Nowadays, on the construction market, there are offered agents for concrete hydrophobization. In most cases, these are preparations that are applied on surfaces of already existing elements. The main ...disadvantage of such agents are strictly specified conditions, under which they can be applied. It is not recommended to apply the preparations for the elements under water level, exposed to contact with water under pressure, and with visible cracks and scratches 1, 2. The article presents the results of tests of an innovative agent for concrete hydrophobization that has not disadvantages of the currently applied materials – application of the developed solution takes place at the stage of creating concrete mix. The preparation may be classified as an admixture for concretes.
A dry gel tumbling (DGT) method, which combines solution and gas phase grafting procedures, is presented as an energy- and cost-effective, and scalable route for the preparation of hybrid ...organosilica materials. For illustration, the preparation, characterization and performance of amine-grafted CO2 adsorbents (AGAs) is presented in detail. Materials prepared by DGT performed better compared to those derived from an optimized water-aided grafting procedure in toluene. Unusually high amine content (4.53 mmol/g), CO2 capacity (2.08 mmol/g) and amine efficiency (0.46) were obtained for this material. DGT offers maximum incorporation of organosilanes during grafting, i.e., an efficient and high yield reaction between the surface silanol groups and the alkoxyl groups of the silane, with grafting efficiencies >95% for propylamine-grafted adsorbents. The method was extended to the synthesis of hydrophobic AGAs, with increased resistance to leaching.
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•A simple dry gel synthesis was developed for preparing grafted organosilicas.•Amine-grafted CO2 adsorbents (AGAs) were presented for illustration.•Materials with unprecedented CO2 uptake were obtained.•Method was applied to impart hydrophobicity to AGAs.•Scalability of proposed method was demonstrated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Waste hemp noil was reassembled into aerogels and used as absorbance.•The hemp aerogel achieved an oil removal of 29.4 times of its own weight.•The ultrafast oil absorption was ...completed within 0.048 s.•The oil contaminated hemp aerogel could be self-cleaned in ethanol solution.•The hemp aerogel achieved high removal efficiency at 94 % of particulate materials.
Environmental pollution and resource waste are two major concerns with the development of civilization. During hemp fiber separation short fiber noil is produced as a waste. This paper demonstrates the reuse of waste hemp noil by dissolution in a precooled NaOH/urea system to form porous aerogels. After hydrophobization, the hemp aerogels exhibited self-cleaning ability and could be used for oil adsorption and air purification. The superhydrophobic hemp aerogels exhibited elastic behavior with 75 % recoverable strain after 10 cycles of compression. The high porosity and compressibility endowed hemp aerogels with excellent oil absorption capacity and reusability. With a fiber concentration of 1.5 %, the hemp aerogel could achieve an oil removal of 29.4 times of its own weight, whilst 85.4 % of the initial absorption capacity remained after 10 absorption/desorption cycles. The ultrafast oil absorption was completed within 0.048 s. The oil contaminated hemp aerogel could be self-cleaned in an ethanol solution. The hemp aerogels also had high removal efficiencies of particulate materials (PM) such as PM2.5 and PM10 at both 94 %. The remodeled waste hemp noil showed great potential in environmental governance and recycling of natural resources.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The purpose of this research was to render hydrophobicity on three different cellulosic nonwovens (NW) using green biobased materials including betulin (Bt), stearic acid (SA), ethyl cellulose (EC), ...and beeswax (BW). A commercially available Alkyl ketene dimer-based hydrophobizing agent (AKD) was also used for benchmarking. A comparative analysis and comprehensive characterization of the coated samples was conducted using various analytical techniques, including scanning electron microscope (SEM), Fourier transform infrared (FTIR), capillary flow porometry, optical tensiometry, and tensile testing. The treatment of NW materials with selected biobased agents significantly enhanced their hydrophobicity. A water-absorbing air-laid NW1 became hydrophobic after functionalization with Bt achieving the highest water contact angle (WCA) of 134° compared with other biobased agents. To achieve complete hydrophobization of NW2 and NW3, which have larger pore sizes, mixtures of EC with SA and EC with Bt were applied, resulting in WCAs greater than 109°. The SEM micrographs of the coated NW2 and NW3 samples revealed that Bt and SA induced microroughness on the coating surface, with specific portions protruding outward over EC. The treatments did not significantly affect the porosity and tensile strength of the nonwovens, except for AKD and SA treated samples.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Lignocellulosic materials with hydrophobic properties are of great interest for developing sustainable products that can be used in various applications such as packaging, water-repellent and ...self-cleaning materials, oil and water separation or as reinforcements in biocomposite materials. The hydroxyl functional groups present in cellulose provide the possibility to perform various chemical modifications to the cellulosic substrates that can increase their hydrophobicity. This review is the second part of a comprehensive review on hydrophobization of lignocellulosic materials and summarizes the recent advances in the chemical modification of such substrates. The methods described in this review can provide changes in the hydrophilicity of the materials that range from a small decrease in the initial hydrophilicity of the substrate (contact angles below 90°) to superhydrophobic properties (contact angles above 150°). Additional attention has been paid to whether the modification is limited to the surface of the substrate or if it occurs in the bulk of the material. We also discuss hydrophobized cellulose material applications in packing and oil/water purification.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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Newtonian liquids, usually used as base oil lubricants, exhibit low viscosity under extreme thermal conditions, needed for the functioning of wind turbines. This is directly affecting ...the colloidal stability and the tribological properties of the formulations containing additives, such as MoS2. Here, it was hypothesized that the surface hydrophobization of MoS2 particles will allow for an increased colloidal stability of the resulting formulations, for temperatures as high as 80 °C.
