有机硅涂料的剖析

采用现代化分析手段———气相色谱 -质谱 (GC -MS)、红外光谱 (IR) ,分析出有机硅涂料的主要成分 ,并对其所用有机硅类型和偶联剂进行定性。     

Recrystallization of silicone release coatings

Summary The degrees of recrystallizability of silicone release coatings with different crosslink densities have been determined via monitoring the recrystallization peak of the temperature scan on the Rheometrics-RMS-800 Spectrometer and DSC. As the crosslink density of the release coating increases, the recrystallization peak of silicone diminishes sharply indicative of the increasing constrains imposed by the high crosslink density which reduces the recrystallizability of the silicone. In addition, Tg of the silicone also increases, together with a lower recrystallization and melting temperatures.     

涂料用硅树脂的开发动向

本文主要介绍硅树脂涂料的最近开发动向.     

A new class of silicone resins for coatings

A new class of silicone has been developed for coatings or as coating additives. Cycloaliphatic silane monomers were prepared and reacted into more easily handled cyclic oligomers. These cyclic oligomers were ring-opened into siloxane polymers. The polymers were functionalized with a variety of groups, including: amino, glycidyl epoxide, cyclohexene epoxide, acrylic, and alkoxysilane. The cycloaliphatic silicones have been designed for a number of different curing conditions: (1) ambient temperature-cure (amino and glycidyl epoxide), (2) cationic ultraviolet (UV)-cure (cyclohexene epoxide), (3) radical UV-cure (acrylic), and (4) moisture-cure (alkoxysilane). The end usages thus far have been focused on silicone coatings; however, usage as coating additives will be a focus for future research. The cycloaliphatic silicone has been UV-cured with mixed sol–gel precursors for usage as aerospace coatings. The cycloaliphatic silicones have also been ambient temperature-cured for release coatings, and have application as anti-fouling coatings. The inherent low surface energy makes the cycloaliphatic silicones prime candidates for surface tension additives. Presented at the 2006 FutureCoat! Conference, sponsored by the Federation of Societies for Coatings Technology, in New Orleans, LA, on November 1–3, 2006.     

Nanostructured coatings approach for corrosion protection

Nanostructured surface treatment coatings based on the Self-assembled Nanophase Particle (SNAP) approach were investigated as potential replacement for chromate-based surface treatments on aircraft aluminum alloys. In the traditional sol–gel method, hydrolysis-condensation processes are followed by condensation polymerization upon film application. This process sequence provides a low temperature route to the preparation if thin coatings which are readily applied to most metallic substrates. The recent discovery of a method of forming functionalized silica nanoparticles in situ in an aqueous sol–gel process, and then cross-linking the nanoparticles to form a thin film, is an excellent example of a nanoscience approach to coatings. This Self-assembled Nanophase Particle (SNAP) process can be used to form thin, dense protective organic surface treatment coatings on Al aerospace alloys. The ability to design coating components from the molecular level upward offers tremendous potential for creating multifunctional coatings.

The important components of Al alloy corrosion inhibition by chromate are storage and release of Cr^VI species, inhibition of cathodic reactions (primarily oxygen reduction), and inhibition of attack at active sites in the alloy. Unlike chromate-based treatments, current SNAP coatings provide barrier-type corrosion resistance but do not have the ability to leach corrosion inhibitors upon coating damage and minimize corrosion of the unprotected area. In this study, organic inhibitors were tested for corrosion protection of aluminum alloys in combination with the (SNAP). Scanning Vibrating Electrode Technique, anodic polarization, electrochemical impedance spectroscopy, and salt spray test were used to study this new approach for chromate replacement.     

Continuous lipase-catalyzed production of wax ester using silicone tubing

Enzymatic synthesis of cetyl palmitate was performed in a solvent-free system at 65°C using immobilized Candida antarctica lipase. Batch reactions at controlled water activity showed that the yield could be increased from 88.8 to 99.1% by decreasing the water activity from 1 to 0.05. A continuous reactor configuration was constructed, where two tubular reactors were run in sequence with a separation container in between, in which the water phase was separated from the wax ester phase. The reactor was run for 1 wk at low flow rate (0.005 g/min) with very good operational stability and a productivity of 7.2 g d⁻¹ using 0.4 g of biocatalyst. The activity of the individual preparations decreased during operation. The first reactor had only 30% activity left after 1 wk of operation whereas the second reactor showed only a 10% decrease. This difference in enzyme stability is a direct result of the different water activity in the two reactors.     

