Durable Hydrophobicity Research Articles

Rigid polyurethane foam with durable hydrophobicity and flame retardancy endowed by novel functional surfactants

Traditional rigid polyurethane foam (RPUF) with flame retardancy might be easily damaged in some moist condition due to its hydrophobicity, which would lead to unsafety. Therefore, novel surfactants with both hydrophobic fluorinated group and flame-retardant phosphorus group were synthesized. With lower surface tension and more hydrogen bonds formed in polyurethane, the mixed surfactants, which were used in the preparation of RPUF, have not only obviously improved the size uniformity and integrity of cells but also enhanced its hydrophobicity, compressive strength and thermal insulating performance. Besides, effective ‘protection’ could be constructed on the surface of RPUF by prepared surfactants, when ammonium polyphosphate (APP) and expandable graphite (EG) were introduced to provide good flame retardancy. As a result, with just 2.8wt% content of those functional surfactants, hydrophobic and flame-retardant RPUF with water contact angle of 126 °, limiting oxygen index of 25%, compressive strength of 1.3MPa and thermal conductivity of 27mW/mK, were finally obtained, which is ahead of other flame-retardant RPUF reported before. It’s worth noting that, this hydrophobic and flame-retardant RPUF exhibits more stable and durable properties when soaking in HCl solution (2mol/L), NaOH solution (2mol/L), NaCl saturated solution and various solvents (THF and EtOH), or under strong fiction for 100 times and high and low temperature cycling test for 20 times. This would provide a novel and effective strategy to endow RPUF with enhanced and durable flame retardancy, hydrophobicity, compressive strength and thermal insulating performance even under extreme conditions.

Dynamic Hydrophobic Behavior of Water Droplet on Siloxane-Based SiO2 Nanoparticle Modified Cotton Fabric

In this paper, modified SiO2 nanoparticles were selected to improve the surface roughness and decrease the surface energy to improve the hydrophobic performance of cotton fabric. Tetraethoxysilane and octadecyltriethoxysilane were used as raw materials to synthesize octadecyltriethoxysilane-modified SiO2 nanoparticles (siloxane-SiO2), and combined with cotton fabric. The chemical composition and surface morphology of the fabric were measured. The contact angles of the modified cotton fabrics prepared under different reaction conditions were approaching or above 150°. In addition, dynamic evolutions of water droplets on the modified cotton fabric surface were discussed. The adhesive force and the energy conversion of droplet during the collision were investigated. The water droplet bounced due to the superhydrophobic properties of the cotton fabric surface producing enough residual energy. Finally, through the acid–base chemical resistance treatments, the rubbing and washing durability, and anti-fouling experiment, the modified fabric indicated excellent hydrophobic durability and self-cleaning performance.

Enzymatic synthesis of self-adhesive zein to impart durable hydrophobicity with antioxidant activity to cotton fabrics

In this study, dopamine (DA) was used as the acyl receptor to modify zein through transglutaminase (TGase)-mediated reaction, producing self-adhesive zein (zein-DA complex). The structure of zein-DA complex was characterized by Fourier transform infrared spectrum (FT-IR), 1H nuclear magnetic resonance spectrum (1H NMR), and circular dichroism spectrum (CD), revealing the successful grafting of catechol structure of DA to zein. The results of SDS-PAGE demonstrated that zein-DA complex exhibited great ability of self-polymerization. The zein-DA complex absorbed on the cotton fabric surface imparted hydrophobicity with a water contact angle value (WCA) of 121.34 ± 1.14° to the fabrics. After 5 washing cycles, the WCA still remained 100.28 ± 4.83°, which indicated the fabrics obtained relatively durable hydrophobicity due to the self-adhesion of zein-DA complex. The results of FT-IR, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and color reaction tests manifested that much more protein attached on the surface of cotton fabric treated with zein-DA complex after washing compared with that with zein, which verified that the zein-DA complex had strong adhesion properties. Due to the introduction of DA, the relative DPPH free radical scavenging activity of cotton treated with zein-DA complex reached 43.60 ± 0.28 %, which was obviously higher than cotton treated with zein. The functionalized fabrics with zein-DA complex had both hydrophobicity and antioxidant activities.

