几种防晒剂及其复配物紫外吸收特征的研究

研究了部分常用化学防晒剂、物理防晒剂和天然紫外吸收剂的紫外吸收特征,并对化学防晒剂之间的复配、化学防晒剂与天然紫外吸收剂之间的复配以及天然紫外吸收剂之间的复配的协同效应进行研究,为防晒化妆品的开发提供参考依据。     

形貌对CeO2纳米颗粒紫外吸收性能的影响

以Ce(NO3)3·6HO和NaOH为原料,采用水热合成法制备了不同晶粒尺寸、形貌各异(球形、棒状、立方体等)的纳米CeO2产物.XRD测试表明所得产物为立方萤石晶型结构.紫外吸收光谱表明:对于球形颗粒CeO2,晶粒尺寸越小,紫外吸收能力越强.颗粒形貌对纳米CeO2紫外吸收能力有较大的影响,在紫外光区吸收能力:纳米棒＞纳米立方体＞纳米球形.研究发现形貌对紫外吸收能力影响与其纳米颗粒的暴露晶面的表面能有关,暴露晶面的表面能越高,紫外吸收能力越强.     

防晒化妆品用纳米氧化钛的表面处理及紫外吸收性能

对作为紫外线吸收剂的纳米氧化钛在化妆品中的应用进行了探讨,详细介绍了纳米氧化钛的表面改性方法,以及纳米氧化钛紫外线吸收效果及其评价方法。     

防晒剂的性能及质量评价

随着臭氧层的日益变薄,到达地面的紫外线不断增多,防晒变得越来越重要,人们对紫外线的防护意识也日益增强。介绍了防晒剂的种类、特点及性能,防晒剂的评价指标及安全性,以及天然防晒剂的发展趋势。     

季也蒙毕赤酵母DQ11发酵酒糟水解液生产木糖醇条件的优化

目的优化季也蒙毕赤酵母DQ11发酵酒糟水解液生产木糖醇的条件。方法通过单因素试验和正交试验,优化季也蒙毕赤酵母DQ11发酵酒糟水解液生产木糖醇的发酵温度、初始pH值、转速和接种量,通过高效液相色谱法测定发酵液中木糖醇的含量;采用最佳发酵条件发酵生产木糖醇,检测木糖醇含量。结果摇瓶发酵酒糟水解液生产木糖醇的最佳条件为:发酵温度28℃,起始pH值5.0,接种量5%(v/v),摇床转速180 r/min;以最佳条件发酵酒糟水解液生产木糖醇的含量为9.016 g/L。结论优化了季也蒙毕赤酵母DQ11发酵酒糟水解液生产木糖醇的条件,为以酒糟生产木糖醇的可能性提供了实验依据。     

紫外老化对聚甲醛纤维结构与性能的影响

研究了聚甲醛(POM)纤维在自然暴露老化以及在紫外老化箱中的加速老化行为,通过单纤维强力仪、扫描电镜、红外光谱仪、白度分析仪分析了老化对POM纤维结构与性能的影响。结果表明:POM纤维的耐老化性能差,自然老化8个月,抗拉强度下降22%,紫外老化14 d,抗拉强度下降84%;在光、氧的作用下,分子链发生断链的端基被氧化成羰基、羧基和羟基,黄色指数逐渐增加;通过添加抗老化母料F可显著提高POM纤维的抗老化性能。当抗老化母料F质量分数为3%、在紫外加速老化14 d时,POM纤维的抗拉强度仅下降8%,比未添加抗老化母料的POM纤维的抗拉强度提高了76%。     

纳米ZnO粉体的制备及紫外-可见光吸收性能研究

采用直接沉淀法,以ZnSO4·7H2O为锌源,以Na2CO3为沉淀剂制得纳米ZnO的前驱体,在不同的热处理温度条件下制备了不同晶粒尺寸的纳米ZnO粉体.用X-射线衍射仪,透射电子显微镜和紫外-可见分光光度计对粉体的晶体结构,显微形貌和紫外-可见光吸收性能进行了表征,并重点探讨了煅烧温度对纳米ZnO粉体在紫外-可见光波段吸收性能的影响.结果表明,前驱体为Zn5(OH)6(CO3)2,300℃以上的煅烧温度下为六方晶系的球形纳米ZnO.合成的粉体在可见光区有很好的透过性,而在紫外光区具有很宽的吸收频段和优异的吸收性能,且随煅烧温度的不同而出现变化.     

