High performance – low VOC-content: innovative and trend-setting coating systems for industrial applications

This paper describes low VOC coating systems successfully implemented and operating in two industrial branches. For Light Alloy Wheels, the innovative coating process comprises ecofriendly chromium-free surface pre-treatment, epoxy polyester powder primer, water-borne base coat and acrylate powder clear coat. The coating process as an example for agricultural machinery includes iron phosphatizing surface pre-treatment for steel substrates; the coating system itself consists of a water-borne stove-type dip priming operation (for all objects). Finish coat type (Plant I): 2-component water-borne PUR top coat; (Plant II): TGIC-free polyester powder top coat. These new coating systems have proved successful in existing series production. All technical requirements and the provisions of the VOC Regulations are fully complied with.     

Adhesives: a new class of polymer coatings for surface acoustic wave sensors for fast and reliable process control applications

Fast and reliable on-line detection of organic vapors for control of chemical processes is a challenging application for a new type of analytical instruments: sensor systems based on an array of differently selective chemical sensors. In this work we present the use of mass-sensitive polymer coated surface acoustic wave sensors (SAWs). The sensors were initially coated with a standard set of polymers consisting of a known composition. But this first approach could not meet all requirements. Therefore, a new class of commercially available polymer coating, namely adhesives, was developed. The coating procedure was optimized and the aging process of the adhesives was carefully investigated. As a result the selectivity for ambitious separation problems arising from similar polarity of the components of typical solvent mixtures could be remarkably increased. The system was then applied in a real testing environment application at a chemical plant: the fast on-line control of a preparative reversed phase process HPLC (RP-PHPLC). Data from this industrial application are shown.     

Preparation,Characterization, and Evaluation of the Anticorrosion Performance of Submicron/Nanocarbon from Jute Sticks

Jute stick, one of the most commonly and abundantly available agricultural waste product, was converted to a value-added submicron/nano jute carbon by using pyrolysis and high-energy ball milling techniques. The submicron/nano jute carbon was characterized using FE-SEM, TEM, EDS, XRD, XPS and Raman spectroscopy. The anticorrosive performance of the submicron/nano jute carbon was investigated through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) and salt spray techniques, on mild steel plates coated with a mixture of epoxy resin and the submicron/nano jute carbon. The electrochemical impedance of the steel coated with the composite coating was two orders of magnitudes higher than that of the specimen coated with neat epoxy. Consequently, the corrosion rate of specimens coated with composite coating was 13–20 times higher than that of steel coated with neat epoxy coating. The salt spray results also indicate an improvement in the corrosion resistance performance of the composite coating compared to the neat epoxy. The uniform distribution of the submicron/nano jute carbon particles in the epoxy resin improved the denseness of the composite coating by acting as a barrier against the diffusion of chloride, moisture, and oxygen, thus, improving the corrosion resistance of the developed coating.     

Electrochemical testing practices of environmentally friendly aerospace coatings for corrosion performance assessment

Hexavalent chromium has been successfully employed for corrosion protection purposes in aerospace coatings for decades. However, legislation will restrict the use of Cr⁶⁺ in the future and therefore the aerospace sector needs to identify alternative environmentally friendly coatings for corrosion protection. Before implementation of newly developed systems into actual components is possible, rigorous and time-consuming testing practices are required to ensure the new systems can achieve the strict aerospace standards requirements. The emerging number of coating systems being developed, and the vast research conducted on the subject worldwide, make the selection of suitable replacements for industrial application challenging. In this work, differently pretreated aluminium AA2024 alloy surfaces are coated with conventional Cr⁶⁺ containing coating and compared with a number of industrial alternative coatings. Corrosion performance is assessed by real-time imaging while immersed, by electrochemical impedance spectroscopy (EIS), and by standardised salt-spray testing (SST). Results reveal that the performance ranking acquired by SST can be readily replaced by short-term immersion tests, and the time to failure in SST can be estimated from key corrosion indicators arising from EIS measurements at specific immersion times.     

