EIS study on failure process of two polyurethane composite coatings

The performance of acrylic polyurethane composite coating and aliphatic urethane composite coating in 3.5% NaCl solution under ultra-violet radiation was studied with methods of EIS, SEM and FTIR. For aliphatic polyurethane coating, the coating resistance decreased and the coating capacitance and porosity increased more quickly than acrylic polyurethane coating. The acrylic polyurethane composite coatings showed better performance than aliphatic polyurethane composite coatings. IR spectra showed that under UV irradiation conditions, the failure mechanism of the two polyurethane coatings was the transformation of sec-amide to primary amides. The fractured bonds in acrylic polyurethane were mainly C–O bonds, while in aliphatic polyurethane they were mainly C–N bonds. The lower protection property of aliphatic polyurethane coating may be mainly attributed to the C–N bonds which are more liable to be broken.     

蓖麻油基聚氨酯-丙烯酸酯复合乳胶膜的水白化研究

采用蓖麻油基聚氨酯作为大分子乳化剂制备聚氨酯-丙烯酸酯(PUA)复合乳液。采用红外光谱表征了PUA乳胶膜的结构;用紫外分光光度计、动态热机械分析仪和差示扫描量热仪对PUA乳胶膜的水白化进行了表征。结果表明:在实验的时间范围内,乳胶膜的水白化程度随其浸水时间和浸水温度的增加而增加;当浸水温度(4 ℃)远低于干膜的玻璃化转变温度(T_g=57.8 ℃)时,乳胶膜浸水24 h不会水白化,湿膜的T_g及其储能模量与干膜相比几乎没有变化;在28 ℃的水中浸泡24 h时,湿膜的T_g小于干膜的T_g,其储能模量也降低,乳胶膜出现轻微水白化,将乳胶膜再次烘干后,胶膜可恢复原有清晰度。当乳胶膜在高于干膜T_g的水中(70 ℃)浸泡24 h时,其储能模量下降,湿膜的T_g大于干膜的T_g,再次烘干乳胶膜不会恢复原有的清晰度,其原因是膜内出现了与PUA分子依靠氢键紧密相连的冻结键合水。     

氟碳涂层在干湿交替环境下失效过程研究

用电化学交流阻抗（EIS）、红外光谱（FTIR）和扫描电镜（SEM）等手段研究了氟碳涂层在干湿交替及全浸泡环境下的失效过程。结果表明,干湿交替环境下氟碳涂层的失效速率快于全浸泡环境下的失效速率,干湿交替环境使得涂层孔隙率增大,涂层的电阻降低,电容增大,加速了电解质溶液在涂层中的渗透;氟碳涂层在干湿交替环境下的失效原因,主要是由于干湿交替循环使涂层经历增大和缩小的往复变化,使得涂层内部孔隙增大,局部产生微裂纹且涂层与基体附着力降低,最终导致涂层起泡及失效。     

不同加速试验对环氧/聚氨酯涂层失效机制的影响

研究了模拟南海海洋大气环境下铝合金表面环氧锌黄/丙烯酸聚氨酯涂层体系的失效过程,通过循环加速、紫外/冷凝和中性盐雾的对比试验,探讨了在循环加速试验中紫外-冷凝试验和盐雾试验分别对复合涂层失效过程以及对聚氨酯面漆和环氧底漆失效机制的影响。结果表明,紫外-冷凝过程对丙烯酸聚氨酯面漆有较强的破坏作用,但对复合涂层体系整体的阻抗变化影响较小;紫外-冷凝过程中,位于面漆玻璃化转变温度范围内的试验温度,以及紫外光对氨基甲酸酯基团的破坏作用,是导致面漆发生破坏的主要原因。盐雾试验对面漆的失光率和色差变化影响不大,但连续的盐雾渗透对涂层体系的阻抗下降具有明显的加速作用,同时导致涂层与基材的附着力显著降低。相比单独的紫外-冷凝试验或盐雾试验,循环加速试验综合考虑了南海海洋大气中强太阳辐射、高温高湿、高盐分和温差等环境因素,能更准确反映南海大气环境中复合涂层的失效过程。     

