Construction of super-hydrophobic, highly effective flame retardant coating for cotton fabric with superior washability and abrasion resistance

Fabrication of superior flame-retardant phosphorylated chitosan biobased porous composites reinforced by superhydrophobic silicone interpenetrating crosslinking networks

Chitosan-based porous materials have potential to develop into a new generation of high performance sustainable thermal insulation materials. In this study, hydrophobic and enhanced phosphorylated porous materials (PCSM) were constructed by the in-situ crosslinking of methytrimethoxylsilane (MTMS), and modified SiO2 nanoparticles (H-SiO2) were further incorporated into the crosslinking networks to fabricate superhydrophobic and reinforced PCSM-H-SiO2 porous composites. The morphology of PCSM-H-SiO2 porous materials exhibited special micro-nanoscale "pearl string-like" rough and interpenetrating pore wall structure, which endowed them superhydrophobicity and self-cleaning ability. The water contact angles (WCAs) of PCSM-H-SiO2 porous composites achieved up to 150o, and the compressive and specific moduli of PCSM2-H-SiO2-2 porous composite significantly increased to 11.0 MPa and 89.6 m2·s-2, 5.39 and 1.74 times higher than those of PCS porous material, respectively. The limited oxygen index (LOI) values of PCSM2-H-SiO2-2 porous composite were above 80 %. The cone calorimeter test result demonstrated the peak heat release rate and total heat release rate values of PCSM-H-SiO2-2 porous composite were lower than those of PCS porous material. The ultra-high flame-retardant PCSM-H-SiO2-2 porous composite with superhydrophobicity and excellent compressive property is a promising biodegradable thermal-insulation material as replacement of petroleum-based material.

Halloysite-based inorganic-organic hybrid coatings for durable flame retardant, hydrophobic and antibacterial properties of cotton fabrics

Developing durable protective cotton fabrics (CF) against potential environmental dangers such as fire hazards and bacterial growth remains an imperative but tough challenge. In this study, flame retardant, antibacterial and hydrophobic CF were successfully prepared via two-step coating. The inner coating entailed polyelectrolyte complexes consisting of polyethyleneimine and ammonium polyphosphate with the goal of enhancing the flame retardancy of CF. Halloysite nanotubes (HNTs), a kind of tubular silicate mineral, were creatively modified and introduced to multifunctional coatings to improve flame retardant and antibacterial properties of CF. N-halamine modified HNTs (HNTs-EA-Cl) and polydimethylsiloxane were applied as the outer coating to endow CF with antibacterial and hydrophobic properties and further improve the flame retardancy of CF. After halloysite-based inorganic-organic hybrid coatings, the limiting oxygen index of the treated samples (PAHP-CF) was over 28 %, and the release of heat and smoke was significantly inhibited. PAHP-CF could inactivate 100 % E. coli and S. aureus within 2 h. More importantly, PAHP-CF showed excellent hydrophobicity with a water contact angle of 148° and exhibited great prevention of bacterial adhesion. PAHP-CF exhibited excellent washing durability undergoing 5 washing cycles. This study promotes the development of multifunctional coatings and offers a new way to manufacture multifunctional cotton fabrics.

Anti-flammable, anti-fouling, anti-bacterial treatment of cotton fabrics with MOF-based hybrid coatings for highly efficient oil-water separation

