A New Kind of Void Soap-free P(MMA-EA-MAA) Latex Particles

Soap-free P(MMA-EA-MAA) particles with narrow size distribution were synthesized by seeded emulsion polymerization of methyl methacrylate (MMA), ethyl acrylate (EA) and methacrylic acid (MAA), and large voids inside the particles were generated by alkali posttreatment in the presence of 2-butanone. Results indicated that the size of void and the particle volume were related with the amount of 2-butanone. The generation mechanism of voids was proposed.

Preparation of multihollow P(St-MAA) particles by sequence soap-free/soap emulsion polymerization and followed by stepwise alkali/acid posttreatment

The effects of ionic emulsifier, sodium dodecylbenzene sulfate (SDBS), on the formation of the multihollow structures in sub-micron sized polymer particles produced by alkali/acid posttreatment were investigated. The original latex particles with narrow size distribution were synthesized by a new sequence emulsifier-free/emulsifier emulsion copolymerization of styrene (St) and methacrylic acid (MAA). Results indicated that the pore size decreased and the pore number increased with the increase of SDBS amount, and the morphology of the posttreated latex particles was also significantly influenced by the introducing time of SDBS in the preparation of the original latex particles, and a suitable introducing time was 3 h of polymerization. (c) 2007 Cheng You Kan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

INFLUENCES OF ACID POST-TREATMENT ON THE MORPHOLOGY OF SOAP-FREE P(MMA-EA-MAA)PARTICLES PREPARED BY SEEDED EMULSION POLYMERIZATION

Soap-free poly（methyl methacrylate-ethyl acrylate-methacrylic acid） latex particles with narrow size distribution were synthesized by seeded emulsion polymerization, and the porous particles were created by a stepwise alkali/acid treatment method. Effects of acid treatment conditions on the particle morphology were investigated. Results show that one to three pores were formed inside most of particles after post-treatment. At pH 7.0, when the treatment temperature was lower than 70℃, the size of particles and the volume of pores remained almost unchanged, and these two values increased significantly when the temperature was higher than 70℃. Both the particle size and the pore volume decreased with the increase of initial pH value and treatment time in the acid treatment. As the pH was below 4.0 and the treatment time was longer than 180 min, the particles shrunk in size.

The Growth of Latex Particles during the VAc/BA Copolymerization

The semi-continuous seeded emulsion eopolymerization of vinyl acetate and butyl acrylate was carried out with hydroxyethyl cellulose as a colloid stabilizer. The morphology of the latex particle and the relationship between the reaction time and the average particle diameter and/or the conversion ratio during the polymerization were invstiguted. The experimental results shaw that the morphology of the latex particle possesses the stable sterie construction. In the seeded polymerizution, the average particle diameter of latex decreased while the conversion ratio increased. At the second term of the emulsion copolymerization （the growth stage of particle size）, the latex particle average diameter increased with copolymerization continuously, but the instantaneous conversation ratio was not large, so it was very necessaO to properly prolong the time during the holding temperature stage.

Influences of Electrolytes on the Soap-free Emulsion Copolymerization of St-MMA-AA

Monodisperse functional polymer microspheres with different particle size and with clean surface were prepared by batch soap-free emulsion polymerization of styrene, methyl methacrylate and acrylic acid in the presence of salts, and the influences of type and amount of electrolytes on polymerization process and particle morphology were investigated. Results showed that there was a critical concentration for different electrolyte to make polymerization process and the resultant emulsion stable, and the particle size increased with the increase of electrolyte concentration. The effect of metal ions was Ca^2＋〉〉K^＋〉Na^＋〉Li^＋, and the effect of haloids was Br〉Cl〉F. Keywords： Electrolyte, soap-free emulsion polymerization, polystyrene, latex particle morphology.

