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1.
Polybutadiene latexes made in emulsifier-free emulsion polymerization with diameters ranging from 50 to 300 nm of both unimodal and bimodal particles size distributions were analyzed by the line-start (LIST) method in a Brookhaven Disk Centrifuge Photosedimentometer (DCP). A special spin fluid was designed to be able to sediment polybutadiene since the density of the polymer is 0.89 gcm–3 and is thus less dense than its suspending medium. Density and viscosity gradients were created simply by adding five different mixtures of ethanol, water, and emulsifier in density sequence to the spinning disk. Coagulation problems caused by diluting polybutadiene latices with ethanol were overcome by using nonionic Triton X-100 surfactant. Good agreement in the average particle size and distribution as well as polydispersity between transmission electron microscope and disk centrifuge data was accomplished. The analysis time for polybutadiene latex particle sizing thus was reduced from several days to approximately 1 h. 相似文献
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IntroductionIn the last decade of this century, the carboxylation of latexes has received more andmore attention because of their practical application[']. The application includes adhesives,coatings, etc.. Many studies on the theory of carboxylation emulsion polymerization havebeen carried out. Most of these studies have focused on ideal monomer and single emulsifier inorder to simplify the system['J. But in practicable application, mixed monomers and mixedemulsifiers are often usedL3j. The… 相似文献
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Charles D. Immanuel Timothy J. Crowley Edward S. Meadows Cajetan F. Cordeiro Francis J. Doyle 《Journal of polymer science. Part A, Polymer chemistry》2003,41(14):2232-2249
This article presents a study on the engineering of multimodal distributions in semibatch emulsion polymerizations with nonionic surfactants. Various methods of producing multimodal distributions are demonstrated, and the sensitivity of the process to the properties of the reagents are analyzed. A test‐bed emulsion polymerization system, equipped with instrumentation to measure particle size distribution (capillary hydrodynamic fractionator) and monomer conversion (densitometer and flow meters), is used for this purpose. The process is monitored and controlled with an industrial distributed control system, which enables the automated operation of the process through sequential or logic controllers operating over lower level proportional integral derivative controllers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2232–2249, 2003 相似文献
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Four monodisperse latices with particle size of 75, 135, 340 and 477 nm were synthesized. The rheo-logical properties of
mixture of the monodisperse latices were inves-tigated as a function of blending ratio, and compared with those of multi-modal
latices, in a range of shear rate from 0.2 to 100 s-1. The maximum packing (highest solid contents) was observed at a weight fraction 80% of large particles with respect to total
solids contents for both bimodal and trimodal latices, and the lowest viscosity was obtained when the ratio of large to medium
to small particles was approximately 80/10/10 (by wt.). It was also demonstrated that this minimum in the viscosity is not
strongly dependent on the actual size of each kind of particles present in the multimodal latices.
Received: 22 November 1996 Accepted: 26 November 1997 相似文献
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Baijun Liu Ming Chen Huixuan Zhang 《Journal of Dispersion Science and Technology》2017,38(9):1295-1301
In this study, sub-200?nm, crosslinked latex particles with a narrow particle size distribution were prepared by one-step emulsion polymerization in the presence of particle coagulation. The relationship between the particle shape and particle coagulation was investigated by varying the time of crosslinking network structure formation and particle coagulation. Particles with irregular shapes such as doublet, triplet, and ellipsoid were obtained using divinylbenzene (DVB) and ethylene glycol dimethacrylate (EGDMA) as the crosslinking agents, because the crosslinking network structure of particles was formed before the particle coagulation. In contrast, latex particles with a uniform spherical shape were also prepared using triallyl isocyanurate (TAIC) or dihydrodicyclopentadienyl acrylate (DCPA) as the crosslinking agents by delaying the time of crosslinking network structure formation. Alternatively, uniform spherical latex particles were prepared by bringing forward the particle coagulation time using cationic initiator, 2, 2′-azobis (2-methylpropionamidine) dihydrochloride (AAPH). This study presents a new idea that would further broaden the application of particle coagulation in emulsion polymerization. 相似文献
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Cationic poly(N-isopropylacrylamide) (NIPAM) copolymer latexes have been prepared at 70°C using methylene-bisacrylamide (MBA) as the crosslinking agent,2-2′-azobis-(2-amidinopropane hydrochloride) (V50) as the initiator and in the presence of 2-aminoethyl-methacrylate hydrochloride (AEM). It was found that the concentration of AEM plays a major role in the polymerization kinetics and particle nucleation. However, too high a concentration (2–5 mol%/NIPAM) caused the latex to be polydispersed together with the production of large amounts of polyelectrolytes. The presence of surface amino groups on the final particles under the protected form was revealed both by an ultraviolet spectrometry and nuclear magnetic resonance methods. It was indirectly evidenced through the electrophoretic mobility behavior of the latex particles (below and above the lower critical solubility temperature of the poly(NIPAM)) as well as by their stability against a monovalent electrolyte. 相似文献
