Preparation and Properties of Poly(urethane‐urea) Crosslinked Coatings from Perfluorocopolyethers and Polyfunctional Isocyanurates

Two model isocyanate terminated resins were synthesized by addition of perfluorocopolyether oligomers (M̄_n ca. 1 000) with cyclic polyisocyanurates of hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI). The resins were characterized by chemical titration, gel permeation chromatography, FT‐IR spectroscopy, and viscosity. The two resins, and some blends of them, were crosslinked through urea bond formation by exposure to atmospheric moisture. The resulting coatings were characterized by dynamic mechanical spectroscopy (DMS), tensile properties, abrasion resistance, adhesion, atomic force microscopy (AFM) and contact angle measurements. Phase separation phenomena and mechanical properties were related to composition and thermal transitions of both hard and soft phase. Adhesion (pull‐off) was poor on inorganic surfaces like glass and aluminium (<1 MPa) and good on organic primers (>5 MPa). The use of organosilane adhesion promoters was successfully investigated. Surface analysis by AFM showed the formation of a chemically heterogeneous very smooth (on a nanoscale) surface. Contact angle determinations with water, diiodomethane and hexadecane were carried out. The total surface energy of coatings was calculated by the harmonic mean approximation and resulted typically low (16.0–17.5 mN/m) and unaffected by the coating bulk composition.     

Transparent and durable SiO2‐containing superhydrophobic coatings on glass

We fabricated novel superhydrophobic coatings based on SiO₂ nanoparticles combined with NH₂‐terminated silicone (SN₂) or SN₂‐modified polyurethane (SN₂‐prePU) by alternately spin‐coating them onto glass slides. The final fabricated surface contained SN₂/SiO₂ or SN₂‐prePU/SiO₂ bilayers. The conditions of spin‐coating method were also explored. SN₂‐prePU with different SN₂/prePU molar ratios were synthesized to study the influence of SN₂ ratio on the water contact angles of ultimate spin‐coated surfaces. The surface was found to be tunable from hydrophobic to superhydrophobic by choosing SN₂‐prePU with different SN₂/prePU molar ratios or SN₂ content. Water droplets easily rolled off on these superhydrophobic surfaces. Surfaces coated with SN₂/SiO₂ bilayers showed better transparency, whereas surfaces coated with SN₂‐prePU(2 : 1)/SiO₂ bilayers exhibited better durability. Droplets of varied pH were prepared to test the anti‐wettability of the coatings. Results showed that the as‐coated surfaces had stable superhydrophobicity to droplets with pH values ranging from 1 to 14. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41500.     

Self‐assembling metal coatings from phosphated and siloxane‐modified polyurethane dispersions: An analysis of the coating–air interface

Polyurethane dispersion coatings containing phosphate and siloxane chains were evaluated for their self‐assembling properties for a single‐coating system. Dynamic contact angles (DCAs) and X‐ray photoelectron spectroscopy (XPS) were used to study the coating–air interface. The siloxane chains were the predominant species on the surfaces of the coatings. The wetting properties of the coating–air interface were reversed when the coated panels were immersed in an ionic solution, and the decrease in hydrophobicity was linear with time. Results from XPS and DCA analyses were similar. The self‐assembling properties of the coatings could be useful in the development of hydrophobic coatings from hydrophilic polymers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 893–899, 2003     

Tribological properties of ethylene–propylene–diene rubber + polypropylene + thermal‐shock‐resistant ceramic composites

