Effect of extenders with narrow and broad particle size distributions on the properties of coatings

Extenders are manufactured in a wide range of finenesses enabling paint formulators to influence specific properties of the finished paint. It is necessary to know the "granulometry" or particle size distribution of the extender to select the appropriate one to achieve the desired properties. Two extenders with practically the same top cut, but one with a broad particle size distribution curve, and the other one with a narrow or "steep" particle size distribution curve, were compared in four different coating systems. The extender with a narrow particle size distribution offered some advantages over the finer one with a broader particle size distribution. The technical advantages of using such extenders over those with broad curves but similar finenesses, are in particular: ease of dispersion, higher opacity, haze-free gloss, shortening of the drying time, and spacing properties for titanium dioxide. Revised version of a paper presented at 1998 FSCT Annual Meeting Technical Program, October 14–16, 1998, New Orleans, LA. Technical Services Laboratory, Paints & Surface Coatings, CH-4665 Oftringen/Switzerland. Contact in the USA: OMYA, Inc., Alpharetta, GA 30022.     

Effect of Ti particle size on mechanical and tribological properties of TiCN coatings prepared by reactive plasma spraying

Titanium carbonitride (TiCN) coatings were successfully fabricated by reactive plasma spraying (RPS) from agglomerated Ti-graphite feedstock. The effect of Ti particle size on the microstructure and phase composition of plasma sprayed TiCN coatings was investigated. The Vickers microhardness of coatings was measured by a Microhardness Test and the corresponding Weibull distribution were also analyzed. In addition, a pin-on-disk tribometer was employed to determine the trobological properties of coatings. Results show that all the coatings consist of TiC_xN_1−x (0 ≤ x ≤1) and minor Ti₂O phases, and the amount of Ti₂O increases with the increase of Ti particle size. The Weibull distribution of Vickers microhardness of all the coatings shows apparent scattering, while the coating sprayed with Ti particle size of 28 µm exhibits a relatively even distribution. Compared with the coating sprayed with Ti particle size of 14 µm or 48 µm, the coating sprayed with Ti particle size of 28 µm exhibits improved mechanical and tribological properties, which are attributed to the high microhardness and strong bonding strength.     

Influence of the particle size on the mechanical and electrochemical behaviour of micro- and nano-nickel matrix composite coatings

The aim of this work is the production and characterization of composite nickel matrix electrodeposits. Pure nickel and composite nickel matrix deposits containing either micro- or nano-particles of silicon carbide were prepared using a Watts type bath. The electrodeposition was carried out under both direct and pulse current conditions at different frequencies. With the same quantity of powder in the bath, the embedded micro-powder content is about 25–30%w while the nano-powder content is always less than 1%w. The mechanical properties of the nano-composites increases despite the low ceramic content. SEM micrographs of the microstructure and XRD-line profile analysis show that the presence of ceramic powder in both baths changes the crystallisation process leading to enhanced mechanical properties even at ceramic contents less than 1%, as in the nano-composite case. The presence of the ceramic phase and changes in the microstructure both decrease the mass loss during abrasion by up to 70% for micro-composites and 45% for nano-composites.     

Effect of particle size distribution on stress development and microstructure of particulate coatings

The role of pigment particle size distribution on stress and microstructure development was studied for coatings prepared from aqueous suspensions of ground calcium carbonate (GCC) and latex binder. Stress development was monitored using a modified beam deflection technique under controlled environment. Microstructure was characterized by scanning electron microscopy (SEM) and cryogenic SEM. For coatings containing only GCC particles and no latex, a wide particle size distribution resulted in a significant particle size gradient in the cross-sectional microstructure and irregular stress development. With latex addition, uniform microstructures were observed in coatings with either wide or narrow GCC particle size distribution. GCC/latex coatings prepared using GCC with a wide particle size distribution developed a higher stress than those prepared using GCC with a similar average particle size but a narrow particle size distribution. The higher stress is related to the particle packing that results in smaller pore sizes and larger capillary pressures that drive compaction. In coatings prepared with the same GCC particles but different latex binders, the stress and cracking behavior of the coating depends on the latex properties.     

