Unsteady stirring method staged used in suspension polymerization of styrene

The results of an unsteady stirring method staged, used in the suspension polymerization of styrene in a lab‐scale batch reactor, are presented. Variation of droplet size during the whole polymerization process under the unsteady stirring condition, compared with that under a steady stirring condition, was found to be small. According to the variable droplet size character, two methods were used to divide the polymerization process into four stages and the unsteady stirring method was used in only one stage of each experimental run. By these operations, the optimum operation of obtaining large particle product with uniform particle size distribution was achieved. The results suggest that controlling the droplet coalescence process is more important than controlling the initial droplet size distribution to obtain uniform final particle products. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1873–1881, 2001     

Effect of an unsteady agitation method on drop coalescence characteristics in suspension polymerization of styrene

A tracer dye technique was used to investigate the effect of the co‐reverse rotational of impeller method, the agitation speed and periodic time interval on the coalescence rate in the suspension polymerization of styrene. The results showed that the extent of coalescence decreased with the use of the co‐reverse rotational method and with the decrease in the periodic time interval or agitation speed. The results also showed that the final particle sizes became small and the particle size distributions became uniform with the use of the co‐reverse rotational method and with a decrease in the periodic time interval.     

Development of a suspension copolymerization process for bone cement production

Copolymers of MMA–STY with the suitable composition, particle size distribution, and molecular weight distribution for its medical application as bone cements have been obtained by means of suspension copolymerization. The influence of the stirring rate on the final mean particle size has been established, and the scale‐up of the process has been performed with successful results. The application of a kinetic model allowed to estimate the copolymer composition during the process, which is essential to obtain polymers with adequate properties. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 814–823, 2000     

Preparation of polystyrene/poly(methyl methacrylate) core‐shell composite particles by suspension‐emulsion combined polymerization

Suspension‐emulsion combined polymerization process, in which methyl methacrylate (MMA) emulsion polymerization constituents (EPC) were drop wise added to styrene (St) suspension polymerization system, was applied to prepare polystyrene/poly(methyl methacrylate) (PS/PMMA) composite particles. The influences of the feeding condition and the composition of EPC on the particle feature of the resulting composite polymer particles were investigated. It was found that PS/PMMA core‐shell composite particles with a narrow particle size distribution and a great size would be formed when the EPC was added at the viscous energy dominated particle formation stage of St suspension polymerization with a suitable feeding rate, whereas St‐MMA copolymer particles or PS/PMMA composite particles with imperfect core‐shell structure would be formed when the EPC was added at the earlier or later stage of St suspension polymerization, respectively. It was also showed that the EPC composition affected the composite particles formation process. The individual latex particles would exist in the final product when the concentrations of MMA monomer, sodium dodecyl sulfate emulsifier, and potassium persulfate initiator were great in the EPC. Considering the feature of St suspension polymerization and the morphology of PS/PMMA composite particles, the formation mechanism of PS/PMMA particles with core‐shell structure was proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

2‐Hydroxypropylmethacrylate based mono‐ and bifunctional gel beads prepared by suspension polymerization

Spherical and swellable gel beads in the size range 35–200 µm were prepared by suspension polymerization of 2‐hydroxypropylmethacrylate (HPMA). In the proposed method, a mixture of cyclohexanol and octanol was used as a diluent phase dispersed in an aqueous medium including poly(vinyl pyrrolidone) (PVP) as the stabilizer. The polymerization was initiated within the organic phase including the monomer and the crosslinker (ethylene glycol dimethacrylate) by an oil soluble initiator benzoyl peroxide. Spherical and swellable gel beads carrying both hydroxyl and carboxyl functional groups were also prepared by suspension copolymerization of HPMA and a water soluble comonomer (methacrylic acid). For this purpose, the suspension polymerization method proposed for HPMA was modified by using poly(vinyl alcohol) as a stabilizer instead of PVP. The effect of initiator concentration, polymerization temperature, monomer/diluent ratio, crosslinker concentration, stirring rate on yield, average size, size distribution, and carboxyl content of the HPMA based gel beads, were investigated. The swelling characteristics of the gel beads were defined. © 2000 Society of Chemical Industry     

Dependence of morphological changes of polymer particles on hydrophobic/hydrophilic additives