This work is part of a program on composites used in thermoelectric devices. Tribological properties of dynamic vulcanizate blends of polypropylene and ethylene‐propylene‐diene rubber filled with 5 wt% of microscale powder have been studied. The microscale thermal‐shock‐resistant ceramic filler contains α‐Al₂O₃, mullite (3Al₂O₃ · 2SiO₂ or 2Al₂O₃SiO₂), β‐spodumene glass‐ceramic and aluminium titanate. We found that our ceramic particles are abrasive; they cause strong abrasion of softer steel ball surfaces during dry sliding friction. To overcome the difficulty of particle dispersion and adhesion, the filler was modified through grafting using three types of organic molecules. Dry sliding friction was measured using four types of counter‐surfaces: tungsten carbide, Si₃N₂, 302 steel and 440 steel. Thermoplastic vulcanizate filled with neat ceramic powder shows the lowest friction compared to composites containing the same but surface‐treated powder. We introduce a ‘bump’ model to explain the tribological responses of our composites. ‘Naked’ or untreated ceramic particles protrude from the polymer surface and cause a decrease of the contact area compared to neat polymer. The ball partner surface has only a small contact area with the bumps. As contact surface area decreases, so does friction and the amount of heat generated during sliding friction testing. Chemical coupling of the ceramic to the matrix smoothens the bumps and increases the contact surface, giving a parallel increase in friction. Copyright © 2012 Society of Chemical Industry     

Preparation,surface wetting properties,and protein adsorption resistance of well‐defined amphiphilic fluorinated diblock copolymers

Novel well‐defined amphiphilic fluorinated diblock copolymers P(PEGMA‐co‐MMA)‐b‐PC₆SMA were synthesized successfully by RAFT polymerization and characterized by FTIR, ¹HNMR and GPC. For copolymer coatings, static contact angles, θ, with water (θ_water ≥ 109.5^°) and n‐hexadecane (θ_hexadecane ≥ 68.9^°) pointed to the simultaneous hydrophobic and lipophobic characteristics of the copolymer surfaces. Dynamic contact angle measurements indirectly demonstrated that copolymer films underwent surface reconstruction upon contact with water, which results in a surface with surface coverage of polar PEG units. Moreover, the distinct nanoscale microphase segregation structures were proved by atomic force microscopy (AFM) images. Finally, using bovine serum albumin (BSA–FITC) as the model protein, copolymers exhibited excellent protein adsorption resistance. It is believed that the combination of surface reorganization and nanometer‐scale microphase segregation structure endows the excellent protein resistance for amphiphilic fluorinated copolymers. These results provide deeper insight of the effect of surface reconstruction and microphase segregation on the protein adsorption behaviors, and these amphiphilic fluoropolymers can expect to have potential applications as antifouling coatings in the field of marine and biomedical. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41167.     

Non‐isothermal crystallization kinetics of Al2O3‐YAG amorphous ceramic coating deposited via plasma spraying

Crystallization kinetics of the newly developed Al₂O₃‐Y₃Al₅O₁₂ (YAG) amorphous ceramic coating fabricated by atmospheric plasma spraying (APS) were investigated via differential scanning calorimetry (DSC) under non‐isothermal conditions. The phase compositions and microstructure of the as‐sprayed coating were characterized by X‐ray diffraction (XRD) and Scanning electron microscopy (SEM). The glass transition temperature T_g, the onset temperature of crystallization T_c and the peak temperature of crystallization T_p presented heating rate dependence. The related kinetic parameters of activation energies (E_g, E_c, E_p) and Avrami exponents (n) were quantified using various methods including Kissinger, Augis–Bennett, Ozawa and Matusita–Sakka, etc., to understand the phase transition mechanism and crystallization process in depth. A series of parameters including devitrification interval ΔT, thermal stability (T_c, E_c), nucleation resistance E_c/RT_g and fragility index F were quantified in order to evaluate the nucleation mechanism, crystallization behavior and thermal stability of Al₂O₃‐YAG amorphous ceramic coating. Excellent thermal stability was witnessed in the studied coating. Furthermore, the YAG crystalline phases can be reasonably controlled and independently precipitated from the amorphous matrix via proper annealing.     