Tribological studies of electroless nickel/diamond composite coatings on steels

In this study, a commercially available process of electroless nickel plating with co-deposited diamond powders was applied to a steel substrate as an intermediate layer prior to diamond deposition by MPECVD. The diamond films show excellent adherence, since they are strongly bounded to the diamond particles, deeply anchored into the electroless plated nickel matrix. A synergism effect of electroless nickel plating and MPECVD diamond growth are discussed. The electroless nickel plate which can be hardened itself by the precipitated phosphide phases after the heat treatment is an efficient diffusion barrier against the inter-diffusion of iron from the steel substrate and carbon from CH₄. A more continuous and smoother diamond film can be formed on the outermost surface. The results of tribotesting indicated that each step in the process of composite formation significantly lowers the friction coefficient (μ), especially the secondary layer of electroless nickel plate (~ 1 μm) is particularly effective and possesses a steadily low value of μ, which has promise for tribological applications. The secondary nickel layer could enhance the adherence of diamonds in the metal matrix, and be responsible for the better continuity of the top diamond film.     

Effect of particle size and grafting density on the mechanical properties of polymer nanocomposites

End-grafting polymer chains to nanoparticles in polymer nanocomposite is a widely used method to disperse inorganic particles in a polymeric matrix in order to improve the material properties. While many fundamental studies have investigated how various factors influence the dispersion or aggregation of the nanoparticles, the effect of grafting on the resulting material properties has received considerably less attention. In particular, the effect of nanoparticle curvature and grafting density on the mechanical properties in polymer nanocomposites remains elusive. In this study, we develop a coarse-grained model of a polymer glass containing grafted nanoparticles and examine the resulting effects on the mechanical properties. By carefully designing the parameters of our polymer nanocomposites model, we can maintain dispersion of the nanoparticles whether they are grafted with polymer chains or not, which allows us to isolate the effect of end-grafting on the resulting mechanical properties. We examine how the nanoparticle size and grafting density affect the elastic constants, strain hardening modulus, as well as the mobility of the polymer segments during deformation. We find that the elastic constants and yield properties are enhanced nearly uniformly for all of our nanocomposite systems, while the strain hardening modulus depends weakly on the grafting density and the nanoparticle size.     

Effect of particle size on mechanical properties of epoxy resin filled with angular-shaped silica

Effect of particle size on the mechanical properties of cured epoxy resins has been studied. Resin was filled with angular-shaped silica particles prepared by crushing fused natural raw quartz. These particles were sorted into six groups having different mean sizes ranging from 2–47 μm. Flexural and compressive moduli of the cured epoxy resin slightly decreased with decrease in the particle size of the silica, whereas tensile modulus slightly increased. Flexural and tensile strengths increased with decrease in particle size. Fractured surfaces were observed using scanning electron microscopy to clarify the initiation point of fracture.     

橡胶粒子粒径对ABS树脂结构与性能的影响

采用乳液技术在聚丁二烯(PB)和丁苯橡胶(SBR)乳胶粒子上接枝共聚苯乙烯和丙烯腈合成了PB质量分数为60％的ABS接枝粉料,将其与苯乙烯-丙烯腈共聚物(SAN树脂)熔融共混获得了一系列不同组成和结构的丙烯腈-丁二烯-苯乙烯共聚物(ABS树脂),研究了橡胶粒子粒径对ABS树脂的形态结构、力学性能的影响.结果表明,PB和SBR橡胶粒子的粒径分别为0.3μm和0.05 μm左右时,橡胶粒子的粒径对ABS树脂力学性能的影响十分显著.单独采用小拉径SBR橡胶粒子不能有效地增韧SAN树脂,而大粒径PB橡胶粒子对SAN树脂具有良好的增韧效果.     

Effect of particle size on the mechanical properties of reaction bonded boron carbide ceramics

In the present communication, effect of boron carbide particle size on the mechanical properties such as hardness, fracture toughness and flexural strength of reaction bonded boron carbide (RBBC) ceramics were investigated. RBBC composites were produced by the reactive infiltration of molten silicon into porous preform containing boron carbide and free carbon. Boron carbide powders with mean particle size of 18.65 μm, 33.70 μm and 63.35 μm were chosen for the RBBC composites. The experimental results show that hardness increases from 1261.70±64.74 kg/mm² to 1674.90±100.00 kg/mm² and fracture toughness drops from 5.76±0.26 MPa m^1/2 to 3.4±0.37 MPa m^1/2. However, flexural strength decreases from 403.41±5.70 MPa to 256.15±25.05 MPa with the increase in particle size. Indentation induced cracks in RBBC are mainly median type and number of cracks increase with the increase of starting particle size.     