Sustainable furfural bis-thymol based benzoxazines: Superhydrophobic, aggregation induced emission and corrosion resistant properties

Sustainable bis-thymol based benzoxazines have been synthesized using furfural bis-thymol (FBT) and paraformaldehyde separately with five different fluorine substituted amines through Mannich condensation process. The molecular structure of the obtained benzoxazines has been verified using spectroscopic analyses. The curing temperature of the synthesized benzoxazines are ranged between 241°C and 277°C. Among the synthesized polybenzoxazines, poly(FBT-pfa) exhibits the highest thermal stability of 52% char yield. All the polybenzoxazines exhibit the value of LOI above the threshold limit of 26 which infers the self-extinguishing property of the polymer. Poly(FBT-pfsa) showed the highest value of water contact angle of 151o, which ascertains that the increased fluorine content contributes to the superhydrophobic nature. Results from hydrophobic durability studies with poly(FBT-pfsa) using coated cotton fabric under acidic and basic conditions indicate its suitability for hydrophobic applications. The corrosion protection ability of polybenzoxazines towards mild steel surfaces was studied and the results obtained suggest that these polybenzoxazines can be used as an excellent coating material. UV-Visible and fluorescence spectroscopic analyses infer that these benzoxazines exhibit aggregation induced emission (AIE) characteristics. Data from different studies suggest that these materials can be conveniently utilized in the form of optical, superhydrophobic and corrosion-resistant coatings.

Polypropylene Blends with Durable Hydrophobicity and Enhanced Mechanical Properties Based on POSS and Alkane Modified Polypentafluorophenyl Methacrylate.

Durable functionalization on polypropylene (PP) surfaces is always a key problem to besolved. Coatings with low surface energy peel off easily especially under extreme conditions, owing to their weak adhesion. In this paper, side groups of both polyhedral oligomeric silsesquioxane (POSS) and alkane are grafted to polypentafluorophenyl methacrylate (PFP), and then PP blends with these side-group modified PFP are obtained through a melt-blending process. It is found that POSS can result in surface segregation and provide hydrophobicity in blends. Microfibers are formed because of the orientation effect during the tensile testing, which furtherly promotes mechanical strength. Significantly, alkaneside-groups can be entangled with PP segments, which brings about cross linking. Therefore, with crosslinking and synchronous orientation of POSS, the elongation at the break of blends is greatly increased up to 974%. The final blend demonstrates quite durable hydrophobicity under many extreme conditions, such as repeated tape peeling, ultrasonic washing, strong friction, and soaking in strong acid (pH = 1), strong alkali (pH = 14) and alcohol. The heat and UV resistance of the blend are also obviously improved. This study will develop anovel and facile strategy to endow PP with durable hydrophobicity as well as greatly enhanced mechanical properties.

Preparation and properties of modified SiO2/epoxy resin superhydrophobic coating

In this study, a superhydrophobic coating with excellent mechanical durability, chemical stability, anti-icing property and self-cleaning property was developed based on epoxy resin integrated with modified SiO2 nanoparticles (m-SiO2 NPs). The surface morphology and roughness of the coating were finely controlled by changing the content of m-SiO2 NPs, with optimal hydrophobicity and self-cleaning efficiency observed at the m-SiO2 NPs incorporation of 30 wt%. Benefitting from the three-dimensional stable micro-nano structure on the coating surface, the coating exhibited durable hydrophobicity upon multiple tape-peeling damages and good resistance to both acidic and alkaline corrosive environments. Furthermore, the SiO2-EP coating showed a prominent anti-icing property which could delay the water freezing time from 96 s to 650 s. This coating underscored its potential for applications in environments prone to ice formation.

