Synthesis and characterization of elastomeric polyester coatings for automotive pre-coated metal

An automotive pre-coated metal system (PCM) has been investigated to replace wet coating process, such as pre-treatment, dip coating and spray coating, to address environmental regulations. However, automotive pre-coated metal sheets must have high flexibility and stiffness to overcome harsh conditions such as cutting, press and stamping processes. For these reasons, elastomeric polyester coatings were designed to improve scratch resistance and to impart reflow characteristic for an automotive PCM. The characteristics, curing behavior and viscoelastic property of the resins were measured by ¹H NMR, GPC, RPT and DMA. The flexibility was evaluated using a texture analyzer. A nano scratch tester, equipped with an optical microscope was used to measure the scratch resistance of coatings and the scratched surface morphology. An Amtec laboratory car wash test and a sharp knife were used to evaluate the reflow property of the coatings. Change of the damaged surface morphology was measured using a mini-SEM.     

Green metal organic coating from recycled PETs and modified natural rubber for the automobile industry

Novel elastomeric polyurethane coating precursors from renewable natural rubber and waste bottle PET were prepared for metal coating applications. The elastomeric PU was synthesized from; modified natural rubber with hydroxyl functional groups (HLNR), modified NR grafted with polysiloxane (PDMS-g-LENR) and modified PETs (P-ET-PA and P-T-PA) such as a polyol/polyacid; a commercial MDI (Millionate MR-200) as an isocyanate. The physical properties such as film-thickness, gloss, hardness, adhesion (cross-cut and scratch-adhesion), impact test, Erichsen, bending and chemical resistance of the coated film were investigated by following the industry standards for automobile coatings. The properties of the coated films were influenced by the ratio of polyol/polyacid and the polyol nature. It was found that the coated film prepared from both of modified NR presented good adhesion with the metallic substrate by absence the surface treatment. Single layer of PU elastomer film prepared from both modified PETs with HLNR35 and MDI with mole ratio of 0.1:0.3:0.75 showed good physical properties following the industry standards for automobile coatings. The presence of PDMS-g-LENR in the coatings improved the thermal stability when compared to HLNR35. Furthermore, salt spray test and electrochemical impedance spectroscopy (EIS) were used to examine the corrosion behavior of the coated steel. It could be concluded that the best anticorrosive behavior was shown by the PDMS-g-LENR and P-T-PA formulas.     

Organic vs inorganic light stabilizers for waterborne clear coats: a fair comparison

As a consequence of regulatory pressure to reduce solvent emissions, there is high growth rate of ??compliant technologies?? such as waterborne (WB) coatings. However, a change from conventional solventborne (SB) to WB technologies should not compromise the protective function of the coatings and the used raw materials. The use of light stabilizers, such as UV absorbers (UVA) and hindered amine light stabilizers (HALS) are state-of-the-art and largely improve the coating durability and service lifetime. Today in the case of UVA one has to differentiate between inorganic and organic products: the most widely used organic UVA for coating applications are 2-(2-hydroxyphenyl)-benzotriazole (BTZ) and 2-hydroxyphenyl-s-triazine (HPT) derivatives. Inorganic products are ideally nano particulate materials??so-called mineral screeners (MS)??comprised of titanium dioxide (TiO₂), zinc oxide (ZnO), or cerium oxide (CeO₂). The challenge here is to convert existing products which are in general hydrophobic substances into product forms that enable easy incorporation and unproblematic dispersion into WB systems. This article describes UV absorbers which are commercially available for waterborne coatings. Different classes are tested with regard to their protective function in joinery coatings as well as with regard to their influence on coatings color and transparency. The findings of this study showed clearly that the 2-hydroxyphenyl-s-triazine class outperforms all other UVA in terms of long-term performance without influencing initial coating properties.     

