High Water Contact Angle Research Articles

A facile and cost-effective fabrication of robust carbon black-based superhydrophobic coatings on aluminum alloy

Frozen contamination, including ice and frost, on the key surface of systems or facilities, can lead to serious problems and substantial financial losses. Superhydrophobic materials with high water contact angle (CA) and low sliding angle (SA) are potentially effective as anti-icing and self-cleaning materials. Herein, we present an inexpensive and durable superhydrophobic material prepared by combining carbon black (CB) and epoxy resin (EP) with polydimethylsiloxane (PDMS) via facile spraying. The as-prepared superhydrophobic material named PDMS@CB has excellent water repellence, and its water CA and SA can reach 171.5° and 4.6°, respectively. PDMS@CB characteristics are systematically investigated via field-emission scanning electron microscopy, laser scanning confocal microscopy, atomic force microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. PDMS@CB exhibits satisfactory chemical and thermal stability. After being dragged for a length of 800 cm, the CAs remain above 150° and the SAs remain below 10° for PDMS@CB, indicating the excellent durability of the material. Furthermore, the superhydrophobicity of PDMS@CB renders the material outstanding anti-icing and photothermal de-icing characteristics. PDMS@CB also exhibits excellent self-cleaning performance under the pollution caused by the daily liquid contaminants.

Low temperature-curable superhydrophobic surface with ultra-mechanical durable and anti-corrosion properties through structural engineering of coniferous ZnO

Superhydrophobic surfaces (SHS) receive considerable attention because of their wide applications, such as building materials, biomedical materials, and different metallic coatings. This study reports a simple and cost-effective approach for fabricating a robust superhydrophobic surface consisting of 1H,1H,2H,2H-perfluorooctyltriethoxysilane-modified SiO2 and coniferous ZnO nanoparticles dispersed in fluoroethylene vinyl ether (FEVE/FS@ZnO) on a stainless steel substrate. The prepared SHS coatings were curable at room temperature and easy to handle. They exhibited unique hierarchical and re-entrant structures, reducing surface energy and resulting in a long lifetime, significant adhesion enhancement, and superhydrophobic and self-cleaning properties. The highest water contact angle (CA) and roll-off angle were 156° and 3°, respectively, achieved at an optimized ZnO:fluoroalkylsilane mass ratio of 10:0.6. The SHS coatings also showed a significant anti-corrosion effect in a corrosion solution (3.5 wt% NaCl solution) and high stability against various acidic (H2SO4, pH = 1) and basic (NaOH, pH = 13) solutions. In addition, the SHS coating layer exhibited improved durability and stability in sandpaper abrasion and tape peel tests, with a CA of 153° after 130 sandpaper abrasion cycles. These results provide a pathway for the future development of multifunctional coating materials. The robust FEVE/FS@ZnO SHS coating with superhydrophobic and self-cleaning properties could be applied to various functionalized solid surfaces.

Green Synthesis of a Carbon Quantum Dots-Based Superhydrophobic Membrane for Efficient Oil/Water Separation.