A durable hydrophobicity hydrazone covalent organic framework coating for solid phase microextraction of polycyclic aromatic hydrocarbons in food and environmental sample

In this study, a durable hydrophobicity hydrazone covalent organic framework (BTCH-PTA-COF) has been developed as fiber coating, which was applied to solid-phase microextraction (SPME) of polycyclic aromatic hydrocarbons (PAHs). The hydrophobic and π-π packing interactions between BTCH-PTA-COF and PAHs were confirmed by contact angle experiments and Van der Waals surface electrostatic potential analysis. Further, large specific surface area, good chemical and thermal stability have positive promoting effect on extraction. The method of wide linearity (0.25–300 µg·L−1), low detection limits (0.03–0.05 µg·L−1) and high enrichment factors (767–1411) for the detection of PAHs is explored, coupling BTCH-PTA-COF based SPME with gas chromatography with hydrogen flame detector (GC-FID). The relative standard deviations (RSDs) for inter-day and intra-day extractions of PAHs are ranging from 4.1 % to 9.6 % and 2.9 % to 6.4 %, respectively. The method successfully detected and quantified trace PAHs in tea beverages and river water samples with recoveries from 88.5 % to 104.8 %. The BTCH-PTA-COF coated fiber is ultra-stable in recycled extraction and reused at least 120 times, which could surpass published and commercial SPME fiber.

Fluoroalkyl trimethoxysilane route to hydrophobic 2K polyurethane clearcoats and their failure mechanism

In this study, three fluoroalkyl trimethoxysilanes (FATMS) with different chain length of fluoroalkyl moiety, i.e., (3,3,3-trifluoropropyl) trimethoxysilane (C1), (1,1,2,2-tetrahydro-nonafluorohexyl) trimethoxysilane (C4), (1,1,2,2-tetrahydro-perfluorooctyl) trimethoxysilane (C6), were incorporated into component A of a two-component polyurethane (2K PU) clearcoat to assure their chemical anchoring with polymer chains, and then cured with polyisocyanate hardener. The hydrophobic durability of FATMS-modified coatings was further examined under various service conditions by water contact angle analyzer, attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and element-mapping. Hydrophobic 2K PU clearcoats could be achieved at FATMS dosage below 5.0 %, 0.5 %, and 0.5 % for C1, C4, and C6 additive, respectively. All coatings maintained their original hydrophobicity after for two years’ ambient storage, immersing in ambient water or mere UV irradiation. But if UV irradiation and/or heat (i.e., high-temperature) were imposed together with water, the coatings would quickly lose their surface hydrophobicity due to the loss of fluoroalkyl groups via hydrolysis break of Si-O-C chemical bond. The UV irradiation-induced synergistic effect on failure of surface hydrophobicity should be resulted from the increased hydrophilicity of PU matrix, which enhanced the affinity of water molecules with the coatings and hence higher hydrolysis probability of Si-O-C bond. Therefore, FATMS route is more suitable for fabrication of hydrophobic 2K PU clearcoats used indoors at room temperature.

Durably antifouling blends of fluorinated multiblock copolymers and polypropylene with micro-nano structures

Fluoropolymers are widely used as hydrophobic coatings on plastics, which have low stability and durability. Therefore, it has been a challenge to strengthen the bond force between plastics and fluoropolymers, to improve their chain entanglement, and to make the hydrophobicity of those materials more stable and durable. In this paper, fluorinated multiblock copolymers (PNANPF6-PCOE) with good hydrophobicity, processability and thermal stability were prepared by macromolecular cross metathesis (MCM) method. Notably, micro-nano structures were formed by simply controlling the reaction time of MCM due to the disparity of rigidity and flexibility and polarity in PCOE and PNANPF6 blocks. The micro-nano structures were also preserved in the blends of PNANPF6-PCOE/polypropylene (PP). The tensile mechanical properties and hydrophobicity of PNANPF6-PCOE/PP blends are affected by the length of PCOE and PNANPF6 blocks in multiblock copolymer. With the high temperature in melt-blending process, fluorinated segment groups could easily move and aggregate to the surface, and alkyl groups also would entangle and compatibly blend with polypropylene, which resulted in good thermal properties, well mechanical performance and great hydrophobicity. Most importantly, the antifouling durability to coffee, cola and ethanol was greatly enhanced by melt-blending process compared with solution coating method. This can provide a new strategy for the preparation of fluorinated multiblock copolymers with micro-nano structures, and would demonstrate a new way to achieve durable hydrophobicity and antifouling properties in general materials.