Preparation and properties of crosslinked network coatings based on perfluoropolyether/poly(dimethyl siloxane)/acrylic polyols for marine fouling–release applications

α,ω‐Triethoxysilane terminated poly(dimethyl siloxane) (PDMS) oligomer, α,ω‐triethoxysilane terminated perfluoropolyether (PFPE) oligomer, and acrylic polyols were first synthesized via an addition reaction and free‐radical polymerization. Then, crosslinked network coatings based on PFPE/PDMS/acrylic polyols for marine fouling‐release applications were prepared by a condensation reaction. The structure of the crosslinked network coating was characterized by Fourier transform infrared spectroscopy. The chemical composition of the coating surface was characterized by X‐ray photoelectron spectroscopy. The thermal properties, surface energy, mechanical properties, adhesion, and antiseawater immersion performance of the coatings were systematically studied. The antibiofouling properties of the crosslinked network coating were evaluated by laboratory biofouling assays with the bacteria Escherichia coli and the fouling diatom Navicula. The results from the preliminary study suggested that this crosslinked network coating had good adhesion and promising antifouling properties that were comparable to a silicone standard. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41860.     

Preparation of novel CNSL‐based urethane polyol via nonisocyanate route: Curing with melamine‐formaldehyde resin and structure–property relationship

In this study, we report preparation of a novel cashew nut shell liquid (CNSL)‐based polyol bearing urethane groups. The urethane group in the polyol was induced via isocyanate free route from the reaction of cyclic carbonate with primary amine. The polyol was characterized by determination of hydroxyl number, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and so forth. The polyol was then used as coating component and cured with hexamethoxy methylene melamine (HMMM). Another CNSL‐based polyol without urethane moiety from our earlier reported work was used for preparation of coating for comparative study to determine the effect of urethane group on the coating properties. The coating formulations based on these two polyols were cured with variable amounts of HMMM hardener to optimize coating properties. All the coatings were evaluated for mechanical properties such as adhesion, flexibility, pencil and scratch hardness, impact resistance, pull‐off, and adhesion. The optimized coatings were also evaluated for chemical and thermal properties. It was observed that the urethane containing polyol resulted in better adhesion to the metal substrate at higher quantity of HMMM hardener compared to the other polyol providing significant improvement in various coating properties. The final coating properties were also compared with the acrylic polyurethane coatings. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41391.     

Influence of pH in the synthesis of ferric tannate pigment for application in antifouling coatings

Ferric tannate was synthesized at pH 4 and pH 7 (FT4 and FT7, respectively) as a new class of environmentally friendly antifouling pigments. The solubility of both pigments was evaluated by gravimetric tests, showing that FT4 is more soluble than FT7. A mixture of rosin/acrylic resin (9:1 w/w) was sufficient to form an antifouling coating due to improved matrix properties. Electrochemical impedance spectroscopy (EIS) measurements were used to determine the apparent water coefficient of diffusion (D) and coating behavior. The D in the coating formulated with FT4 exhibited better values than that obtained with FT7. EIS results showed that both coatings present Fickian behavior at the initial stages of immersion, while flat Nyquist plots revealed penetration of water in the films. The physicochemical characteristics of FT4 pigment were determined by thermogravimetry and Fourier transform infrared. Immersion tests in the Mediterranean Sea demonstrated the excellent efficacy of the FT4-containing coating against marine fouling after six months of immersion.     

Properties and interfacial bonding for regenerated cellulose–polyurethane/amylose acetate sipn composite films

Composite films were obtained by placing a polyurethane/amylose acetate semi‐interpenetrating polymer network (SIPN) coating onto the surfaces of regenerated cellulose (RC) film. The properties of the composite film, such as tensile strength, 79.9 MPa (in dry state), 49.5 MPa (in wet state), water resistance (R), 0.62, dimensional stability (S_c), 3.0%, and water vapor permeability (P), 5.96 × 10⁻⁵ Kgm⁻²h⁻¹, are better than those of the uncoated RC film or RC film with PU coating. The interfacial strength was characterized with infrared spectroscopy (IR), ultraviolet spectroscopy (UV), transmission electron microscopy (TEM), and electron probe microanalysis (EPMA). The results showed the existence of covalent and hydrogen bonds between the SIPN coat layer and the RC layer. It was also found that the PU prepolymer in the coating layer penetrated into the cellulose bulk, and reacted with the cellulose molecules, which formed another SIPN.     

