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The electrical properties of cement are gaining importance for the application in building construction. Polypyrrole (PPy) has been widely applied in most fields because of its excellent conductivity performance, environmental friendliness, easy fabrication, and other specialties. These features made them useful for self-sensing applications. In this work, waterborne polypyrrole (WPPy) was prepared via the chemical oxidative polymerization with three kinds of hydrophilic agents: sodium lignosulfonate (LGS), sodium dodecyl sulfonate (SDS), and sodium dodecyl sulfate (SLS), and then WPPy/cement composites were prepared by mixing cement with it. The contact angle, conductivity, and microstructure of WPPy were characterized by contact angle tester, four-point probes, and SEM. The composition, microstructure, and properties of WPPy/cement composites were characterized by FTIR, TGA, XRD, and SEM. The content of LGS was 40 wt%, WPPy got the optimal comprehensive performance, the conductivity was 15.06 times of the control sample and the contact angle was reduced by 69.95%. SEM analysis showed that hydrophilic agent content had great effect on the particle size of WPPy, the average diameter of WPPy particles decreased from 200 nm to 50 nm with the increase of LGS content. The results also showed that the adding of WPPy in WPPy/cement composites can significantly improve the conductivity and compactness, optimize the microstructure of cement composite. When the content of WPPy was 1.25 wt%, WPPy/cement composite showed the lowest resistivity and saturated water content of cement composite was 8 wt%. In addition, it could also inhibit the formation of Ca(OH)2 in the early hydration process. [ABSTRACT FROM AUTHOR]

Aqueous foam is widely used in fire extinguishing and dust suppression technologies. Improving the foaming ability is the key to reducing the added concentration of foaming agents as well as the economic cost. In this work, the effect of a water-soluble polymer (polyvinyl alcohol, PVA) on the foaming ability of anionic surfactant (sodium dodecyl ether sulfate, SDES) was studied by an experiment and molecular dynamics simulation. The experimental results showed that PVA greatly improves the foaming ability of SDES solutions when the surfactant concentration is less than 0.1%, which is attributed to the fact that the polymer can enhance the stability of bubble films and reduce the bubble rupture rate during the foam generation process. The simulation results indicate that PVA can enhance the hydration of surfactant head groups and contribute to the formation of a three-dimensional hydrogen bond network between surfactants, polymers, and water molecules, thus greatly improving the stability of bubble liquid films. The above results suggest that water-soluble polymers can be used to improve the foaming ability of surfactant solutions by enhancing the bubble film stability, which is beneficial as it reduces the added concentration of foaming agents in aqueous foam applications. [ABSTRACT FROM AUTHOR]

Improving the foamability of anionic surfactants in hard water is essential to reduce the adding concentration and economic cost of foaming agents for dust control. In this work, sodium dodecyl sulfate (SDS) and sodium dodecyl ether sulfate (SDES) were selected to explore the mechanism of polyethylene oxide (EO) groups improving the foamability of anionic surfactants in hard water by experiments and molecular dynamics simulations. The experimental results show that SDES containing EO groups has better foaming performance in hard water compared with SDS. The simulation results indicate that the presence of EO groups can inhibit the combination of SO 4 − groups and Ca2+ ions at the air/water interface, which makes part of Ca2+ ions migrate from the interface layer to the bulk water. In addition, EO groups attract some Ca2+ ions to distribute around them, thereby further reducing the number of Ca2+ ions combined with SO 4 − groups, which helps to improve the surface activity and foamability of anionic surfactants in hard water. An increase in the number of EO groups can enlarge the interfacial thickness and the number of hydrogen bonds between surfactants and water molecules, enhancing the strength of bubble film. Moreover, the farther the EO group is from the SO 4 − group, the smaller the contribution to the hydration of anionic surfactants. [ABSTRACT FROM AUTHOR]