A study on the effect of presence of CeO2 and benzotriazole on activation of self‐healing mechanism in ZrO2 ceramic‐based coating

In this study, the effect of presence of CeO₂ and benzotriazole inhibitor agent on activation of self‐healing reactions and the corrosion behavior of ZrO₂ ceramic‐based coating are evaluated. The ZrO₂ and ZrO₂‐CeO₂‐benzotriazole ceramic‐based coatings were synthesized using sol–gel process and heat treated at 150°C. Afterward, X‐ray diffraction analysis (XRD), and Field Emission Scanning Electron Microscopy (FE‐SEM) were utilized to evaluate the phase analysis and morphology of these coatings. In addition, Energy Dispersive Spectroscopy (EDS) was used for elemental analysis of obtained coatings. Corrosion and self‐healing behavior of the coatings were investigated in 3.5 wt% NaCl solution using Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization tests. The results of XRD analysis revealed the amorphous nature of both coatings. FE‐SEM observations and EDS analysis results showed the presence of benzotriazole inhibitor agent and self‐healing reactions in the cracks and defects of ZrO₂‐CeO₂‐benzotriazole ceramic‐based coating. Moreover, results of electrochemical tests revealed that the presence of CeO₂ and benzotriazole inhibitor agent in the ZrO₂ ceramic‐based coating results in intense increases in the corrosion resistance of this coating by activating the self‐healing mechanism and forming passive layers.     

Characterization of novel soybean‐oil‐based thermosensitive amphiphilic polymers for drug delivery applications

Hydrolyzed polymers of soybean oil (HPSO) and of epoxidized soybean oil (HPESO) were developed previously. Owing to their natural food origin and biocompatibility, we exploited further their potential as a drug delivery system and pharmaceutical excipients. This work aimed to investigate self‐assembly, thermal transition, interaction with various drugs and surface activity of these novel amphiphilic polymers. The critical micelle concentration of HPSO and HPESO was determined by the surface tension method. The molecular interaction between HPESO and anticancer drug doxorubicin HCl was examined. The effect of the polymers on the solution contact angle and surface energy of compressed tablets of hydrophobic drugs ibuprofen and nifedipine was measured. The thermal transition temperatures T_tr (cloud points) of the polymers in aqueous solutions increased with increasing polymer concentration. HPSO exhibited lower T_tr than HPESO. The critical micelle concentration was found to be 0.05 mg mL^?1 for HPSO and 0.08 mg mL^?1 for HPESO. Strong molecular interactions between HPESO and doxorubicin were observed. Both polymers reduced the interfacial energy and contact angles of drug tablets with more effect on ibuprofen tablets with the use of HPSO. These results suggest that the novel soybean‐oil‐based amphiphilic polymers have great potential for drug delivery and pharmaceutical formulations. Copyright © 2012 Society of Chemical Industry     

Potassium sodium niobate (KNN)‐based lead‐free piezoelectric ceramic coatings on steel structure by thermal spray method

For the first time, potassium sodium niobate (KNN)‐based lead‐free piezoelectric ceramic coating with strong piezoelectric response was fabricated on stainless steel substrates by thermal spray process, after introducing NiCrAlY and yttria‐stabilized zirconia (YSZ) intermediate layers. A large effective piezoelectric coefficient (d₃₃) of 125 pm/V was obtained with the thermal‐sprayed KNN‐based ceramic coating on the steel substrates. The mechanisms of improving the structure and enhancing the properties of the KNN‐based piezoelectric ceramic coatings by introducing the intermediate layers were analyzed. Ultrasonic transducers were designed and fabricated from the KNN‐based coatings directly formed on a steel plate structure, and the feasibility for generation and detection of ultrasonic waves for structural health monitoring using the thermal‐sprayed lead‐free piezoelectric ceramic coating was demonstrated.     