激光粒度仪在涂料分析测试中的应用

介绍了激光粒度仪的测试原理,讨论了两种分散方法分析测试试样时仪器参数的设置原则。并以锌粉的分析测试为例,对两种分散方法的测试结果进行了比较,提出了获得准确粒度分析结果的测试条件。     

不同粒度金刚石微粉对PCD微结构与性能的影响

在烧结温度为1550℃、合成压力为5.7士0.1GPa、烧结时间180s时,采用国产六面顶压机进行了微米级聚晶金刚石的合成试验,研究不同粒度(10μm、5μm、2μm,1μm)的金刚石微粉对合成的PCD微结构与性能的影响.分别采用了SME、XRD和Raman对合成的PCD样品的微结构进行表征,并测试其耐磨性和耐热性.结果表明,PCD试样中均形成了D-D结合,且当金刚石原料粒度为2μm时,样品中存在石墨;随着金刚石原料粒度的减小,Co元素的扩散更加均匀,合成PCD样品的磨耗比越小,耐热温度越低.     

Effect of vibro-milling time and calcination condition on phase formation and particle size of nickel niobate nanopowders

The effect of milling time on the phase formation and particle size of nickel niobate, NiNb₂O₆, powder synthesized by a solid-state reaction via a vibro-milling technique was investigated. Powder samples were characterized using DTA, XRD, SEM and laser diffraction techniques. It was found that the smallest particle size of 32 nm was achieved at 25 h of vibro-milling after which a higher degree of particle agglomeration was observed on continuation of milling to 35 h. In addition, by employing an appropriate choice of the milling time, a narrow particle size distribution curve was also observed.     

Effect of microbubbles and particle size on the particle collection in the column flotation

Particle-bubble collection characteristics from microbubble behavior in column flotation have been studied theoretically and experimentally. A flotation model taking into account particle collection has been developed by particle-bubble collision followed by the particle sliding over the bubble during which attachment may occur. Bubble size and bubble swarm velocity were measured as a function of frother dosage and superficial gas velocity to estimate the collision and collection efficiency. Separation tests were carried out to compare with theoretical particle recovery. Fly ash particles in the size range of <38, 38-75, 75-125, >125 mm were used as separation test particles. Theoretical collision and collection efficiencies were estimated by experimental data on the bubble behavior such as bubble size, gas holdup and bubble swarm velocity. Collection efficiency improved with an increase of the bubble size and particle size but decreased in the particle size up to 52 mm. Also, flotation rate constants were estimated to predict the optimum separation condition. From the theoretical results on the flotation rate constant, optimum separation condition was estimated as bubble size of 0.3-0.4 mm and superficial gas velocity of 1.5-2.0 cm/s. A decrease of bubble size improved the collection efficiency but did not improve particle recovery.     

Effect of the particle size and particle agglomeration on composite membrane performance

One of the most used methods for studying the rigidification of polymer matrices in composite membranes is differential scanning calorimetry. Glass‐transition temperatures give information about filler–polymer interaction and the rigidity of the polymer matrix. In this study, optical microscopy, mechanical property testing, and X‐ray diffraction, instead of differential scanning calorimetry, were used to study both poly(ether imide) (PEI) matrix rigidification and activated carbon–PEI interfacial adhesion. Then, the permselective properties of the mixed matrix membranes were interpreted. The change in rigidity in these composite membranes was in agreement with the decrease in the flexibility of the composite materials as the filler content increased. This fact was confirmed by the tension and elongation data and X‐ray diffraction (DRX) measurements. However, the Young's modulus value decreased as the carbon content increased. There was an increase in all of the gas permeability coefficients measured in the composites compared with that of PEI. As the particle size grew, a low particle surface area and a poor interfacial adhesion were observed. The carbon agglomerates acted as sites of stress concentration within the polymeric matrix. This decreased the intercatenary distances and limited the movement of polymer chains, which resulted in a more rigid matrix. The higher selectivity of the H₂/CH₄, H₂/CO₂ and O₂/N₂ systems observed in the composite membranes revealed that there were both a preferential sorption of certain gases in the carbon surface or carbon–polymer interface and a molecular size exclusion, which were responsible for that increment, despite the poor interfacial adhesion. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

二氧化硅磨料粒径分布对蓝宝石化学机械抛光的影响

针对蓝宝石晶圆化学机械抛光(CMP)高去除速率和高抛光质量的要求,对比了分别采用单一粒径、连续粒径和混合粒径的SiO2磨料对蓝宝石晶圆的抛光效果.结果表明,将粒径为120 nm的40％(质量分数)硅溶胶与粒径为30 nm的20％(质量分数)硅溶胶按体积比8:2混合作为磨料对蓝宝石晶圆进行CMP时,去除速率最高,抛光后蓝宝石晶圆的表面粗糙度(Ra)低至0.158 nm,无明显的划痕、划伤等缺陷.     

