Wood Preservative Solutions for Creative and Sustainable Bridge Design and Construction

Timber bridges can provide an economical alternative to concrete and steel structures, particularly in rural areas where vehicle traffic is light to moderate. The wooden components of bridges have historically been preserved with either an oil type or waterborne preservative system to protect the wood from decay in order to maintain required performance standards for an extended period of time. The focus of this paper is to describe some of the key preservatives, research and case studies that support use of preserved wood, and some important steps to follow for the appropriate and safe use of preserved wood when the planned application will be in or over aquatic and wetland environments. A wealth of scientific information has been collected and analyzed that clearly suggests the use of preserved wood does not present a significant adverse effect on aquatic and wetland environments. This conclusion is based on two decades of empirical research and case study evaluating the environmental fate and effects of preserved wood, level of migration of contaminates into aquatic and marine environments, and the preserved wood environment. This is particularly true when risks are properly assessed on a project site, the appropriate preservative is selected and the wood is preserved to the Western Wood Preservers Institute＇s BMPs （best management practices）, along with properly installing and maintaining the preserved material. To assist with the assessment process, peer-reviewed risk assessment models for 11 commonly used preservatives have been developed that provide for streamlined data entry by users and allow for evaluation of a structure above and below water. A companion preliminary screening level assessment tool is also available. When these measures are properly utilized engineers, biologists and other responsible officials can be confident that the service life of the preserved wood components will more than likely meet the required performance standards in an environmentally safe manner for up to 50 or more     

无纺布增强用水性聚氨酯乳液的制备

以聚氧化丙烯二醇(N-210)、甲苯二异氰酸酯(TDI)和二羟甲基丙酸(DMPA)为原料,采用内乳化法合成了无纺布增强用水性聚氨酯乳液。研究了R值(nNCO:nOH)、DMPA用量、不同二醇扩链剂和乳液扩链剂间苯二胺的用量对水性聚氨酯乳液外观、粘度和稳定性以及对乳胶膜的强度、硬度和耐水性的影响。结果表明:R值=3.7、nDMPA:nN-210=0.7、采用新戊二醇和间苯二胺扩链,合成的水性聚氨酯乳液储存稳定、耐水性好,用于无纺布增强,制造树脂抛光轮。     

Associative behavior of hydrophobically modified hydroxyethyl celluloses (HMHECs) in waterborne coatings

The associative behavior of hydrophobically modified hydroxyethyl cellulose (HMHEC) in polymer dispersions has been determined as a function of the composition of both the associative thickener (AT) and the latex. How changes in interaction between HMHEC and the latex influence the rheology of the latex thickener systems is discussed. Adsorption of HMHECs onto an acrylic emulsion strongly depends on the hydrophobe type and degree of substitution, as well as on the molecular weight of the associative thickener. The degree of latex adsorption is influenced dramatically by the stabilization system utilized, that is choice and level of surfactant and carboxylic acid content, in addition to the composition of the monomer mix. Rheological measurements demonstrate that HMHECs of specific composition can provide gloss emulsion paints with a balance of rheological properties, combining excellent levelling with sag resistance.     

水性聚氨酯的合成及应用

本文对水性聚氨酯的合成单体、化学原理及工艺进行了介绍。     

Chlorine and ozone disinfection of Encephalitozoon intestinalis spores

Microsporidia are intracellular eukaryotic parasites which have the potential for zoonotic and environmental, including waterborne, transmission. Encephalitozoon intestinalis is a microsporidian pathogen of humans and animals and has been detected in surface water. It is also on the Contaminant Candidate List of potential emerging waterborne pathogens for the US EPA. We performed disinfection studies using chlorine and ozone on E. intestinalis spores with a cell-culture most-probable-number assay to determine infectivity. Chlorine experiments were performed at 5 degrees C at pH of 6, 7, and 8 with 1mg/L initial chlorine concentrations, while ozone experiments were performed at 5 degrees C and pH 7 with initial ozone doses of 1 and 0.5mg/L, both in buffered water. A derivation of Hom's model for disinfection kinetics under dynamic disinfectant concentrations was used to fit observed data and calculate concentration-time product (C*t) values. Chlorine C*t values varied with pH such that 99% (2-log(10)) C*t ranged from 12.8 at pH 6 to 68.8 at pH 8 (mg min/L). Ozone C*t values were approximately an order of magnitude less at 0.59--0.84 mg min/L, depending on initial concentration.     