抗紫外性能的研究

研究了用添加结晶控制剂和光稳定剂的方法改善N*PP(A)纤维拉伸性能和抗紫外性能。结果表明,高等规度N-PP(A)纤维的力学性能优于低等规度N-PP(B)纤维,N-PP(A)纤维的抗紫外性能优于普通PP(3702)纤维;添加的结晶控制剂(0．1％)使N-PP(A)初生纤维的拉伸性能变好;光稳定剂A的加入(0．25％)使N-PP(A)纤维抗紫外性能显著提高,户外老化1344小时后,强度仅下降5．5％,明显优于试验所用涤纶。抗紫外N-PP(A)纤维(含抗氧剂和光稳定剂)具有优良的力学性能,特别是加入少量结晶控制剂的抗紫外N-PP(A)纤雏,其环扣强度没有明显降低。     

紫外预处理对饮用水净化PVDF膜生物性能的影响

分别对紫外预处理-混凝-超滤工艺与混凝-超滤短流程膜工艺处理得到的水体污染情况进行了对比,深入探讨了紫外预处理方法对超滤膜生物污染产生的影响。研究结果表明:不管是否采取紫外预处理并未引起絮体颗粒尺寸的明显改变;经过紫外预处理得到的絮体粒径尺寸平均等于228μm。随着紫外预处理之后膜池中的微生物含量发生了降低。紫外预处理能够降低膜表面的微生物附着量,降低了蛋白质和多糖含量,从而避免膜的严重污染。采用两种预处理方式得到了具有相近的滤层表面形貌,紫外预处理不会对絮体产生明显影响。细菌浓度比真菌高出了近10倍,说明采用紫外预处理方法不会使膜表面微生物群落发生了较大改变。     

紫外老化对聚甲基丙烯酸甲酯结构和性能的影响

通过人工加速老化试验,研究了聚甲基丙烯酸甲酯(PMMA)在不同紫外辐照条件下的性能变化规律。利用力学试验、凝胶渗透色谱(GPC)、傅里叶红外光谱(FTIR)等表征技术,分析了紫外老化对PMMA力学性能、分子结构、分子量及分子量分布的影响。结果表明,随着紫外老化的环境温度提高、老化时间延长,样品的拉伸强度、冲击强度均呈现下降趋势。样品在环境温度100℃条件下,老化280 min后,冲击强度下降最明显。老化后,红外光谱的羰基吸收带加宽,并且在1615 cm^-1处和1640 cm^-1处出现了包含不饱和键和羰基生色团的新吸收峰,样品的分子量微分分布宽度变宽,分子量移向低分子端的趋势明显,分子量多分散性增加。     

中药对黑素生物合成上调作用影响的研究

通过考察单味中药薄荷、降香和得方中药七宝美髯红方的水提物对酪氨酸酶促黑素生物合成的影响作用，表明：薄荷、降香和复方中药七宝美髯组方提物有促进黑素生物合成的作用，同时紫外光波长对黑素合成上调率的影响更为显著。实验范围内，波长330nm的紫外光使100mg/mL薄荷水提物参与黑素合成物（Ⅰ）的上调率达617％，使100mg/mL降香水提物参与黑素合成物（Ⅱ）的上调率达685％；波长300nm的紫外光使200mg/mL七宝美髯组方水提物参与黑素合成物（Ⅲ）的上调率提高到544％。Ⅰ和Ⅱ在UVB、UVA段均有强吸收；Ⅲ在UVB在有强吸收，但在UVA段的吸收减弱。     

Application of benzotriazole reactive UV absorbers to cellulose and determining sun protection of treated fabric spectrophotometrically