Fairly uniform microspheres of poly(styrene‐co‐methyl methacrylate) were prepared by employing a microporous glass membrane [Shirasu porous glass (SPG)]. The single‐step SPG emulsification, the emulsion composed mainly of monomers, hydrophobic additives, and an oil‐soluble initiator, suspended in the aqueous phase containing a stabilizer and inhibitor, was then transferred to a reactor, and subsequent suspension polymerization followed. The droplets obtained were polymerized at 75°C under a nitrogen atmosphere for 24 h. The uniform poly(styrene‐co‐methyl methacrylate) microspheres with diameters ranging from 7 to 14 μm and a narrow particle‐size distribution with a coefficient of variation close to 10% were prepared by using SPG membrane with a pore size of 1.42 μm. The effects of the crosslinking agent and hydrophobic additives on the particle size, particle‐size distribution, and morphologies were investigated. It was found that the particle size decreased with a narrower size distribution when the additives were changed from long‐chain alkanes to long‐chain alcohols and long‐chain esters, respectively. Various microspheres with different morphologies were obtained, depending on the composition of the oil phase. The spherical poly(styrene‐co‐methyl methacrylate) particles without phase separation were obtained when using an adequate amount of the crosslinking agent and methyl palmitate as an additive. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1013–1028, 2000     

表面羧基化聚丙烯酸酯多孔微球的制备及其铜离子吸附性能研究

以浓乳液作为悬浮聚合的油相,采用水（W）/油（O）/W浓乳液/悬浮聚合方法制备出了内部具有通孔结构、粒径均一的聚甲基丙烯酸叔丁酯多孔微球。结果表明,通过研究乳化剂含量、搅拌速度等参数对多孔微球的内部微孔形貌与微球粒径的影响,发现当乳化剂含量为4 %时,得到的聚合物微球内的微孔结构分布均匀;而聚合物微球的平均粒径会随着搅拌速度的增大而减小。将不同粒径的多孔微球进行酸化水解后得到了表面羧基官能化的聚合物多孔微球,利用其丰富的通孔结构实现了对铜离子（Cu²⁺）的有效吸附,当微球平均粒径介于200~300 μm时,铜离子的去除率最高,可达99.3 %。     

非稳态体系合成聚丙烯酰胺

主要研究了非稳态体系中合成聚丙烯酰胺（PAM）。非稳态体系即在油包水的环境下,通过剧烈搅拌使单体水溶液在油相中分散成小液滴进行自由基聚合,可有效地提高体系的散热效率,同时可大幅提高聚合物的固体质量分数。非稳态体系停止搅拌后,聚合物颗粒与油相可以自行分层,过滤、洗涤后就可以得到较纯的PAM。实验以聚二甲基硅氧烷为油相,探究了丙烯酰胺单体在非稳态体系中,不同聚合温度、单体水溶液浓度和pH的聚合效果,以及油水比、搅拌速度对体系内聚合物的固体质量分数、粒径的影响,并用游标卡尺精确测量颗粒的粒径。同时,用溴化法和一点法分别测量反应转化率和分子量,采用红外透射光谱和核磁共振氢谱的表征手段,对非稳态体系聚合的产品进行分析。结果表明,非稳态体系在4：3的油水比和大于300r/min的转速下,可合成转化率超过99%、溶解性优良的高分子量的聚丙烯酰胺产品颗粒。     

在无机分散剂存在下苯乙烯悬浮聚合宏观成粒的特征

以苯乙烯悬浮聚合为体系,考察羟基磷酸钙(HAP)或HAP与聚乙烯醇(PVA)复合为分散剂体系时,各种因素如分散剂浓度、油水比、搅拌速度等与瞬时液滴大小及分布之间的关系,并分析讨论瞬时液滴分散、合并的过程特征.结果表明,悬浮苯乙烯液滴聚合宏观成粒的特征与分散剂的分散机理无关,仅体现液滴分散、合并的过程特点.当采用分批加分散剂时,实验观察到瞬时液滴大小分布呈由单峰过渡到双峰,再发展成单峰分布的特征,从而找出了以分批加分散剂方式制备窄分布聚合物颗粒的理论依据.     

Effects of polymerization conditions on particle size distribution in styrene‐graphite suspension polymerization process

Suspension polymerization in the presence of graphite has been studied in order to determine the effects of some operational parameters on the particle size distribution (PSD). The results showed that, with increasing graphite content, the particle size of the polystyrene/graphite (PS/G) beads increased. Moreover, instability of the suspension polymerization system was found at high amounts of graphite. With increasing initiator concentration, the particle size of the polymer beads increased and the PSD became slightly narrower. Changing the concentration of the suspending agent proved to be an efficient way of controlling the particle size, although its increase led to a broadening of the PSD. Adding the suspending agent in two portions at different times decreased the particle size, maintained a lower concentration of suspending agent, and kept the suspension polymerization system stable. Adjusting the stirring speed proved to be a very efficient means of manipulating the PSD of the PS/G composite beads. The Sauter mean diameter decreased and the PSD was broadened with increasing stirring speed; 400 rpm was identified as an appropriate value to obtain polystyrene/graphite beads with desirable particle size and distribution. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44270.     

