Latex particle size and CPVC

Monodisperse vinyl acetate/butyl acrylate (85/15) latexes were prepared with particle sizes between 200 and 1200 nm. These were used in a simple paint formulation with TiO₂ as the only pigment. Two optical methods were used for determination of the critical pigment volume concentration (CPVC) of these paints. These are specular gloss at an incidence angle of 85 ° and CIE Z (lightness) values of a blue tinted formulation. Both methods gave coincident results for the CPVC as a function of latex particle size. Our data fit the expression X = 1.44Y^2.65 where X = number of latex particles/number of pigment particles, at CPVC and Y = diameter of pigment particles/diameter of latex particles. Earlier, Bowell reported the same exponential relation, with a different pre-exponential factor, for acrylic latexes. The common exponent is explained with a model in which the latex and pigment particles assume a condition close to minimum porosity during packing. CPVC reflects the packing of particles during the initial stages of dryness of the latex. The ‘universal’ relation reported here permits facile prediction of the effects of latex particle size on the CPVC and binding capacity in water-based paints.     

The structure of model coatings: latex-bound plastic pigment coatings

The immobilization and consolidation of model coatings based on monodisperse polystyrene (plastic pigment) and S/B latexes of known particle sizes were studied in terms of their packing volumes and the extent of latex shrinkage, which was found to increase with increasing pigment volume up to the critical pigment volume concentration (CPVC). The maximum latex shrinkage was estimated from the CPVC. Then, the porosity of model coatings was calculated based on three proposed latex shrinkage models: maximum, minimum, and linearly decreasing latex shrinkage. The number of pores and the average equivalent spherical pore diameters were subsequently calculated. The opacity and gloss of model coatings on polyester films were measured and their porosity was also determined by a simple coat weight-thickness method. The CPVC values determined by the opacity, gloss, and porosity versus PVC relationships, respectively, agreed very well with each other. The CPVCs determined by the opacity and porosity versus PVC curves were identical. The comparison between the theoretically calculated and experimental porosity values showed that the linearly decreasing value between the maximum and minimum latex shrinkage would best fit the experimental porosity data. The effect of plastic pigment particle size on the optical properties and porosity of model coatings was also studied and it was observed that the coating opacity and porosity increased with increasing plastic pigment particle size, but the gloss decreased. Additionally, a minimum crack-free temperature (MCFT) of latex-bound coatings was proposed to better predict the behaviors of latexes as pigment binders. The wet state of model coating dispersions, the surfaces of consolidated model coatings, and their internal structure were examined by both electron and atomic force microscopy, and their micrographs were found to be consistent with our immobilization and consolidation models.     

Correlation of hardness with MFFT and CPVC of latex/ceramic coatings

Hardness, porosity, and microstructure of film-forming in polyvinyl acetate/alumina coatings from aqueous suspensions were investigated with a minimum film formation temperature (MFFT) bar, Vickers hardness tester, and scanning electron microscopy (SEM). The hardness of opaque composite coatings (alumina:latex=1:2 by volume) increased abruptly at the MFFT of the latex, suggesting that the alumina particles did not change the latex film formation behavior and that the hardness measurement is an alterative to the optical criterion. Studies of coatings from latex particles that were smaller or larger than a common size of ceramic particles indicated that the composition of maximum hardness, called critical Vickers hardness concentration (CVHC), matched conventional critical pigment volume concentration (CPVC). More efficient polymer binding in the coatings from the smaller latex gave them higher peak hardness and CPVC. Department of Chemical Engineering & Materials Science, 421 Washington Ave., SE, Minneapolis, MN 55455-0132.     