Epoxy resin based multilayered microwave absorbing coating system

A coating system based on different combinations of natural magnetite and carbon black filled epoxy resin has been developed. The influence of filler concentration and the ordering of the layers in the absorbing structure on the coefficients of attenuation and reflection of the electromagnetic waves in the frequency range 6.5‐12.0 GHz have been investigated. The results show that the coating system (total thickness of about 2.5‐3.0 mm) developed can be successfully used to reduce the overall signature and to prevent scattering from the sharp edges of complex shaped objects by attenuating surface currents.     

Cycloaliphatic epoxy resin coating for capillary electrophoresis

Coating the interior surface of a fused-silica capillary with a polymeric material has long been used in capillary electrophoresis (CE) to reduce or eliminate electroosmotic flow and suppress adsorption. A cycloaliphatic epoxide-based resin was bonded to silane treated capillaries and crosslinked with a curing agent. The epoxy resin coating significantly reduced electroosmotic flow over a pH range of 3-10. This coating was sufficiently hydrophilic to suppress protein adsorption. The epoxy resin coated capillary was used to separate several acidic and basic proteins and peptides. Separation efficiencies greater than 400,000 theoretical plates were achieved. The relative standard deviations in migration times for proteins were <0.8%. Speed and simplicity are important advantages of the coating procedure compared to other published coating methods.     

Corrosion processes below organic coatings

The protective mechanisms of paint systems of a 1-pack polyurethane- and an epoxy/2-pack polyurethane-coating system with zinc dust priming coats were investigated on blast-cleaned and on hand-cleaned steel substrates. The coated panels were exposed to the salt spray test and to a cyclic alternating test (VDA 621-415). The protective effect was assessed in determining adhesion, undermining at scratches, water uptake and the corrosion potential. On blast cleaned steel substrates the adhesion of the investigated coating systems was not influenced by water uptake of the coatings. Scratches are especially cathodically protected. On hand-cleaned steel surfaces the rust layer between steel substrate and coating can participate in the corrosion process with rust reduction as cathodic partial reaction. The change of rust morphology is the reason for the loss of adhesion of coating. At scratches rust reduction takes also place at the edge of the defect which is independent from pigments of the base coating.     

Powder coatings for corrosion protection

Powder coatings found a wider use in corrosion protection of steel structure. In Europe very often double-layer systems are used, based on an adhesion promoting epoxy (EP) primer and a weathering stable top coat, mostly polyester (SP) sometimes EP/SP-hybrid powders. An interesting development is the use of zinc filled EP powders as primer to offer a cathodic protection to the steel surface. Powder systems with and without zinc were compared to proved coating systems based on liquid paint materials, where powder coating systems showed results comparable to these systems. Besides many advantages of powder coatings for corrosion protection there are still some problems. The workshops carring out the powder coating have to be in control of the surface pretreatment like chromating, but espescially phosphating and the work with the chromate-free pretreatment methods for galvanized steel. As always in the field of corrosion protection it is the surface pretreatment and preparation which determines the quality of the whole coating system decisively. This problem can be solved by appropriate working. In some years the problem with the general maintenance of powder coatings after weathering and ageing will be actual. This problem should be solved because of the homogeneous coatings on larger areas. Of importance will be the adhesion on the old coating and the appearance of the maintenance coating. The touch up of smaller parts as transport damages will be much more difficult in order to the appearance.     

Improvement of environmental stress cracking resistance of polycarbonate by silicone coating

To explore the possibility of using surface coating to reduce environmental stress cracking (ESC) of transparent polycarbonate (PC) parts, silicone coated and SiO₂ coated PC were tested in a self-made three-point bending apparatus in the presence of ethanol. The variation of stress with time was recorded, and the surface cracking was observed to evaluate the ESC resistance of samples. Slower stress relaxation rates and fewer surface cracks indicated that silicone coating improved the ESC resistance of PC, but SiO₂ coated PC was found to be no better than that of uncoated PC. Silicone coating reduced the absorption of ethanol in PC, weakening the surface plasticization, thus hindering the formation and development of cracks in PC. Nanoindentation test results showed that the mechanical properties such as hardness and elastic modulus of silicone coating are a better match for PC than SiO₂ coating. This allows the silicone coating to have a favorable effect in providing continuous protection for PC under the combined action of ethanol and stress.     