Construction of multifunctional surface to fabricate wood-derived cellulose electrothermal composites with flame retardant and hydrophobic performance for harsh operating conditions

As a renewable resources, wood is limited to functional applications due to its defects of moisture deformation, water swelling, and flammability. At present, wood-derived cellulose electrothermal composites has excellent Joule heating performance, but it faces the dilemma of limited operating environment. To this end, multiwall carbon nanotubes (MWCNTs) were deposited on the wood-derived cellulose skeleton (WCS) surface by multiple dipping-drying cycles to obtain electrothermal performance. Ammonium polyphosphate and trichloro (1 H,1 H,2 H,2 H-tridecafluoro-n-octyl) silane were then sequentially deposited on MWCNTs/WCS surface to obtain better flame retardant and hydrophobic performance. The resultant multifunctional MWCNTs/WCS (MMW) achieved an average surface temperature of 119.3 °C at 4.0 V and retaining repeatability under power ON/OFF cycles. The residue amount of MMW was increased by 105.6% and the heat release capacity was decreased by 92.9% compared with WCS, which exhibited an excellent flame retardancy. Moreover, MMW had a water contact angle of 145.6° and showed durable hydrophobicity in harsh operating conditions. It is believed that MMW with electrothermal, flame retardant, and hydrophobic properties has promising applications in thermal therapy, aircraft deicing, indoor heating, and smart electronic wallpaper.

Hydrophobic durability and anti-corrosion of plasma nitriding layer: Evolution mechanisms of corrosion behavior under variations in local hydrochemistry

Mechanisms for the effects of nitrogen on the durability of hydrophobic and corrosion resistance of modified layers prepared on the surface of AH32 steel by plasma nitriding have been investigated. It was found that plasma nitriding can significantly improve the hydrophobicity of AH32 steel. All the contact angles (CAs) of the AH32 steel with 1 h, 3 h and 5 h nitriding were higher than 120°, which had excellent hydrophobicity. The acidification degree of the solution within the nitriding layer’s micro-zone was effectively reduced due to the dissolution of nitrogen. The micro-nano structures of the nitriding layers corroded severely after 15 days of exposure to NaCl solution. When the nitriding time is extended to 5 h, the acidification degree of the solution was intensified due to the enhanced blocking effect, and the nitrogen in the nitriding layer saturated that cannot provide enough nitrogen ions to offset the acidification of the solution, so the durability decreased instead. In comparison, the modified layer with 3 h nitriding in this study had the best durability and long-term service protective effect on AH32 steel.

Inducing hydrophobicity in saline soils: A comparison of hydrophobic agents and mechanisms

Hydrophobized soils (or so-called artificial hydrophobic soils) are a novel geomaterial with a great potential in engineering applications due to its low affinity to water. For saline soils, hydrophobizing such soils can mitigate the soil salinization and subsequent engineering disasters such as salt expansion and corrosion by chlorides. To induce soil hydrophobicity, hydrophobic agents are widely used such as organo-silanes, fatty acids, and waxes. Correspondingly, the engineering properties and durability of these hydrophobized soils have been comprehensively investigated. However, all these studies focused on the clean mineral soils, i.e., the soils without salts and in a moderate pH. For saline soils, the feasibility, stability and durability of these hydrophobic agents are unclear. This paper aims to propose suitable and feasible hydrophobic agents in hydrophobizing saline soils, by investigating its hydrophobicity change and having an insight into the mechanisms. The saline soils used were collected from Qinghai, China, and were treated by five different hydrophobic agents at different concentrations, with the hydrophobicity quantified by water drop penetration time, surface tension and contact angle. The soil hydrophobicity change was recorded after the treatment and wetting-drying cycles, in order to assess its stability and durability. Fourier transform infrared spectroscopy (FTIR), Raman spectrum and N2 adsorption experiment were carried out to study the mechanism of soil hydrophobicity formation and degradation. The results showed two agents, namely Sodium methyl siliconate and Polymethylhydrosiloxane, provided the greatest and most durable hydrophobicity in saline soils. Their different formation mechanisms at particle- and nano-scale were also discussed. A further assessment on the soil mechanical properties revealed that both compaction behavior and strength were negligibly influenced by these two agents.