The effect of the PVC/CPVC ratio on the corrosion resistance properties of organic coatings

The effect of the ratio of the pigment volume concentration (PVC) to the critical pigment volume concentration (CPVC), denoted hereafter by Λ, on the corrosion resistance properties of paint films has been investigated by a.c. impedance and potential-time measurements. Painted mild steel electrodes were studied during exposure to 3% NaCl solution for up to 90 days. Paints based on alkyd, epoxy and chlorinated rubber/chlorinated paraffin (CR/CP) were prepared containing zinc phosphate as inhibitive pigment. The paints were prepared at Λ values 0.48, 0.51, 0.55, 0.58, 0.61, 0.64 and 0.67. It is concluded that, for all systems, corrosion resistance can be affected greatly by the PVC/CPVC ratio and each system has its own optimum Λ value. The optimum percentage of inhibitive pigment in the above systems has also been evaluated.     

乳胶漆的PVC和CPVC

介绍了乳胶漆的PVC及CPVC和涂膜性能的关系;讨论了乳液的粒径大小、成膜温度等因素对CPVC的影响。     

Influence of extender type of performance of modified lamellar zinc primers

The objective of this work was to gain a deeper insight into the behavior of zinc primer, containing either lamellar zinc alone or lamellar zinc mixed with an extender by means of accelerated tests in salt spray (fog) chamber and a 100% relative humidity cabinet. Mica, kaolin, and synthetic calcium silicate were used as extenders. Several series of coatings were designed and manufactured employing the following binders: 20 cP chlorinated rubber, a vinyl copolymer, an unsaturated polymer, or an epoxy resin. A simultaneous analysis of the experimental data was performed taking into account that the best performance is attained at pigment volume concentration (PVC) values equal to or slightly lower than the critical one (CPVC). Results indicate that for every lamellar zinc primer, it is possible to select an extender of high oil absorption as the spacer of the zinc particles attaining both very good blistering resistance and anticorrosive performance.     

基料和颜料对乳胶漆光泽的影响

研究了建筑涂料中常用的相同基料、不同颜料,及相同颜料、不同基料时,漆膜光泽随颜料体积浓度（ＰＶＣ）变化的关系。随着ＰＶＣ的增加,漆膜光泽逐渐减弱,但不同的基料及颜料对漆膜光泽的变化影响程度不同。主要探讨了漆膜光泽与基料颜料的折射率、密度、粒径的关系。漆膜的光泽随着基料和颜料折射率的增大、粒径的减小而增大;随着颜料密度增加、颜料分散性降低而减弱。     

PB橡胶粒径对CPVC/PVC/ABS共混体系结构与性能的影响

采用乳液聚合技术合成了一系列不同PB橡胶粒径的ABS核壳改性剂,将其与CPVC、PVC共混,考察了CPVC/PVC/ABS共混物的结构与性能。动态力学分析表明：CPVC与PVC比例为90/10时,CPVC/PVC共混物部分相容,CPVC/PVC/ABS共混物也是部分相容;扫描电子显微镜分析其形态结构表明：共混物中ABS分散受PB橡胶粒径影响,PB橡胶粒径为113 nm的ABS在CPVC中分散最均匀。力学性能测试表明：随着PB橡胶粒径的增加,共混物的冲击强度先增大后减小,拉伸强度并无明显变化。     

氯化专用聚氯乙烯树脂颗粒特性的研究——非离子型表面活性剂和链转移剂的影响

水相悬浮法生产氯化聚氯乙烯(CPVC)时,氯化速度和氯化均匀性取决于Cl2在聚氯乙烯(PVC)颗粒中的扩散程度,因而需要有能满足氯化要求的PVC专用树脂。采用以聚乙烯醇(PVA)和羟丙基甲基纤维素(HPMC)为主的复合分散剂,考察Span系列非离子表面活性剂、链转移剂等对PVC颗粒特性的影响。实验结果表明,表面活性剂的加入使PVC树脂增塑剂吸收率、平均粒径和比表面积增大,粒径分布变窄,而表观密度下降;随着链转移剂的加入,PVC树脂增塑剂吸收率、平均粒径和表观密度都增加。     