A flame-retardant and hydrophobic coating was deposited on the surface of the cotton fabric via a two-step spray deposition technique. Specifically, the coating was composed of flame-retardant component (guanidine phosphate) and hydrophobic components (Ti-MOF and bis(3-aminopropyl)-terminated poly(dimethylsiloxane) (PDMS)) and crosslinked with glutaraldehyde. The limiting oxygen index (LOI) of the coated cotton fabrics increased from 18.0 % to 32.0 % (15#) and 26.5 % (15#-Ti-PDMS) relative to that of the original cotton fabric, and the coated cotton fabrics also self-extinguished in the UL-94 flammability test. Compared with that of the original cotton fabric, the PHRR of the coated fabrics was significantly lower, reaching 80 %. The coated cotton fabrics (15# and 15#-Ti-PDMS) had good antibacterial properties against Staphylococcus aureus (S. aureus). In addition, 15#-Ti-PDMS had high hydrophobicity, good washing and abrasion resistance and good water-oil separation performance. Its water contact angle was 146°. The water contact angle remained above 130° after 10 laundering cycles and 50 scratch cycles. Even under strongly acidic and strongly basic conditions, the water-oil separation efficiency of 15#-Ti-PDMS was greater than 99 %, and it was still greater than 90 % after 10 cycles. Therefore, a simple and effective method for preparing flame-retardant, hydrophobic and antibacterial cotton fabric was developed.

Biomimetic Multifunctional Graphene-Based Coating for Thermal Management, Solar De-Icing, and Fire Safety: Inspired from the Antireflection Nanostructure of Compound Eyes

Due to the ubiquitous and inexhaustible solar source, photothermal materials have gained considerable attention for their potential in heating and de-icing. Nevertheless, traditional photothermal materials, exemplified by graphene, frequently encounter challenges emanating from their elevated reflectance. Inspired by ocular structures, this study uses the Fresnel equation to enhance the photo-thermal conversion efficiency of graphene by introducing a polydimethylsiloxane (PDMS)/silicon dioxide (SiO2) coating, which reduces the light reflectance (≈20%) through destructive interference. The designed coating achieves an equilibrium temperature of ≈77 °C at one sun and a quick de-icing in ≈65 s, all with a thickness of 5 µm. Simulations demonstrate that applying this coating to high-rise buildings results in energy savings of ≈31% in winter heating. Furthermore, the combination of PDMS/SiO2 and graphene confers a notable enhancement in thermal stability through a synergistic flame-retardant mechanism, effectively safeguarding polyurethane against high temperatures and conflagrations, leading to marked reduction of 58% and 28% in heat release rate and total heat release. This innovative design enhances the photo-thermal conversion, de-icing function, and flame retardancy of graphene, thereby advancing its applications in outdoor equipment, high-rise buildings, and aerospace vessels.

A bio-based durable reactive flame retardant for cotton fabric based on lentinan

Cotton fabric has extensive application due to its comfort and breathability. However, the inherent flammability limits its wide application. Durable polysaccharide-based flame retardants with a low impact on the softness of fabrics are rarely reported. In this work, a novel flame retardant ammonium phosphate of lentinan (APLNT) was synthesized and grafted on the surface of cotton fabric. The treated cotton fabric had a high limiting oxygen index (LOI) value of 43.3 % and passed the vertical burning test (VBT) with a 21.1 % weight gain of APLNT. Compared with control cotton, the peak heat release rate and total heat release values of Cotton-APLNT2 decreased by 92.8 % and 50.9 %, respectively. In addition, the cotton fabric still passed the VBT and kept an LOI value of 27.0 % even after 50 laundering cycles, indicating that the fabric can be used for daily needs. More importantly, the treated fabric remains soft. This research provided a new strategy for preparing bio-based durable flame retardant cotton fabrics.

Construction of composite self-assembly coating based on chitosan for enhancing the flame-retardant and antibacterial performances of cotton fabric

In this work, the step-by-step dip-coating (SBS) method was used to effectively improve the drawback of LBL by reducing the construction of a multilayer polyelectrolyte. Bio-based flame retardants, phytic acid (PA), and chitosan (CS) were further self-assembly on the surface of cotton fabric treated by epichlorohydrin-modified aramid nanofibers (AEP), ionic liquid (IL), and Cu ion. The pure cotton fabric was immersed in each dipping liquid only once, improving fire safety and antibacterial performance. The treated cotton self-extinguished with a 59 mm char length in the vertical flammability test, and the limiting oxygen index (LOI) value increased from 18.5 % to 38.5 %. The result of the cone calorimeter test (CCT) revealed that the fire hazard of flame-retardant cotton noteworthy declined (e.g., ~44.1 % and 55.4 % decline in peak heat release rate (pHRR) and total heat release rate (THR)). Conspicuously, the treated cotton exhibited a remarkably inhibiting effect on E. coli and S. aureus activity. The cotton fabric after flame-retardant finishing exhibited excellent fire safety and antibacterial performance.