食品软包装用透明高阻隔涂料：PVA涂料研究进展

聚乙烯醇（PVA）因其良好的透明性和成膜性以及优异的氧气和有机溶剂阻隔性，可用于透明、易回收、环境友好型的食品高阻隔软包装材料。但因其涂层对湿度敏感性差且不具备水蒸气阻隔性能而制约其发展。针对这一问题，目前主要有两种解决方法：一种是PVA化学交联，PVA能进行多元醇的酯化、醚化、缩醛化等化学反应；另一种是制备PVA-纳米复合涂料，PVA与纳米层状材料如蒙脱土（MMT）以及氧化石墨烯（GO）复合涂料的研究已取得较大进展。为此，分别从PVA的阻隔性及其影响因素、化学交联PVA涂料以及PVA-纳米复合涂料的最新研究进展进行了综述，分析了改性PVA涂料面临的问题，展望其未来研究方向。     

Adhesion promotion and corrosion prevention using thin anisotropic coatings

Using sol-gel technology, thin organic/ceramic (ceramer) coatings have been applied to metal surfaces to enhance such surface properties as adhesion promotion and corrosion prevention. Isotropic coatings have been found to be effective in certain applications such as corrosion prevention, but the formation of anisotropic (functionally gradient) coatings permits greater flexibility over the resulting properties. Isotropic coatings derived from tetraethoxysilane, for example, have been found to effectively inhibit corrosion while being only 100-1000 A thick. These coatings do not, however, promote adhesion. Thin coatings made from traditional silane adhesion promoters alone are unable to prevent corrosion of metallic substrates. Using monomers with appropriate reactivities permits the single-step synthesis of anisotropic coatings that can both promote adhesion and prevent corrosion. These types of anisotropic coatings allow the physical and chemical properties of a coating to be varied as a function of the distance from the substrate and confer properties to the substrate that would not be possible from a single isotropic coating. The principle behind the construction of these anisotropic coatings is general enough that it can be used in many applications where microengineering of surface structures is important.     

Rheology parameters controlling spray atomization and roll misting behavior of waterborne coatings

Formation of small coating droplets is a phenomenon common to spray and roll application of coatings. Generation of small droplets, referred to as atomization, is the mechanism of controlling the quality and thickness of the applied coating layer in spray technology. In roll coating application, small coating droplets are formed at the nip–exit region under certain conditions. Because of the high-shear rates at roll nips and spray nozzles, it is common to relate high-shear viscosity with atomization and roll misting behavior of coatings. This paper will review the relative importance of shear and extensional flows, and the response of coatings to such flows, in affecting misting and atomization behavior. Experimental efforts to quantify the effect of shear and extensional rheological parameters have clearly established a lack of correlation of high-shear viscosities with both spray atomization and roll misting behavior of coatings. However, extensional viscosity is shown to have a strong correlation. Finally, how rheology modifiers can be selected to circumvent misting problems in roll coating applications and atomization problems in spray applications is discussed.     

Design,preparation, and characterization of new high-refractive index hybrid organic–inorganic polysiloxanes: Innovative coatings for optoelectronic applications

The current demand for high-refractive index materials is very high due to their importance in optoelectronic applications. Such materials already exist in the market, but they present many disadvantages. They might contain toxic metals; their preparation can be challenging or produce high quantity of waste. Consequently, there is an urgent need to produce new friendly coatings with high-refractive index. Hybrid organic–inorganic polysiloxanes can offer a solution to this problem. They can be easily prepared from nontoxic alkoxy silanes using the sol–gel chemistry process. Herein, a series of new hybrid polysiloxanes are synthesized from the monomer 1–(2–(triethoxysilyl)ethyl)triphenylsilane and other silanes. The preparation of the macromolecules is optimized at both stages of the sol–gel process. The polymers are characterized by gel permeation chromatography and NMR spectroscopy. Spin coating of the materials on silicon wafers, followed by film thickness and refractive index measurements, indicates that the new polysiloxanes can have refractive indexes as high as 1.6 with thicknesses varying from 2200 to 3700 nm. Consequently, it is expected that the new materials described in this report are valuable for optoelectronic applications such as high-dielectric constant (high-k) gate oxides, interlayer high-k dielectrics, or high-refractive index abrasion resistant coatings.     