高性能聚脲弹性体防水涂料的制备及成型工艺对力学性能的影响

通过分子结构设计,成功合成了高性能聚脲弹性体涂料,通过黏度-温度曲线选定了最佳的喷涂工艺参数。采用拉伸、红外光谱、凝胶含量和扫描电镜等表征手段,研究了成型工艺对材料力学性能的影响。结果表明,采用喷涂工艺成型制备聚脲样片的拉伸强度值为25MPa,而采用溶液涂膜法制备聚脲样片的拉伸强度为54.2MPa,综合分析后认为,二者拉伸强度的差异是由于喷涂及固化过程中在聚脲样片内部产生了大量气孔所致,并通过扫描电镜照片进行了验证。     

On the role of an unconventional rigid rodlike cationic surfactant on the styrene emulsion polymerization. Kinetics, particle size and particle size distribution

An unconventional amphiphile (1-[ω-(4′-methoxy-4-biphenylyloxy)octyl]pyridinium bromide, PC8) was used as surfactant in the emulsion polymerization of styrene. At low surfactant concentration (6, 12 or 36 mmol l⁻¹), curves of polymerization rate versus conversion obeyed the typical behavior characterized by intervals I, II and III. However, at high concentration (48 or 72 mmol l⁻¹) the interval II was not observed. The particle size distribution curves showed two families of polymer particles, indicating the participation of at least two mechanisms of particle formation, one being the simple micellar nucleation and the other probably the coagulative nucleation of precursor particles. The latter was considered to occur during the nucleation interval.     

Adhesion of diamond coatings on steel and copper with a titanium interlayer

Adherent diamond coatings on steel and copper were obtained by using a titanium interlayer. The adhesion of the coatings was evaluated by scratch tests and micro-indentation tests. The diamond coating on steel exhibited a much higher critical load than on copper, as revealed by the scratch tests. However, an observation on the back of the scratch-delaminated film and on the corresponding substrate surface showed that the detachment occurred between the diamond film and the titanium interlayer. Therefore, the difference in the critical scratch load is due mainly to a substrate effect, making it difficult to compare the adhesion of different coatings.On the other hand, Knoop indentation tests showed interesting results: a small indentation load causes round spallation in the film with no observable crack. An exponential sink-in deformation under the indentation is proposed, y=−a exp(−bx). The coating adhesion is considered to be equivalent to the deformation stress at the edge of the spallation zone. The adhesion of diamond coatings on steel and copper with a titanium interlayer is evaluated quantitatively using this model. Furthermore, a thermal quench method is proposed to estimate the coating adhesion. The results found are in agreement with the indentation model.     

Effect of particle size distribution on the performance of two-component water-reducible acrylic polyurethane coatings using tertiary polyisocyanate crosslinkers

A two-component waterborne polyurethane system with a 250 g/l VOC has been formulated to meet the performance requirements of the automotive refinish market. This paper discusses an experimental study to develop a two-component water-reducible polyurethane coating using a tertiary aliphatic polyisocyanate crosslinker with dry times, appearance, and reactivity equivalent to a two-component solventborne system. The effects of acrylic polyol monomer composition, glass transition temperature (T_g), and hydroxyl concentration on drytime and ambient cure film performance have been determined. The effects of particle size distribution of the formulated coating on performance were examined. It was found that smaller particle size provides overall improved film properties, i.e., faster dry time, increased hardness, and faster development of solvent resistance. The relationships of both acrylic polyol composition and formulation variables on the particle size distribution are discussed. Presented at 76th Annual Meeting of FSCT in New Orleans, LA, on Oct. 11–16, 1998. 1937 West Main Street, Stamford, CT 06904.     

Preparation of composite electrochemical nickel–diamond and iron–diamond coatings in the presence of detonation synthesis nanodiamonds

In the work it is shown that addition of individual pure detonation synthesis nanodiamonds to nickel- and iron-plating electrolytes results in an increase in microhardness (2–3.5 times) and wear-resistance (3–6 times) and a decrease in porosity (3–4 times) of a coating. The use of nanodiamonds as a component of diamond-containing blend (a semi-product of synthesis of the nanodiamonds) results in deterioration of all of the above properties for a nickel–diamond coating and great improvement of the same properties for an iron–diamond coating.