Superhydrophobic, Highly Conductive, and Trilayered Fabric with Connected Carbon Nanotubes for Energy-Efficient Electrical Heating

Current electrically heated fabrics provide heat in cold climates, suffer from abundant wasted radiant heat energy to the external environment, and are prone to damage by water. Thus, constructing energy-efficient and superhydrophobic conductive fabrics is in high demand. Therefore, we propose an effective and facile methodology to prepare a superhydrophobic, highly conductive, and trilayered fabric with a connected carbon nanotube (CNT) layer and a titanium dioxide (TiO2) nanoparticle heat-reflecting layer. We construct polyamide/fluorinated polyurethane (PA/FPU) nanofibrous membranes via first electrospinning, then performing blade-coating with the polyurethane (PU) solution with CNTs, and finally fabricating FPU/TiO2 nanoparticles via electrospraying. This strategy causes CNTs to be connected to form a conductive layer and enables TiO2 nanoparticles to be bound together to form a porous, heat-reflecting layer. As a consequence, the as-prepared membranes demonstrate high conductivity with an electrical conductivity of 63 S/m, exhibit rapid electric-heating capacity, and exhibit energy-efficient asymmetrical heating behavior, i.e., the heating temperature of the PA/FPU nanofibrous layer reaches more than 83 °C within 90 s at 24 V, while the heating temperature of the FPU/TiO2 layer only reaches 53 °C, as well as prominent superhydrophobicity with a water contact angle of 156°, indicating promising utility for the next generation of electrical heating textiles.

Biomimetic Nanoporous Transparent Universal Fire-Resistant Coatings

The inherent flammability of most polymeric materials poses a significant fire hazard, leading to substantial property damage and loss of life. A universal flame-retardant protective coating is considered as a promising strategy to mitigate such risks; however, simultaneously achieving high transparency of the coatings remains a great challenge. Here, inspired by the moth eye effect, we designed a nanoporous structure into a protective coating that leverages a hydrophilic-hydrophobic interactive assembly facilitated by phosphoric acid protonated amino siloxane. The coating demonstrates robust adhesion to a diverse range of substrates, including but not limited to fabrics, foams, paper, and wood. As expected, its moth-eye-inspired nanoporous structure conferred a high visible light transparency of >97% and water vapor transmittance of 96%. The synergistic effect among phosphorus (P), nitrogen (N), and silicon (Si) largely enhanced the char-forming ability and restricted the decomposition of the coated substrates, which successfully endowed the coating with high fire-fighting performance. More importantly, for both flexible and rigid substrates, the coated samples all possessed great mechanical properties. This work provides a new insight for the design of protective coatings, particularly focusing on achieving high transparency.

A molecularly engineered fully bio-derived phosphorylated furan-based flame retardant for biomass-based fabrics

With the increasing awareness of environmental protection, the demand for eco-friendly bio-derived flame-retardant for textiles has received increasing attention. In this work, a fully bio-derived phosphorylated furan-based flame retardant (FAP) was synthesized by the Schiff reaction of furan-based compounds (furfural and furfurylamine). To evaluate the application scope and flame retardant efficiency of FAP, cotton fabrics and PLA nonwovens were selected as biomass-based representatives of natural fiber materials and synthetic fiber materials, respectively. Significantly, based on the composition of furan ring, phosphorus and nitrogen containing components of FAP, excellent charring and flame retardant properties of coated cotton fabrics and PLA nonwovens can be expected. TGA results showed that the residual char of C-FAP-3 and P-FAP-3 were 39.7% (increased by 267.6%) and 16.7% (increased by 215.1%), respectively, higher than those of control cotton (10.8%) and PLA nonwoven (5.3%). Cone test results exhibited that the peak heat release rate (PHRR) and total heat release (THR) values of C-FAP-3 were sharply decreased by 69.4% and 37.8%, respectively. P-FAP-3 also displayed a significant reduction in PHRR, implying high flame retardancy of C-FAP-3 and P-FAP-3. Notably, through the weight gains of FAP coating on cotton and PLA as well as the final LOI and VBT results of the flame retardant treated fabrics, it can be preliminarily inferred that control cotton fabrics are more likely to achieve better flame retardant effects than PLA. Additionally, the facile synthetic strategy of fully bio-derived flame retardants is expected to promote the development of green flame retardant strategies for high-performance textiles.