Adhesion of electron beam curable coatings on metal substrates

Electron beam (EB) curing is growing more and more important as a curing technique in industrial coatings, for example on substrates like wood, paper and plastics. However, commercial applications of EB curing on metal substrates are rather limited. The main technical cause for this originates from the insufficient adhesion and flexibility shown by EB cured coatings when applied on metal parts. However, adhesion and flexibility can be improved by various ways, in particular via a proper choice of the chemical pretreatment of the substrate. Adhesion of coatings, based on acrylated resins, on hot dipped galvanized steel can be improved dramatically by using a pretreatment, which is not usual in the current field of commercial coil coating. Pretreatments investigated show no relationship to surface tension, so it is highly probable that a chemical graft reaction, initiated by the electron beam, occurs at the interface of the coating and pretreatment layer. Experiments also show that cationic curing binder systems show promise with respect to adhesion and flexibility. Without optimizing the coating formulation (no wetting agents or other additives are used) relatively good adhesion and flexibility can be obtained on hot dipped galvanized steel, under both wet and dry conditions. The adhesion and flexibility are shown to be dependent on the radiation dose, and can be further improved by post-heating. In this case the polymer network gets the opportunity to relax internal stresses that are built up during the cure reaction.     

Synthesis of UV-curable polysiloxanes containing methacryloxy/fluorinated side groups and the performances of their cured composite coatings

Three novel UV-curable polysiloxanes consisting of polysiloxane backbone with methacryloxy/fluorinated side groups were synthesized, and their structures were characterized by FT-IR, ¹H NMR and ¹³C NMR. A series of UV-cured composite coatings based on the synthesized polysiloxanes and an epoxy methacrylate were obtained through photopolymerization. Their gel content, flexibility, hardness, gloss, contact angle, thermal behavior as well as water absorption ratio were investigated. Results found that the siloxane component could enhance the flexibility and gloss of coatings, while the presence of fluorinated groups could improve the hardness. The combination of silicon and fluorine in the same polymer could increase thermal stability and water resistance of the coatings and decrease their surface energy simultaneously. The observation of the fractured-surface morphology showed that the polysiloxanes could be well dispersed in the epoxy methacrylate to some extent. A suitable addition of such polysiloxane in photocurable coating matrixes may provide excellent properties for the cured coatings and widen their applications.     

Lightweight Ballistic with Additional Stab Protection Made of Thermally Sprayed Ceramic and Cermet Coatings on Aramide Fabrics

Ceramic and cermet coatings on fiber fabrics used in lightweight protection should enhance their performance in stab protection. Based on thermal spray technologies a coating process for hard material layers even on temperature-sensitive fiber substrates has been developed, so that the coated fabrics retain their flexibility. High-speed and high-rate cermet and ceramic coatings are deposited with simultaneous substrate cooling in order to apply thick, hard, and refractory cermet and oxide ceramic coatings. These coatings can be applied on lightweight aramide fabrics without damaging the fibers. The hard material, aramide composite fabric combines the advantages of aramide fabrics and hard, refractory materials. A fully flexible, highly tenacious and lightweight fabric with a hard and refractory top coating is developed. The penetration of knives and blades through such hard material-coated multilayer fabrics is effectively prevented.     

Synthesis and characterization of flexible polyester coatings for automotive pre-coated metal

An automotive pre-coated metal system has investigated to remove the wet coating process, such as pre-treatment, dip coating and spray coating for environmental regulations. However, automotive pre-coated metal sheets must have high flexibility and formability to overcome the harsh conditions such as cutting, press and stamping process. For these reasons, flexible polyester coatings were designed to control flexibility using polycarbonatediol. The characteristics, curing behavior and viscoelastic property of the resins were measured by FT-IR, GPC, rheometer, DSC, RPT and DMA. The flexibility was evaluated using a texture analyzer. A nano-scratch tester, equipped optical microscope can measure the scratch resistance of coatings and the scratched surface morphology.With increasing polycarbonatediol content, the final frequency and the storage modulus increased and the T_g of the coatings decreased. This is related to the high mobility of the chain segment in polycarbonatediol. In terms of the flexibility and scratch resistance, CP-3 had high elongation value and good scratch resistance resulting from optimized stamping, pressing and cutting process in automotive pre-coated metal system. Therefore, polycarbonatediol is a powerful factor affecting the flexibility and scratch resistance of polyester coatings.     