Photothermal ultra-high molecular weight polyethylene/MXene aerogel for crude oil adsorption and water evaporation

The frequent oil spill accidents during oil exploration and transportation have caused large economic loss and catastrophic environmental disasters. Due to low cost and simplicity, adsorption and filtration materials are often chosen to deal with oil spills, but the outcomes are not satisfactory mainly because of the awfully high viscosity of crude oil. Herein a photothermal ultra-high molecular weight polyethylene/MXene composite aerogel with a high light absorption (99.97%) and water repellency (water contact angle >148°) is developed by thermally induced phase separation method. The composite aerogel endows durable hydrophobicity with which the water contact angle is more than 142° in acidic/alkaline environments, and the maximum absorption capacity of 81 g g−1. In addition, it exhibits an excellent photothermal performance, rising surface temperature to 70 °C within 60 s under 1 sun irradiation, that can drastically reduce the crude oil absorption time from 60 min to 60 s, saving 98% of absorption time and reaching a crude oil absorption capacity of 21 g g−1. More interestingly, the designed solar evaporation device with the obtained composite aerogel can achieve an evaporation rate of 1.15 kg m−2h−1 and evaporation efficiency of 74%. The designed composite aerogel opens a possible pathway for solar-powered crude oil adsorption applications.

Design of fluorine-free waterborne fabric coating with robust hydrophobicity, water-resistant and breathability

Hydrophobic functionalized coatings have attracted widespread attention in fabric finishing fields, which exhibit breathable properties and can significantly enhance wearer comfort. However, the inadequate hydrophobic durability of inorganic coating and poor biologically safety of fluorine-containing coatings limited the further development of fabric finishing coating, thus it remains a significant challenge to develop fluorine-free and durable fabric finishing coating. In this study, a glyceryl monostearate (GMO)-modified fluorine-free waterborne polyurethane (WPU) emulsion (WSiPU) was synthesized and applied as a hydrophobic coating on different type of fabrics successfully. The optimal additive amount of GMO was determined by investigating the particle size and size distributions of the emulsions, solvent swell rates, wettability of water and oil on the coatings, and hydrophobicity. Cotton fabric treated with optimized WSiPU 8 emulsion exhibited excellent hydrophobicity, durability, reusability, solvent resistance, breathability, and bio-safety. Furthermore, clothing and gloves treated with WSiPU 8 emulsion exhibited excellent water repellency under flowing water and after soaking in sewage. The treated cotton fabric showed excellent hydrophobicity (water contact angle > 140°), durability (>50 resistance cycles of abrasion and laundry), and self-cleaning performance. The findings of this study provided novel insights for various applications such as oil–water separation and hydrophobic coatings.

Binder-free in-situ reinforced nanofibrous membrane with anti-deformable pore structures for seawater concentration

