Studies for a new generation of acrylic binders for exterior wood coatings

Modern acrylic binders for water-based exterior wood coatings should give films which are tack-free, hard and blocking resistant and at the same time very flexible to guarantee a long service life. This study shows that multiphase acrylic emulsions with controlled particle morphology give a means to overcome these contradictory requirements. Binder parameters such as polarity, particle size and surface functionality as well as the type and quantity of surfactants used in the process also have a strong influence on fundamental wood coating properties, such as water protection, blushing resistance, viscosity, wet adhesion and durability.     

High performance anticorrosive coatings based on new phosphonic methacrylate terpolymers

This article describes the synthesis of new methacrylic‐phosphonated monomer PM(B) obtained from the diethyl‐1,2‐epoxide‐propyl 2‐phosphonate opening by methacrylic acid in presence of the tetrabutyl ammonium bromide as catalyst. Both its homopolymerization and copolymerization with methyl methacrylate (MMA) have been achieved in acetonitrile at 80 °C in the presence of 4,4′‐azobisisobutyronitrile. The determination of the reactivity ratios evidenced a statistical copolymer structure. Then, terpolymer of low degree of polymerization and composed of MMA, butyl methacrylate (BuMA) and PM(B) was synthesized and showed a high thermal stability (no degradation before 300 °C). This phosphonate terpolymer was incorporated in an acrylate formulation, polymerized under UV‐light, and the resulting coating was subjected to the salt spray test. High resistance towards corrosion was observed as no corrosion occurred even after 1100 hrs to the salt spray test. This result was also confirmed by Electrochemical Impedance Spectroscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5090–5100, 2009     

Nitrogen-rich plasma-polymerized coatings on PET and PTFE surfaces improve endothelial cell attachment and resistance to shear flow

Low seeding efficiency and poor cell retention under flow-induced shear stress limit the effectiveness of in vitro endothelialization strategies for small-diameter vascular grafts. Primary-amine-rich plasma-polymerized coatings (PPE:N) deposited using low- and atmospheric-pressure plasma discharges on PET and PTFE are evaluated for their ability to improve endothelial cells' kinetics and strength of attachment. PPE:N coatings increase cell adhesion and adhesion rate, spreading, focal adhesion, and resistance to flow-induced shear compared with bare and gelatin-coated PET and PTFE. In particular, about 90% of the cells remain on coated surfaces after 1 h exposure to shear. These coatings, therefore, appear as a promising versatile approach to improve cell seeding strategies for vascular grafts.     

Fabrication of Fe3O4@SiO2 nanocomposites to enhance anticorrosion performance of epoxy coatings

SiO₂‐coated Fe₃O₄ (Fe₃O₄@SiO₂) nanocomposites were prepared by sol–gel method, and the anticorrosion performance of composite coatings was discussed. The structure of the Fe₃O₄@SiO₂ nanocomposites was verified through Fourier transform infrared, X‐ray diffraction, and scanning electron microscopy. Composite epoxy coatings with same concentrations of Fe₃O₄ and Fe₃O₄@SiO₂ were measured by scanning electron microscopy contact angle meter. More importantly, the Fe₃O₄@SiO₂ nanocomposites not only obtained a homogeneous dispersion and compatibility in epoxy resin but also exhibited an obvious superiority in enhancing the anticorrosion performance of epoxy coatings. Furthermore, the anticorrosion mechanism of Fe₃O₄@SiO₂/epoxy composite coating was tentatively discussed. Copyright © 2015 John Wiley & Sons, Ltd.     

