Screening the origin and weathering of oil slicks by attenuated total reflectance mid-IR spectrometry

The combination of attenuated total reflectance-fourier transform mid-infrared spectrometry (ATR-FTMIR) and multivariate pattern recognition is presented as a fast and convenient methodology to ascertain the source product an oil slick comes from and to evaluate the extent of its weathering. Different types of hydrocarbons (including crude oils, several heavy distillates and the Prestige's heavy fuel oil) were spilled on metallic containers designed ad hoc and their fate monitored by ATR-FTMIR. Not only environmental conditions were considered for weathering but artificial IR- and UV-irradiation. Pattern-recognition studies revealed that the different hydrocarbons clustered at different locations on the score plots and that the samples corresponding to each oil became ordered according to the extent of their weathering. Among them, fuel oil samples coming from the recent disaster of the Prestige tanker off the Galician shoreline showed a distinctive behaviour. Comparison of natural-, IR- and UV-weathering of a crude oil showed that IR solar radiation can be important in oil-weathering, in addition to broadly-reported UV degradation.     

Rheological investigation of the influence of molecular structure on natural and accelerated UV degradation of linear low density polyethylene

Metallocene and Ziegler-Natta (ZN) linear low density polyethylenes (LLDPEs) of different branch types and contents as well as linear high density polyethylene (HDPE) were exposed to natural and accelerated weather conditions. The degree of UV degradation of exposed samples was measured by rheological techniques and results were compared with unexposed polymers. Dynamic shear measurements were performed in an ARES rheometer in the linear viscoelastic range. The degree of enhancement or reduction in viscosity and elasticity was used as a measure of the degree of cross-linking or chain scission, respectively. The degradation results of LLDPE suggest that both cross-linking and chain scission are taking place. Chain scission dominated the degradation at high levels of short chain branching (SCB) and long exposure times. The degradation mechanism of m-LLDPE and ZN-LLDPE is similar; however, m-LLDPE showed a higher degradation rate than ZN-LLDPE of similar M_w and average SCB. ZN-LLDPE was found to be more stable than a similar m-LLDPE. Comonomer type had little influence on degradation. Dynamic shear rheology was very useful in revealing the influence of different molecular parameters and it exposed the degradation mechanism.     

Influence of Natural and Accelerated Weathering on the Mechanical Properties of Low-Density Polyethylene Films

Natural and accelerated weathering tests were performed to inspect the effect of antioxidants on low-density polyethylene (LDPE) films used as greenhouse covering materials. The LDPE pellets were extruded and blown into a film using a twin-screw extruder and film blowing machine, respectively. The film with 0.2 wt.% Alkanox-240 (AN-0.2) stabilizer showed the highest tensile strength (11 MPa) among all samples during 90 days of natural as well as accelerated weathering. The elastic modulus of the film with 0.5 wt.% of Good-rite (GR-0.5) increased after weathering from approximately 91.8 to 138.9 MPa, and showed the best performance. Morphological images of the neat LDPE film during weathering showed some cracks and grooves, while those of stabilized films showed fewer cracks. Moreover, the estimation of the rapidity of the accelerated method compared to the natural one was approximately nine times faster in Riyadh during the summer season (June–August). The present study suggests that the addition of antioxidants can improve the tensile strength, stability, and, hence, the effectiveness of these films. The best antioxidants were found to be 0.2 wt.% Alkanox and 0.5 wt.% Good-rite antioxidants.     

Effect of annealing on hydrophobic stability of plasma deposited fluoropolymer coatings

Fluorinated amorphous carbon (a-C:F) films e.g. plasma polymerised perfluorocyclobutane have long attracted much consideration due to their low surface energy, hydrophobicity, low refractive index, good electrical and thermal insulation and good thermal stability. Although a-C:F films have many advantages, hydrophobic stability over time in air and water remains a major concern. In this study, the effects of weathering conditions on the hydrophobicity of fluorocarbon films prepared from perfluorocyclobutane precursors were examined using water contact angle measurements. It was found that the high initial hydrophobicity of as-deposited films degrades rapidly in humid conditions. The stability of hydrophobicity can be significantly improved when a suitable treatment such as annealing is employed. The mechanism of weathering was explained with the help of a number of morphological and chemical characterisation techniques such as Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS). In particular, XPS results demonstrated that a reduction in the overall amount of -CF₃ radical, oxygenation of surface fluorides and the formation of an overlayer all influence the degradation of fluorocarbon in aquatic environment.     

重庆地区露天石刻早期封护材料老化产物及其影响研究

重庆市市委会办公大楼旧址前有一组露天存放的清代砂岩石狮子,表面覆盖着黑色硬壳状物质, 发生大面积脱落,起翘和卷曲。为了揭示黑色硬壳状结构组成,研究其形成过程及对文物产生的影响,利用环境扫描电子显微镜(SEM),X-射线衍射仪(XRD),X-射线荧光光谱仪(XRF),傅里叶变换红外光谱仪(FTIR)和X-射线光电子能谱(XPS)对黑色硬壳及文物表层砂岩样品进行了检测分析研究。结果发现：黑色硬壳断面Mapping元素分布图显示其分为底漆层,中间层和表层,系石刻早期封护层的老化产物;中间层含有立德粉(硫化锌和硫酸钡),黑色外观源于表层中含铅颜料(铅白)变色形成黑色硫化铅及树脂碳化所致;红外光谱与光电子能谱显示出黑色硬壳中含有强的羟基(-OH)特征峰,说明封护层中有机物老化后形成了大量羟基,从而增强了自身亲水性,造成易吸水溶胀与干燥收缩情况,导致大面积脱落,起翘和卷曲现象;黑色硬壳起翘和卷曲部位与下层石刻表面之间形成了易于积水的微空隙,能够聚集雨水中的有害物质,造成石刻表层岩石发生腐蚀,例如黑色硬壳背面及下层岩石表面中高含量硬石膏(CaSO₄),经生水化作用后转化为石膏(CaSO₄·2H₂O),发生体积膨胀造成岩石表面松动和酥粉。因此,当露天文物表面上封护层已老化时,及时地进行清除是十分必要的。     