Polymethyl methacrylate/montmorillonite nanocomposite beads through a suspension polymerization‐derived process

Polymethyl methacrylate (PMMA) polymer beads with montmorillonite (MMT) were prepared using a suspension polymerization method for applying acrylic bone cements. The polymer beads were characterized by X‐ray diffraction and transmission electron microscopy to examine MMT dispersion. The change in the shape and size of the polymer beads due to the preparation conditions, such as stirring speed, degree of polymerization, and concentration of polyvinyl alcohol (PVA) as a suspension stabilizer, and MMT contents, etc. was observed by scanning electron microscopy and particle size analysis. The prepared polymer beads were composed of polymer‐intercalated nanocomposites with partially exfoliated MMT layers. The size of the polymer beads was decreased by increasing the stirring speed. The bead size was decreased with increasing the degree of polymerization and the concentration of PVA molecules. MMT addition into the monomer portion increased the size of the corresponding polymer beads. The bead size was slightly reduced by adding of styrene to the MMA solution. The incorporation of PMMA into monomer portion enlarged the bead size. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2340–2349, 2005     

In situ polymerization of uniform poly(urea–formaldehyde) microcapsules containing paraffins under the high-speed agitation without emulsifier

In this paper, uniform spherical poly(urea–formaldehyde) (PUF) microcapsules containing paraffins, which can be used as phase change materials for energy storage, were prepared by in situ polymerization method under high-speed agitation (≥10,000?rpm) without emulsifier. The influence of high-speed agitation on particle size of as-prepared microcapsules and the tightness of microcapsules were also investigated. The results show that, all the microcapsules have <10?μm mean particles-size and narrow-size distribution, and the mean particle size decreases with the increase of agitation rate. Furthermore, when the agitation rate is >16,000?rpm, the effectiveness of reducing particle size by high-speed stirring is not as remarkable as that of lower speed agitation. In order to gain good tightness of PUF microcapsules under the high-speed agitation conditions, the final pH value of reaction solution should be lower down compared with that of conventional agitation. In our investigation, when the agitation rate was 10,000?rpm, microcapsules fabricated at pH value <2.0 were sealed and own good tightness, however, those fabricated at pH value >2.2 were not sealed.     

Influence of the geometric factors of the experimental device used in suspension polymerization on the properties of poly(styrene‐co‐divinylbenzene) microparticles

The prediction of the final particle size for reactive systems such as the reactions of suspension polymerization is a complex matter. Thus, the preparation of very small microparticles is specially challenging, probably because of the coalescence of the polymeric beads taking place during the later stages of the polymerization. In this work, very small gel‐type styrene‐co‐divinylbenzene beads were synthesized by using a previously determined set of experimental synthesis conditions in which the stabilization of the dispersion of the monomeric droplets was ensured, and, under these conditions, the factors related to the geometry of the experimental device were modified to determine their actual effect on the final size of the microparticles. From the experimental results, a very simple and useful model was obtained that was able to predict the final size of the microparticles as a function of the values of the geometric factors of the reactor. This model indicates that the most influential factors in the final size of the microparticles are the liquid depth inside the reactor and the stirrer diameter; thus, an increase in the liquid depth produces larger particles, and, conversely, the particle size decreases when using larger stirrer diameters. Additionally, the model permits the design of polymerization experiments aimed at obtaining microparticles with a diameter smaller than 50 μm. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

基于动态光散射下纳米二氧化硅分散性的影响因素研究

纳米二氧化硅是目前应用最为广泛的一种纳米材料,但其团聚行为对粒径测量和应用效果有不利的影响。为减少纳米二氧化硅颗粒的团聚行为,应用动态光散射粒度分析方法,考察了分散方式、分散剂种类、悬浮液条件对不同纳米二氧化硅的粒径及多分散性指数（PDI）的影响规律。实验结果表明,磁力搅拌条件下,0.1%（质量分数）的PEG-2000对各类纳米二氧化硅均具有较好的分散效果;随着悬浮液pH增大,硅溶胶悬浮液粒径和PDI均呈下降趋势,是因为悬浮液pH影响了硅溶胶的溶解平衡;而固态二氧化硅悬浮液的粒径和PDI则呈先上升后下降的趋势,这是由于悬浮液pH影响了双电层结构。实际测试和应用中应注意悬浮液配制条件和纳米二氧化硅类别对粒径和PDI的影响。     