UV‐curable coatings with nano‐TiO2

Nano‐TiO₂ particles were first milled into butyl acetate or trimethylolpropane triacrylate (TMPTA) to obtain TSB and TST slurries, then embedded into epoxy acrylate to obtain UV‐curable coating. The influence of nano‐TiO₂ particles on the photopolymerization kinetics, tack free time, thermal and optical properties of UV‐curable coatings was investigated. It was found that TST‐based coating had a decreasing but TSB‐based coating had an increasing UV cured rate in comparison with the pristine epoxy acrylate. Nevertheless, the TST‐based coating occupied shorter tack free time, good thermal property and UV absorbance than their corresponding TSB‐based coating. POLYM. ENG. SCI. 46:1402–1410, 2006. © 2006 Society of Plastics Engineers.     

Nonisothermal crystallization kinetics of flame‐sprayed polyamide 1010/nano‐ZrO2 composite coatings

Polyamide1010 (PA1010) and its composite with nanometer‐sized zirconia (PA1010/nano‐ZrO₂) coatings were deposited using a flame spray process. The kinetics of nonisothermal crystallization of PA1010/nano‐ZrO₂ composite coatings was investigated by differential scanning calorimetry (DSC) at various cooling rates. Several different analysis methods were used to describe the process of nonisothermal crystallization. The results showed that the modified Avrami equation and Mo's treatment could describe the nonisothermal crystallization of the composite coatings very well. The nano‐ZrO₂ particles have a remarkable heterogeneous nucleation effect in the PA1010 matrix. The values of halftime and Z_c showed that the crystallization rate increased with increasing cooling rates for both PA1010 and PA1010/nano‐ZrO₂ composite coating, but the crystallization rate of PA1010/nano‐ZrO₂ composite coating was faster than that of PA1010 at given cooling rate. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis,curing behavior and thermal properties of silicon‐containing hybrid polymers with Si−C≡C units

Three novel kinds of linear silicon‐containing hybrid polymers with Si?C≡C units were synthesized by polycondensation reactions using the Grignard reagent method. All the polymers were thermosetting, highly heat‐resistant, moldable and easily soluble in common organic solvents. The structure, curing behavior, thermal and oxidative properties were characterized using Fourier transform infrared spectroscopy, ¹H NMR, ¹³C NMR, gel permeation chromatography, differential scanning calorimetry and thermogravimetric analysis. The results obtained can provide theoretical guidance for determining the curing of the resin system. In addition, the cured polymers exhibit excellent thermal and oxidative stabilities with temperatures of 5% weight loss (T_d5) above 480 °C and 450 °C in nitrogen and air respectively; the residues at 1000 °C were above 70.0% and 45.0% respectively. The thermal and oxidative stabilities of the polymers are attributed to a crosslinking reaction between the Si?H and C≡C bonds or C≡C bonds. These polymers have the potential for use as high‐temperature‐resistant resins and ceramic precursors. © 2013 Society of Chemical Industry     

Microhardness and wear resistance of Al2O3-TiB2-TiC ceramic coatings on carbon steel fabricated by laser cladding

Al₂O₃-TiB₂-TiC ceramic coatings with high microhardness and wear resistance were fabricated on the surfaces of carbon steel substrates by laser cladding using different coating formulations. The microstructures of these ceramic coatings with the different coating formulations were investigated using X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometer. The wear resistance and wear mechanism were analyzed using Vickers microhardness and sliding wear tests. The results showed that when the amount of independent Al₂O₃ was increased to 30%, the ceramic coatings had a favorable surface formation quality and strong metallurgical bond with the steel matrix. The cladding layer was uniformly and densely organized. The black massive Al₂O₃, white granular TiB₂, and TiC distributed on the Fe substrate significantly increased the microhardness and wear resistance. The laser cladding ceramic coating had many hard strengthening phases, and thus resisted the extrusion of rigid particles in frictional contact parts. Therefore, the wear process ended with a “cutting-off” loss mechanism.     