水性聚氨酯与丙烯酸酯乳液交联反应的研究

将由双丙酮丙烯酰胺（DAAM）参与共聚的丙烯酸酯乳液与含有肼基的聚 氨酯水分散体混合后，得到了交联型聚氨酯／丙烯酸酯复合乳液，利用红外光谱和透射电镜技术证实了酮羰基与肼基之间的交联反应的发生。对乳液膜性能的研究结果表明，交联反应极大地提高了乳液膜的耐水性，耐溶性，断裂强度，断裂伸长率。     

Development of Functional Polyurethane–ZnO Hybrid Nanocomposite Coatings from Thevetia peruviana Seed Oil

The present article reports eco‐friendly multi‐functional polyurethane–ZnO hybrid nanocomposite coatings obtained from Thevetia peruviana seed oil (TPSO). Initially, the polyols were prepared by treating TPSO with glycerol and the formation was supported by Fourier transform infrared (FT‐IR) and ¹H‐NMR studies. In the next stage, siloxane functionalized ZnO nanoparticles were added to the polyol mixture in different weight percentages (0, 1 and 2 %) and then treated with excess 4,4′‐diisocyanatodicyclohexylmethane (H₁₂MDI) in order to synthesize isocyanate terminated polyurethane nanocomposites. The polyurethane hybrids were then casted as thin films and cured under atmospheric moisture. After complete curing they were characterized by using FT‐IR, ¹H‐NMR, ¹³C‐NMR, X‐ray diffraction, scanning electron microscopy, thermogravimetric analysis, and dynamic mechanical thermal analysis techniques. The hybrid nanocomposites showed superior thermo‐mechanical and anti‐corrosive properties compared to pristine polyurethane. Also, due to the presence of nano ZnO in the polyurethane matrix, the composite coatings are showing excellent resistance towards various bacterial and fungal stains.     

The effect of interfacial chemistry on coating adhesion and performance: A mechanistic study using aminobutylphosphonic acid

Failure of adhesion of organic coating (paints) to steel and other metallic substrates is one of the key mechanisms for local coating failure and for consequent restriction of coating lifetime. This study thus focuses on modification to the chemistry of the metal interface in order to promote enhanced (dry and wet) coating adhesion. The work uses an appropriate bi-functional amino alkyl phosphonate to provide the desired interfacial properties. The study uses X-ray photoelectron spectroscopy and water contact angle measurement to examine changes in the interfacial surface chemistry and electrochemical impedance spectroscopy and cathodic disbonding to determine improvements to the anti-corrosion performance. Choosing 4-amino-butyl-phosphonic acid as the surface modifier a significant influence on its efficiency as an adhesion promoter was observed as a function of pH. Thus, when the amino group was protonated at a pH of 5.3, the molecule demonstrated attachment to carbon steel at both ends with no significant improvement in performance. However at pH 8 the molecule demonstrated greatly improved surface packing density with the amino group outwards from the surface in the preferred orientation. In this condition, an epoxy coating demonstrated substantial resistance to interfacial hydrolysis with overall improved adhesion and reduced cathodic disbondment rate.     