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A series of carboxylated acrylate copolymer latexes were prepared via two different emulsion polymerization technologies with different carboxylic‐group distribution and morphologies. The effects of the emulsifier, the initiator, and the carboxylic monomers [acrylic acid (AA) or monobutyl itaconate (MBI)] on the total conversion of the monomers and the properties of acrylate latexes and films have been investigated. The distribution of carboxylic groups (?COOH) measured by conductometric titration shows that the concentration of surface –COOH (Cs) and embedded –COOH (Cb) both increase with the increase of the amount of carboxylic monomers. For the latexes containing AA, –COOH tends to distribute on the surface of latex particles and in the aqueous phase, whereas –COOH tends to concentrate inside the core of latex particles for the latexes containing MBI. Transmission electron microscopy demonstrates that the latex particles are regular with narrow size distribution and have significant differences in morphologies when different carboxylic monomers and polymerization technologies were used. The stability of latex is satisfactory through the results of common stability and zeta potential tests. Moreover, the water absorption and contact angle experiment tests also revealed that the water resistance of the latex films is good. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Unseeded semibatch emulsion polymerization of butyl acrylate (BA) using sodium lauryl sulfate as emulsifier and potassium persulfate as initiator was carried out at the conditions where secondary nucleation was probable. This was achieved by using no emulsifier in the initial reactor charge. The effects of changes in monomer emulsion feed rate, initiator concentration and distribution, emulsifier concentration in the feed, and temperature on the evolution of particle size averages and distribution were investigated. Bimodal particle size distributions (PSD) were obtained for most of the latexes. Inhibition effects were found to be important in the development of PSD. Primary particle formation occurred through micellar nucleation, whereas secondary nucleation probably occurred through homogenous nucleation. The polydispersity index (PDI) of the latexes increased with the decreasing monomer emulsion feed rate. The application of a larger amount of initiator to the reactor charge or using a higher temperature, reduced the formation of secondary particles and resulted in a formation of an unimodal PSD. The overall steady‐state rate of polymerization was found to approach the rate of monomer addition (Rp ≈ Ra ), if the emulsifier concentration in the aqueous phase was appreciable. This is different from the correlation 1/Rp = 1/K + 1/Ra obtained for the BA semibatch process with neat monomer feed. This suggests that different rate expressions can be used for BA semibatch emulsion polymerization at different conditions. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 528–545, 2000 相似文献
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Samantha I. Applin Russell C. Schmitz Pacita I. Tiemsin Jan Genzer John W. Connell Christopher J. Wohl 《Journal of polymer science. Part A, Polymer chemistry》2017,55(13):2249-2259
Polymeric microspheres have been used in a broad range of applications from chromatographic separation techniques to analysis of air flow over aerodynamic surfaces. The preparation of microspheres from many polymer families has consequently been extensively studied using a variety of synthetic approaches. Although there are a myriad of polymeric microsphere synthesis methods, free‐radical initiated emulsion polymerization is one of the most common techniques. In this work, poly(styrene‐co‐methyl methacrylate) microspheres were synthesized via surfactant‐free emulsion polymerization. The effects of co‐monomer composition and addition time on particle size distribution, particle formation, and particle morphology were investigated. Particles were characterized using dynamic light scattering and scanning electron microscopy to gain further insight into particle size and size distributions. Reaction kinetics were analyzed through consideration of characterization results. A particle formation mechanism for poly(styrene‐co‐methyl methacrylate) microspheres was proposed based on characterization results and known reaction kinetics. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2249–2259 相似文献
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C. M. Miller E. D. Sudol C. A. Silebi M. S. El-Aasser 《Journal of polymer science. Part A, Polymer chemistry》1995,33(8):1391-1408
The mechanism of the miniemulsion polymerization of styrene was investiaged through a combination of calorimetry to monitor the polymerization rate and transmission electron microscopy (TEM) to follow the evolution of the particle size distribution. These techniques proved to be a powerful combination for gaining detailed mechanistic information regarding these polymerizations. Particle size analysis of the latexes withdrawn during the course of the reaction revealed that most of the polymer particles were formed by a relatively low conversion (i.e., 10% conversion). However, nucleation continued well past this point (to 40-60% conversion). In fact, it was observed that nucleation in miniemulsion polymerizations using cetyl alcohol continued past the maximum in the rate of polymerization. As a result of these long nucleation periods, the latex particle size distributions produced from these miniemulsion polymerizations were broader than their conventional emulsion polymerization counterparts, and were negatively skewed with a tail of small particles. The amount of negative skewing of the particle size distributions was found to decrease with increasing initiator (potassium persulfate) concentration. Finally, a correlation was observed between the length of time to the maximum polymerization rate and the breadth of the particle size distribution as reflected in the standard deviation. © 1995 John Wiley & Sons, Inc. 相似文献
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A method for characterizing the particle size and size distribution of multi-sized polymer lattices was developed by combining
quasielastic light scattering (QELS) with a centrifuge. Lattices were first fractionated by centrifugation and the different
populations of particles were separated in successive steps. The size of these particles was measured by QELS, and the mass
fraction of the particles was determined gravimetrically. The particle size and size distribution of several blends of monodisperse
lattices and two industrial multi-sized lattices have been measured by this method. The results show that the particle sizes
obtained using this method are in good agreement with the expected particle diameters, and that the relative amounts of the
different groups of particles in the blends can be accurately determined. The efficiency of centrifuge-QELS was also confirmed
by comparison with other techniques such as transmission electron microscopy (TEM), QELS, field-flow fractionation (FFF) and
capillary hydrodynamic fractionation (CHDF). However, this method is not suited for the analysis of continuous, broad distributions
or mixtures with a high number of different populations. It is better suited for distributions with a small number of families
of particles, and then can be used for preparative propose on a laboratory scale.