悬浮聚合法制备磁性微球的粒度分布特性

本文研究了含有微细铁黑颗粒的混合单体悬浮聚合产物的粒度分布特性。分析了分散剂、超声预分散和无机铁黑颗粒对形成粒度多峰分布的影响。结果表明,分散剂是体系中形成小颗粒的主要因素;超声波的预分散作用使悬浮体系的液滴破裂以“腐蚀破碎（erosive breakage)”为主;无机铁黑颗粒由于其表面亲水性,倾向于分布在油性单体液表面,不仅有利于悬浮液滴的“磨蚀破碎”,同时也对分散液滴具有良好的稳定作用。上述因素的共同作用使得聚合产物的粒度呈三峰分布。     

悬浮聚合法制备彩色墨粉的研究

通过悬浮聚合法制备的彩色墨粉为球形、粒径小且分布均匀。研究了水油比、PVA用量和反应搅拌速度对墨粉粒径的影响,同时研究了影响彩色墨粉粒子荷电性能及热力学性能的因素,为悬浮聚合法制备的彩色墨粉的进一步研究奠定了基础。     

界面聚合法制备阿维菌素微胶囊悬浮剂

为了摸索界面聚合法制备阿维菌素微胶囊悬浮剂的方法,探索了以水为反应介质的界面聚合法制备壁材为聚脲的阿维菌素微胶囊悬浮剂的实验方法,研究了乳化剂的种类、分散剂的种类、壁材的用量、搅拌速度、界面聚合时间等因素对微胶囊的粒径和包覆率的影响。结果表明,选用甲苯-2,4-二异氰酸酯和乙二胺作为壁材,聚合时间为4 h,搅拌速度为1000 r/min,乳化剂选择OP–10,以GY–DS02+GY–D05(m/m,3/2)作为分散剂,可制得平均粒径2μm、包覆率在90%以上的微胶囊。     

搅拌速率及其改变点对高抗冲聚苯乙烯相转变的影响

以四官能度过氧化物JWEB50为引发剂,本体接枝共聚法制备高抗冲聚苯乙烯（HIPS）。分别采用透射电镜以及相对扭矩变化对聚合体系的粒子结构、黏度变化进行研究,来分析恒定搅拌以及分段搅拌条件下聚合过程的相转变。研究发现,两种分析方法所得结果相近,相转变时的转化率随恒定搅拌速率的增大而降低。采用分段搅拌方式时,相转变前降低搅拌速率可使相转变时的转化率增大,相转变后降低搅拌速率对相转变时的转化率无影响;相转变过程对应的搅拌速率才是影响相转变的“有效搅拌速率”。上述结果对HIPS的产品性能控制具有极其重要的参考价值。     

无外加表面活性剂的苯乙烯悬浮聚合

针对传统悬浮聚合制备聚苯乙烯颗粒粒径分布宽、有效粒子收率低的问题,采用过硫酸铵/磷酸钙复合分散剂体系,在无外加表面活性剂情况进行苯乙烯悬浮聚合,制备了聚苯乙烯珠粒。通过对聚合稳定性、聚苯乙烯珠粒粒径及分布的测定与分析,考察了磷酸钙、过硫酸铵的用量及比例对悬浮聚合的影响,并分析了过硫酸胺对悬浮聚合的分散稳定机理。结果表明,当过硫酸铵和磷酸钙的用量分别为单体质量的0.01%和1.00%时,悬浮聚合体系稳定,得到的粒子透明性好,平均粒径为1.35 mm,粒径分布窄;通过改变过硫酸铵和磷酸钙的用量,可以调节聚苯乙烯珠粒的平均粒径。     

Inverse suspension polymerization of sodium acrylate: Synthesis and characterization

Crosslinked Poly(acrylic acid) was synthesized by inverse suspension polymerization. This process was investigated to determine the influence of different parameters like temperature, stirring speed, solution pH, and crosslinker concentration and to obtain the best control of the kinetics. An aqueous phase containing partially neutralized acrylic acid, crosslinking agent, and initiator agent was dispersed in an organic phase and stabilized by a surfactant. The inverse suspension was carried out in heptane as the organic phase with a different ratio of neutralization of the monomer, different crosslinker concentrations, and several stirring speeds. The polymerization was initiated by potassium persulfate (K₂S₂O₈) with N‐N′‐methylenebisacrylamide (MBA_C) as the crosslinker and sorbitan monooleate as the surfactant. The influence of several parameters on the bead size and the swelling capacity was investigated. Particle diameters ranged from 10 to 130 μm. The kinetic results obtained by differential scanning calorimetry showed that conversion and polymerization rates are a function of the solution pH, and they fell when the concentration of the crosslinking agent was higher than 7.5% in the mass of MBA_C. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2621–2630, 2000