UV absorbers for treating cotton textiles with the aim of increased protection against harmful effects of UV component of solar radiation have been prepared by reactions of five different aminophenylsulfobenzotriazoles with the condensation product of 4‐aminophenyl‐sulfatoethylsulfone and cyanuric chloride. The UV absorbers with two different reactive groups (monochlorotriazine and aromatic vinylsulfone), capable of formation of covalent bonds with hydroxyl groups of cellulose, were applied to one cellophane foil and two cotton fabrics of different porosities. This treatment increased the ultraviolet protection factor from a value of UPF = 3 to UPF = 100 and above. For attaining a high UPF value, the cotton material should exhibit low porosity. The UV absorbers with 2‐hydroxyphenyl group are stable in light and do not fluoresce on the fabric on contrary to derivatives without 2‐hydroxyphenyl group or with 2‐methoxyphenyl group. The high photostability of absorbers is explained by the possibility to disperse the absorbed energy of UV radiation in the form of harmless energy such as IR radiation (heat) through the reversible hydrogen bond between phenolic hydroxyl group and triazine cycle. The UV filters block the effect of optical brightening agents on cotton by quenching the fluorescence. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Bioconversion of corn stover hydrolysate to ethanol by a recombinant yeast strain

Three corn stover hydrolysates, enzymatic hydrolysates prepared from acid and alkaline pretreatments separately and hemicellulosic hydrolysate prepared from acid pretreatment, were evaluated in composition and fermentability. For enzymatic hydrolysate from alkaline pretreatment, ethanol yield on fermentable sugars and fermentation efficiency reached highest among the three hydrolysates; meanwhile, ethanol yield on dry corn stover reached 0.175 g/g, higher than the sum of those of two hydrolysates from acid pretreatment. Fermentation process of the enzymatic hydrolysate from alkaline pretreatment was further investigated using free and immobilized cells of recombinant Saccharomyces cerevisiae ZU-10. Concentrated hydrolysate containing 66.9 g/L glucose and 32.1 g/L xylose was utilized. In the fermentation with free cells, 41.2 g/L ethanol was obtained within 72 h with an ethanol yield on fermentable sugars of 0.416 g/g. Immobilized cells greatly enhanced the ethanol productivity, while the ethanol yield on fermentable sugars of 0.411 g/g could still be reached. Repeated batch fermentation with immobilized cells was further attempted up to six batches. The ethanol yield on fermentable sugars maintained above 0.403 g/g with all glucose and more than 92.83% xylose utilized in each batch. These results demonstrate the feasibility and efficiency of ethanol production from corn stover hydrolysates.     

ORP对酿酒酵母在木质纤维素水解液抑制物中发酵的影响

木质纤维素水解液中的毒性副产物对酿酒细胞具有抑制作用,采用氧化还原电位(oxidoreduction potential, ORP)调控,能够提高细胞对抑制物的耐受性。考察了代表性抑制物乙酸、糠醛及苯酚对酵母细胞生长和代谢的影响,并通过添加氧化剂赤血盐(K₃[Fe(CN)₆])和还原剂二硫苏糖醇(DTT)调节发酵液ORP初始值在(305±5)mV、(157±8)mV及(-150±5)mV,研究不同ORP条件下细胞对抑制物的耐受性影响。结果表明,氧化态能提高生物量并缩短发酵时间。除苯酚外,氧化态也利于提高乙醇的收率。对细胞保护剂甘油合成的方面,氧化态和还原态都会促进甘油合成。在水解液脱毒方面,氧化态表现比还原态要好,因为氧化态促进生物量积累,有利于通过细胞自身代谢脱毒。     

Effect of microstructure of fluorinated acrylic coatings on UV degradation testing

This paper presents research results on the relationships between the microstructure and the performance/weatherability of fluoropolymer/acrylic coatings. We studied fluoropolymer/acrylic blends of identical composition, prepared as films using three different methods: 2-stage emulsion polymerization followed by latex film formation; cold-blending (physically mixing) acrylic and fluoropolymer latex dispersions followed by latex film formation; and solution casting using an organic solvent. We investigated the effects of the mixing method, and the level of acrylic in the blend on the microstructure/morphology and on the durability-related physical properties of the fluoropolymer/acrylic films. Small angle neutron scattering was performed to determine the microstructure/morphology of fluoropolymer-rich micro-domains in the coatings prepared using these three methods. The physical properties tested included the glass transition temperature, the crystallinity fraction, and the tensile strength. The mass loss rates observed during UV exposure testing correlate with the final microstructures of the films.     

