Effect of curing conditions on the morphology of wax modified coil coatings

Raman spectroscopy and optical light microscopy were applied to analyze the morphology within the bulk and on the surface of wax modified topcoats. To vary the processing conditions resin formulations were coated on primed steel sheets and cured at peak metal temperatures of 230, 240 and 250 °C. By Raman spectroscopy dispersed, spherical wax domains within the bulk and on the surface were detected. These features revealed residues of the polyester based resin and the TiO₂ pigment. While the size of the identified lubricant features showed only a slight shift to smaller diameters with increasing peak metal temperature, a significant effect of the curing conditions on the overall number of wax domains and the relative area covered by wax was ascertained. A direct linear correlation between peak metal temperature and relative area covered by wax within the bulk and on the surface of the topcoats was established.     

Performance of polyester and modified polyester coil coatings exposed in different environments with high UV radiation

Coil coating is a continuous strip coating technology, which enjoyed rapid growth. It provides a cost-effective method of applying a coating to a metal substrate with a low solvent emission, and nowadays paints of different nature are applied this way on a range of metal substrates, for a large variety of products and uses.

Coil coatings can be more or less degraded by high UV radiation. However, differences in distribution of light intensity as a function of wavelength between exposure environments, can lead to significant differences in the degradation results, depending on coating nature. In this work, the behaviour of polyester and silicone polyester coatings exposed in three different high UV environments (natural atmosphere and two accelerated UV tests), was studied. Coatings of two different colours (blue and brown) were considered for each paint system. Colour change, gloss and chalking measurements and, visual inspections of coating defects were carried out. In order to explain their corresponding performance, chemical changes on coil coated exposed surfaces were studied by to Fourier transform infrared spectroscopy equipped with a photoacustic detector (PAS/FTIR).     

Depth profiling of clear coil coating by confocal Raman microscopy

Confocal Raman microscopy (CRM) has been demonstrated to be very effective in the analysis of the distribution of chemical moieties within polymeric coil coatings. To verify the compatibility of CRM with commercial coil coatings, a multi-layer coil coating system was prepared and depth profiled by CRM with both dry and immersion oil objectives (non-destructive method). The cross-section of the same sample was then scanned by CRM (destructive method). It was found that the CRM depth profiling resolution was affected by both the intrinsic and extrinsic factors of the objective lens. The use of an immersion oil objective improved depth resolution and minimised the refraction effect, however the oil contaminated the coating surface. The dry method yielded the lowest depth resolution but was completely non-destructive. The CRM lateral scanning of the sample cross-section yielded the most accurate depth profile information; however, the destructive nature of this method is a major disadvantage. It was also found that pigments incorporated in the coil coating formulation affected the CRM depth profiling accuracy due to the strong Raman scattering of these materials.     

Confocal Raman microscopy study of the melamine distribution in polyester–melamine coil coating

Hexamethoxymethylmelamine, a common crosslinker used in combination with polyester resins to prepare thermosetting coatings, can self-condense during curing and in theory build up regions with high crosslink density (melamine enrichment). This distribution may affect such properties as the “local” glass transition temperature and structural heterogeneity and thereby modify formability, stain resistance, and weatherability. The self-condensation regions have not previously been observed in detail so their distribution in the film is unclear. Confocal Raman microscopy (CRM) has been used to characterize the melamine distribution in three polyester–melamine paint systems: one clear and two pigmented coil coatings. Both the surface mapping and depth profiling features of CRM were used to perform a 3D analysis. The depth profiling of the clear coating was performed in a nondestructive way, but due to the opaque nature of the pigments, cross sections of the pigmented coatings were prepared in order to facilitate the analysis of the melamine distribution through the film thickness. Melamine-enriched zones were found on the surfaces of all three samples. They appeared to be approximately spherical with diameters of around 5 μm. It was also observed from the cross sections that the melamine-enriched zones appeared as “particles” distributed randomly through the coating. The Raman spectra collected at these regions show significantly higher triazine ring band intensity. All of these findings confirm the hypotheses constructed over the past 20–30 years. This paper was awarded Second Place in the 2008 FSCT Roon Awards competition held as part of the FutureCoat! conference sponsored by the Federation of Societies for Coatings Technology, in Chicago, IL, on October 14–16, 2008.     