Preparation and thermostability of a Si/P/N synergistic flame retardant containing triazine ring structure for cotton fabrics

A new synergistic flame retardant named Bisiminopropyl trimethoxysilane-1,3,5-triazine-O-bicyclic pentaerythritol phosphate (BTPODE) was synthesized, which is a type of Si/P/N flame retardant. This was accomplished by grafting aminopropyl trimethoxysilane and bicyclic pentaerythritol phosphate onto a triazine ring structure, serving as an intermediate. The structure of BTPODE was determined using nuclear magnetic resonance (1H NMR, 13C NMR, and 31P NMR) and Fourier transform infrared spectroscopy (FT-IR). SEM was used to detect the surface morphology of cotton fabrics, which suggested that BTPODE had been resoundingly stick to cotton fabrics. The flame retardant properties of cotton fabrics were evaluated by measuring the limiting oxygen index (LOI) and conducting vertical flammability experiments. Cotton fabrics with a weight gain of 20.73 % achieved an LOI value of 32.5 %. Thermogravimetric (TG) experiments demonstrated the samples' good thermostability. Furthermore, under nitrogen conditions, the char residue of cotton fabric with a weight gain of 20.73 % was 36.85 %. The cone calorimetry test (CONE) showed a significant reduction in the TSP value, indicating a certain level of smoke suppression performance. Finally, based on the obtained experimental results, the fire-retardant mechanism principle of the flame retardant was deduced.

Construction of Janus structures on thin silk fabrics via misting for wet-thermal comfort and antimicrobial activity

Owing to their small fiber diameter (10-15 μm), silk fabrics are always thin (32-90 g m-2). Therefore, construction of the Janus surfaces of silk fabrics that possess excellent multifunctionality remains a formidable challenge. Herein, first, silk fabrics were grafted using glycidyltrimethylammonium chloride to form a superhydrophilic surface (G-side). Then, a unilateral hydrophobic surface (O-side) was readily fabricated by mist coating octadecyltrichlorosilane-functionalized SiO2 nanoparticles (NPs) to produce hierarchical surface textures. To prevent NP penetration from the G-side to the O-side, a "fireproof isolation" method was employed. Consequently, Janus silk fabrics (JanSFs) bearing asymmetric wettability were prepared, and their wetting gradient could be conveniently regulated. With the mist time ranging from 4 to 7 min, the unidirectional transport index and efficiency of the unidirectional water transport increased and decreased by 13.2 and 10.4 times, respectively. Sweat could be effectively drained away from human skin to ensure that the skin was dry and comfortable. Compared with the surface temperature of the raw fabric, the raw fabric of JanSFs increased by 2.7 °C. Furthermore, the breathability of JanSF was negligibly affected, and the outer O-side of the JanSF showed substantial antibacterial activity. This study is important for designing JanSFs that exhibit unidirectional water transport.

