Chemical reactions in the course of curing of organosilicate composites and aging of organosilicate coatings

The chemical processes occurring in organosilicate composites at temperatures ranging from 20 to 1100°C are considered. The polycondensation reaction of silanol groups of modified polydimethylphenylsiloxane (PDMPS) at a temperature of 250–300°C is complicated by the interaction with vanadium oxide V₂O₅. The BaO₂ peroxide has an effect on the thermooxidative destruction of the composite. It is revealed that new glass-ceramic phases, as well as vanadium-containing and barium-containing phases, are formed in the “PDMPS-muscovite-chrysotile asbestos-aluminoborosilicate glass-ZrO₂-V₂O₅-BaO₂” system at temperatures in the range 660–1000°C.     

Vapor and water permeabilities and moisture absorbability of organosilicate coatings

A setup was designed for determining the vapor and water permeabilities of coatings and films on porous metal substrates at temperatures of 40°C and higher. The setup was used to determine the vapor and water permeabilities of five organosilicate coatings, namely, OS-51-03 (green), OS-51-03A (green), OS-11-07 (green), OS-11-07A (green), and OS-12-03 (white). The thickness of the coatings was in the range 90–130 μm. The water permeability of all the coatings under investigation was found to be higher than their vapor permeability. The lowest vapor and water permeabilities were observed for the OS-51-03 coating (the vapor permeability was 2.76 × 10^?5 mg/m h Pa). The moisture absorption of the green coatings, the OS-12-03 white composite, and the varnish coatings based on the KO-921 varnish and a mixture of the KO-915 and KO-075 varnishes were investigated. No correlation between the moisture absorption and the water permeability was revealed. It was established that the KO-921 varnish coating possesses the lowest water absorbability (0.85%).     

表面能对冰晶形貌的影响

本工作从介科学概念出发,提出了表面能对冰晶生长形貌调控的科学假设.通过在水中添加不同添加剂(蔗糖、氯化钠、表面活性剂SDS),改变水溶液的表面张力,利用激光共聚焦显微镜原位实验装置开展了冰晶生长动力学研究.结果 表明,在相同过冷度条件下,随溶液表面张力降低,冰晶形貌由具有对称性的枝状变为无序的海藻晶,这种变化在不同溶液...     

Synthesis of double pyrophosphates of sodium and chromium for pigmentation of organosilicate coatings

The conditions for synthesis of double pyrophosphate of sodium and chromium in the Cr(NO₃)₃-Na₄P₂O₇-H₂O system have been considered. The characteristic properties of organosilicate coatings of the “polyorganosiloxane-layered hydrosilicate-Cr₂O₃-rutile” composition with a finely dispersed green pigment synthesized have been determined.     

Effect of sintering on surface chemistry and surface energy of pigmented latex coatings

Drying in the absence of water (sintering) of pigmented coatings made of styrene–butadiene (SB) latex and kaolin clay at different levels of pigmentation was investigated. As found from X-ray photoelectron spectroscopy, sintered coatings showed a higher SB area percent on the surface than did latex with a high glass-transition temperature (T_g) and dried at room temperature. This was a result of latex spreading at the surface. Sintering the high-T_g coatings that were dried at room temperature caused a decrease in the surface energy. Drying in the presence of water (wet coalescing) was compared to drying in the absence of water (sintering). Even though sintered coatings were more porous and had higher gloss, no significant difference was found in the SB/clay ratio at the surface or in the surface energy above the critical pigment volume concentration (CPVC). However, at and below CPVC, the sintering process yielded a higher SB content at the surface and a lower surface energy than the wet-coalescing process. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 968–975, 2001     

Relationship between surface chemistry and surface energy of different shape pigment blend coatings

The influence of pigment shapes and pigment blends on the surface energy was investigated and compared with the surface chemistry of pigmented latex coatings. The coatings were made of different volume ratios of two pigments: plate-like kaolin clay pigment and prismatic precipitated calcium carbonate (PCC) pigment. These were mixed together with carboxylated styrene–butadiene–acrylonitrile latex (SBA), and applied over nonabsorbent substrates as well as absorbent substrates. The composition of the surface of the coatings was investigated by X-ray photoelectron spectroscopy (XPS). Two approaches were used to estimate the total surface energy and the components of the coatings: a conventional approach—“the Kaelble approach”—and a more modern approach—“the van Oss approach.” Pigment blends with different shapes and increments caused a change in the surface chemistry and the surface energy of the latex coatings. As the prismatic PCC pigment particles increased in the kaolin/SBA coating system, the SBA latex content at the coating surface increased and the total surface energy of the coating decreased. This is valid for both nonabsorbent as well as absorbent substrates. It was found that there was a strong correlation between the surface energy and the surface composition. The surface energy of the coatings estimated by the Van Oss approach was always lower than that estimated by the Kaelble approach. Colloidal interactions between pigment–pigment and/or pigment–binder were thought to play an essential role in determining the final coating surface energy and its components. Changes in the surface latex content and the surface energy due to the different pigment blends investigated were found to fit straight-line equations.     