Preparation and characteristics of polyacrylic ester‐based water‐free powder coatings in supercritical carbon dioxide

Powder coating for dry coating technique of paper as the promising method has attracted more and more attentions in recent years due to its advantages in reducing the dosage of water and saving energy compared with conventional coating. This study focused on the in situ polymerization of methyl methacrylate (PMMA) under a water‐free condition in supercritical carbon dioxide in the presence of inorganic kaolin. The effects of varying the concentrations of the monomer, initiator, and stabilizer on the molecular weight and morphology of the resultant PMMA were investigated and discussed. Then the powder coating was systematically evaluated and characterized by gel permeation chromatography, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Meanwhile, the feasibility of manufacturing PMMA/kaolin powder coatings was explored, and the mechanism of polymerization and the thermal degradation kinetics of powder coating were studied. The experimental results showed that the properties of PMMA as a film former were suitable with the molecular weight and narrow molecular weight distribution close to that in conventional coating when the concentration of monomer was about 10 wt %, concentration of initiator ～1–1.5 wt % and stabilizer about 10 wt % with respect to monomer. Moreover, the interfacial bonds and dispersion situation of polyacrylic ester‐based water‐free powder coating particles were fairly well, the powder coating possesses good film‐forming property combined with outstanding thermal‐stability performance. The combination of these characteristics makes PMMA/kaolin powder coating an excellent candidate for dry coating technique of paper applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42439.     

Swelling behavior of chitosan/poly(acrylic acid) complex

This study investigates the improved swelling behavior of chitosan/poly(acrylic acid) complex by solvent (methanol, ethanol, and acetone) extraction. The complex is developed by photoinitiated free‐radical polymerization of acrylic acid in the presence of chitosan. The swelling ratio of the complexes depends on the cosolvency effect of poly(acrylic acid) to the extracted solvent, which in turn affects the polymer network structure and ionic states characterized by dynamic force microscopy (DFM), Raman, and FT‐IR spectroscopy. The DFM investigation displays the improved structural changes of the polymer network structure after solvent extraction and its relation to the improved swelling property of the chosen system in different environmental conditions (pH, solvent, and salt concentration) are discussed. A high swelling ratio of about 600 times its dry weight is observed in water as well as in low salt and solvent concentration after methanol extraction. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2930–2940, 2004     

Synthesis of click‐coupled graphene sheets with hyperbranched polyurethane: Effective exfoliation and enhancement of nanocomposite properties

Graphene oxide (GO) was functionalized with hyperbranched polyurethane (HBPU) via click coupling between azide‐functionalized HBPU and alkynyl‐decorated GO. HBPU‐functionalized GO composites of various compositions were prepared. The azide‐containing HBPU was characterized using Fourier‐transform infrared (FT‐IR) spectroscopy and ¹H‐nuclear magnetic resonance spectroscopy. The HBPU‐functionalized GO composites were characterized using transmission electron microscopy and FT‐IR spectroscopy. The functionalized GO showed excellent dispersion in the HBPU matrix, giving composites with enhanced mechanical and thermal properties. The material properties were effectively regulated by click‐coupled exfoliation of GO with HBPU, enabling the production of high‐performance materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44631.     

Chemical structure of hemicellulosic polymers isolated from bamboo bio‐composite during mold pressing

Hemicelluloses were analyzed by Fourier‐transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA), and derivative thermogravimetric analysis (DTG) in order to investigate the chemical structure of hemicellulose isolated from bamboo natural polymers bio‐composites prepared under different mold pressing conditions. The results show that a temperature of 230°C with a pressing time of 20 min resulted in optimal yield of hemicellulosic polymers and relative content of sugars and uronic acids. The thermal degradation of xylose can be restrained through the addition of lignin. The FT‐IR, the TGA, and the DTG analysis backed the findings. FT‐IR spectra of bamboo and bamboo bio‐composites (BBC) were similar. TGA curves of Ram, H1, and H2 were similar, other curves were similar. Whereas DTG curves of Ram and H1 were similar, and other curves were similar. The addition of lignin could potentially decrease the thermal degradation of hemicellulose during mold pressing. POLYM. COMPOS., 38:2009–2015, 2017. © 2015 Society of Plastics Engineers     

A novel method to control microcapsule release behavior via photo‐crosslink polyurethane acrylate shells