The efficient separation of oil and water is a significant challenge worldwide due to the increasing frequency of industrial oily wastewater. Previous work by our group utilizes biological metal-organic framework-based superhydrophobic (S.P) textile fabric for oil/water separation. However, this system is limited due to the low mechanical stability, so there is a need for producing a more robust S.P membrane for oil/water separation. In this study, we report on the synthesis of carbon quantum dots (CQD) from banana leaves via a hydrothermal process and their application in producing a robust S.P coating on textile fabric for oil/water separation. The CQDs were characterized using various techniques including TEM, XRD, absorbance spectroscopy, and the BET method. The TEM images showed that the CQDs were circular in shape with a size of 4.4 nm, while the XRD micrograph indicated that the CQDs were crystalline in nature. The UV-vis graph showed a peak at a wavelength of 278 nm, suggesting strong absorption in the ultraviolet region. The BET-specific surface area of the prepared CQDs is 845 m2/g, with a pore volume of 0.33 cm3/g, and a mean pore diameter of 1.62 nm. We examined the surface wettability, morphology, composition, oil absorption capacity, oil/water separation performance, flux rate, chemical stability, and mechanical stability of the S.P membrane. Our findings indicate that the developed CQD-based S.P membrane possesses excellent S.P properties, displaying high water contact angles of 163° and low water sliding angles of 1°. The membrane demonstrated superior oil absorption capacity, separation efficiency, and flux rate towards three different oils-petroleum ether, n-hexane, and silicone oil. Petroleum ether has the highest separation efficiency (99.5%), and flux rate (13,500 L m-2 h-1), while silicone oil has the lowest. However, silicone oil has the highest absorption capacity (218.9 g/g) and petroleum ether has the lowest (194.8 g/g). For the absorption capacity and separation efficiency, a one-way ANOVA test was conducted. The statistical analyses revealed significant differences in absorption capacity and separation efficiency for the three oils, highlighting the efficacy of the superhydrophobic membrane for tailored oil/water separation. Additionally, the S.P membrane exhibited good mechanical (the membrane maintains its superhydrophobicity until an abrasion length of 850 cm) and chemical stability (the membrane maintains its superhydrophobicity in pH range 1-13), withstanding abrasion and immersion in solutions of varying pH values. The CQD-based S.P membrane shows great potential as a promising material for oil/water separation applications, with excellent performance and stability under various environmental conditions.

Investigating wettability and corrosion resistance of the titanium alloy surface engineered by the WEDM process

Ti-6Al-4V or the grade 5 titanium alloy, is widely used as a biomedical implant material because of its high specific strength and corrosion resistance. The formation of oxide layer over the Ti-6Al-4V alloy produced by electrical discharge machining (EDM) process was reported to act as a corrosion barrier and promote biocompatibility. In this study, surface engineering was conducted by machining micro-channels and micro-pillars over Ti-6Al-4V surface using wire-EDM (WEDM) process to investigate surface topography, corrosion resistance and wettability for improved biocompatibility. Four different samples were produced using varied micro features and varied surface topography generated by WEDM. Two of the samples were prepared by multi-pass surface finishing before fabricating micro-patterns on the surface, whereas the other two samples containing micro-patterns were first machined by single pass WEDM process. The corrosion testing was carried out on fabricated samples in simulated body fluid. Surface wettability of the engineered Ti-6Al-4V samples were carried out by measuring water contact angles of the surfaces. Surfaces with micro-channels and micro-pillars with multi-pass surface finishing provided better results in terms of corrosion resistance compared to the samples prepared by conventional WEDM process. The machined surface with micro-channels that underwent multi-pass finishing exhibited the highest corrosion resistance as well as the highest water contact angle among the four samples.

Preparation of superhydrophobic sponge and its application in oil-water separation and treatment of polymer-containing wastewater.

At present, the application prospect of superhydrophobic materials in oil-water separation, an-tibacterial and other aspects have attracted more and more attention. However, preparing a simple and low-cost superhydrophobic material remains a challenge. Using acetone as solvent, candle soot, silver/silica nanoparticles and polydimethylsiloxane were uniformly mixed to form a mixed solution, and the superhydrophobic sponge was successfully prepared by spraying method. The results show that the superhydrophobic sponge has high water contact Angle (162°) and excellent oil-water separation efficiency, which can realize effective treatment of polymerized wastewater. In addition, the superhydrophobic sponge showed better antibacterial properties on the surface of Escherichia coli and Staphylococcus aureus. In this work, a simple way to prepare superhydro-phobic oil-water separation material is proposed. The preparation process is green, the material is easy to obtain, and it is expected to be widely used in practical production.