Stainless steel as new substrate for coil coating

Increasing needs of very high resistance to cosmetic corrosion, of more extended service life and reduced maintenance costs for infrastructures, civil and industrial buildings open new fields of application for coil coated stainless steel. This paper describes the adhesion and corrosion properties of new coil coated stainless steel materials produced in industrial coil coating lines. The use of an electrochemical test (electrochemical impedance spectroscopy) can give detailed information on the reactivity of the system and allow the performance of different substrates (AISI 409, 430, 316 and 304) coated with different polymers (polyvinylidene and polyester) to be compared. The results obtained show the interesting properties of this new class of coil coated products. The materials were tested for a long time (about 200 days) in an aggressive environment (3.5% sodium chloride solution) also in the presence of macrodefects. In particular, VIVINOX 430, 304 and 316 revealed no reactivity, corrosion or disbonding, thus supporting the expectancy of very long trouble free exposure also in very aggressive natural environments. (VIVINOX is the brand name of the AST (Acciali Speciali Terni) line of coil coated stainless steel.)     

Effect of curing conditions on the morphology of wax modified coil coatings

Raman spectroscopy and optical light microscopy were applied to analyze the morphology within the bulk and on the surface of wax modified topcoats. To vary the processing conditions resin formulations were coated on primed steel sheets and cured at peak metal temperatures of 230, 240 and 250 °C. By Raman spectroscopy dispersed, spherical wax domains within the bulk and on the surface were detected. These features revealed residues of the polyester based resin and the TiO₂ pigment. While the size of the identified lubricant features showed only a slight shift to smaller diameters with increasing peak metal temperature, a significant effect of the curing conditions on the overall number of wax domains and the relative area covered by wax was ascertained. A direct linear correlation between peak metal temperature and relative area covered by wax within the bulk and on the surface of the topcoats was established.     

氟硅改性无溶剂环氧涂料的制备与性能

采用甲基丙烯酸十三氟辛酯（TFM）改性氨基硅油（AS）制备氟化氨基硅油（FAS）,并用其改性环氧树脂（EP）探究氨基硅油及氟化氨基硅油添加量对环氧涂层性能的影响。本文通过红外光谱对改性结果进行表征,通过柔韧性测试、画圈附着力测试、铅笔硬度测试、耐冲击测试、热失重测试、接触角测试、紫外加速老化实验和Tafel极化曲线测试,分别评价涂层的柔韧性、附着力、硬度、耐冲击性、耐热性、疏水性、耐候性和防腐性能,通过扫描电镜对涂层断面进行分析,并通过EDS对涂层进行表面元素分析。结果表明,氟添加量为15%制备氟化氨基硅油改性环氧树脂时,氟硅改性EP涂层相对于未改性EP涂层,硬度由2H提升至3H,附着力由2级提升至1级,柔韧性由1mm提升至0.5mm,耐冲击由45cm提升至50cm,热稳定性增强,接触角由70.5°提升至123°,耐紫外老化（432h）由3级提升至1级,E_corr由-0.6187V正移至-0.1720V,I_corr由1.9858×10^-8A/cm²减小至3.7125×10^-10A/cm²。适量氟化氨基硅油的引入,显著提升了环氧涂层的机械性能、耐候性能和防腐性能。     

EIS study of environmentally friendly coil coating performances

The corrosion protection of metal structures by the application of organic coatings is obtained using complex paint cycles. The metal pretreatment as well as primer, intermediate and top coat are the usual layers composing the protection system. Although chromate pretreatment processes and chromate containing primers are widely used, they require highly toxic chromic acid solutions, with consequent effluent disposal and ecological problems. This fact pushed many research laboratories to develop new chromium-free pretreatments and primer inhibitors. Electrochemical impedance spectroscopy (EIS) proved to be a very useful technique to study the protection properties of the organic coating because of the possibility of evaluating the corrosion process on the metal substrate and to measure the electric and dielectric characteristics of the coating. In this study, new chromium-free pretreatments and new primers containing ecological inhibitors were applied to steel substrates coated using an Al-Zn alloy. The results were compared with those obtained using traditional protection systems. The characterization of the complete system (pretreatment and primer) in sodium sulfate solution clearly showed the different water uptake behavior of the two primers, which highlights the better barrier properties of the one containing phosphate. However the corrosion protection of the primer containing chromates is also due to the inhibitive action of the chromates. Hence such a type of primer better withstands the presence of defects in the coating. Moreover the presence of environmentally friendly pretreatments do not worsen the corrosion protection which appears comparable to that observed when chromatation is employed.     

Depth profiling of coil coating using step-scan photoacoustic FTIR

Photoacoustic (PA) Fourier Transform Infrared Spectroscopy (FTIR) has been demonstrated to be very useful in the analysis of molecular distribution and/or degradation in polymeric materials in a non-destructive manner. Step-scan (SS) PA FTIR has been found to be especially suitable to depth profile multi-layered polymer coating/laminate systems. In this current study, the capability of SSPA-FTIR in assessing industrial coil coatings was evaluated. Two multi-layered model coil coating samples were prepared, one had a pigmented Polyvinylidene Fluoride (PVdF) top coat and the other had a clear Polyethylene Terephthalate (PET) laminate film on the surface; both were depth profiled by SSPA-FTIR. The signal magnitude and phase angle were used to obtain a modulation frequency and a phase angle resolved depth profile, respectively. The advantages and disadvantages of the technique were also investigated. Optical microscopy was used to determine the true thicknesses of the PET and PVdF layers from the sample cross-sections. The values were compared with those predicted by SSPA-FTIR. It was found that a precise depth profile was only obtained with the PET sample whereas in the high pigmented coating system, the predicted values were smaller than the true PVdF thickness, possibly due to the high thermal diffusivity of the inorganic pigment.     