Effect of the hard segment on the properties of UV curable waterborne blocked polyurethanes

Two types of UV curable waterborne blocked polyurethanes (PUs) were obtained from 2,4-tolylene diisocyanate(TDI) and isophorone diisocyanate (IPDI), which had the same soft segments and different hard segments. The PUs contained both the UV curable C=C bond and the blocked NCO groups which could be de-blocked when heated. Effect of the hard segment on the properties of the two types of PUs was investigated. The FTIR spectra method was employed to confirm the structure of the PUs. The photo-DSC was used to study the photo-polymerization rate of the PUs under UV irradiation in the presence of a photo-initiator and the C=C conversion behaviors. Heating-up IR analysis was used to track the de-blocking process and the heat curing process. The thermal degradation analysis (TGA) was employed to investigate the thermal stability of the UV cured films before and after heat curing process. Dynamic mechanical properties of the UV and heat cured films were investigated by the dynamic mechanical thermal analysis (DMTA).     

Epoxy coatings with modified montmorillonites

Two types of modified layered aluminosilicates (montmorillonites) with different grain size and gallery spaces were tested as nanofillers in epoxy coating compositions for a steel substrate. Organophilic montmorillonites, in the amount of 2.5 and 5 wt% were introduced to waterborne and to solvent-type epoxy coating materials (based on bisphenol-A epoxy resins and various curing agents). The results of this work indicate that processing properties of coating compositions (leveling and drying time) as well as mechanical properties of coatings (hardness, scratch and abrasion resistance, adhesion to steel) were positively affected by a layered aluminosilicate nanofiller. Enhanced water resistance (lower water absorbance) of coats, especially those formed from waterborne compositions, has been found.     

全氟烷基丙烯酸酯对全氟丙烯酸酯乳液性能的影响

在十八烷基三甲基氯化铵(1831)和含氟乳化剂N,N-二甲基-N'-(2-三氟甲基-1-五氟乙基)(FS)的复合乳化作用下,以全氟烷基丙烯酸酯(FM)、丙烯酸丁酯(BA)、甲基丙烯酸甲酯(MMA)、甲基丙烯酸二甲基胺基乙酯(DM)为反应单体,以过硫酸钾(KPS)为引发剂,制备了全氟烷基聚丙烯酸酯乳液(FPE)。通过红外光谱(IR)、热失重分析(TG)对聚合物的结构和热稳定性进行了表征,并用接触角、原子力显微镜(AFM)分析了乳液的防水性能,表明FM成功地接枝到了聚合物上,随着含氟量的增加,分解温度达351.5℃;在含氟量达到w(FM)=12%时,水接触角达127°;采用Z粒度仪以及透射电镜(TEM)对共聚物外观形貌进行了表征,结果表明,乳胶粒的形态呈球形,呈单分散,平均乳液粒径为220 nm。     

防粘纸离型性能研究

本研究通过比较以3种不同有机硅树脂为防粘剂的防粘纸离型性能,从中优选出水性有机硅树脂作为后续混合正交实验的防粘剂,重点探讨了底涂主剂类型、底涂压光条件、防粘层涂布量和防粘层配比对防粘纸离型性能的影响.结果表明,以不同配比水性有机硅树脂为防粘剂制备的防粘纸,剥离强度范围为0.3 ～ 1.9N/15mm;在探讨的4个影响因素中,防粘层配比对离型性能的影响最大.     

Method validation for norovirus detection in naturally contaminated irrigation water and fresh produce

Human enteric viruses are shed in extremely high numbers in the feces of infected individuals, becoming environmental contaminants and eventually leading to contamination of a variety of foodstuffs at the pre-harvest stage. Among these foods at risk is fresh produce and irrigation water is a major vehicle for crop contamination. In the present study, a standardized molecular method for quantitative virus assay has been evaluated in different types of fresh produce and in irrigation water for human norovirus (NoV) detection. Two different virus concentration procedures, polyethylene-glycol precipitation (PEG) and organic flocculation (OF), were employed. The procedures were initially assayed in spiked samples and later validated on naturally contaminated samples from the Nile Delta in Egypt.