HVOF喷涂用于提高锅炉换热面耐磨损耐腐蚀性能综述

火力发电是我国的主要发电方式,在燃用煤、生物质等固体燃料时会面临锅炉换热面的冲蚀磨损或腐蚀问题,导致管道失效停炉,严重影响了电厂的安全稳定运行。超声速火焰（HVOF）喷涂作为热喷涂工艺的一种,可以通过在换热管道表面添加防护涂层来缓解磨损或腐蚀问题。因其制备的涂层具有与基体结合强度高、孔隙率低等优异的特点,在锅炉换热面的耐磨损耐腐蚀方面研究及应用前景广阔。综述了HVOF喷涂的发展、工艺流程以及涂层的特性,并重点总结了用于提升锅炉换热面耐磨损耐腐蚀性能的HVOF涂层材料,以及不同材料应用时需要考虑的环境因素。最后从工艺优化、材料进步以及实验方法创新三个方面对HVOF工艺在锅炉换热面上的应用做出展望。     

水性超疏水涂层的制备、调控与应用的研究进展

基于可持续发展和绿色环保的要求,以水替代有机挥发性溶剂的新型水性超疏水涂层逐渐成为研究热点,但是水性涂料的分散性及涂层的疏水稳定性、涂层性能等相关问题也随之而来。本文介绍了水性超疏水涂层制备方法的发展现状,针对水性超疏水涂层力学耐久性能差的问题提出可行性方案,例如制备内外一致的一体化复合结构,加强涂层内界面相互作用,交联作用或设计自修复水性超疏水涂层等。此外,还对水性超疏水涂层在油水分离、防结冰、自清洁等领域的进展进行阐述,并探讨了水性超疏水涂层的规模化制备、涂层力学性能的强化和耐久性研究将成为主要探索方向,只有夯实水性超疏水涂层的基础研究,工业应用才能突破。     

Antiswelling and robust supramolecular polyurea hydrogels induced by the synergy of hydrogen bond and hydrophobic interaction for constructing durable underwater anti-oil-fouling coatings

Hydrogels are attractive materials for constructing underwater antifouling coatings on solid substrates. However, the application of hydrogel coatings usually faces the obstacles of complex preparation process and poor durability. Herein, we present a facile method to prepare durable hydrogel coatings on metal foils based on rationally designed supramolecular polyurea (PU) hydrogels. PU hydrogels are designed to be cross-linked with hydrogen bonds (H-bonds) and hydrophobic interactions in the hard segment domains by using dihydrazides with different alkyl spacer lengths ( (CH₂)_m ) as chain extender. The synergy of H-bond and hydrophobic interaction can stabilize H-bonds in water, as confirmed by Raman spectroscopy. As a result, PU hydrogels exhibit antiswelling capacity and robustness in both deionized water and seawater. Subsequently, PU hydrogel coatings on Cu/Al foils are prepared by convenient brush coating and subsequent swelling. The resulting hydrogel coatings exhibit excellent underwater anti-oil-adhesion and self-cleaning property, and are durable enough to withstand various static and dynamic damaging tests. The good durability of PU hydrogel coatings should be ascribed to the robust adhesion interface and excellent antiswelling capacity of PU hydrogels. The combination of facile preparation and good durability makes PU hydrogel coatings promising candidates for reliable underwater antifouling.     

Synthesis,Properties and Applications of Biodegradable Polymers Derived from Diols and Dicarboxylic Acids: From Polyesters to Poly(ester amide)s

Poly(alkylene dicarboxylate)s constitute a family of biodegradable polymers with increasing interest for both commodity and speciality applications. Most of these polymers can be prepared from biobased diols and dicarboxylic acids such as 1,4-butanediol, succinic acid and carbohydrates. This review provides a current status report concerning synthesis, biodegradation and applications of a series of polymers that cover a wide range of properties, namely, materials from elastomeric to rigid characteristics that are suitable for applications such as hydrogels, soft tissue engineering, drug delivery systems and liquid crystals. Finally, the incorporation of aromatic units and α-amino acids is considered since stiffness of molecular chains and intermolecular interactions can be drastically changed. In fact, poly(ester amide)s derived from naturally occurring amino acids offer great possibilities as biodegradable materials for biomedical applications which are also extensively discussed.     