Multi-functionalization of cotton fabrics with excellent flame retardant, antibacterial and superhydrophobic properties

Cotton fabric is widely used in many fields for its excellent comfortability, breathability and hygroscopicity. However, the development of multifunctional cotton fabrics to meet the requirements of different scenarios is a top priority. In this study, multifunctional coating was constructed through facile layer-by-layer assembly phytic acid and chitosan, and spraying divalent copper ion and polydimethylsiloxane (PDMS) on cotton fabrics, anticipating to endow them with flame retardancy, antibacterial and superhydrophobic properties simultaneously. The treated cotton fabric achieved a limiting oxygen index (LOI) value of 32 %, with the char length reducing to 10.7 cm revealing excellent flame retardancy. The water contact angle of multifunctional treated cotton fabric was above 150°, demonstrating it had superhydrophobicity. The antibacterial rates of multifunctional cotton fabrics against E. coli and S. aureus reached to higher than 99 %, indicating that the excellent antibacterial properties. Combined with the thermal stability of cotton fabrics and their char residues analysis, these results demonstrated that the multifunctional coating could act through intumescent flame retardant mechanism to flame retardant cotton fabrics. This research provides a facile way to prepare multifunctional cotton fabrics to broaden the application prospect.

Integrating multifunctional highly efficient flame-retardant coatings with superhydrophobicity, antibacterial property on cotton fabric

There has been a growing interest in bio-based flame-retardant coating layer with good antibacterial activity for cotton fabric owing to the arising environmental pollution and viral and bacterial infectious risks. In this study, multifunctional flame-retardant coatings with superhydrophobicity and antibacterial property were integrated on cotton fabric through two-step method. The first layer of phosphorylated chitosan (PCS) biobased coating (C4) endowed the fabric highly efficient flame retardancy and antibacterial activity, and the second layer of modified poly(2-hydroxyethyl methacrylate phosphate ester) (PHEMAP) coating by perfluorooctyltriethoxysilane (P/F) provided the fabric excellent superhydrophobicity and self-cleaning ability. The C4-P/F fabric exhibited a shorter damage length of only 6.2 cm and achieved a higher char yield of 22.3 % than the C4 fabric in the vertical combustion test, and the limited oxygen index of the C4-P/F fabric increased to 32.5 %. The water contact angle (WCA) of the C4-P/F fabric reached above 150 o. Moreover, the C4-P/F fabric exhibited excellent antibacterial activity against Escherichia coli and Staphylococcus aureus. The highly efficient flame-retardant, superhydrophobic, antibacterial fabric is promising in home and public decoration, fire protection fields.

Halogen-Free Waterborne Polymeric Hybrid Coatings for Improved Fire Retardancy of Textiles

Wildfires are becoming more intense and more frequent, ravaging the habitations and ecosystems in their path. One solution to reducing the risk of damage to buildings and other structures during a fire event is the use of fire-retardant coatings that can stop or slow down the spread of flames, especially for textile materials. The present study focuses on the preparation and application of halogen-free boron/bentonite-based polymeric fire-retardant (FR) hybrid coating formulations for fabrics such as cotton (CO) and polyester (PE) fibers. For the preparation of FR composites, two types of boron derivatives, disodium octaborate and zinc borate, were used in combination with sodium bentonite. A styrene-acrylic copolymer was specifically synthesized and used as a coating binder for FR components to apply on fabrics. The properties of the synthesized copolymer and FR composites were characterized with a particle size analysis, FTIR spectroscopy, a dynamic mechanical thermal analysis (DMTA), and rheological measurements. The obtained hybrid composites based on styrene-acrylic copolymers and two different inorganic fillers were applied on cotton (CO) and polyester (PE) fabrics with a screen-printing technique, and the flame retardancy performance of the finished textile samples was investigated by means of flame spread and limit oxygen index (LOI) tests. The findings showed that the FR-composite-coated fabrics had higher LOI values and much decreased flame spread rates in comparison with uncoated ones. Among the boron derivatives, the composites prepared with disodium octaborate (FR-A) had much more pronounced LOI values and decreased flame spread behavior in comparison with the composite with zinc borate (FR-B). When compared to a commercial product, the FR-A composite, in conjunction with the specially synthesized polymer, demonstrated commendable fire retardancy performance and emerged as a promising candidate for a halogen-free waterborne fire-retardant coating for fabrics.