Enhancement of the hydrophobicity and oleophobicity of a polyurethane coating using a fluorine-free polyfarnesene-based polyol

The development of hydrophobic and oleophobic surfaces on materials has attracted significant attention in various research fields. Fluoropolymers, which possess low surface energy and are both highly hydrophobic and oleophobic in nature, are widely used to enhance the liquid repellency of materials. However, during fluoropolymer manufacture, fluorine-containing compounds are released into the environment; thus, alternatives to fluoropolymers are required for maintaining environmental safety and realizing a sustainable society. Notably, the development of such alternative materials has been limited. Thus, we herein report the application of a novel polyurethane (PU) coating synthesized from bio-based raw materials. The prepared hydrogenated polyfarnesene PU (HHPF PU), which possesses an amorphous bottlebrush-like polyalkyl structure, was found to exhibit higher hydrophobicity and oleophobicity than polytetrafluoroethylene (PTFE), which is a typical low-surface-energy material. The water and n-hexadecane contact angles of the HHPF PU were determined to be 119° and 68°, respectively, whereas those of PTFE were 108° and 46°, respectively. In addition, the density depth profile of the PU thin film was confirmed through x-ray reflectometry. This study provides a novel approach for enhancing the hydrophobicity and oleophobicity of materials using bottlebrush-like polyalkyl structure instead of fluorine.     

Study on electrochemical behavior of Nano‐ZnO modified alkyd‐based waterborne coatings

A nano‐composite coating was formed using nano‐ZnO as pigment in different concentrations, to a specially developed alkyd‐based waterborne coating. The nano‐ZnO modified composite coatings were applied on mild steel substrate by dipping. The dispersion of nano‐ZnO particles in coating system was investigated by scanning electron microscopic and atomic force microscopic techniques. The effect of the addition of these nano‐pigments on the electrochemical behavior of the coating was investigated in 3.5% NaCl solution, using electrochemical impedance spectroscopy. Coating modified with higher concentration of nano‐ZnO particles showed comparatively better performance as was evident from the pore resistance (R_po) and coating capacitance (C_c) values after 30 days of exposure. In general, the study showed an improvement in the corrosion resistance of the nano‐particle modified coatings as compared with the neat coating, confirming the positive effect of nano‐particle addition in coatings. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mussel-inspired catechol-based chemistry for direct construction of super-hydrophilic and waterproof coatings on intrinsic hydrophobic surfaces

Super-hydrophilic coatings are useful in many applications such as agricultural greenhouses. However, the direct modification of super-hydrophilic coatings on intrinsic hydrophobic surfaces is still a challenge, particularly without any pretreatment. Here, highly transparent super-hydrophilic and waterproof coatings on intrinsic hydrophobic surfaces were prepared via layer-by-layer (LbL) assembly catechol-grafted polymer-branched poly(ethylenimine) (bPEI)-3-(3,4-dihydroxyphenyl)propionic acid (denoted as C) and poly(acrylic acid) (PAA)-dopamine (denoted as D) inspired by the mussel. The catechol-functionalized polymer facilitates a mechanically robust coating that is tightly attached to the surface of the intrinsic hydrophobic polymers. This gives the coating excellent antifogging ability with a lowest contact angle of 0°. These coatings also demonstrated excellent stability after cross-linking with Fe³⁺ or alkali species. The super-hydrophilic and waterproof coatings on intrinsic hydrophobic surfaces can also be prepared by the spray method. The super hydrophilic coating exhibits favorable antifogging ability, making it potentially useful in numerous applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48013.     

Hierarchical growth of BiOCl on SrO‐Bi2O3‐B2O3 glass‐ceramics for self‐cleaning applications

We have grown hierarchical structure of bismuth oxycloride (BiOCl) on SrO‐Bi₂O₃‐B₂O₃ (SBBO) transparent glass‐ceramic. SBBO glass‐ceramics were fabricated via conventional melt‐quenching technique while BiOCl was grown by etching the glass via HCl. Enhanced visible light driven photocatalytic activity and increasing hydrophobic feature were observed on BiOCl grown SBBO than as‐quenched SBBO glass‐ceramics. Contact angle analysis showed maximum contact angle of 130.7° on the surface of most BiOCl grown SBBO glass‐ceramic. Furthermore, under visible light illumination water contact angle decreased from 130.7° to 30.8°. Such photo‐induced hydrophilicity and catalytic performance in translucent glass‐ceramics lead self‐cleaning applications.     