亲水性有机硅杂化防雾涂料的制备及性能

采用Sol-Gel技术制备了二乙醇胺/有机硅杂化涂料, 并用FTIR、UV-Vis、AFM、TGA及接触角等测试技术对涂料及其涂层进行了分析表征. 结果表明, 该杂化涂料具有良好的成膜性. 由于膜层中存在大量的亲水性羟基基团, 使膜层具有良好的亲水性能和防雾效果. 固化后的聚合物膜层中无机相形成了三维交联网络, 赋予了膜层优异的耐磨性和热稳定性.     

Delamination of organic coating on carbon steel studied by scanning Kelvin probe force microscopy

Corrosion‐induced delamination of an epoxy coating on the AISI/SAE 1045 carbon steel was studied under a humid atmospheric condition (temperature of 25 °C, 1 standard atmospheric pressure, relative humidity of 90%) by the technique of scanning Kelvin probe force microscopy (SKPFM). Surface‐polished 1045 samples were first cold‐coated with the epoxy and then subject to the atmospheric corrosion under the specified condition. At predetermined time intervals, surface Volta potential differences of the samples were measured using the SKPFM over the dry surface of epoxy coating. The map of Volta potential differences demonstrated high contrasts among three characteristic zones: intact steel‐epoxy interface, delaminated interface, and interface with active corrosion, which was then linked to the actual corrosion potential of the steel (measured using a potentiostat with respect to a saturated calomel electrode) based on a rigorous calibration procedure. It was found that the SKPFM was able to provide direct and nondestructive detection of early active corrosion and coating delamination on steels at a submicroscopic resolution, which outperformed the conventional electrochemical techniques for the same purposes. Copyright © 2012 John Wiley & Sons, Ltd.     

Characterization of the coating layer on glass fibre used as reinforcement in polyepoxyde matrix

R glass fibre for the reinforcement of epoxy matrices has been coated with epoxy prepolymer (as film-former or sizing agent) or γAPS aminosilane (as coupling agent) or a mixture of these two products. The structure of the coating layer and its interaction capabilities with fibre and matrix have been studied by coupled calorimetry-gravimetry of sorption of different model reactants and by Fourier Transform infra-red analysis.     

Investigation of coating delamination on steels by surface topography and Volta potential difference

Corrosion-induced delamination of an epoxy coating on the AISI/SAE 1045 carbon steel was studied under a humid atmospheric condition (temperature of 25 °C, one standard atmospheric pressure, and relative humidity of 90 %) by the technique of scanning Kelvin probe force microscopy (SKPFM). Surface-polished 1045 samples were first cold coated with the epoxy and then subject to the atmospheric corrosion under the humid atmospheric condition. At specified time intervals, surface Volta potential of the samples was measured using the SKPFM over the dry surface of epoxy coating. The map of Volta potentials demonstrated high contrasts among three characteristic zones: intact steel-epoxy interface, delaminated interface, and interface with active corrosion, which based on a rigorous calibration procedure were then linked to the actual corrosion potential of the steel (measured using a potentiostat w.r.t. a saturated calomel electrode). The SKPFM was found to be able to provide a mean of direct and nondestructive detection of early active corrosion and coating delamination of steels at a submicroscopic resolution, which outperformed the conventional electrochemical techniques for such purposes.     