The antifriction properties and the thermal stability of the designed formulations were determined on submicron MoS2 particles dispersed in poly-α-olefins (PAO) base oils of different dynamic viscosities (from 32 to 1650 mPa·s at 25 °C). The submicron particles of MoS2 (300–500 nm in diameter) were synthesised by a simple one-pot solvothermal method under mild conditions. The resulting particles were hydrophobized in situ in PAO base oils using alkyltrichlorosilane grafting agents with two chain lengths (C8 and C18).
The covalent grafting of alkylsilanes through Mo-O-Si bonds was confirmed by DFT calculations and FT-IR measurements. Turbiscan optical analysis revealed that thermal and colloidal stabilities can be significantly improved depending on oil viscosity and chain length of the grafting agent. The formulations in the PAO65 oil remained highly stable (TSI < 1), even at 80 °C. Herein, we demonstrate the impact of hydrophobization degree on the tribological properties of the lubricants, which, importantly, could reach ultra-low friction coefficients, less than 0.02.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The notoriously poor stability of perovskite solar cells is a crucial issue restricting commercial applications. Here, a fluorinated perylenediimide (F‐PDI) is first introduced into perovskite film ...to enhance the device's photovoltaic performance, as well as thermal and moisture stability simultaneously. The conductive F‐PDI molecules filling at grain boundaries (GBs) and surface of perovskite film can passivate defects and promote charge transport through GBs due to the chelation between carbonyl of F‐PDI and noncoordinating lead. Furthermore, an effective multiple hydrophobic structure is formed to protect perovskite film from moisture erosion. As a result, the F‐PDI‐incorporated devices based on MAPbI3 and Cs0.05 (FA0.83MA0.17)0.95 Pb (Br0.17I0.83)3 absorber achieve champion efficiencies of 18.28% and 19.26%, respectively. Over 80% of the initial efficiency is maintained after exposure in air for 30 days with a relative humidity (RH) of 50%. In addition, the strong hydrogen bonding of F···H‐N can immobilize methylamine ion (MA+) and thus enhances the thermal stability of device, remaining nearly 70% of the initial value after thermal treatment (100 °C) for 24 h at 50% RH condition.
Fluorinated perylenediimide (F‐PDI) is first introduced to optimize photovoltaic performance and stability of perovskite solar cells. Conductive F‐PDI effectively passivates defects and promotes charge transfer. The hydrophobicity of F‐PDI preventing moisture penetration as well as the strong hydrogen bonding immobilizing methylamine ions, thereby, endow excellent moisture and thermal stability with nearly 70% efficiency retention after thermal treatment at 100 °C.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The article shows changes in certain mechanical properties of polyvinyl chloride (PVC) depending on the quality of added limestone as a filler. Natural limestone and limestone hydrophobicized with ...stearic acid were added. Modification experiments were carried out with "wet" and "dry" processes in order to find out the required amount of stearic acid for a complete surface coating of limestone-degree of coating 99.90%. Coating of the limestone surface was achieved in the "wet" process with 1.5% stearic acid, while in the "dry" process the same degree of coating was achieved with 3% stearic acid. A significant amount of both "wet" and "dry" modified limestone was prepared. Such a product was added to PVC mixture in order to investigate mechanical properties of the obtained PVC product. Research into the mechanical properties of PVC has shown that PVC containing limestone modified by the "wet" process exhibits better mechanical properties than that containing limestone modified by the "dry" process. For example, PVC obtained from a mixture containing limestone modified by the "wet" process with 1.5% stearic acid shows a better tensile strength of 54.20 MPa, while limestone modified by the "dry" process with 3% stearic acid shows a tensile strength 53.20 MPa.
Because of the severe risk of oil pollution and increasing concerns about the sustainability of sorbent materials, there are considerable interests across the world to develop cost-effective, ...reusable, and environmentally friendly oil sorbents derived from renewable resources. Nanocellulose is a new family of promising cellulosic materials with a cellulose fibril width in the order of nanometer range (i.e., 2–100 nm). As a class of newly developed cellulose aerogels, nanocellulose-derived ones combine intriguing interconnected three-dimensional porous characteristics of aerogel-type materials such as high porosity, large surface area, and low density with fascinating advantages related to naturally occurring nanocellulose: impressive mechanical properties, abundant sources, natural renewability, excellent biodegradability, and ease to surface modification. Therefore, nanocellulose-based aerogels are very ideal “green” oil sorbents after either appropriate hydrophobic modifications or carbonization. This present review summarizes the state-of-the-art in the aerogel-type oil sorbents derived from nanocellulose, including hydrophobized nanofibrillated cellulose (NFC)-based aerogels, hydrophobized bacterial cellulose (BC)-based ones, and the carbon ones prepared through the pyrolysis NFC or BC aerogels. Their respective preparation methods, structure, and oil-absorption performance are summarized. And the existing problems in the current research and the future development perspectives are also presented.
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IJS, KILJ, NUK, PNG, UL, UM
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