Fabrication of dual physically cross-linked polyvinyl alcohol/agar hydrogels with mechanical stability and antibacterial activity for wound healing

Bacterial infection is one of the most critical obstacles in wound healing, and severe bacterial infections can lead to inflammatory conditions and delay the healing process. Herein, a novel hydrogel based on polyvinyl alcohol (PVA), agar, and silk-AgNPs was prepared using a straightforward one-pot physical cross-linking method. The in situ synthesis of AgNPs in hydrogels exploited the reducibility of tyrosine (Tyr tyrosine) in silk fibroin, which endowed the hydrogels with outstanding antibacterial qualities. In addition, the strong hydrogen bond cross-linked networks of agar and the crystallites formed by PVA as the physical cross-linked double network of the hydrogel gave it excellent mechanical stability. The PVA/agar/SF-AgNPs (PASA) hydrogels exhibited excellent water absorption, porosity, and significant antibacterial effects against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Furthermore, in vivo experimental results confirmed that the PASA hydrogel significantly promoted wound repair and skin tissue reconstruction by reducing inflammation and promoting collagen deposition. Immunofluorescence staining showed that the PASA hydrogel enhanced CD31 expression to promote angiogenesis while decreasing CD68 expression to reduce inflammation. Overall, the novel PASA hydrogel showed great potential for bacterial infection wound management.

Multifunctional composite coatings with hydrophobic, UV-resistant, anti-oxidative, and photothermal performance for healthcare

Personal protective textiles have attracted extensive interest since Corona Virus Disease 2019 has broken out. Moreover, developing eco-friendly, multifunctional waterproof, and breathable surface is of great importance but still faces enormous challenges. Notably, good hydrophobicity and breathability are necessary for protective textiles, especially protective clothing and face masks for healthcare. Herein, the multifunctional composite coatings with good UV-resistant, anti-oxidative, hydrophobic, breathable, and photothermal performance has been rapidly created to meet protective requirements. First, the gallic acid and chitosan polymer was coated onto the cotton fabric surface. Subsequently, the modified silica sol was anchored on the coated cotton fabric surface. The successful fabrication of composite coatings was verified by RGB values obtained from the smartphone and K/S value. The present work is an advance for realizing textile hydrophobicity by utilizing fluorine-free materials, compared with the surface hydrophobicity fabricated with conventional fluorinated materials. The surface free energy has been reduced from 84.2 to27.6 mJ/m2 so that the modified cotton fabric could repel the ethylene glycol, hydrochloric acid, and sodium hydroxide solutions, respectively. Besides, the composite coatings possesses lower adhesion to deionized water. After 70 cycles of the sandpaper abrasion, the fluorine-free hydrophobic coatings still exhibits good hydrophobicity with WCA of 124.6 ± 0.9°, with overcoming the intrinsic drawback of the poor abrasion resistance of hydrophobic surfaces. Briefly, the present work may provide a universal strategy for rapidly creating advanced protective coatings to meet personal healthcare, and a novel method for detecting RGB values of composite coatings by smartphone.

Sustainable Flame-Retardant Flax Fabrics by Engineered Layer-by-Layer Surface Functionalization with Phytic Acid and Polyethylenimine

New generation of mission-oriented fabrics meets advanced requirements; such as electrical conductivity, flame retardancy, and anti-bacterial properties. However, sustainability concerns still are on-demand in fabrication of multi-functional fabrics. In this work, we used a bio-based phosphorus molecule (phytic acid, PA) to reinforce flax fabrics against flame via layer-by-layer consecutive surface modification. First, the flax fabric was treated with PA. Then, polyethylenimine (PEI) was localized above it to create negative charges, and finally PA was deposited as top-layer. Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), and inductively-coupled plasma atomic emission spectrometry (ICP-AES) proved successful chemical treatment. Pyrolysis-combustion flow calorimetry (PCFC) showed significant drop by about 77% in the peak of heat release rate (pHRR) from 215 W/g for untreated to 50 W/g for treated flax fabric. Likewise, the total heat release (THR) decreased by more than three times from 11 to 3.2 kJ/g. Mechanical behavior of the treated flax fabric was completely different from untreated flax fabrics, changing from almost highly-strengthened behavior with short elongation at break to a rubber-like behavior with significantly higher elongation at break. Surface friction resistance was also improved, such that the abrasion resistance of the modified fabrics increased up to 30,000 rub cycles without rupture.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10694-023-01387-7.