Characterization of coil coatings by thermal analysis

The interrelationship between the network formation process and performance properties makes cure process studies critically important in the coil‐coating industry. The objective of this work was to introduce thermal analysis into the evaluation of curing of uncured samples and in studies of the glass‐transition temperatures of cured samples. Thermal analysis, dynamic mechanical analysis (DMA), and differential scanning calorimetry (DSC) were used to characterize gelation and curing of three types of samples: paints, coated sheets, and free films. In addition to the generally used three‐point‐bending and extension geometries, a cup‐and‐plate geometry also was used in analyzing gelation and curing of liquid samples. These thermal analyses are suited to the purpose of characterizing coil coatings. A correlation between PMT (peak metal temperature) and measured T_g (glass‐transition temperature) was found, as well as effectively distinguishing different curing conditions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2016–2022, 2003     

Epoxy coatings with modified montmorillonites

Two types of modified layered aluminosilicates (montmorillonites) with different grain size and gallery spaces were tested as nanofillers in epoxy coating compositions for a steel substrate. Organophilic montmorillonites, in the amount of 2.5 and 5 wt% were introduced to waterborne and to solvent-type epoxy coating materials (based on bisphenol-A epoxy resins and various curing agents). The results of this work indicate that processing properties of coating compositions (leveling and drying time) as well as mechanical properties of coatings (hardness, scratch and abrasion resistance, adhesion to steel) were positively affected by a layered aluminosilicate nanofiller. Enhanced water resistance (lower water absorbance) of coats, especially those formed from waterborne compositions, has been found.     

甲基三甲氧基硅烷改性硅溶胶憎水膜的制备

制备了用于增强玻璃表面憎水性的甲基三甲氧基硅烷（MTMS）/硅溶胶/丙烯酸羟丙酯透明薄膜。讨论了MTMS的水解温度、pH值、MTMS与硅溶胶的反应时间、MTMS用量与薄膜憎水性的关系。采用红外光谱和原子力显微镜表征了涂膜表面的官能团种类、数量和微观结构。研究表明,将MTMS在40℃、pH=3的条件下水解,再与酸性硅溶胶的体积比（r）为0.1,在60℃下反应2 h,所得的产物制备的涂膜的憎水性最好,水接触角可达127°。     

建筑涂料现状及展望

介绍了氟树脂,丙烯酸酯,环氧树脂,聚氨酯树脂的外墙,内墙及地面涂料的特点及组成,概述了建筑涂料市场的现状并作出展望。     

Morphology and properties of UV-curing epoxy acrylate coatings modified with methacryl-POSS

In this work, the morphology and properties of UV-curing epoxy acrylate (EA) coatings modified with methacryl polyhedral oligomeric silsesquioxanes (M-POSS) were studied. The M-POSS nanocages were introduced into EA UV-curing system via copolymerization at loadings between 0% and 10 wt%. The XRD and FTIR analysis indicated that M-POSS chemically incorporated into the hybrid materials and formed a cross-linked network between M-POSS and EA. The morphological analysis showed that the discrete spherical POSS-rich particles were dispersed in the EA matrix uniformly, and both of the number and mean diameter of POSS-rich particles increased with the increasing M-POSS loadings. The influence of M-POSS on the kinetics of the photopolymerization was determined by real time FTIR spectroscopy and the result showed that the addition of POSS enhanced both of the UV-curing rates and final double bond conversion. The DMA analysis showed that increasing the amount of M-POSS nanocages caused an increase on the nanocomposite's T_g. TGA curves showed that at the later period of degradation process, the thermal stability of nanocomposites was enhanced by M-POSS. With respect to the mechanical properties, the most remarkable trend was an improvement on the impact resistance of nanocomposites with the increasing POSS contents. Because both of the craze and plasticity deformation caused by POSS nanocages would absorb impact energy, hinder the growth of craze.     

Study on nano-CaCO3 modified epoxy powder coatings

Powder coatings are widely used for their environmental and economical advantages. In this work nano-CaCO₃ modified powder coatings were prepared using epoxy resin/nano-CaCO₃ composites obtained through in situ and inclusion polymerization and the nano-CaCO₃ can be well dispersed in the resultant coatings by this preparation method. Their tensile property, cupping property and neutral salt spray corrosion resistance were distinctly improved. The mechanism of property improvement was discussed.     