Durable Co(OH)2/stearic acid-based superhydrophobic/superoleophilic nanocellulose membrane for highly efficient oil/water separation and simultaneous removal of soluble dye

The discharge of industrial oily wastewater is threats to the environment. A long-lasting Co(OH)2/stearic acid (STA)-based superhydrophobic/superoleophilic nanocellulose-based membrane (SSNM) for extremely effective oil/water and simultaneous removal of soluble dye was created to offer solutions to this problem. The mechanical durability of the prepared Co(OH)2/STA-based SSNMs was reinforced by depositing Co(OH)2 and STA on the cellulose fibers. The Co(OH)2/STA-based SSNM shows a high water contact angle of 164 ± 2° and an oil contact angle of ∼0°, exhibiting excellent superhydrophobicity and superoleophilicity. With good usage stability, high separation efficiencies (>94.0%) and high separation fluxes (>130 L·m−2·h−1) were achieved for four oils. The separation flux and efficiency of N-hexane did not change obviously after repeated separation. Furthermore, it exhibited reliable photocatalytic ability, which contributed to the reduction of organic contamination. As a result, Co(OH)2/STA-based SSNM shows strong potential for practical applications such as oil/water separation and photocatalytic degradation of organic pollutants.

Superhydrophobic polytetrafluoroethylene/polyvinylidene fluoride coating for passive daytime radiative refrigeration

Passive daytime radiation refrigeration (PDRR) is a new type of refrigeration that requires no extra energy consumption and also cools objects by reflecting radiant heat from sunlight and mid-infrared wavelengths. However, the properties of ordinary radiative refrigerative (RR) materials are degraded by surface dust accumulation during use. In this work, superhydrophobic radiative refrigerative (SRR) polytetrafluoroethylene/polyvinylidene fluoride (PTFE/PVDF) coating was prepared by one-step spraying method with PTFE as white pigment, PVDF as binder, and N, N-dimethylacetamide (DMAC) as solvent. The PTFE/PVDF coating (containing 20 wt% of PTFE) exhibits synergistic effect with high water contact angle (CA, 153.7°), low water sliding angle (SA, 7.7°), high solar reflectivity (SR, 93.7%), and high infrared emissivity (IE, 93.3%). Under a clear sky and direct sunlight, the coating achieves a RR temperatures of 5.8 °C (shielding convection heat) and 5.3 °C (without shielding convection heat) respectively under two measurement conditions. In addition, the coating exhibits excellent self-cleaning properties that can automatically remove dust accumulated on the surface with the assistance of rainfall, thus maintaining its RR performance for a long time. More importantly, the mechanical robust self-cleaning function also provides excellent corrosion resistance and anti-UV aging ability. The PTFE/PVDF SRR coating developed in this work is simple to fabricate, can be applied over a large area, and has good durability, which is conducive to promoting the practicalization of RR coatings.

Effect of Chemical and Steam Explosion Pulping on the Physical and Mechanical Properties of Sugarcane Straw Pulp Trays.

Sugarcane straw fiber (SSF) samples were prepared by chemical pulping (CP) and steam explosion (STE). CP (5, 10, 15% NaOH + 0.2% w/w anthraquinone at 121 °C for 1 h) and STE pressure (1.77, 1.96, and 2.16 MPa at 220 °C for 4 min) SSF trays were molded with a hydraulic hot-press machine at 120 °C, 7 min, and 1.72 MPa. The yield (%) of SSF from STE (54-60% dry basis (db.)) was higher than CP (32-48% db.). STE trays had greater tensile strength than CP. However, STE's elongation and compression strength was lower than CP tray samples. The trays made from SSF using STE had less swelling in thickness, longer water wetting time, and a higher water contact angle than those made from CP. The micrographs displayed a smaller size of SSF obtained in STE than the CP. The appearance and area of peaks in ATR-FTIR spectra and XRD diffractograms, respectively, revealed that the STE trays had a larger residual lignin content from the lignin study and a lower crystallinity index than the CP trays. Moreover, the lightness values of the STE trays were lower than those of the CP trays due to lignin retention. The study results indicate that CP is the preferred method for producing SSF packaging material with high flexibility and fiber purity. However, when considering the specific SF of 4.28, the STE treatment showed superior physical and mechanical properties compared to CP. This suggests that STE could be an excellent alternative green pulping technique for producing durable biobased trays. Overall, the findings highlight the potential of STE as a viable option for obtaining trays with desirable characteristics, providing a sustainable and efficient approach to tray production.