Axisymmetric peel test for adhesion measurement of polymer coatings

A novel axisymmetric peel test for measuring the adherence of coatings has been developed. The method utilizes a thin elastomeric membrane as a support for an uncured coating. Application of a pressure differential across this membrane brings the coating into contact with the substrate of interest, allowing it to cure while in contact with the substrate. The peel energy of the fully cured coating is determined by the measured peel force and by the geometry at the peeling front. Use of the test is illustrated with a model glassy polyurethane coating on an aluminum substrate. We show that the test is ideally suited for testing the effects of substrate preparation and cure conditions on the resultant coating adhesion. The upper limit on the adhesion strength that we were able to measure was about 50 J/m², a limit that is determined by the tensile strength of the coating. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Grain characterization of nanostructured TiN coatings prepared by reactive plasma spraying

Nanostructured TiN coatings were prepared by reactive plasma spraying, and the microstructure and the grain morphology of the coatings were analyzed by XRD, SEM and TEM. The results show that the coatings were mainly composed of TiN and Ti₃O phases (other phases were not detected), and they had the typical sprayed lamellar structures with few pores being visible. In the planar view, nanoscale grains with particle diameters ranging from 60 to 120 nm were observed in the coatings, and both fine equiaxial and columnar grains were found in some zones of the coatings. But in the cross‐sectional view, the TiN coatings were mainly composed of columnar grains, with no qualities of equiaxial grains being found. Thus, it can be concluded that the TiN coatings are composed of columnar grains, and the columnar grains are nanostructural, equiaxial grains in their cross‐section. Copyright © 2007 John Wiley & Sons, Ltd.     

Two mechanisms of the fragmentation of thin coatings on rubber substrates

The fragmentation of thin platinum films, nanometers thick, deposited on isoprene rubber and poly(ethylene terephthalate) substrates was studied. Light and scanning electron microscopy was used. The length of a fragment depends on the thickness of the coating film and the tensile stress applied to the specimen. An equation describing the tensile stress in an elastic coating fragment is derived. The equation is used to analyze the fragmentation of a coating film under tension. Two stages of fragmentation are distinguished. At low strains, when the length of the fragments is lower than the ineffective length, fragmentation is occasional, as determined by defects in the coating. At high strains, the mechanism of fragmentation changes to the division of the fragments into halves. The division repeats when the load is doubled. During this stage of fragmentation, the crack density is proportional to the applied stress and reversibly proportional to the thickness of the coating. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 10–18, 2002     

Effects of coating composition and surface pre-treatment on the adhesion of organic-inorganic hybrid coatings to low density polyethylene (LDPE) films

Organic-inorganic hybrid coatings, obtained through the sol-gel chemistry from tetraethoxysilane and polyethylene-poly(ethylene glycol) block copolymer, have been prepared in different compositions and applied to untreated and plasma treated LDPE films by spin coating. The mechanical properties of the coatings and the adhesion between coating and substrate have been characterized by fragmentation test. An increase in coating strength, elongation at break and adhesion has been observed with increasing the organic fraction in the hybrid coating. A plasma treatment of the LDPE surface, just before the application of the coating, lead to an increase of the adhesion between coating and substrate (interfacial shear strength), leaving almost unaffected coating strength and strain at fragmentation onset.     

The influence of surface treatment on the tensile and tribological properties of wood fiber‐reinforced polyimide composite

In this paper, the effect of coupling agent surface treatment of wood fiber on tensile and tribological property of wood fiber‐reinforced thermoplastic polyimide (PI) composites was experimentally investigated. Experimental results revealed that coupling agent surface treatment could effectively improve the interfacial adhesion between wood fiber and PI matrix. Compared with the untreated wood fiber/PI composite, the coupling agent‐treated composite had better interfacial adhesion. The fracture surfaces and worn surface of samples were investigated by scanning electronic microscopy to analyze the effects of surface treatment methods.     

Studies on the effect of the size of waterborne polyurethane nanoparticles on properties and performance of coatings

Present research work was performed utilizing prepolymer mixing process and varying NCO:OH mole ratios. Waterborne polyurethane dispersions (WBPUs) were prepared from phosphorous containing polyester polyol and isophorone diisocyanate. These prepolymers were neutralized by triethylamine followed by the addition of optimized quantity of water. Diethylenetriamine was used as a chain extender. These WBPUs were further coated on mild steel panels, glass panels, and wood. Chemical structure was confirmed using instrumental methods. Microtrac particle size analyzer was used to analyze the particle size. An impact of the size of nanoparticles on the performance of coatings was explained by different testing methods.     