Hydrophobic benzoxazine-cured epoxy coatings for corrosion protection

A hydrophobic benzoxazine-cured epoxy coating (EPB) was prepared by a dip coating and thermal curing method using benzoxazine monomer (B-TMOS) as curing agent. Fourier transform infrared (FTIR) analyses confirmed the presence of thermal curing reactions and hydrogen-bonding interactions in the epoxy/polybenzoxazine system. The hydrophobicity of epoxy coatings induced by the incorporation of B-TMOS was enhanced significantly, and the water contact angles of resultant EPB coatings were higher than 98°. The corrosion protection ability of epoxy coatings was investigated by open-circuit potentials, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) methods. The results showed that the charge transfer resistance (R_ct) of EPB coatings was increased by about three orders of magnitude compared with bare mild steel, and the protection efficiency values of all EPB samples were more than 98%. This increased corrosion protection property could be attributed to the high hydrophobic performance of EPB coatings.     

Smart coating for corrosion protection by adopting nano particles

Nano containers with a shell possessing controlled release properties can be used to fabricate a new family of active coatings that can respond quickly to change the environment/integrity of the coatings. The release of corrosion inhibitors encapsulated within nano containers can prevent further corrosion. The structural evolutions and morphological characteristics of nano particles are investigated using XRD, SEM, FT-IR and AFM. The author reports an in situ encapsulation method demonstrating over an order of magnitude size reduction for the preparation of urea-formaldehyde capsules filled with a healing agent, linseed oil and corrosion inhibitors. Capsules with diameters as small as 30–40 μm are achieved using stirring techniques. Cracks in paint film were successfully healed when linseed oil and nanoparticles was released from microcapsules ruptured under stimulated mechanical action. Further linseed oil healed area was found to prevent corrosion of the substrate.     

Smart hybrid coatings for natural stones conservation

The protection of stone monuments against deterioration has recently attracted much attention from scientists. An accurate analysis of the degradation mechanisms of stones has led to the conclusion about the necessity of protection especially against the condensed water and the salts formation. In this study, the strengthening effect of nanoparticles-based treatments is compared to that exhibited by a silane commercial polymer. The surface properties of these types of smart coatings were investigated by different analytical techniques such as contact angle measurements and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS). Aimed at evaluating the coating performance, exposure tests both to UV ageing and to environmental atmospheric pollution were carried out. Diffuse reflectance spectroscopy (DRS) was employed for the CIELab colorimetric coordinates assessment; while ion chromatography (IC) was adopted to evaluate the coating capacity to avoid salts (Cl⁻, NO₃⁻ and SO₄²⁻) formation.     

纳米材料在涂料中的应用进展

综述了纳米材料在涂料中的应用及其表现的优异性能(光催化、耐老化、隐身等),介绍了纳米涂料制备中纳米材料的分散方式,指出了纳米材料在涂料中应用的一些难点。     

应用于漂洗型织物柔顺剂的新型有机硅产品

介绍了瓦克新型有机硅有效提高织物护理剂柔软性能和亲水性能的原理,并通过手感测试、消光测试、浸润测试和类毛效测试,证明作为织物护理剂的活性成分——瓦克新型有机硅所提供的优异功效。同时,通过配比不同浓度的有机硅,研究了使用量与性能之间的关系。     

The network structure of silicone release coatings

Silicone release coatings are used by the pressure-sensitive adhesive industry for labeling applications. A background discussion of silicone release coatings is presented. Methodology for determining the network structure of photolytically cured systems prepared by the cationic ring opening polymerization of an epoxy silicone fluid is described. Under typical polymerization conditions, these networks contain no unreached epoxides and have very low degrees of polymerization (D _p), indicating that termination is competitive with propagation. A method has also been developed to determine the network structure of thermally cured systems prepared by the platinum-catalyzed hydrosilylation of silicone vinyl compounds with silicone hydrides. The nature of the cross-links and the types of residual functionality have been determined and the systems have been shown to undergo a postcure.This paper was presented at the Second International Topical Workshop, Advances in Silicon-Based Polymer Science.     