Flame retardant cotton fabrics with anti-UV properties based on tea polyphenol-melamine-phenylphosphonic acid

A novel, high-efficiency, phosphorus-nitrogen flame retardant based on tea polyphenol-melamine-phenylphosphonic acid (named TP-MA-PPOA) for cotton fabrics was prepared successfully. TP-MA-PPOA coating gives the cotton fabrics flame retardancy and anti-UV properties. The results reveal that the TP-MA-PPOA coating enables cotton fabrics to self-extinguish, the damage length is only 7.4 cm in vertical flame test, and the limiting oxygen index increases to 28.7%. Meanwhile, Cotton/TP-MA-PPOA also performs well in cone calorimetry test, as evidenced by 88.5% reduction of peak heat release rate, and 92.9% decrease of the fire growth rate compared with that of cotton fabrics. And the risk of fire is sharply reduced. In addition, the ultraviolet protection factor value of Cotton/TP-MA-PPOA is 35.2. Encouragingly, the TP-MA-PPOA coating shows little deterioration in the handle of the cotton fabrics.

Advances in the Fabrication and Characterization of Superhydrophobic Surfaces Inspired by the Lotus Leaf

Nature has proven to be a valuable resource in inspiring the development of novel technologies. The field of biomimetics emerged centuries ago as scientists sought to understand the fundamental science behind the extraordinary properties of organisms in nature and applied the new science to mimic a desired property using various materials. Through evolution, living organisms have developed specialized surface coatings and chemistries with extraordinary properties such as the superhydrophobicity, which has been exploited to maintain structural integrity and for survival in harsh environments. The Lotus leaf is one of many examples which has inspired the fabrication of superhydrophobic surfaces. In this review, the fundamental science, supported by rigorous derivations from a thermodynamic perspective, is presented to explain the origin of superhydrophobicity. Based on theory, the interplay between surface morphology and chemistry is shown to influence surface wetting properties of materials. Various fabrication techniques to create superhydrophobic surfaces are also presented along with the corresponding advantages and/or disadvantages. Recent advances in the characterization techniques used to quantify the superhydrophobicity of surfaces is presented with respect to accuracy and sensitivity of the measurements. Challenges associated with the fabrication and characterization of superhydrophobic surfaces are also discussed.

Experimental Evaluation of Fire Resistance Limits for Steel Constructions with Fire-Retardant Coatings at Various Fire Conditions

The experimental evaluation of fire resistance limits for steel constructions with fire-retardant coatings consists of a lot of experiments on the heating of steel structures of buildings by solving a heat engineering problem at various fire conditions. Building design implies the assessment of compliance of actual fire resistance limits for steel constructions with the required limits. Fire resistance limits for steel constructions are determined for “standard” temperature mode, and this can lead to overestimated fire resistance and underestimated heat influence for a real fire. Estimation of the convergence for “standard” temperature mode and possible “real” fire mode, as well as of the compliance of actual fire resistance limits with real fire conditions, was realized in the following stages: mathematical modeling of real fire development by the field model in software package Fire Dynamics Simulation (FDS) with various fire loads and mathematical modeling of steel construction heating for the standard temperature mode obtained by modeling “real” fire modes (the finite difference method of solving the Fourier heat conduction equation at external and internal nonlinearities was used for modeling the process of steel structure heating with the implementation in the ANSYS mechanical software package). Experiments of the assessment of fire-protective paint’s effectiveness were carried out for standard temperature mode and obtained by modeling “real” fire modes. The equivalent fire duration dependence on fire load type was determined. This dependence can be taken into account in determination of fire resistance limits for steel constructions in warehouse building roofing. Fire-protective paint effectiveness was estimated for “standard” temperature mode and various other temperature modes.