Comparison of the adhesion forces in single and double-layer coatings on the MEMS surfaces by JKR and DMT models

In many medical and industrial applications, some strategies are needed to control the adhesion forces between the materials, because surface forces can activate or hinder the function of the device. All actual surfaces present some levels of roughness and the contact between two surfaces is transferred by the asperities on the surfaces. The force of the adhesion, which depends on the operating situations, can be influenced by the contact region. The aim of the present study is to predict the adhesion force in MEMS surfaces using the JKR and DMT models. The surfaces of the coating material in this research consisted of the single-layer coating of Gold and Silver, and the double-layer coating of TiO₂/Gold and TiO₂/Silver on the silicon (100) substrates. The depositing was done by the thermal evaporation method. The results showed that the double-layer coating developed by the new deposition method helped the reduction of the adhesion forces between the probe tip and the specimen surface. The predicted adhesion forces between the probe and the specimens with DMT and JKR models were compared with the experimental results. For all specimens, the simulated data by applying the JKR theory were in a good agreement with the adhesion force experimental values.     

Inhibition of cellulases by impurities in Steam-Exploded wood

Steam explosion of hardwood chips produces impurities that reduce the activity and stability of cellulases. Washing the exploded wood with water removes the inhibitors and permits hydrolysis equivalent to that with purified cellulose. IREX Fellow on leave from Moscow State University.     

Preparation of VPS and PVD coatings for metallographic and TEM investigations

The aim of the first part of the paper is to give some advice for the faultless metallographic preparation of vacuum plasma sprayed coatings. Several coating/substrate combinations using metals, alloys and ceramics were investigated to derive some general rules. The second part deals with a preparation technique for cross-sections- of physical vapour deposition coatings. This technique was optimized for TiN and Ti(C, N) coatings on hardmetals which were examined in an analytical transmission electron microscope.     

Effect of graphene oxide-based nanostructured coatings on the electrical performance of cross-linked polyethylene

The electrical withstand capabilities of polyethylene films and ad hoc prepared PE sandwich samples containing controlled cavities inside, both coated with organic-inorganic hybrid thin layers also modified with graphene oxide, have been investigated. While films have been subjected to breakdown tests, samples with cavities have been exposed to partial discharge (PD) induced electrical ageing, valuating the different evolution of the damage due to PD activity. Experimental results highlight the positive effect brought by the presence of the hybrid coating and in particular of the coating containing also graphene oxide on the electrical performance of the samples.     

Influence of velocity and surface temperature of alumina particles on the properties of plasma sprayed coatings

In this paper are described the main characteristics of the plasma spraying process of alumina deposits, i.e., the temperature and flow field of the plasma jets obtained with the classical spraying torches, the injection of the particles into the plasma jet, the particle surface temperature and velocities in the plasma (measured for calibrated alumina particles), and the coating generation. The measurements on the alumina particles are compared with the predictions of a mathematical model. The experimental and computed particle velocities are in rather good agreement. However, this is not the case for the particle surface temperature. Possible reasons for the discrepancy are proposed (influence of the carrier gas, thermophoretic forces, and poor penetration of the particles into the plasma core even for an injection velocity twice that of the optimal calculated one, as shown by recent measurements). Finally the correlations between the particle velocities and surface temperature, and the properties of the alumina coating (porosity, crystal structure, mechanical properties) are studied.     

锰基氧化物与冷等离子体协同催化氧化VOCs研究进展

挥发性有机化合物(VOCs)对环境的严重污染和对人体的危害引起了人们的重视。冷等离子体与催化剂耦合形成的协同效应可显著提高VOCs低温转化速率,减少二次污染和降低能耗,具有较好的应用前景。协同催化效果主要取决于催化剂物化性能,可通过调控催化剂的组成、粒径和结构改善协同催化活性。锰基氧化物因其具有较高的储氧能力、稳定的晶体结构、较好的氧气活化性能和良好的抗中毒能力等优点而被广泛应用于冷等离子体协同催化净化VOCs的应用研究。通过金属离子掺杂调控锰基氧化物的离子价态、氧迁移率和氧气吸附量,是改善催化剂与等离子体协同催化性能主要方法。本文总结了近年来锰基氧化物与冷等离子体协同催化氧化VOCs的研究进展,主要包括氧化锰晶型、分散度和掺杂金属离子对协同催化氧化VOCs的活性影响趋势及反应机理。分析冷等离子体与锰基氧化物催化剂协同氧化VOCs中存在的问题并对其发展前景进行了展望。     