A microcapsule system with polyurethane acrylate (PUA) shell is prepared by interfacial polymerization between acrylic polyurethane diisocyanate and water to achieve controlled release via UV irradiation. The size of the microcapsule is influenced by the concentration of protecting colloid and property of acrylic polyurethane diisocyanate. When concentration of polyvinyl alcohol (PVA) is 5% and molar ratio of TDI and acrylic ethoxylated pentaerythritol (acrylic PP50) rises to 1.50, average diameter of the microcapsule is only 3.3223 μm. Delivery of 4‐hydroxy‐4′‐isopropoxydiphenylsulfone (D‐8) encapsuled by PUA microcapsule in solution can be prevented effectively by 30‐min UV irradiation. Lightness (L*) is used to measure color changes of reaction between D‐8 in PUA microcapsule and 2‐anilino‐6‐dibutylamino‐3‐methylfluoran (ODB‐2) under thermal treatment. In dry state, irradiated PUA microcapsules are much harder to release D‐8 than those not irradiated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical Properties Improvement of Waterborne Polyurethane Coating Films After Rewetting and Drying

Drying behavior of waterborne polyurethane coating under ambient conditions displays the typical three-stage drying process on compact hard substrates. When the naturally dried samples are further dried at thermal condition of 105°C, the loss of residual water was accompanied with an increase in the hardness of the films. When the coating films were immersed in water and dried at ambient condition again, the hardness and modulus increased significantly. After 180-min immersion followed by natural drying, the hardness of the film increased to almost 10 times that of the initial value. The possible reason is that the interaction between water and the hydrophobic amorphous phase of polyurethane led to a compacted amorphous phase, which decreased the free volume of the films, resulting in the increase in the hardness and modulus of the coating films.     

Influences of feeding strategies on AA and MAA carboxylated latexes

Semibatch, power feed, and shot‐addition feeding strategies were employed to synthesize carboxylated latex under acidic conditions, using emulsion polymerization. As a source of carboxyl groups, acrylic (AA) or methacrylic acid (MAA) was used. The distribution of carboxyl groups between feeding strategies were investigated using rheology, potentiometric/conductometric titrations, transmission electron microscopy, and FT‐IR spectroscopy. Upon alkalization, particle swelling was observed using dynamic light scattering. With increasing pH, both the AA‐ and MAA‐based latexes showed significant increase in hydrodynamic diameter as a consequence of the dissociation state of carboxyl groups. However, only MAA‐based latexes exhibit very pronounced increase in viscosity and storage modulus, and were therefore characterized as gels. The effect of feeding strategies was found to be more pronounced with the MAA functionalized latexes. By employing mentioned three procedures, significant differences in the rheological behavior of the neutralized dispersions were detected. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42062.     

Studies on acrylic acid–grafted polyester fabrics by electron beam preirradiation method. II. Novel intelligent immersion‐resistant and moisture‐permeable fabrics

Moisture regain, water vapor permeability, and water‐impermeable ability of polyester fabrics before and after grafting by acrylic acid (AA) were investigated. The results showed that the AA‐grafted fabric presents novel properties. When it is dry it possesses a higher water vapor transmission rate. Once it comes into contact with water, the grafted poly(acrylic acid) layer on the fibers' surface begins to swell and seals the intervals between fibers and yarns to prevent water from penetrating, a phenomenon known as immersion resistance. This kind of immersion‐resistant and moisture‐permeable fabrics might be a suitable candidate for the immersion‐resistant layer fabrics of Type B immersion‐resistant suits. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3939–3943, 2003     

Characterization of Polymer‐Coated RDX and HMX Particles

Fourier transform‐infrared spectroscopy (FT‐IR) in transmission and photoacoustic detection (PAS) techniques have been used for the characterization of polymeric coating of cyclotrimethylenetrinitramine (RDX) using a fluoroelastomer (Viton^®). Although the bands of the polymer were indicated by two different techniques, the transmission (casting film) showed better evidence of absorption of fluoroelastomer for the polymer coating of the energetic material. Also attenuated total reflectance (ATR), another FT‐IR technique, has been used to analyze a cyclotetramethylenetetramine (HMX)/Viton system for the characterization of Viton bands and it showed excellent results without sample preparation.