Calcium tripolyphosphate: An anticorrosive pigment for paint

The objective of this work was to evaluate the performance of calcium tripolyphosphate in anticorrosive paints. Its anticorrosive properties were studied in pigment suspensions and in solventborne paints with 10% and 30% of the pigment by volume and a pigment volume concentration/critical pigment volume concentration (PVC/CPVC) equal to 0.8. The behavior of paints formulated with epoxy and alkyd resins was assessed by accelerated (salt spray cabinet and humidity chamber) and electrochemical tests (corrosion potential, ionic resistance, and polarization resistance). Calcium tripolyphosphate was proven to inhibit steel corrosion when incorporated in a paint film. Good protection was achieved employing only 10% by volume of the pigment, instead of 30%, as was suggested in the case of phosphates. The anticorrosion protection afforded by alkyd paints was impaired when the pigment content was increased. Epoxy paints seemed to be less sensitive to the pigment content. Centro de Investigación y Desarrollo en Tecnología de Pinturas (CIC-CONICET), Calle 52 e/121 y 122. (1900) La Plata. Argentina. Fax: 54.221.427. 1537. email: cidepint@ba.net     

Formation of Particle Layer Within Coated Slurry Characterized by Thickness Variation

An understanding of the conversion process from slurry to particle layer on a substrate is required for the precise control of the particle alignment and the material distribution in the coated slurry. In this work, variation of coated slurry thickness during drying was applied to evaluate drying and particle layer formation simultaneously. The slurry used consisted of micron-sized silica or poly (methyl methacrylate) particles and an aqueous solution of poly-vinyl alcohol (PVA) possessing differing degrees of hydrolysis. During the drying process, initially the thickness of the coated slurry was observed to decrease at a constant rate in the concentration stage, and subsequently it began to show large fluctuations due to the emergence of particles on the drying surface in the packing stage. In the final fixing stage, the fluctuation of film thickness was restricted because particles were immobilized by highly viscous concentrated PVA or by PVA molecule bridging. Based on the variation and fluctuation of film thickness, we introduced two characteristic dimensionless time ratios: (a) void fraction in a packed particle layer at the end of concentration stage; and (b) the time required to fix particle position after the end of the packing stage. We concluded that the dispersed state and settling velocity of the particle determines the space between particles in a loose packing layer, and we found that the distribution of polymers in a particle layer has a strong influence on the mobility of particles in a tightly packed layer.     

Development of a new experimental method to determine critical pigment–volume–concentrations using impedance spectroscopy

The critical pigment–volume–concentration (CPVC) of a solvent-based epoxy coating with various pigment–volume–concentrations (PVC) was analyzed. It was shown that electrochemical impedance spectroscopy (EIS) is a suitable method to detect the CPVC of coatings. The CPVC can be derived from EIS Bode plots or by fitting the EIS-curves using simple equivalent circuit diagrams. The parameters pore resistance R_P, capacitance C of the constant phase element (CPE), the relative dielectric constant _R derived from C, and the exponent n of the CPE allow the determination of the CPVC.     

Studies of polymer mobility in composite blends of poly(vinyl butyral) and alumina

Solid-state NMR and thermal analysis techniques were used to compare the mobility of poly(vinyl butyral) (PVB) in the presence and absence of both alumina filler particles and plasticizer. The relative mobility of main-chain and side-chain carbons increases in the presence of both plasticizer and alumina as seen from an increase in the average cross-polarization rates, 〈T_CH〉, and from a general decrease in the rotating frame spin-lattice relaxation rates, ^CT_1ρ. Unlike the main-chain carbons, inversion recovery cross-polarization (IRCP) data on solution cast composites show that the side-chain methyl groups in neat PVB samples are best characterized by a monoexponential cross-polarization model. However, in the presence of alumina, a fraction of the methyl groups becomes less mobile as indicated by the biexponential IRCP behavior. Polymer phase mobility also increases below the critical pigment volume concentration (CPVC) as seen from decreasing transition temperatures using dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). This is accompanied by an increase in the rigidity of a portion of the polymer phase above the CPVC as indicated by an increase in the apparent T_g, along with an increase in the mobility of another portion as indicated by the appearance of a low-temperature DMA transition. These trends are consistent with an increase in polymer chain packing heterogeneity in the presence of alumina. © 1993 John Wiley & Sons, Inc.     

