Potential of Bayesian networks for adaptive management in water recycling

Water recycling is an important solution to increasing water scarcity. However, universal wastewater treatment standards deter uptake of recycling schemes. Lack of data also impedes fit-for-purpose water recycling and water managers are challenged by decision making under uncertain conditions. Bayesian networks (BNs) are increasingly recognised as a valuable tool for decision making under uncertainty. In this study BNs are used to model health risks associated with wastewater irrigation of a public open space. Three BNs based on quantitative microbial risk assessment model risk reduction potential along a treatment chain and at the site of reuse. The BNs simulate multiple exposure profiles and scenarios, providing conditional probability of infection or illness, comparable with health-based targets. Study findings highlight the significant impact of post treatment risk mitigation, despite challenging conditions. BNs provide a transparent, defensible evidence base for mapping and quantifying risk pathways, comparing decision options and predicting outcomes of management policies.     

新型环保固体胶的研制与性能研究

用水性环氧树脂(自制)改性羧甲基纤维素钠(CMC),硬脂钠为赋型剂、乙二醇为保湿剂制备出粘接性好的新型环保固体胶。通过探索实验条件,初步确定配方中各因素的种类及用量,然后采用响应面法优化配方中主要因素用量对固体胶性能的影响。实验结果表明:羧甲基纤维素钠用量为3.23%,水性环氧树脂在29.89%,硬脂酸钠用量为2.03%,水为55%,乙二醇为10%,反应温度80℃时制得的无毒固体胶成型好、粘结能力强,可用于常见的纸张粘结及纸箱包装等。     

Waterborne latex coatings of color: III. Triblock polyether influences on color development and viscosity

Oxyethylene (PEO)/oxypropylene (PPO) triblock polymers are added to colorant formulations to determine the influence of molecular weight and other structural variances on the rheology and color development of tinted latex paints. Waterborne coatings are a matrix of many coating components. In this study, a 108- or a 600-nm latex was thickened with a nonassociative thickener, hydroxyethyl cellulose, or an associative telechelic HEUR thickener. Triblock polymers with internal PPO segments and PEO terminal segments added as a dispersant to colorant packages, lead to better color development than PPO/PEO/PPO triblocks dispersants in carbon black (CB) tinted paints. The increase in color development with high molecular weight (MW) triblocks starts at a very low concentration (2 mM) and plateaus in a Langmuir-type adsorption isotherm. Lower molecular weight triblock polymers also exhibit this behavior in CB-, red-, and yellow-tinted latex coatings; however, increasing the terminal PEO segment sizes leads to better color development only in the CB-tinted coatings. With large PEO terminal units red and yellow tints are high only at very low concentrations (2 mM) of the triblock. This parabolic response in color development, in contrast to CB-tinted formulations, is attributed to the high surface area and porosity of CB that limits the amount of large PEO segments interacting with the talc particle present at twice the volume fraction of the colorant. With the lower surface areas of the red and yellow colorants, the interaction of the large PEO terminal segments with talc particles accounts for the limited triblock concentration for which good color development is observed. This can be reversed by decreasing or eliminating talc from the formulation.     

Recent advances in aqueous two-component systems for heavy-duty metal protection

Although waterborne coatings have successfully replaced their solventborne counterparts in a variety of areas, their use generally has been limited to applications with relatively modest performance requirements. Recently, advances in technology have allowed for the design of waterborne coatings with performance suitable for more demanding applications. The emergence of two-component waterborne polyurethane coatings exemplifies this trend. These coatings can provide performance similar to that of solventborne 2-pack urethanes, but with much lower VOC. The chemistry of these coatings is discussed, in light of its relevance to some of the technical challenges, e.g., pot life and CO₂-gassing in thick films, unique to these systems. The use of 2-pack waterborne urethane topcoats in combination with low VOC waterborne acrylic/epoxy primers and intermediate coats is also described. Such multiple coat systems offer the promise of long term corrosion protection in severe industrial and marine environments, coupled with very low VOC.     