木材中五氯苯酚的检测方法研究进展

综述木材中五氯苯酚的检测方法。高效液相色谱法不需要复杂的衍生化操作,具有良好的选择性与较高的灵敏度,是高沸点、热稳定性较差的五氯苯酚较理想的分析方法,该方法简便,检测成本较低,易于在检测机构及企业推广应用;采取乙酰衍生化,应用毛细管色谱柱进行分离的气相色谱法(电子捕获检测器)是目前五氯苯酚常用的检测方法,该方法简单,但易存在假阳性结果且无法识别;电极法可避免使用有机溶剂,减少环境污染,但苦味酸根离子有明显干扰;气相色谱-质谱法可以准确地进行定性定量分析,有效地去除基质干扰,该方法选择性好,灵敏度高,检出限低,具有良好的发展前景。     

Enhancement of tribological performance of epoxy bulk composites and composite coatings using micro/nano fillers: a review

Epoxies in the form of bulk and coatings have been used throughout the years for a wide spectrum of applications in various industries ranging from aerospace, oil and gas, petrochemical and marine to several others. Their use in tribological applications, those involving a range of contact conditions and where the requirement is exceptionally low wear and friction coefficient, is often limited by the properties of the pristine epoxy matrix such as low load bearing capacity combined with low thermal conductivity values. These properties have been improved by the addition of nano‐fillers, and numerous studies have been carried out in this regard. This paper presents a detailed review of the works carried out in the recent years where addition of nano‐fillers to formulate epoxy‐based composites and coatings has shown a substantial improvement in wear and friction properties thereby enhancing their potential to be used in demanding tribological applications such as solid lubricant in bearings, as wear‐resistant protective coatings in rotating and stationary equipment and for applications in the construction industry such as floorings and airport runway repairs. Copyright © 2016 John Wiley & Sons, Ltd.     

Recycle of the cellulase— enzyme complex after hydrolysis of steam-exploded wood

Cellulases can be recovered in high yields by contacting fresh substrate with hydrolysis filtrate and by extraction of spent hydrolysis residue with pH 7 buffer. Recycled enzymes give hydrolysis rates about equal to those with fresh enzymes. Steam-exploded wood (SEW) is washed with water to remove sugars and byproducts from breakdown of hemicellulose, and recycle of enzymes proceeds better if lignin is also removed prior to hydrolysis. Oven drying of SEW interferes with recycle, and the recovery of enzymes is only one-half of that with SEW that is kept moist. Effectiveness of enzyme recovery depends on the completeness of hydrolysis, as determined by contact time and enzyme concentration. For cost-effective operation, enzyme should not be recovered until appreciable filter paper activity and carboxylmethylcellulase activity appear in the hydrolysate.     

Preparation of fluorine containing hybrid coatings: investigation of coating performance onto ABS and PMMA substrates

UV‐curable fluorinated organic–inorganic hybrid coatings were prepared by the sol–gel technique. Perfluorinated urethane modified alkoxysilane was synthesized by the reaction between perfluoro alcohol and 3‐isocyanatopropyltrimethoxysilane. The prepared formulations were applied onto poly(methyl methacrylate) (PMMA) and acrylonitrile butadiene styrene (ABS) panels and polymerized by UV‐curing. The properties of the hybrid coatings such as hardness, chemical resistance, thermal stability, surface morphology, double bond conversion, and also contact angle measurements were investigated. Contact angle measurements have shown that the addition of fluorinated silane precursor to the hybrid system improved the water repellency and increased the contact angle from 65° to 106°. Copyright © 2009 John Wiley & Sons, Ltd.