Membrane distillation (MD) is a prospective thermal-membrane coupling technology suitable for desalination and concentrating hypersaline water. However, the structural instability and vulnerable salinity tolerance of membrane impede the large-scale implementation of MD technology. In particular, the defective pore structure and fragile hydrophobicity of the porous membrane compromise the repellency of salt components when dealing with hypersaline water. Herein, we engineered a binder-free in-situ reinforced nanofibrous membrane with remarkably anti-deformable pore structures and hydrophobic durability by a one-step electrospinning process. The mixing of different polymers changed the physicochemical properties of the solution, allowing the nanofibers to accumulate densely, reinforcing the pore structure of the membrane instead of the cumbersome post-treatment compaction process. In addition, the incorporation of PTFE nano-powders synchronously consummated the roughness and surface energy of the membrane. More significantly, the binder-free in-situ reinforced nanofibrous membrane operated stably during the 168 h desalination testing and was 2.5 times that of the commercial PVDF membrane when penetration occurred in concentrating synthetic seawater, demonstrating excellent permeability and durability. Mechanistic analysis of membrane structure stability has also been systematically elucidated.

Fire-resistant MXene composite aerogels for effective oil/water separation

Oil spills pose an enormous threat to marine ecosystems and human health, and, thus, arouse widespread concern. Physical adsorption is an effective and environmentally friendly method for remediation of oily wastewater. Finding absorbents with outstanding mechanical robustness, enduring superhydrophobicity, high absorption efficiency, and good regeneration capability remains challenging. In this paper, a hydrophobic composite aerogel (PDMS-Fe-MXene/A-HA) is fabricated using MXene nanosheets as a skeleton, artificial humic acid (A-HA) as a reinforcing phase, and polydimethylsiloxane (PDMS) as a hydrophobic modifier via an induced self-assembly process with a suitable Fe2+ crosslinking agent. Owing to the strong interaction between A-HA and MXene, the as-prepared PDMS-Fe-MXene/A-HA aerogel exhibits durable hydrophobicity (WCA=135°) and a highly efficient absorption capacity for a variety of hydrophobic organic pollutants (64–121 g g−1). Superelastic mechanical properties and excellent thermal stability endow the hybrid aerogel with good recyclability. The flux value for the PDMS-Fe-MXene/A-HA aerogel for an oil-water combination is determined to be 23478 L h−1 m2. Therefore, the new aerogel offers a viable alternative for successful oil/water separation.

A green and sustainable strategy for leather manufacturing: Endow dehydrated hide with consistent and durable hydrophobicity

A green and sustainable approach for leather-making was explored by imparting dehydrated hide (DL) with durable hydrophobicity through reacting with silane coupling agent (TMS). The rational control of hydrolysis and condensation rates of TMS was the key point for achieving efficient penetration and full reaction of TMS in DL, so as to obtain hydrophobic leather (HL-TMS). It was found that the leather-like HL-TMS could be fabricated when the DL with 5% water content reacted with TMS for 12 h under 30 °C at pH 6.0. In these conditions, TMS was evenly distributed in HL-TMS and provided HL-TMS with excellent water resistance, owning a dynamic waterproof time up to 163 h. Moreover, HL-TMS displayed exceptional hydrophobic durability against pH, UV, friction and organic solvents. Compared with DL, the collagen fibers of HL-TMS were well dispersed, and the porosity of which was 59.6% higher than chrome-tanned leather. In addition, the shrinkage area of HL-TMS in heating was 5.03%, remarkably less than chrome-tanned leather (12.11%), while its physical strengths and softness (9.6 mm) were higher than those of chrome-tanned leather. The results suggested that hydrophobic modification could substitute conventional tanning for manufacturing leather, and this hydrophobic modification-based strategy might push leather-making into a cleaner process.

Facile fabrication of robust epoxy resin monolithic superhydrophobic materials with excellent mechanical-chemical stability, biocompatibility and photothermal conversion capacity