无毒有机硅低表面能防污涂料表面性能研究

制备了不同组分的无毒低表面能有机硅防污涂料,并就其表面性能进行了研究.结果发现,颜基比能够显著影响低表面能防污涂料的表面性能;高苯基含量的PDMDPS硅油能够渗出到涂层的表面,并能够改变其表面性能;低表面能有机硅防污涂料在海水中具有良好的稳定性,经过海水的冲刷作用,污损海生物能够轻易脱落.     

A new approach to testing the flammability characteristics of surface coatings

This paper describes the background information which led to the development of a technique specifically designed to test the flammability performance of coatings applied to metal substrates. Design parameters for the new test are discussed and the prototype apparatus is described in detail. The mode of operation is explained and some results are tabulated for a range of typical coating materials. Conclusions based on the behaviour of the coatings tested are drawn in the text. These conclusions are, however, biased towards the Naval environment and application, and may not be universally applicable. The main implications of this work so far are that it is possible to improve the performance of existing fire retardant paint systems by: (1) ensuring that only the minimum thickness is applied to non-flammable substrates; (2) that adequate time is allowed for solvent elimination before deliberate exposure to risk; (3) using a white coating if possible; (4) increasing the durability of the coating to reduce the need for cosmetic overcoating, (i.e. re-coating purely to improve appearance), e.g. by using a thermosetting resinous binder in place of the conventionally used alkyd resin.     

Low surface energy coatings covalently bonded on diamond-like carbon films

In the present work, a chemical treatment with perfluorinated peroxides is proposed to obtain protective layers covalently linked to a diamond-like carbon (DLC) surface. The lubricant properties of perfluorinated compounds and the stability of the chemical modification of DLC surface simultaneously cooperate in this technical approach. Each fluorinated layer is deposed on an bare DLC surface by a dip coating application technique and the covalent linkage of the fluorinated layers is obtained by the thermal decomposition of the peroxidic moieties of the perfluorinated peroxides. Reactive perfluorinated radicals are generated close to the sp² sites of the DLC surface, allowing the formation of covalent bonds. The fluorinated peroxides used in this work belong to the class of the PFPE peroxides and to the class of the perfluorodiacyl (PFDA) peroxides. The effect of the fluorinated coatings on the DLC surface is studied using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), with contact angle (CA) measurements and, in particular, the friction forces are evaluated by means of lateral force microscopy (LFM).     

低表面能防污涂料的防污特性理论分析

从海洋污损物的粘附机理出发 ,理论上分析了低表面能防污涂料 (主要氟碳树脂防污涂料及有机硅弹性防污涂料 )防污性能的影响因素 ,并综述了低表面能防污涂料的设计思路。     

船舶用低表面能防污涂料的性能研究

以一种有机硅弹性体作基料,制备了低表面能船舶防污涂料,研究了该涂料在不同温度条件下的复涂间隔、与环氧树脂涂料的配套性和防污性能。结果表明,有机硅弹性体漆与环氧防锈漆之间的复涂间隔非常窄,在环氧底漆上喷涂有机硅弹性体时必须严格控制复涂时间;有机硅弹性体漆在高温高湿下,可更好的快速固化;该涂料可以有效防止海洋生物的生长繁殖,且不释放任何重金属有害物质。     

Changes in surface characteristics of compacted coal during isothermal decomposition

Isothermal decomposition of coal compacts was carried out in nitrogen between 200–700°, and weight loss was recorded against time. Surface area changes, measured by nitrogen adsorption, were determined at 300° and 500°. The porous structure of the coal disappeared for a while during the decomposition owing to blocking of the pores by tarry matter. The surface area then increased when this tarry matter was driven off.     