Received: 9 October 1996 Accepted: 7 July 1997 相似文献
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氧化-还原低温引发苯乙烯/丙烯酸丁酯细乳液聚合粒度分布和成核机理的研究 总被引:8,自引:0,他引:8
用氧化还原引发剂(NH4)2S2O8/NaHSO3研究了苯乙烯(St)/丙烯酸丁酯(BA)低温下的细乳液共聚合,细乳液单体液滴在亚微米级(100~400nm).测定了聚合过程中粒子大小及分布的变化,发现细乳液聚合随引发剂、乳化剂和共乳化剂浓度的增加,乳胶粒子尺寸变小,分布变宽,并且比相同条件下传统乳液聚合的粒子大.计算了聚合过程中粒子数变化规律及乳化剂覆盖率,讨论了细乳液与传统乳液中引发剂、乳化剂对反应过程的影响及成核机理的差异. 相似文献
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Soap‐free poly(methyl methacrylate‐ethyl acrylate‐acrylic acid or methacrylic acid) [P(MMA‐EA‐AA or MAA)] particles with narrow size distribution were synthesized by seeded emulsion polymerization of methyl methacrylate (MMA), ethyl acrylate (EA) and acrylic acid (AA) or methacrylic acid (MAA), and the influences of the mass ratio of core/shell monomers used in the two stages of polymerization ([C/S]w) and initiator amount on polymerization, particle size and its distribution were investigated by using different monomer addition modes. Results showed that when the batch swelling method was used, the monomer conversion was more than 96.0% and particle size distribution was narrow, and the particle size increased first and then remained almost unchanged at around 600 nm with the [C/S]w decreased. When the drop‐wise addition method was used, the monomer conversion decreased slightly with [C/S]w decreased, and large particles more than 750 nm in diameter can be obtained; with the initiator amount increased, the particle size decreased and the monomer conversion had a trend to increase; the particle size distribution was broader and the number of new particles was more in the AA system than in the MAA system; but the AA system was more stable than the MAA system at both low and high initiator amount. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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单分散磁性P(St/BA/MAA)微球的制备 总被引:10,自引:0,他引:10
在共沉淀法合成超细磁流体的基础上 ,以苯乙烯 (St)、丙烯酸丁酯 (BA)和甲基丙烯酸 (MAA)为共聚单体 ,在不同的介质体系中采用无皂乳液聚合法制备了单分散 ,粒径范围为 80~ 2 30nm的磁性P(St BA MAA)微球 .详细探讨了介质极性、磁流体中表面活性剂含量对磁性高分子微球粒径和单分散性的影响 .实验结果表明 ,在一定范围内随介质极性降低 ,磁性高分子微球的单分散性提高 ,随表面活性剂用量增加 ,单分散性变差 .总体来看 ,磁性高分子微球的单分散性与其表面静电斥力密切相关 ,过大或过小的静电斥力均会导致磁性高分子微球单分散性的降低 . 相似文献
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Hari Babu Sunkara Jagdish M. Jethmalani Warren T. Ford 《Journal of polymer science. Part A, Polymer chemistry》1994,32(8):1431-1435
Latexes of 100 nm diameter were synthesized by emulsifier-free copolymerization of styrene, sodium styrenesulfonate, and 1–5 wt% divinylbenzene using persulfate initiator at 91°C. A shot growth method was used to incorporate a high density of sulfonate groups. Coefficients of variation of particle size were 0.04–0.08 without resort to seed growth polymerization. Redox initiation at 40–50°C produced larger, more polydisperse, and less colloidally stable crosslinked latexes. © 1994 John Wiley & Sons, Inc. 相似文献
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Pengzong Liang Zhun Meng Zhanglin Jiang Jun Nie Yong He 《Journal of polymer science. Part A, Polymer chemistry》2010,48(24):5652-5658
The copolymer microspheres of styrene (St) and maleic anhydride (MA) were synthesized by stabilizer‐free dispersion polymerization, and the polymerization process was explored in detail. The results showed that the homopolymerization of St formed in initial polymerization period served as stabilizer, and reaction solvent of closer solubility parameter would benefit the stabilizer‐free dispersion polymerization. In addition, some principal factors affecting the microspheres size, such as reaction time, reaction temperature, monomer concentration, molar feed ratio, reaction media, and cosolvent, were investigated as well. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献