Evaluation of paper coated with cationic starch and carnauba wax mixtures regarding barrier properties

Studies of single-use packaging have aimed to replace materials obtained from non-renewable sources with biodegradable materials from renewable sources in response to environmental concerns. Their barrier properties maximize shelf life and product safety. To provide such green packaging, this work aimed to describe the chemical, physical, morphological, and barrier properties of bilayer coatings made from mixtures of cationic starch (S) and carnauba wax (W) on kraftliner paper (86 ± 1 g/m²). Two coating layers (15.0 ± 0.5 g/m²) of both materials in different proportions were compared to uncoated paper and doublewet-and-dry paper. The addition of cationic starch to carnauba wax raised the melting point of the wax, preventing it from completely entering the paper's pores but instead producing a layer on top of them. The hydroxyl groups present in coated paper S contributed to its hydrophilicity, showing a high Cobb value, absorbing 153 g/m² more water than control samples. Further, the mixtures showed higher hydrophobicity than the cationic starch-treated samples, with a high-water contact angle (100 ± 4°), similarly found for the W treatment. In addition, mixtures showed 0.35°/s less wettability than the W treatment. In terms of mechanical strength, the lower tensile strength and Young's modulus of the coated sheets brought on by hornification appear to have been predominantly caused by water in the suspensions. The addition of carnauba wax to the cationic starch decreased the resistance of coated papers to oil. However, there was an improvement in the water barrier by decreased water absorption and wettability and an increase in water contact angle.

A facile approach to fabricating fluorine‐free superhydrophobic cotton fabric with excellent oil–water separation performance

AbstractWith the increasing deterioration of environmental and ecology caused by industrial wastewater pollution and petroleum spill accidents, superhydrophobic materials for oil–water separation have attracted considerable attention. Herein, we propose a facile approach to fabricate fluorine‐free superhydrophobic cotton fabric (CF) for oil–water separation after the coverage of chitosan (CS) and titanium dioxide (TiO2) nanoparticles and the subsequent hydrophobization modification by hexadecyltrimethoxysilane (HDTMS). The obtained HDTMS‐TiO2/CS@CF showed superhydrophobicity with a high water contact angle of 160.6° as well as excellent self‐cleaning capability, non‐adhesion capability and surface stability. Moreover, the CF was successfully applied for the separation of various oil–water mixtures. The separation efficiency for trichloromethane‐water mixture reached 95.8%, and still maintained 95.6% after 30 separation cycles. In addition, the CF also possessed superior photocatalytic degradation capability for organic contaminant such as oil red O and the degradation rate was 86.2% under UV irradiation for 180 min. The preparation method in this work is simple, environmentally friendly, low‐cost, and easy to produce on a large scale. The findings conceivably stand out as a new method to fabricate superhydrophobic materials and show great application potential in the fields of oil–water separation and water purification.

Loofah plant—Derived biodegradable superhydrophobic sponge for effective removal of oil and microplastic from water

Recently, oil spills and microplastic have become vital worldwide environmental issues. In this study, inspired by the natural phenomenon, two types of biodegradable superhydrophobic sponges derived from the loofah plant were fabricated to deal with those contaminants. Loofah is a niche vegetable for food and eco-sponges and is very popular in Europe and Asia. A facile fabrication process is carried out with dip-coating techniques, which help to functionalize the surface of the natural loofah sponge with two types of natural wax (bee wax and palm wax). The fabricated materials named LS-B(2) and LS-P(2) showed excellent superhydrophobicity with a high water contact angle, which was fundamental for separating oil in the water mixture and capturing microplastics. The derived superhydrophobic sponges displayed a high oil absorption capacity in the range of 72–81 g g−1 for LS-B(2) and LS-P(2). The separation efficiency reached over 99 % for the immiscible kerosene/water mixture and the fabricated material’s excellent recyclability via simple squeezing. The sponges also can capture the microplastics at different concentrations with very high adsorption capacity (381–569 mg/g), reaching over 99% polystyrene microplastics from aqueous suspensions under continuous stirring conditions. With the natural abundance of the base material in nature and the ease of the fabrication process, this work could open the novel direction for a low-cost, high-performance, and large-scale application material in the future toward environmental sustainability.