Biobased step-growth polymers in powder coating applications

Co- and terpolyesters based on 1,4:3,6-dianhydro-d-glucitol (isosorbide), 1,4:3,6-dianhydro-l-iditol (isoidide) and succinic acid were evaluated for their applicability in solvent-cast and powder coatings. These biobased polyesters have functionalities and T_g values in the appropriate range for such applications and were cross-linked using conventional curing agents. Introduction of poly-functional monomers such as glycerol and citric acid led to coatings with enhanced performance with respect to mechanical and chemical resistance, compared to formulations based on linear polymers. The curing behavior of these systems was investigated with DSC and rheological experiments. Formulations containing citric acid-modified polyester resins showed rapid curing, probably facilitated by anhydride formation at the chain ends. Hydroxy- as well as carboxylic acid-functional 1,4:3,6-dianhydrohexitol-based polyesters proved to be suitable materials for coating applications with respect to solvent resistance, impact resistance and hardness, with performance comparable to commercially available systems. Accelerated weathering experiments showed that functional groups such as hydroxyl groups, carboxylic acids, anhydrides and peroxides are formed during UV-exposure. The weathered coatings have reduced impact stability. On the other hand, the appearance of the coatings does not change significantly. Isosorbide-based coating systems appear to have similar weathering resistance as conventional terephthalic acid-based poly(ester urethane) coatings.     

有机硅在聚氨酯中的应用

综述了有机硅在聚氨酯材料中的应用。聚硅氧烷可与聚氨酯形成共聚物，用于医学材料等；有机硅化合物还用作聚氨酯的改性剂，用于涂料，胶粘剂，密封剂，涂饰剂，织物整理剂等领域。对于提高聚氨酯性能，有机硅是一类十分有用的化合物。     

On the electrochemical and structural behavior of biologically degraded automotive coatings; Part 1: Effect of natural and simulated bird droppings

Environmental factors can potentially deteriorate automotive coatings. These include UV radiation, humidity, hot–cold shocks as well as aggressive chemical compounds. In addition, natural occurring materials such as bird droppings and tree gums are also enable to affect the coatings. The present work aims to study the degradation of an automotive coating system exposed to natural and simulated bird droppings. To this end, structural analysis of samples was studied using FT-IR spectroscopy, optical and atomic force microscopes. Also, the mechanical and electrochemical behaviors of coatings were investigated by DMTA and electrochemical impedance spectroscopy (EIS). It was found that the biological materials significantly affect the mechanical and chemical properties of the coatings, resulting in a decrease in corrosion resistance. A two-time constant semicircle was observed for degraded coatings after a short time as a result of electrolyte diffusion into the coating/metal interface. The behavior of the coatings was then discussed based on the formation of surface defects.     

Oberflächenstruktur von beschichteten kunststoff-folien

Plastic foils are increasingly used for packing. In order to make the foils gas- and steamproof, they are coated by machine with an adhesive layer and then with a top coat mainly of vinylidenchlorid copolymers. Some time these coated foils look spotted owing to the fact that some regions are more, others less transparent. The microscopic and the electron microscopic investigation of these foils showed that the surface, in sharply defined regions, has a small difference of level between 500 and 1000 Å, same depending on the kind of dispersion. When rolling up the foil the surface structure of the uncoated back is imprinted on the higher regions of the top coat while the lower regions of the top coat are not touched and thus remain smooth. Owing to the different scattering of the transmitted light on the structured and the smooth surface the regions are showing a different transparency. Foils without a surface structure of their own have an equal constant transparency after the coating although the top coat shows the same differences of level. Apart from this kind of structured top coating also a surface structure is to be stated which is due to slightly crystallized or harder polymer particles. This surface structure is demonstrated by means of two examples.     

Synthesis and characterization of acrylic-grafted polyester coatings for automotive pre-coated metal

An automotive pre-coated metal (PCM) system has been investigated to remove the wet coating process, such as pre-treatment, dip coating and spray coating for environmental regulations. However, automotive pre-coated metal sheets must have high flexibility and stiffness to overcome the harsh conditions such as encountered in cutting, press and the stamping process. For these reasons, a series of acrylic-grafted polyester coatings (i.e., AGP-0, AGP-10, AGP-20, AGP-30) were designed to satisfy both the surface hardness and the formability for an automotive PCM. The characteristics of the resins were measured by GPC, FT-IR and ¹H NMR. The viscoelastic behavior and flexibility was evaluated using DMA and UTM. The physical properties such as pendulum hardness, pencil hardness and adhesion were measured to define the effect of incorporating acrylates. A cylindrical deep drawing tester was used to evaluate the formability of coatings.