Water-repellent coatings for surface and 3D wood processing

The paper presents the results of research in organic chemical compositions for hydrophobic protection of wood with the use of surface and three-dimensional coating techniques of impregnation and chemical compositions. Water absorption indicators, angles of contact on the surface of treated samples are detected herein. Kinetic equation of the moisture diffusion transition in capillary-porous structure of wood is suggested

Impact of Water-Repellent Products on the Moisture Transport Properties and Mould Susceptibility of External Thermal Insulation Composite Systems

External Thermal Insulation Composite Systems (ETICS) are constructive solutions widely used to increase the thermal insulation in new and retrofitted buildings. However, these systems can present several anomalies due to their constant exposure to weathering agents and anthropic factors. Water is generally the major cause of degradation. Thus, the application of water-repellent products can minimize the appearance of anomalies and increase the durability of the systems. In this paper, acrylic-based and siloxane-based hydrophobic products were applied to ETICS, with the aim of assessing the compatibility, effectiveness, and durability of these products. The moisture transport properties and mould susceptibility were assessed through laboratory tests on untreated and treated specimens. The durability of the hydrophobic treatments was also evaluated through artificial aging tests (heat-cold and freeze-thaw cycles). Results show that the protection products generally decreased water absorption, slightly decreased the drying rate, and presented adequate water vapor permeability. After aging, the products still had reasonable effectiveness and, with one exception, improved the water vapor diffusion of the systems. Additionally, ETICS underwent an alteration in the finishing coat (possible modification of the porosity) due to the aging cycles. No clear linear correlation was found between the contact angle values and water absorption results, evidencing the influence of other factors related to the composition of the water-repellent products.This research was funded by Portuguese Foundation for Science and Technology (FCT) within research project PTDC/ECI-EGC/30681/2017 (WGB_Shield-Shielding building' facades on cities revitalization. Triple resistance for water, graffiti and biocolonization of external thermal insulation systems) and for the scholarship 2020.05180.BD (J. L. Parracha).info:eu-repo/semantics/publishedVersio

In situ polymerization of soil organic matter by oxidative biomimetic catalysis.

Background: Agricultural practices that enhance organic matter content in soil can play a central role in sequestering soil organic carbon (SOC) and reducing greenhouse gases emissions. Methods: We used a water-soluble iron-porphyrin to catalyze directly in situ oxidative polymerization of soil organic matter in the presence of H2O2 oxidant, with the aim to enhance OC stabilization, and, consequently, reduce CO2 emissions from soil. The occurred SOC stabilization was assessed by monitoring soil aggregate stability, OC distribution in water-soluble aggregates, soil respiration, and extraction yields of humic and fulvic acids. Results: Soil treatment with H2O2 and iron-porphyrin increased the physical stability of water-stable soil aggregates and the total OC content in small aggregates, thereby suggesting that the catalyzed oxidative polymerization increased OC in soil and induced a soil physical improvement. The significant reduction of CO2 respired by the catalyst- and H2O2-treated soil indicated an enhanced resistance of polymerized SOC to microbial mineralization. The catalyzed oxidative polymerization of SOC also significantly decreased the extraction yields of humic and fulvic acids from soil. Conclusions: The oxidative catalytic technology described here may become an efficient agricultural practice for OC sequestration in soils and contribute to mitigate global changes

Hybrid inorganic-organic fluorescent silica nanoparticles—influence of dye binding modes on dye leaching

Silica nanoparticles with embedded fluorescent dyes represent an important class of markers for example in biological imaging. We systematically studied the various incorporation mechanisms of fluorescent xanthene dyes in 30–40 nm silica nanoparticles. An important parameter was the interaction of the dye with the matrix material, either by weak electrostatic or strong covalent interactions, which also has implications on the stability of fluorescence and brightness of the dyes. Factors that can influence leaching of dyes such as the position of the dyes in particles and the intensity of the particle-dye interaction were investigated by using the solvatochromic effect of xanthene dyes and by stationary fluorescence anisotropy measurements. We compared uranine and rhodamine B, which were physically embedded, with modified fluorescein isothiocyanate and rhodamine B isothiocyanate, which were covalently bound to the silica matrix within a usual Stöber synthesis. Systematic leaching studies of time spans up to 4 days revealed that covalent bonding of dyes like fluorescein isothiocyanate or rhodamine B isothiocyanate is necessary for fluorescence stability, since dyes bound by physical interaction tend to leach out of porous silica networks. Coverage of silica particles with hydrophobic protection layers of alkyltrialkoxysilanes or hydrophilic polyethylene glycol (PEG) groups resulted in a better retention of physisorbed dyes and provides the possibility to adapt the particles to the polarity of the medium. Best results were archived with PEG groups, but even small trimethylsilyl (TMS) groups already reduce leaching

Изменение структуры молекул смол и асфальтенов битума месторождения баян-эрхэт в процессе акватермолиза

Проведен акватермолиз битума месторождения Баян-Эрхэт (Монголия) в докритических и сверхкритических условиях. Показаны различия вещественного состава жидких продуктов в зависимости от условий термолиза. Рассчитаны структурно-групповые параметры средних молекул смол и асфальтенов исходного битума и продуктов его акватермолиза. Установлены закономерности изменения структур высокомолекулярных соединений (смол и асфальтенов) битума в протекающих процессах

Drying shrinkage of hydrothermally cured cements with reactive magnesia and clay brick waste

In recent years, worldwide research and development in the cement industry has gathered momentum with an aim to explore innovative and sustainable methods to deliver environmentally responsible Portland Cement (PC) based construction products. This study investigated physical and mechanical properties of autoclaved cement-quartz sand blends with the addition of clay-brick waste (CB waste) and reactive magnesia (MgO) with the aim to lower CO2 emissions through the reduction of PC consumption. Mechanical properties and drying shrinkage showed improvements with the incorporation of CB waste due to increased amounts and crystallinity of Al-tobermorite. The addition of reactive MgO to PC in hydrothermal conditions was observed to have a negative effect on the compressive strength. XRD data indicated that MgO did not take part in the reaction during the hydration of the cement and may even retard tobermorite formation. However, the expansive nature from the hydration of MgO to brucite may have compensated for drying shrinkage