Physical and mechanical characterization of near-zero shrinkage polybenzoxazines

A new class of phenolic-like thermosetting resins has been developed that is based on the ring-opening polymerization of a benzoxazine precursor. These new materials were developed to combine the thermal properties and flame retardance of phenolics with the mechanical performance and molecular design flexibility of advanced epoxy systems. The polybenzoxazines overcome many of the traditional shortcomings of conventional novolak and resoletype phenolic resins, while retaining their benefits. The physical and mechanical properties of these new polybenzoxazines are investigated and are shown to compare very favorably with those of conventional phenolic and epoxy resins. The ring-opening polymerization of these new materials occurs with either near-zero shrinkage or even a slight expansion upon cure. Dynamic mechanical analysis reveals that these candidates for composite applications possess high moduli and glass transition temperatures, but low crosslink densities. Long-term immersion studies indicate that these materials have a low rate of water absorption and low saturation content. Impact, tensile, and flexural properties are also studied. Results of the dielectric analysis on these polybenzoxazines demonstrate the suitability of these materials for electrical applications. © 1996 John Wiley & Sons, Inc.     

Quantitative surface analysis of coated materials by SNMS

A great number of coating techniques and coating materials have been developed and are in practical use. To meet all requirements in quality of technical coating systems methods of quality control and quality assurance are essential. In connection with the production of coated steel secondary neutral mass spectrometry (SNMS) can be looked upon as a new tool for further approach.The investigations reported started with the determination of sputter erosion rates and experiments with calibration standards produced by vacuum coating.For the quantification of SNMS signals the relative sensitivity factors of all elements in question must be known. The use of complex composed reference materials for this purpose may lead to wrong results. That is due to matrix effects and occurs also for the determination of sensitivity factors for elements at low contents. Therefore the production of reference materials by pressing of metallic and oxidic powders was proposed and tested. The experiments described have proved the applicability of pressed samples for the determination of sensitivity factors, for the investigation of oxides, nitrides and carbides, and for the analysis of chips and dusts by SNMS.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

Scaffolds for Sustained Release of Ambroxol Hydrochloride,a Pharmacological Chaperone That Increases the Activity of Misfolded β‐Glucocerebrosidase

Ambroxol is a pharmacological chaperone (PC) for Gaucher disease that increases lysosomal activity of misfolded β‐glucocerebrosidase (GCase) while displaying a safe toxicological profile. In this work, different poly(ε‐caprolactone) (PCL)‐based systems are developed to regulate the sustained release of small polar drugs in physiological environments. For this purpose, ambroxol is selected as test case since the encapsulation and release of PCs using polymeric scaffolds have not been explored yet. More specifically, ambroxol is successfully loaded in electrospun PCL microfibers, which are subsequently coated with additional PCL layers using dip‐coating or spin‐coating. The time needed to achieve 80% release of loaded ambroxol increases from ≈15 min for uncoated fibrous scaffolds to 3 days and 1 week for dip‐coated and spin‐coated systems, respectively. Furthermore, it is proven that the released drug maintains its bioactivity, protecting GCase against induced thermal denaturation.     

Colon targeted delivery systems of metronidazole based on osmotic technology: development and evaluation

Colon targeted delivery systems of metronidazole (MTZ) based on osmotic technology were developed. The developed systems consisted of osmotic core (drug, osmotic agent and wicking agent), coated with semipermeable membrane (SPM) containing guar gum as pore former, coated core were then further coated with enteric coating to protect the system from acidic environment of stomach. The effect of various formulation variables namely the level of wicking agent (sodium lauryl sulphate), osmotic agent in the osmotic core, the level of pore former (guar gum) in SPM, and the thickness of SPM, were studied on physical parameters and drug release characteristics of developed formulations. MTZ release was inversely proportional to SPM thickness, but directly related to the level of pore former, wicking agent and osmotic agent. On the other hand burst strength of the exhausted shells was decreased with the increase in level of pore former in the membrane but increased with the increase in the thickness of SPM. The drug release from the developed formulations was independent of pH, and agitation intensity, but dependent on the osmotic pressure of the release media. The thickness of enteric coating could prevent formation of delivery pores before contact with simulated colonic fluid, but had no effect on drug release. Result of SEM studies showed the formation of in-situ delivery pores in the membrane from where the drug release occurred, and the number of pores formed were directly related to the initial level of pore former (guar gum) in SPM. The manufacturing procedure was found to be reproducible and formulations were found to be stable during 3 months of accelerated stability studies.     