Improving waterproof-breathable capability of degradable macroporous film/hemp hydroentangled nonwovens composite membranes by porous structure and surface wettability modification

Due to recent serious COVID-19 pandemic, medical protective materials with outstanding microbial barrier and liquid barrier property have attracted much attention. However, the crucial issue of improving the waterproof-breathable capability and degradable properties of medical protective material is still challenging. In this research, poly(butyleneadipate-co-terephthalate) (PBAT)/hemp@silica-polyvinylsilsesquioxane (SiO2-PVSQ) composite membranes with good moisture permeability and waterproof property were fabricated. Firstly, hemp and cotton fibers were mixed and hemp/cotton hydroentangled nonwovens were produced to endow the membranes with outstanding water vapor penetration and mechanical properties. Then, degradable PBAT macroporous membranes were prepared by non-solvent induced phase separation (NIPS) method, and combined with hemp/cotton hydroentangled nonwovens to endow the composite membranes with waterproof property. Finally, SiO2 particles were hydrophobically modified by vinyltrimethoxysilane (VTMOS) and grafted on the surface of PBAT/hemp composite membranes. The waterproof property of composite membranes was further improved by hierarchical rough structure and low surface tension hydrophobic groups on the membrane surface. The prepared PBAT/hemp@SiO2-PVSQ composite membranes showed excellent tensile strength with high moisture permeability, good waterproof and water contact angle of 139.5°, indicating promising candidates for the new generation comfort and degradable medical protective textiles.

Prevention of marine biofouling in the aquaculture industry by a coating based on polydimethylsiloxane-chitosan and sodium polyacrylate

In this study, a series of novel hydrophobic/hydrophilic hybrid (HHH) coatings with the feature of preventing the fouling phenomenon was fabricated based on polydimethylsiloxane (PDMS), as matrix and two hydrophilic polymers: chitosan and sodium polyacrylate, as dispersed phases. Antibacterial activity, pseudo-barnacle adhesion strength, surface free energy, water contact angle, and water absorption were performed for all samples. Evaluating field immersion of the samples was performed in the natural seawater. The results showed that the dispersed phase containing PDMS coatings showed simultaneously both of antibacterial activity and foul release behavior. Among the samples, the PCs4 coating containing 4 wt% Cs indicated the lowest pseudo barnacle adhesion strength (0.04 MPa), the lowest surface free energy (18.94 mN/m), the highest water contact angle (116.05°), and the percentage of fouling organisms 9.8 % after 30 days immersion. The HHH coatings can be considered as novel eco-friendly antifouling/foul release coatings for aquaculture applications.

Hybrid Hemp Particles as Functional Fillers for the Manufacturing of Hydrophobic and Anti-icing Epoxy Composite Coatings.

The development of hydrophobic composite coatings is of great interest for several applications in the aerospace industry. Functionalized microparticles can be obtained from waste fabrics and employed as fillers to prepare sustainable hydrophobic epoxy-based coatings. Following a waste-to-wealth approach, a novel hydrophobic epoxy-based composite including hemp microparticles (HMPs) functionalized with waterglass solution, 3-aminopropyl triethoxysilane, polypropylene-graft-maleic anhydride, and either hexadecyltrimethoxysilane or 1H,1H,2H,2H-perfluorooctyltriethoxysilane is presented. The resulting epoxy coatings based on hydrophobic HMPs were cast on aeronautical carbon fiber-reinforced panels to improve their anti-icing performance. Wettability and anti-icing behavior of the prepared composites were investigated at 25 °C and -30 °C (complete icing time), respectively. Samples cast with the composite coating can achieve up to 30 °C higher water contact angle and doubled icing time than aeronautical panels treated with unfilled epoxy resin. A low content (2 wt %) of tailored HMPs causes an increase of ∼26% in the glass transition temperature of the coatings compared to pristine resin, confirming the good interaction between the hemp filler and epoxy matrix at the interphase. Finally, atomic force microscopy reveals that the HMPs can induce the formation of a hierarchical structure on the surface of casted panels. This rough morphology, combined with the silane activity, allows the preparation of aeronautical substrates with enhanced hydrophobicity, anti-icing capability, and thermal stability.