Effect of pore content and pH on the corrosion behavior of hydrophobic ceramic coatings

In this paper, superhydrophobic ceramic coatings were successfully prepared on stainless steel substrates (S304) by sol–gel method, and the effects of pore content and pH conditions on the corrosion resistance of hydrophobic ceramic coatings were studied. As the porosity increases, the contact angle of the coating increases. Among them, the contact angles of the coatings with 15% and 20% porosity in different pH solutions are all greater than 150°, achieving superhydrophobic surfaces. The contact angle results before and after corrosion show that the solution with a higher pH has a greater damage to the hydrophobicity of the coating. The corrosion resistance of the coatings was evaluated comparatively from polarization curves and electrochemical impedance spectroscopy. As the hydrophobicity improves, the corrosion resistance of the hydrophobic ceramic coating is enhanced. The impedance moduli at .01 Hz of the coating are 1.04 × 10³ times (pH 4), .13 × 10³ times (pH 7), and .74 × 10³ times (pH 10) of the bare steel, respectively. With the increase of pH, the corrosion resistance of hydrophobic ceramic coatings decreases, because OH⁻ in the corrosion solution is more easily adsorbed on the surface of the coating, thereby destroying the long hydrophobic chains.     

Self‐cleaning,titanium dioxide based,multilayer coating fabricated on polymer and glass surfaces

A photocatalytic self‐cleaning titanium dioxide (TiO₂) coating was prepared as a multilayer coating structure by the spin‐coating method. Three substrate materials (two thermoplastics and one ceramic) were used: (1) high‐density polyethylene (HDPE), (2) poly(vinyl chloride), and (3) borosilicate glass (BK7). The multilayer structure consisted of a polyurethane protective layer on the substrate, two layers of photocatalytic TiO₂ on the protective layer, and finally immobilized TiO₂ particles bound in a diluted polyurethane dispersion. Photocatalytically active surfaces were achieved by reactive oxygen‐plasma surface etching of the fabricated coatings. The structure and properties of the coating surfaces were characterized with scanning electron microscopy and contact‐angle measurements. The coatings on HDPE and BK7 were rendered superhydrophilic by an oxygen‐plasma treatment. The photocatalytic activity and self‐cleaning properties of the prepared surfaces were studied with palmitic acid (model soil), the degradation of which was confirmed by contact‐angle measurements and gas chromatography analysis. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polyacrylate‐core/TiO2‐shell nanocomposite particles prepared by in situ emulsion polymerization

We report the preparation of polyacrylate‐core/TiO₂‐shell nanocomposite particles through in situ emulsion polymerization in the presence of nano‐TiO₂ colloid obtained by the hydrolysis of titanium tetrachloride. The resultant colloidal system can be stable for months without any precipitation. In a typical sample, the diameter of nanocomposite particles was about 150 nm, and the thickness of TiO₂‐shell was 4–10 nm. Only cetyltrimethylammonium bromide was employed to provide the latex particles with positive charge, which was enough for the formation of fine TiO₂ coatings. Three initiators were tested. Ammonia persulfate was the most suitable one, because the cooperative effect was formed by the negatively charged TiO₂ particles and the terminal anionic group (SO₄^2?, the fraction of Ammonia persulfate) of the polymer chain on the surface of latex particles to maintain the stability of nanocomposite system. The pH value played a vital role in obtaining a tight TiO₂ coating. Transmission electron microscopy, X‐ray diffraction and Atomic force microscopy were used to characterize this nanocomposite material. It was found that rutile and anatase coexisted in the nanocomposite film. This may suggest a potential application in the field of photocatalytic coating. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1466–1470, 2006