A comparative study between Cr(VI)-containing and Cr-free films for coil coating systems

In this work, the protection conferred by Cr(VI)-containing and Cr-free pre-treatments and primers used in hot dip galvanized steel (HDG) coated systems were studied. The EIS results showed a differentiated behaviour for the specimens with Cr(VI) compared to the chromium-free ones. The samples with Cr(VI), both in the pre-treatment and in the primer, presented a better corrosion performance when compared to the Cr-free ones.

Moreover, it can be said that the pre-treated and primed samples without Cr(VI) presented lower resistive properties and higher delamination fractions throughout the immersion time. The amount of Cr in the primer also influenced the coating resistance for shorter periods of immersion, but for long periods the passivating effect of Cr seems to be determinant.

When topcoat was applied, i.e. for a complete system, the Cr-free specimens performed better than the Cr(VI)-containing ones, perhaps due to a better adhesion of the topcoat to the primer in the former case. This leads to the conclusion that there is a risk in assessing the behaviour of a paint scheme on the basis of the individual behaviour of each layer.     

A comparative study between experimentally measured mechanical attributes and users’ perception of soft feel coatings: Correlating human sense with surface characteristics of polyurethane based coatings

Different soft feel coating formulations using waterborne resins composed of soft and hard polyurethane resins were prepared. The effects of resins mixtures on the soft feel properties were studied. Attempts were made to find out the correlation between users perception and experimentally measured surface characteristics of the coatings. To this end, 72 people were asked to touch the coatings in a similar testing environment and to express their feeling in order to rank them between 1 (lowest soft feel effect) and 4 (highest soft feel effect). The coatings physical characteristics were studied by tensile test, micro Vickers hardness, atomic force microscope (AFM) and friction coefficient measurement. It was shown that the mixtures of 25:75 of soft and hard resins resulted in the best soft feel effect. Users did not consider low or high hardness films as soft. Instead, those coatings having greater toughness were ranked as the best soft feel effect. Also, coatings with lower friction coefficient and lower surface roughness were preferred by users. However, the lowest friction coefficient did not result in the best soft feel appeal. In fact, the mechanical properties, surface roughness and friction coefficient were found to play as the criteria to show soft feel effect. It is thus concluded that by selecting appropriate surface characteristics of coatings related to soft feel effect, good agreement between these properties and human feeling can be made.     

Electrochemical and anticorrosion performances of zinc-rich and polyaniline powder coatings

In this work, hydrochloride polyaniline (PANI-Cl) powder was incorporated as a conductive pigment into powder zinc-rich primer (ZRP) formulations in order to enhance the electronic conduction paths between zinc particles inside the coating and the steel substrate (i.e. percolation). Coatings were applied onto steel substrates and immersed in a 3% NaCl solution at ambient temperature.The protective properties and electrochemical behaviour of coatings were investigated by monitoring the free corrosion potential versus time and by using EIS. It was found that corrosion potential remains cathodic and constant for a long time up to 100 days of immersion. From EIS results, it was shown that the coatings exhibit larger impedance values than those observed with liquid or other zinc-rich powder formulations containing carbon black. From Raman spectroscopy results, it may be proposed that zinc particles in contact with PANI-Cl pigments were passivated. Other zinc particles remain still active which ensures the cathodic protection of the substrate. Moreover, coatings exhibit good barrier properties.     

用杜仲胶/碳纳米管改性环氧树脂制备导电防腐涂料及其性能

以杜仲胶(EUG)和环氧树脂(E-51)为涂层基质、碳纳米管为导电填料制备了导电防腐涂料,考察了 EUG用量对复合涂层导电性和耐腐蚀性的影响.采用差示扫描量热仪和动态热机械分析仪研究了复合涂层的热性能,用四探针测试仪研究了导电性能,分别通过电化学阻抗谱及盐雾测试和附着力测试研究了耐腐蚀性和附着力.结果表明,当EUG用量...     

水性环氧树脂地坪漆在建筑物中的涂装工艺

介绍了6种常见的环氧地坪漆的应用范围。讨论了水性环氧地坪漆在建筑物中的涂装前处理、底涂、中涂和面涂的工艺要求。研究了石英砂含量对以不同固化剂固化的环氧中涂层抗压强度的影响。结果表明,使用端氨基聚醚和脂肪胺类固化剂时,当石英砂含量达到85%(质量分数)时,中涂层的抗压强度依然能满足环氧地坪漆的施工要求。地坪漆的性能测试结果证明,新开发的水性环氧地坪漆达到甚至超过了常用的地坪漆的性能指标。