Recent Advances in Dual-Function Superhydrophobic Antibacterial Surfaces.

Bacterial adhesion and subsequent biofilm formation on the surfaces of synthetic materials imposes a significant burden in various fields, which can lead to infections in patients or reduce the service life of industrial devices. Therefore, there is increasing interest in imbuing surfaces with antibacterial properties. Bioinspired superhydrophobic surfaces with high water contact angles (>150°) exhibit excellent surface repellency against contaminations, thereby preventing initial bacterial adhesion and inhibiting biofilm formation. However, conventional superhydrophobic surfaces typically lack long-term durability and are incapable of achieving persistent efficacy against bacterial adhesion. To overcome these limitations, in recent decades, dual-function superhydrophobic antibacterial surfaces with both bacteria-repelling and bacteria-killing properties have been developed by introducing bactericidal components. These surfaces have demonstrated improved long-term antibacterial performance in addressing the issues associated with surface-attached bacteria. This review summarizes the recent advancements of these dual-function superhydrophobic antibacterial surfaces. First, a brief overview of the fabrication strategies and bacteria-repelling mechanism of superhydrophobic surfaces is provided and then the dual-function superhydrophobic antibacterial surfaces are classified into three types based on the bacteria-killing mechanism: i) mechanotherapy, ii) chemotherapy, and iii) phototherapy. Finally, the limitations and challenges of current research are discussed and future perspectives in this promising area are proposed.

Fabrication of Hydrophobic Poly(vinylidene fluoride) Membranes with Manipulated Micromorphology and Enhanced Strength

In this work, an ethanol/water/glycerol ternary coagulation bath system was used to fabricate a hydrophobic PVDF membrane, which will have a considerable impact on the micromorphology. This change will further affect the performance of the membrane. After introducing glycerol into the coagulation bath, the precipitation process was finely regulated. The obtained results implied that glycerol could inhibit solid-liquid separation and promoted liquid-liquid separation. A pleasant discovery was that the mechanical properties of the membrane were improved because of the more fibrous polymers formed by liquid-liquid separation. Besides, a more uniform pore size can be achieved. A fascinating symmetrical interconnected fibrous and spherulitic structure was depicted by membranes fabricated with a coagulation bath consisting of 6% water, 34% ethanol, and 60% glycerol. This membrane had a high water contact angle of 146.6° and a small mean pore size of 0.46 μm. Enhanced tensile strength and elongation at break evidenced that the membrane enjoyed good robustness and flexibility. This facile approach provided the possibility to prepare membranes with tailored pore size and the required strength.

Beeswax coating improves the hydrophobicity of sodium alginate/ anthocyanin/ cellulose nanocrystal indicator film

This study investigates the waterproof layer formed by beeswax (BW) to improve the hydrophobicity of sodium alginate/black soybean seed coat anthocyanin/cellulose nanocrystal indicator films. The concentrations of BW and the fabrication method of the waterproof layer, including spraying, coating (CO), and soaking, were optimized. The results showed that the optimal concentration of BW in the waterproof layer was 5% owing to its high water contact angle of 111.5°. Different methods of fabricating waterproof layers with BW led to the formation of particles of different sizes on the microscopic film surface. Hydrophobic films with a waterproof layer of BW-CO had high transmittance and pH sensitivity, ensuring the basic properties of indicator films. Meanwhile, they exhibited excellent water barrier properties based on the water contact angle, water vapor adsorption, water vapor permeability, water content and water solubility. In particular, these films remained highly hydrophobic after 10 days of storage at 100% humidity, with a water contact angle of 108.3°. The findings indicated that hydrophobic sodium alginate/black soybean seed coat anthocyanin/cellulose nanocrystal indicator films were prepared using BW, which improved their potential application in intelligent food packaging.