Electrochemical study of protective behavior of organic coating pigmented with zinc aluminum polyphosphate as a modified zinc phosphate at different pigment volume concentrations

Electrochemical impedance spectroscopy was employed to evaluate protective performance of the solvent-borne epoxy coatings pigmented with zinc aluminum polyphosphate as a representative of phosphate-based anticorrosion compounds at different Lambda values. Furthermore, the effective ratio of the pigment volume concentration (PVC) to the critical pigment volume concentration (CPVC) was determined. To compare the function of zinc aluminum polyphosphate and zinc phosphate incorporated into coatings, electrochemical noise method as well as electrochemical impedance spectroscopy was taken into consideration. The trend and magnitude of charge transfer, coating and noise resistances plus the amplitude of the current noise fluctuation indicated superiority of the modified pigment. In order to provide an insight into the mechanism by which anticorrosion pigments improve protective behavior of coating, performance of bare metals exposed to pigment extracts was assessed through taking advantage of electrochemical impedance spectroscopy and electrochemical noise method as well.     

Das Verhalten organischer Pigmente in Polymeren

The importance of colouring matter is of prime importance in the plastics industry. The individual behaviour of organic pigments in the various polymer materials necessitates, however, on the part of the plastics manufacturer a precise knowledge of ?which pigment for which plastic”?. For example, a well known Thioindigo pigment behaves very differently in various polymer materials : In polystyrene, depending on the concentration used, it is monomolecularly dissolved, in associated solution or present as undissolved particles. In PVC, however, the good migration fastness is indicative of the insolubility of the pigment in this medium and so it is not surprising that PVC is the ideal plastic medium for this pigment. The behaviour of organic pigments in polymers is largely a function of molecular structure, e. g. intermolecular H-bonds can cause a decrease in solubility of a pigment in a polymer material, which in turn results in improved migration fastness. This is demonstrated by the improved migration fastness of variously substituted β-hydroxy naphthoic acid arylamide derivatives. Many phenomena exist however, which as yet can only be explained on the basis of the crystal structure of the pigment particles, i. e. the presence of aggregates or agglomerates. Such a phenomenon is, for example, the dispersibility of pigments in polymers. Here pigment surface, wettability by polymer and intermolecular forces are all of importance. In general, the dispersibility is better the smaller the specific surface area, as is shown for a typical quinacridone pigment. The influence of the rate of wetting on dispersibility is demonstrated using polyethylene wax. A further effect, which demonstrates the intermolecular forces between pigment and polymer, is the way in which certain pigments influence the rate of crystallization of partly crystalline polymers. This itself is connected with the shape and size of the pigment particles embedded in the polymer material. Such effects are demonstrated by measurements on various polyethylene objects. The pigment in this case was a naphthalene tetra carbonic acid derivative in both cis and trans form with widely varying specific surface areas.     

Pigment inhomogeneity and void formation in organic coatings

The conventional theory of organic coatings assumes that the volume density of pigment particles is uniform throughout the sample. The coating is then described in terms of the pigment volume concentration Π, which equals the volume of pigment divided by the volume of pigment and polymer. Voids form in the coating when the pigment particles are randomly dense-packed, which implies that Π exceeds the critical pigment volume concentration (Φ_c or that Λ=Π/Φ_c > 1. Due to fluctuations in the local density of pigment however, some regions in the coating may become randomly dense-packed even below Φ_c. Hence, voids may form in the densely-packed islands even when Λ<1. Our model for void formation contains two fitting parameters: N_o is the smallest number of pigment particles in a densely-packed cluster that may contain a void; C_q is the coarseness of the polymer space-filling in the volume of the sample not occupied by pigment. When C_q=0 and Π > 1, the polymer completely fills the interstitial volume and the void concentration vanishes. But when C_q > 0, voids may form in the densely-packed regions of the coating even below Φ_c. The coarseness parameter C_q, depends on the sample preparation, on the properties of the pigment and polymer, and on the pigment volume concentration Π. For any nonzero C_q we conclude that optical measurements will systematically underestimate Φ_c. On the other hand, since the density of polymer is less than half the density of pigment, the peak in the mass density p(Π) of the coating will overestimate Φ_c. Unless C_q is abnormally large, the void percolation threshold value Φ_v is larger than Φ_c and is a decreasing function of the coarseness C_q. The predictions of this simple model are in good agreement with experiment, and are relevant to the general class of random concentrated composites which include organic coatings, ceramic polymer slips, composite solid polymer electrodes and some forms of battery separators.     