Improving the durability of superhydrophobic materials is the key factor to promote their practical application. Here, a facile one-pot synthesis procedure is used to prepare epoxy resin monolithic superhydrophobic materials (ER-MSM) with excellent mechanical strength, chemical stability, oil-water separation, stain liquids repellency, biocompatibility and excellent photothermal conversion capacity. The mechanical strength and hydrophobic durability of ER-MSM are improved by synchronously processes of bubbles impact, high temperature curing and chemical bonding of epoxy resin to form micropores. The prepared monolithic material can maintain water repellency even after sandpaper abrasion, ultrasonication, multiple knife scratch, finger wiping, and exposure to UV irradiation and high-temperature calcination. The biocompatibility of ER-MSM was further proved by the 95 % cell viability of the PC12 cells after contacting with ER-MSM for 70 min. ER-MSM has excellent photothermal conversion ability by dopamine coreaction in the one-pot synthesis procedure (named as PER-MSM). The photothermal conversion capacity of PER-MSM can be regulated by adjusting the concentration of dopamine. The surface temperature easily exceeds 70 °C after 808 nm laser irradiating for 200 s under power density of 1 W/cm2 and dopamine concentration larger than 10 mg/mL or under power density of 2 W/cm2 and dopamine concentration larger than 2 mg/mL. The alcohol-based reaction system without complex fabrication steps, expensive, or toxic fluoride, satisfies the environment-friendly requirements. Therefore, the prepared mechanochemically stable and photothermal superhydrophobic materials have great potential applications in oil-water separation, self-cleaning and other industrial fields.

Non‐chromate conversion process for zinc coating with durable hydrophobicity and enhanced corrosion resistance

AbstractA Zn‐based coating with durable hydrophobicity and good corrosion resistance was formed on a mild steel substrate, which involves electroplating Zn from a non‐aqueous electrolyte, followed by passivation in an oleic acid (OA) solution. The electrodeposited Zn coatings were porous, which facilitated the formation of a chemical conversion layer of Zn oleate (ZO) during OA passivation. The Zn coating after passivation had a two‐layer structure, which included an outer layer of ZO with a thickness of ∼26 μm and an inner layer of Zn with a thickness of ∼6 μm. The outer layer ZO is a type of metal soap with a smooth surface and durable hydrophobicity, such that water droplets can easily slip off its surface. Corrosion testing and electrochemical measurements in 3.5 wt.% NaCl aqueous solution indicate that the Zn coating after OA passivation exhibits outstanding anti‐corrosion properties compared with those exhibited by pure Zn coating. The corrosion products and mechanism of the two‐layer coating were explored. This study shows that smooth metal oleate coatings can provide hydrophobicity and corrosion resistance simultaneously to mild steel substrates.

Preparation of hydrophobic and high‐strengthpolymer microspheres based on constructing a “Functionalmonomer‐St‐DVB” copolymer structure:Ultra‐low‐densityproppants

AbstractUltra‐low‐density proppants are of great significant in slick water fracturing system, but the polymer composite microspheres can hardly promise the quality of oil and gas due to their poor hydrophobicity. To address the issue, we prepared several types of modified styrene‐divinyl benzene copolymer microspheres (MSDBs) with long‐term durable hydrophobicity and high strength, including O‐MSDBs (hydrophobic MSDBs), LO‐MSDBs (long‐time hydrophobic MSDBs), and CO‐MSDBs (coated O‐MSDBs) on the basis of a molecular structure of “KH570‐styrene (St)‐divinyl benzene (DVB)” copolymer. In this article, the design concept and the structure of MSDBs was clarified, and performances of MSDBs are systematically discussed and compared with commercially available hydrophobic microspheres. The O‐MSDBs, a kind of nanoparticle patterned St‐DVB copolymer microspheres, were prepared by a one‐step suspension polymerization undergoing a sol–gel process, showing strong hydrophobicity with a water contact angle up to 140.7°, but short durability in strong hydrochloric acid or hydrofluoric acid; On the contrary, LO‐MSDBs perform better in the stability and durability of hydrophobicity with a slightly lower water contact angle about 135.9°. The LO‐MSDBs were designed by coating functionalized St‐DVB copolymer microspheres with fluororesin. Similarly, CO‐MSDBs from fluororesin‐coated O‐MSDBs were designed. As expected, CO‐MSDBs have a stronger hydrophobicity (139.0°) than LO‐MSDBs and longer durability than O‐MSDBs. Moreover, the MSDBs exhibit better properties than the commercially available hydrophobic polymer and ceramic microspheres.