Evaluation of solubility parameters during polymerisation of amine‐cured epoxy resins

A new procedure for the calculation of solubility parameter evolution during polymerisation has been developed for amine‐cured epoxy systems, which allows quantitative thermodynamic modelling of chemically induced phase separation (CIPS). Solubility parameters calculation, chemical analysis based on near infrared spectroscopy and curing kinetics results obtained by differential scanning calorimetry will allow to model the evolution of the Flory–Huggins interaction parameter in amine‐cured epoxy blends. The resin system investigated was based on a diglycidyl ether bisphenol A (DGEBA) epoxy resin cured with isophorone diamine (IPD) blended with various reactive epoxydised dendritic hyperbranched polymer modifiers (HBP), yielding a CIPS‐controlled morphology. The analysis showed the evolution of the different contributions to the solubility parameters to follow the polymerisation kinetics. The dispersive contribution had the highest value at all stages of polymerisation, but the hydrogen and polar contributions showed the largest variation. By evaluating the dynamic evolution of the solubility parameter components, the Flory–Huggins interaction parameter in the epoxy resin‐hyperbranched polymer blends has been modelled as a function of time. This procedure, combined with thermodynamic modelling, will enable to predict phase diagrams in CIPS thermosetting blends quantitatively. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1883–1892, 2000     

Epoxy polymer coating to prevent the corrosion of aluminum nanoparticles

Aluminum nanoparticles were coated by epoxy polymer in order to prevent the corrosion reaction. The coverage of the epoxy polymer film was controlled from 0% to 100%, which changed the corrosion rate of nanoparticles quantitatively. The surface of the polymer coating was investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM), and the corrosion resistance of these nanoparticles was estimated by the wet/dry corrosion test on platinum (Pt) plate with a NaCl solution. From a TEM analysis, 10 mass% polymer‐coated Al particles in the synthesis were almost 100% covered on the surface by a polymer film of 10 nm thick. On the other hand, 3 mass% polymer‐coated Al was partially covered by a film. In the AFM–Kelvin force microscopy, the potential around the Al particles had a relatively low value by the polymer coating, which indicated that the conductivity of the Al was isolated from Pt plate by the polymer. Both the corrosion and H₂ evolution reaction rates were quantitatively reduced by the mass% of polymer coating. In the case of 10 mass% coated sample, there was very little corrosion of Al nanoparticles. This fact suggested that the electrochemical reaction was suppressed by the polymer coating. Thus, it was found that the corrosion reaction rate of Al nanoparticles could be quantitatively suppressed by the mass% of epoxy coating. Copyright © 2015 John Wiley & Sons, Ltd.     

环氧氯丙烷修饰的对位和间位芳纶涂覆剂研究

制备了具有环氧丙基侧链的对位芳纶(PPTA-ECH)和间位芳纶(PMIA-ECH),并将其用做对位芳纶(PPTA)织物/环氧树脂复合材料中PPTA织物的涂覆剂。采用场发射扫描电子显微镜(FE-SEM)及XPS等方法对PPTA织物表面的PPTA-ECH涂层结构进行了表征。考察了PPTA-ECH和PMIA-ECH涂覆的PPTA织物/环氧树脂复合材料的层间剪切强度和面内剪切强度,并与未经涂覆的PPTA织物复合材料的性能作比较。结果表明,PPTA-ECH和PMIA-ECH可显著改善PPTA织物和环氧树脂之间的界面性能。涂覆了PPTA-ECH及PMIA-ECH的PPTA织物/环氧树脂复合材料的层间剪切强度(ILSS)比未经涂覆的复合材料分别提高了26.20%和14.76%,面内剪切强度(ISS)分别提高了26.98%和11.86%。由于PPTA-ECH对PPTA纤维具有更强的亲和能力,因此PPTA-ECH在层间剪切强度和面内剪切强度方面的增强效果均优于PMIA-ECH。对PPTA-ECH在PPTA纤维表面铺展与吸附及对复合材料的增强机理也进行了初步探讨。作为新型涂覆剂,PPTA-ECH在对位芳纶复合材料的开发应用方面具有潜在的应用前景。