PVC木塑复合材料的耐热增强改性

采用模压成型制备了一系列聚氯乙烯(PVC)/氯化聚氯乙烯(CPVC)配比不同、无机刚性粒子含量不同的木塑复合材料。通过力学性能测试、热变形温度测试、扫描电子显微镜观察等手段对上述木塑复合材料的耐热性及力学性能进行了研究。结果表明,CPVC和无机刚性粒子均显著改善了PVC木塑复合材料的耐热性和力学性能。与PVC木塑复合材料相比,当PVC/CPVC配比为50/50,白云母或凹凸棒土的用量为3份时,改性木塑复合材料的热变形温度分别提高了14.3℃和19.7℃,且力学性能较好。凹凸棒土对木塑复合材料的耐热增强改性效果优于白云母。     

High PVC film‐forming composite latex particles via miniemulsification,part 1: Preparation

Miniemulsification technology was used to encapsulate TiO₂ particles inside a styrene/n‐butyl acrylate copolymer with high loading levels (11 to 70% PVC (pigment volume concentration)). In this approach, a St/BA copolymer dissolved in toluene in the presence of a costabilizer (hexadecane) was mixed with a dispersion of TiO₂ particles in toluene and sonified, and then emulsified in an aqueous surfactant solution by sonification. The effect of sonification time on both the dispersibility of the TiO₂ particles in the presence of the copolymer and hexadecane and on the encapsulated particle size was investigated. Particle size analysis by dynamic light scattering showed that these composite latexes are quite stable. It was also found that as the TiO₂ loading increased from 11 to 43% PVC, the particle size of the TiO₂ dispersion decreased while the polymer‐encapsulated TiO₂ particle size increased. The effect of surfactant concentration (sodium lauryl sulfate, SLS) on the encapsulated particle size was investigated using four different SLS concentrations in the 11% PVC system. The results showed that as the SLS concentration increased the particle size decreased, as expected. Also it was found that the minimum surfactant concentration that gives stable encapsulated TiO₂ particles is above 10 mM SLS. The role of HD in the recipe was studied for an artificial latex containing no TiO₂ and one prepared at 11% PVC, in terms of particle size before and after solvent stripping, and its effect on the T_g. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4504–4516, 2006     

Studies on polymer latex films: I. A study of latex film morphology

Polymer films have been formed from poly (butyl methacrylate) latices prepared by surfactant-free emulsion polymerisation. The latices having also been cleaned by microfiltration constitute model colloid particles and hence form ‘model’ films. A novel freeze fracture replication and transmission electron microscopy technique was employed to study film morphology. It demonstrated the presence of interparticle boundaries between latex particles deformed into dodecahedra and the particle packing order without the need for a staining technique. The time and temperature of film formation and storage was shown to affect the degree of particle coalescence. Solvent cast films were also studied for comparison purposes.     

Study of the kinetic stability of pigmented polyurethane solutions

The effect of the nature of a pigment and the degree of its dispersity on the kinetics of particle sedimentation in pigmented polyurethane solutions is studied. The studies are performed using the sedimentation method. The effect of the adsorption modification of a pigment surface with surfactants on the stability of polyurethane solutions is also investigated, as well as the structure of coatings containing different pigments. It is established that, in coatings where carbon black with high surface activity is used, pigment particles are surrounded by adsorption layers with a larger packing density of structural elements relative to the polymer bulk. It is shown that the structure of coatings depends to a considerable extent on the procedure of component compatibility during the preparation of pigment paste.