Dynamics analysis of an age distribution model of oscillating yeast cultures

The ability of an age-population balance model to capture experimentally observed oscillatory dynamics of continuous cultures of budding yeast was investigated through numerical simulations. Experiments with continuous yeast cultures have shown that several oscillatory modes can occur at the same operating condition, and that the mode attained depends on the start-up conditions. Numerical simulations of the model did reveal the existence of several stable periodic solutions. However, each occurred over a different range of dilution rates. Experiments also have shown that the steady state in continuous yeast cultures is stable, even under conditions that allow oscillatory dynamics. The stability of the steady state of the age population balance model under conditions that allow oscillatory dynamics was not resolved. The Jacobian matrix at the steady state is highly ill conditioned, with some eigenvalues very close to the imaginary axis. Using different integration routines to solve the model gave different results with regard to the stability of the steady state, one solver finding the steady state to be stable, another finding the steady state to be unstable.     

纳米TiO2对胶原的紫外屏蔽作用

采用紫外光谱分析法在体外研究了纳米TiO2对胶原的紫外屏蔽作用。结果表明纳米TiO2对胶原具有显著的紫外屏蔽作用。并且2．5％TiO2比0．5％TiO2的添加量对胶原的紫外屏蔽作用更强。     

Effect of UV aging on electrochemical behavior of an anticorrosion paint

The effect of the photochemical artificial ageing (UVA) on the electrochemical behavior of an anticorrosion paint has been studied by electrochemical impedance spectroscopy (EIS). Two types of coatings have been tested: a formulated tri coat system (FS) formed by a primer (epoxy), an intermediate coat (epoxy) and a topcoat (alkyd) which presents a total film thickness of 240 μm and, on the other hand, a non-formulated varnish (NFV) which presents a total film thickness of 70 μm. Panels have been aged in a QUV chamber and the maximal exposure's time was about 1000 h. EIS testing were carried out with a naturally aerated 3% NaCl solution.     

CO2 absorption rate in an algal culture: Effect of pH

In a CO₂-limited algal culture, grown in a tubular loop photobioreactor, the maximum rate of CO₂ absorption increased about 1.5-fold when the culture pH value was increased from 6.5 to 7.5 with a fixed initial P_CO2. The mean volumetric CO₂ transfer coefficient (K_La) increased about 1.8-fold. The bicarbonate ion concentration would be increased 10-fold by the pH increase. The effect of pH on the absorption rate is attributed to changes in either the CO₂ diffusivity, the gas bubble size, or the CO₂ reaction kinetics at the gas/liquid boundary.     

Moisture absorption and desorption in a UV cured urethane acrylate adhesive based on radiation source

A photopolymerizable urethane acrylate (UA) adhesive was cured using two different sources: a conventional UV‐lamp and a UV‐emitting light emitting diode (LED). Moisture uptake in cured specimens was characterized by immersion in deionized water at 21.8, 30, 37.5, and 45°C for a period of 6 months. Additionally, desorption experiments were performed for selected specimens under vacuum at room temperature. Material degradation in the form of mass loss was observed in all samples after attainment of a maximum water uptake level, with the phenomenon being more pronounced at higher immersion temperatures. This degradation is attributed to leaching and dissolution of uncured monomers and lower weight molecular species from the samples. A two stage moisture uptake model is proposed to account for mass loss and excellent agreement between the tested mass loss and the loss‐rate parameters determined from the model is shown. Performance of specimens was characterized with dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). It was found the LED source was not as effective in curing surfaces, due to which there is a higher level of mass and lower T_g from hygrothermal exposure as compared to the core regions of the LED cured specimens and the overall lamp cured specimens. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008