香港花岗岩风化分级化学指标体系与风化壳分带

火成岩的化学风化过程实质上就是碱、碱土金属组分水解淋失与脱硅富铁铝化的地球化学过程。不同风化程度的岩石处于整个化学风化过程的不同阶段,因而具有不同的化学成分和风化度指标。笔者在对香港九龙两个地方5个钻孔共计150件不同深度、不同风化程度的样品化学全分析结果与岩土风化程度宏观判别结果的相互对比、选择和确认的基础上,建立了香港地区花岗岩风化岩土风化程度工程分级的化学指标体系。这一研究成果的提出不仅有利于提高花岗岩风化岩土工程分类的科。学性、可靠性和实用性,而且可以为风化岩土工程特性与风化作用关系研究提供理论依据。     

宁波大桥主墩墩址软弱带成因机制研究

通过对宁波大桥主墩墩址软弱带详细的地质勘测和综合方法研究，内中包括粘土泥质物Ｘ射线衍射分析，软弱带岩石化学成分和不同成因砂和砾石的成分和特征研究，特别是软弱带的显微构造和物质来源的研究，本文对这一软弱带的成因机制着重进行了探讨。研究发现，这一软弱带在结构上可划分为三部分或三层结构，下部为挤压破碎带、中部为风化产物、上部为地表水贯入充填堆积。它表明这一软弱带经历了三种不同的地质作用的演化过程或具有三种物质来源。这一研究结论对大桥的设计和施工有重要的影响和意义。     

Deformation and stress from in-pore drying-induced crystallization of salt

The deformation and the fracture of porous solids from internal crystallization of salt is explored in the framework of the thermodynamics of unsaturated brittle poroelasticity. In the first place the usual theory of crystal growth in confined conditions is further developed in order to include both the deformation and the drying of the porous solid. The thermodynamics reveals the existence of a dilation coefficient associated with the crystallization process, and provides a solute-crystal equilibrium condition which involves the relative humidity, the supersaturation, and the salt characteristics. This thermodynamic condition and the mechanical equilibrium of the solution-crystal interface combine to give the current crystallization pore radius. Upscaling this information at the macroscopic scale, and taking into account the salt mass supplied by the invading solution, the approach leads to a quantitative analysis of the role of the pore size distribution on the crystal growth under repeated imbibition-drying cycles. The deformation and the fracture of the porous solid from drying-induced crystallization are then considered in the context of brittle poroelasticity. The current unsaturated macroscopic poroelastic properties are upscaled from the microscopic elastic properties of the solid matrix and from the current liquid, crystal and gas saturations. The adoption of a fracture criterion based on the elastic energy that the solid matrix can ultimately store finally leads to the determination of how long a stone can resist repeated cycles of drying-induced crystallization of salt.     

Wax treatment of wood slows photodegradation

Waxes and wax emulsions are one of the most important solutions for non-biocidal wood protection. Wax treated wood is designed for outdoor use, therefore it is of considerable importance to elucidate the influence of weathering on the photodegradation processes. It is presumed, that wax treatment will reduce water uptake and thus reduce or slow down photodegradation processes. In order to test this hypothesis, three types of wax emulsions at two different concentrations were vacuum impregnated into Norway spruce wood specimens: an emulsion of montan wax (LGE), an emulsion of polyethylene (WE1) and an emulsion of oxidized polyethylene (WE6) wax. The samples were exposed to artificial accelerated weathering (AAW) for 500 cycles. Before and after AAW colour, the contact angle of water and moisture content were determined. Chemical and morphological changes at exposed surfaces were also investigated with FTIR spectroscopy and SEM. In parallel, the uptake of wax emulsions and water into the axial surfaces of samples was determined with a tensiometer. The moisture content measurements showed that the best hydrophobic effect was achieved with LGE treated wood, where the lowest colour and FTIR changes were observed as well. These results were supported by tensiometer measurements as well. Presented data clearly showed that high loadings of waxes reduce or at least slow down weathering. Among tested waxes, montan wax was found the most effective.     

埋藏哈密翼龙化石的雅丹风化的光谱分析——以大海道2号水源地雅丹为例

新疆哈密地区翼龙化石具有极高的科学研究价值.哈密翼龙动物群主要埋藏在早白垩世湖相地层形成的雅丹中,富集在风暴沉积层.化石一旦暴露地表,就会发生不同程度的自然风化破碎,尤其是见水或受潮后风化更为严重.哈密大海道2号水源地附近的雅丹底部由于地下水和间歇性地表水的作用,发生了严重的盐碱析出导致的强烈风化现象,造成雅丹下部剥落...