Electrochemical impedance spectroscopy and corrosion behaviour of Al2O3-Ni nano composite coatings

In this paper, the results on the electrochemical impedance spectroscopy and corrosion properties of electrodeposited nanostructured Al₂O₃-Ni composite coatings are presented. The nanocomposite coatings were obtained by codeposition of alumina nanoparticles (13 nm) with nickel during plating process. The coating thickness was 50 μm on steel support and an average of nano Al₂O₃ particles inside of coatings at 15 vol.% was present. The structure of the coatings was investigated by scanning electron microscopy (SEM). It has been found that the codeposition of Al₂O₃ particles with nickel disturbs the nickel coating's regular surface structure. The electrochemical behavior of the coatings in the corrosive solutions was investigated by polarization potentiodynamic and electrochemical impedance spectroscopy methods. As electrochemical test solutions 0.5 M sodium chloride and 0.5 M potassium sulphate were used in a three electrode open cell. The corrosion potential is shifted to more negative values for nanostructured coatings in 0.5 M sodium chloride. The polarization resistance in 0.5 M sodium chloride decreases in 24 h, but after that increases slowly. In 0.5 M potassium sulphate solution the polarization resistance decreases after 2 h and after 30 h of immersion the polarization resistance is higher than that of the beginning value. The corrosion rate calculated by polarization potentiodynamic curves obtained after 30 min from immersion in solution is smaller for nanostructured coatings in 0.5 M potassium sulphate (4.74 μm/year) and a little bit bigger in 0.5 M sodium chloride (5.03 μm/year).     

Developing and testing a new generation of protective coatings for outdoor bronze sculpture

Outdoor bronze sculpture is vulnerable to acid rain-induced corrosion and the present protection schemes utilized by conservators do not provide adequate protection under many circumstances. To replace the current most common clear bronze protection systems, wax or Incralac^® with a top coat of wax, work is underway to develop different options for conservators that include new longer-lasting, more durable systems having improved corrosion protection. The use of improved matrix binders based on fluorocarbon polymers, the use of nano-sized TiO₂ for UV absorption, and the extended use of UVAs and HALS are under examination in a search for improved UV resistance and longer lived corrosion protection in clear bronze coatings. Advanced spectroscopic and electrochemical methods are being used to characterize new coatings candidates with respect to UV resistance and corrosion resistance.     

Understanding corrosion of ancient metals for the conservation of cultural heritage

Corrosion studies on ancient metallic objects are performed with the aim of evaluating their stability for a very long term. They have crossed centuries and should be transmitted in good shape to future generations. They are generally protected from aggressive conditions by a layer formed by corrosion products and this layer stability has to be checked. This work intends to show that coupling an in situ technique like Raman spectroscopy to electrochemical measurements allows a mechanism of corrosion layer formation and stability to be proposed. For bronze the beneficial presence of tin IV oxide to slow down copper corrosion is evidenced. For steel, the hypothesis of lepidocrocite reduction to be coupled with iron corrosion is infirmed.     

Sol-gel coatings for corrosion protection of 1050 aluminium alloy

The formation of organic-modified sol-gel coatings on 1050 aluminium alloy has been examined. The coatings were prepared by the combination of a completely hydrolysable precursor of tetra-n-propoxyzirconium (TPOZ), with a partly hydrolysable precursor of glycidoxypropyltrimethoxysilane (GPTMS). Influences of GPTMS/TPOZ ratio, withdrawal speed and curing temperature on the barrier-type corrosion protection of the alloy were examined. By control of process parameters and ratios of organic and inorganic moieties, crack-free sol-gel coatings with improved corrosion protection were produced on the alloy surface. Optimum protection was achieved by a coating formed with a GPTMS/TPOZ ratio of 2.7, a withdrawal speed of 180 mm/min and curing at 110 °C. The coating formed under the optimum conditions revealed good adhesion to the etched and desmutted alloy substrate. The pitting potential of the coated alloy increased significantly, indicative of an improved corrosion protection of the alloy.     

纳米硅溶胶在水性木器涂料中的应用

介绍了纳米硅溶胶在水性木器涂料中的应用情况,解析了纳米硅溶胶在水性木器涂料应用过程中受到制约的几个因素。     

重防腐涂料施工推荐方案

对适用于埋地管道和架空管道的重防腐涂料的涂装工艺流程以及普通钢材、铸铁和镀锌钢材的埋地管道、无保温层架空管道和有保温层架空管道的防腐配套方案分别进行了介绍。对其表面处理和涂装环境要求、油漆调配、施工、涂层检验以及钢结构件耐高温重防腐涂料涂装方法等进行了说明。指出了各环节注意事项。