absorbers studied.     

Evaluation of Schiff bases of 2,5-dimercapto-1,3,4-thiadiazole as photostabilizer for poly(methyl methacrylate)

The photostabilization of poly(methyl methacrylate) (PMMA) films by Schiff bases of 2,5-dimercapto-1,3,4-thiadiazole compounds was investigated. The PMMA films containing concentration of complexes 0.5% by weight were produced by the casting method from chloroform solvent. The photostabilization activities of these compounds were determined by monitoring the hydroxyl index with irradiation time. The changes in viscosity average molecular weight of PMMA with irradiation time were also tracked (using benzene as a solvent). The quantum yield of the chain scission (Φ_cs) of these complexes in PMMA films was evaluated and found to range between 4.19 × 10^?5 and 8.75 × 10^?5. Results obtained showed that the rate of photostabilization of PMMA in the presence of the additive followed the trend:[1] > [2] > [3] > [4] > [5].According to the experimental results obtained, several mechanisms were suggested depending on the structure of the additive. Among them, UV absorption, peroxide decomposer, and radical scavenger for photostabilizer mechanisms were suggested.     

Water sorption in UV degraded clear and pigmented epoxy coatings assessed by dielectric sorption analysis

Degraded clear and pigmented epoxy coatings were investigated by dielectric sorption analysis (DSA). Differences in dynamics of absorption, due to increased hydrophilicity, crosslinking and porosity, were found between UV degraded and undegraded epoxy coatings. Desorption was observed for longer degradation times, caused by swelling of the coating, squeezing out the excess of water. Model system measurements of pigmented coatings with various filters on top reproduced the desorption behaviour. Due to crack formation during DSA measurements, clear coatings showed fluctuating results, a result of release of tension of the UV degraded clear coating by humidified nitrogen. Pigmented coatings did not show this behaviour, resulting in an increasing water absorption trend with increasing degradation times. Larger desorption peaks were found for lower frequencies, indicating that either polarization takes place or water-hydrophilic interaction. Based on these results, DSA is suitable for non-destructive investigation of degraded coatings and paints.     

Photostabilization of an entomopathogenic fungus using composite clay matrices

To provide photostabilization for entomopathogenic fungi by anionic dyes, composite matrices based on clay-biopolymer combinations were prepared. In the first step, the negative surface charge of various clays (montmorillonite, attapulgite, bentonite and kaolinite) was reversed to positive by adsorption to the polycationic biopolymer chitosan. The second step involved adsorption of the toxicologically safe anionic dyes fast green (FG) and naphthol yellow S (NYS) to the clay complexes. Compared with cytotoxic photoprotectants like berberine, palmatine and acriflavine, the anionic dyes have no adverse effects up to a concentration of 1 M. In assays using various clay-chitosan-dye matrices and UV irradiation from a lamp source, it was evident that both FG and NYS provided considerable photostabilization for conidia of the entomopathogenic fungus Aschersonia spp. that served as a model biocontrol agent. Apparently, because of the light-dispersing property, bentonite and attapulgite per se provided significant photoprotection. All clay matrices containing FG provided a substantial photostabilization effect.     

Peptide Cysteine Thiols Act as Photostabilizer of Avobenzone through Stabilizing the Transition State of Keto-Enol Tautomerization

Photostabilizers have been used to impart stability to an FDA-approved chemical UV-A filter avobenzone against the UV-A radiations and sunlight. The thiol group of glutathione plays a critical role in imparting the photostabilization activity of glutathione on avobenzone. The current report aims to evaluate the photostabilization activity of multiple thiols containing cysteine peptides on avobenzone. Cysteine-tripeptide and cysteine-pentapeptide were chemically synthesized and characterized using mass spectrometry. Synthetic peptides were assessed for their photostabilization activity on the enolic-form of the avobenzone under natural sunlight using UV spectroscopy in both protic and aprotic solvents. Unlike glutathione, which has pronounced activity in protic solvents, cysteine-pentapeptide exhibits similar photoprotection activity in both protic and aprotic solvents. Computational calculations using DFT suggest that peptide cysteine thiols may assist in the reversal of the photoketonization process of avobenzone thereby exhibiting the photoprotection activity to the enolic-form of avobenzone. Peptide cysteine thiols lower the activation energy barrier of keto-to-enol tautomerization of avobenzone by 30 kcal mol⁻¹ by assisting the proton shuttle through a six-membered transition state. The current report emphasizes the applications of peptide thiols in cosmetics and may help in the development of peptides as aesthetic medicines.     

EFFECT OF COMPOSITION AND PROCESSING CONDITION ON MICROSTRUCTURAL PROPERTIES AND DURABILITY OF FLUOROPOLYMER/ACRYLIC BLENDS

Fluoropolymer blends have been widely used as binders for exterior coatings because of their excellent resistance to ultra-violet (UV) radiation as well as to many corrosive chemical agents.It is known that the fluorinated component usually has a lower glass transition temperature and easily crystallizes in the final structure depending upon the blend composition and sample annealing condition.We investigated the effect of blend composition and annealing process (slow and fast cooling) on the surface mor...