塑料复合膜用水性聚氨酯胶粘剂的研制

以聚酯二元醇、甲苯二异氰酸酯(TDI)、二羟甲基丙酸(DMPA)等为原料，利用两步法工艺，合成出阴离子型聚氨酯(PU)乳液，并配合交联剂制得性能良好的双组分水性PU胶粘剂。研究结果表明：控制-COOH质量分数在1．6％～1．8％、NCO／OH值在1．3～1．4，合成的阴离子型PU乳液粒径较小；随着-COOH的增加，乳液的粘度和胶膜的吸水性增大。以该乳液配制的胶粘剂，贮存稳定，无毒、无污染，剥离强度高，可用于多种塑料复合膜材料的粘接。     

反应性阳离子聚氨酯对羊绒针织物起球性能的影响

以自制的反应性阳离子水性聚氨酯对纯羊绒针织物进行抗起毛起球整理,研究整理剂对纯羊绒针织物整理效果及其服用性能的影响。研究结果表明：在整理剂最佳的应用工艺下（整理剂质量浓度50g/L、浴比1：35、整理液pH5.5、40℃下处理20min、100℃烘干）,可显著提高羊绒针织物的抗起毛起球性能,其起毛起球等级从2.0级提高到4.0级,且织物的手感和白度等风格不受整理剂的影响。     

Water resistance of the membranes for UV curable waterborne polyurethane dispersions

The water absorption of the membranes made from UV curable waterborne polyurethane dispersions (UV-PUDs) was investigated systematically and correlated with the nature of the polymer and its gel content after curing. It was found that the water absorption of the membranes was reduced significantly by using polyester polyols, reducing the COOH content and increasing the gel content through a higher CC level. In particular, the membranes made from polyurethanes having hydroxyl-terminated polybutadiene (HTPB) or modified with dihydroxybutyl-terminated polydimethylsiloxane (PDMS) presented a superior water resistance. The results showed a linear relationship between the water absorption and the surface tension of the membrane.     

Structure of waterborne coatings by electrochemical impedance spectroscopy and a thermostimulated current method: influence of fillers

Electrochemical impedance spectroscopy (EIS) was coupled with a thermostimulated current (TSC) method to investigate the effect of fillers on the barrier properties of an epoxy-polyamido amine waterborne coating on a 2024 aluminium alloy. Four systems were studied: a clear coat and three pigmented coatings (with and without chromates). The results obtained by TSC highlight the specific action of chromates which decrease the molecular mobility (hardening) of the coating by comparison with neutral fillers. This has been explained by the high polarity of chromates that enhances interactions with the binder. Impedance measurements carried out for free-standing films and for coated aluminium alloy have corroborated the role of chromates on the barrier properties of the coating which remain high as a function of exposure time in a 0.5 M NaCl solution. TSC was also used to measure the glass transition temperature (T_g) of the hydrated systems. T_g was significantly decreased when the coatings were hydrated due to a strong plasticization effect induced by water uptake. For the different systems, we conclude that the weak barrier properties of the films (attached films) or the decrease of the barrier properties with time (free-standing films) were linked to the variation of the glass transition temperature by water uptake.     

Mechanical Properties Improvement of Waterborne Polyurethane Coating Films After Rewetting and Drying

Drying behavior of waterborne polyurethane coating under ambient conditions displays the typical three-stage drying process on compact hard substrates. When the naturally dried samples are further dried at thermal condition of 105°C, the loss of residual water was accompanied with an increase in the hardness of the films. When the coating films were immersed in water and dried at ambient condition again, the hardness and modulus increased significantly. After 180-min immersion followed by natural drying, the hardness of the film increased to almost 10 times that of the initial value. The possible reason is that the interaction between water and the hydrophobic amorphous phase of polyurethane led to a compacted amorphous phase, which decreased the free volume of the films, resulting in the increase in the hardness and modulus of the coating films.     

Electrochemical impedance spectroscopy study of waterborne coatings film formation

In order to establish electrochemical impedance spectroscopy (EIS) as a viable quantitative method for characterization of latex film formation, three waterborne acrylate and styrene–acrylate polymer dispersions were periodically analyzed during a course of 2 weeks. Impedance spectra were fitted on the base of equivalent circuit consisting of a capacitor in parallel with a Warburg element representing film capacitance and the extent of ion diffusion through the film. Calculated EIS parameter values showed a decrease in Warburg diffusion over time, which is a result of particle coalescence and in agreement with the established theory of latex film formation. Atomic force microscopy (AFM) of the samples showed a smoothing of the surface and blurring of interparticle boundaries which confirmed that EIS can be used to study film formation of latex.