Composition and surface energy characteristics of new petroleum resins

We investigated the composition and surface energy properties—the surface free energy, acid–base and dispersive components, acid and base parameters (according to the van Oss–Chaudhury–Good method) and acidity parameter (according to the Berger method) for several types of aromatic petroleum resins (PR). We could see that the Berger, nonlinear systems, and spatial methods provide slightly different information about the acid–base properties of PRs. For acid–base properties, relevant proton content was determined for each sample by nuclear magnetic resonance spectroscopy. Correlations between the composition and surface characteristics of the studied aromatic PR have been revealed. According to the data obtained from the acid–base approach and nuclear magnetic resonance spectroscopy, we can predict the possible combinations of PR–polymer with the best interface interaction, which can lead to high mechanical properties. POLYM. ENG. SCI., 57:1028–1032, 2017. © 2016 Society of Plastics Engineers     

On the impact of accessible surface and surface energy on particle formation and growth from the vapour phase

This work investigates effects of reduced accessible surface area of aggregate particles and surface energy on titania particle formation and growth. It is taken into consideration that surface-related growth mechanisms, i.e. surface reaction and condensation, are limited to the fraction of the surface area of primary particles which is exposed to the collision with single molecules. Surface energy data determine the critical particle size with respect to evaporation and values are varied within the published range. This implies to develop a model which considers “surface shielding” and accounts for the formation of stable clusters from a supersaturated vapour due to nucleation and condensation besides considering the generation of monomers due to chemical reaction, growth due to surface reaction, agglomeration and sintering. Taking the accessible surface area into account is found out to be especially important if agglomerates contain a large number of primary particles or if agglomerate structure is rather compact. In this case, precursor consumption and primary particle growth turn out to be significantly retarded. Surface energy data are shown to be decisive with respect to the thermodynamic barrier to the formation of particles, thus to active particle formation and growth mechanisms, besides affecting sintering kinetics. Elevated surface energy data typically retard precursor consumption and favour primary particle growth.     

The formation, structure and properties of urethane-diacetylene copolymers as optical strain-sensitive surface coatings

Segmented copolyurethanes comprising ductile polyether-urethane (PE-U) and rigid diacetylene-urethane (DA-U) phases, have been prepared via a one-shot, bulk polymerisation process. Subsequent thermal treatment (100 °C/40 h) of the as-prepared linear copolymers effected solid-state topochemical reactions within the DA-U phase, producing crosslinked and intensely coloured materials. The cross-polymerised copolymers had values of T_g between −32°C and 70°C depending on composition, and were elastically isotropic with tensile moduli and strengths ranging, respectively, from 20–1800 MPa, and 8–67 MPa. The copolymers exhibited optical properties similar to those of polydiacetylene single crystals, and produced intense resonance Raman spectra. In particular, the CC triple bond stretching Raman band at ˜ 2080 cm⁻¹ was well defined and shifted to lower frequency under the application of tensile stress/strain. The copolyurethanes may be readily applied as surface coatings to various substrates, and their use as optically stress/strain-sensitive materials (optical strain sensors) is demonstrated.     

Surface pattern formation in UV-curable coatings

Some UV-curable coatings display matte surfaces after cure if they have undergone a certain period of leveling at a temperature above their glass transition temperature and the melting point of any crystalline co-reagents present in the formation. The matte finish of these coatings is due to the presence of coherent surface wrinkles after cure, which are similar in appearance to those induced by differential thermal contraction, when a metal layer is sputtered onto a rubbery or viscous substrate. However, the wrinkles in the UV-cured coatings appear under isothermal conditions, and it is, therefore, inferred that they are due to the dynamics of internal stresses induced by through-thickness variations in the extent of curing.     

Electrophoresis in the sol-gel formation of heterophase thin-film coatings

The electrophoretic precipitation of a nanodispersed BaTiO₃ powder in titanium and silicon alkoxide sol systems instead of organic solvent media has been investigated. The conditions leading to formation of heterophase thin-film coatings with uniformly distributed filler particles in the SiO₂ or TiO₂ filmforming matrices have been found. The dependence of the BaTiO₃ aggregate shape and percolation cluster type on the nature of sols has been studied.     

Physico-chemical properties of siloxane surfactants in water and their surface energy characteristics

A simple but efficient method has been followed for the synthesis of water soluble siloxane amphiphile by grafting poly(ethylene glycol) (PEG) onto the hydrophobic poly(hydromethyl siloxane) backbone. Systematic variations in the amount of PEG incorporations were carried out to get water soluble oligomers. The structural analysis of the systems was done by ¹H NMR and GPC analysis. The solution behavior of these amphiphiles was studied. The presence of nonpolar microdomains was observed at concentrations ≥0.01 g/dL for all the systems. Interestingly, I₃/I₁ ratio of pyrene fluoroprobe solubilised in aqueous solution of amphiphile suggests greater nonpolarity of microdomains in the system containing a higher PEG graft. The oligomers were shown to be surface active wherein, critical aggregation concentration decreased systematically with the decrease in the hydrophilic PEG substitutions. However, the system with a higher PEG substitution shows the close packed aggregates in the solution as suggested from the viscosity and fluorescence measurements. The contribution of polar and dispersion component towards the total surface energy was studied by the contact angle measurement by the sessile drop method.