Preparation of Cu/CuO@Stearic acid layer with superhydrophobicity to provide multiple barriers for corrosion protection of carbon steel

Carbon steel is a widely used metallic material. It is prone to corrosion. In this study, we designed and fabricated a superhydrophobic layer with corrosion resistance for protection of carbon steel substrate. Multiple layers were formed that acted as barriers to protect the substrate from corrosion. This superhydrophobic layer reduced the contact area between the substrate and the corrosive medium owing to the superhydrophobicity. The experimental results showed that a copper layer uniformly covered the carbon steel substrate, and the outer surface of the copper layer was converted into copper oxide, which had a multi-scale structure. The Cu/CuO double layer was modified with stearic acid (SA) to form a Cu/CuO@SA superhydrophobic layer. The superhydrophobic layer exhibited a high water contact angle (up to 160°) and a low sliding angle (<3°). The superhydrophobic layer also exhibited repulsive effect to salt, acidic and alkaline solutions. Atmospheric stability test and UV irradiation test were conducted and the results indicated that the superhydrophobic layer was stable throughout the test period. The corrosion potential of the superhydrophobic sample was −0.18 V and the corrosion current density was 7.72 × 10−7 A cm−2, which was one order of magnitude lower than that of the carbon steel substrate. These results indicate that the superhydrophobic sample had a low corrosion tendency and corrosion rate. The polarization resistance and impedance modulus of the superhydrophobic sample were two orders of magnitude higher than the bare steel sample, indicating corrosion resistance and effective protection to the carbon steel substrate.

Comparison of biodegradable chitosan-based composite films reinforced by different micron-sized plant fibers for food packaging

To provide a fully degradable food packaging film with excellent performance, a chitosan (CS)-based film containing micron-sized plant fibers was prepared by the casting method. With the addition of different plant fibers—wheat straw fiber (WF), maize straw fiber (MF), rice straw fiber (RF), and sisal fiber (SF), a significant improvement in mechanical, water resistance, water vapor barrier, and thermal properties was observed. By comparison, the most significant enhancement effect was observed in CS/SF-based film. The tensile strength and elongation at break of this film were 58.44 MPa and 14.42%, respectively. Moreover, it exhibited excellent properties such as the highest water contact angle (118°), a moisture absorption rate of 5.14%, a low water vapor transmission rate (110.73 g·m-2·d-1), and high thermal stability. Considering the sustainability and attractive physical properties, the improved films showed great potential for food packaging.

Bio‐based fluorine‐free branched polyurethane@organosilicon water‐repellent agent for cotton fabric

AbstractIn recent years, with the increasing consciousness on environment protection, fluorine‐free water‐repellent agents in textile industry have attracted considerable attention. Herein, we proposed a new strategy to prepare bio‐based fluorine‐free branched polyurethane@organosilicon water‐repellent agent for cotton fabric (CF). Branched polyurethane (BPU) with long alkyl chains was firstly synthesized through the reaction of glycerin monostearate extracted from natural palm fruit, toluene diisocyanate, trimethylopropane and N‐methyl diethanolamine, and then utilized to coat the C24‐28 olefin modified hydroxyl silicone oil (C24‐28 HSO) by emulsification procedure to obtain branched polyurethane@organosilicon (BPU@C24‐28 HSO) water‐repellent agent. Fourier transform infrared spectroscopy and1H nuclear magnetic resonance spectroscopy confirmed the chemical structures of BPU, C24‐28 HSO and BPU@C24‐28 HSO water‐repellent agent. The biomass carbon content of the water‐repellent agent reached 54.0%. Transmission electron microscope demonstrated that the BPU@C24‐28 HSO water‐repellent agent appeared obvious spherical shape with core‐shell structure. Owing to the introduction of organosilicon, the water‐repellent agent significantly improved the softness of the CF. In addition, the CF finished by the BPU@C24‐28 HSO water‐repellent agent also exhibited excellent water‐repellent score of 90+, high water contact angle of 141.6° and superior surface stability. Our findings provided a direction to prepare environmental‐friendly and high‐performance water‐repellent agents for various fabrics.