STUDY ON THE FORMATION MECHANISM OF MONODISPERSE PARTICLES IN THE EMULSIFIER-FREE EMULSION POLYMEAIZATION OF METHYL METHACRYLATE AND BUTYL ACRYLATE

The formation mechanism of monodisperse polymer latex particles in the emulsifier-free emulsion polymerizationof methyl methacrylate and butyl acrylate with potassium persulfate as initiator was investigated. A multi-step formationmechanism for the monodisperse polymer particles was proposed. The nucleation mechanism is considered to be thecoagulation of the precursor particles by homogeneous nucleation when the primary particles reach a critical size with highsurface charge density and sufficient stability. It had been proved by a special experiment that the early latex particles formedby the coagulation were stable. The primary particles grow by absorbing monomers and radicals in the polymerization systemand then become colloidally unstable again due to the understandable decrease of particle surface charge density, which leadsto the aggregation of the growing particles and the formation of larger latex pedicles therefrom. Aner the nucleation period,the preferential aggregation of the smaller particles in the propagation process leads to the change of the particles towards auniform size and narrower particle size distribution. The coexistence and competition of homogeneous nucleation,coagulation, propagation and aggregation result in the increase of the polydispersity index (U = D_(43)/D_(10)) in the first Stage,then its decrease in the later stage because of the competition of propagation and aggregation, and the gradual formation ofthe monodisperse particles.

EFFECT OF PARTICLE SIZE ON THE FILMING PROCESS OF POLYSTYRENE LATEX STUDIED BY AFM

The film formation process of micro-PS particles (diameter 742 nm) and nano-PS particles (diameter 29 nm) was studied by atomic force microscopy and differential scanning calorimetry. During a step heating process, the particles were annealed for 0.5 h at each selected temperature. It was found that the deformation and interdiffusion temperatures of the micro-PS particles are ca. 120-130degreesC and 140-150degreesC, that of the nano-PS particles are 90degreesC and 100-110degreesC respectively. The DSC traces of nano-PS particles showed that there was an exothermic peak near T-g after annealing for 0.5 h at the selected temperatures below 90degreesC; otherwise, the exothermic peak disappeared after annealing at 100degreesC or above. Compared with the micro-PS particles, the sintering process of nano-PS particles occurs at much lower temperature determined by the confined state of polymer chains with higher conformational energy in nano-particles, and completes in a much narrower temperature range driven mainly by the larger total surface energy.

Determination of Size Distribution of Nano-particles by Capillary Zone Electrophoresis

A new method was developed for the determination of the size distribution of nano-particles by capillary zone electrophoresis (CZE). Scattering effect of nanoparticles was studied . This method for the determination of size distribution was statistical.

动态光散射测量仪粒度标准物质的研制

【目的】解决国内尚缺动态光散射测量法专用粒度标准物质的问题。【方法】采用微乳液聚合法合成标称粒径为40、80 nm的态光散射粒度标准物质,标准物质编号分别是QBW12001和GBW12011b;采用动态光散射多家定值法测定2种粒度标准物质的散射光强调和平均粒径,定值结果溯源至动态光散射法(ISO 22412:2017)。【结果】合成的2种粒度标准物质均匀且稳定,散射光强调和平均粒径分别为(40.0±0.5)、(80±2)nm。【结论】不同厂家生产的激光粒度仪测的散射光强度调和平均粒径一致性最好;散射光强度平均粒径一致性较好;体积平均粒径一致性较差;颗粒数目平均粒径一致性最差。

DESIGN AND CONTROL OF SOAP-FREE HYDROPHILIC-HYDROPHOBIC CORE-SHELL LATEX PARTICLES WITH HIGH CARBOXYL CONTENT IN THE CORE OF THE PARTICLES

Soap-flee hydrophilic-hydrophobic core-shell latex particles with high carboxyl content in the core of the particles were synthesized via the seeded emulsion polymerization using methyl methacrylate （MMA）, butyl acrylate （BA）, methacrylic acid （MAA）, styrene （St） and ethylene glycol dimethacrylate （EGDMA） as monomers, and the influences of MMA content used in the core preparation on polymerization, particle size and morphology were investigated by transmission electron microscopy, dynamic light scattering and conductometric titration. The results showed that the seeded emulsion polymerization could be carried out smoothly using ＂starved monomer feeding process＂ when MAA content in the core preparation was equal to or less than 24 wt%, and the encapsulating efficiency of the hydrophilic P（MMA-BA-MAA- EGDMA） core with the hydrophobic PSt shell decreased with the increase in MAA content. When an interlayer of P（MMA- MAA-St） with moderate polarity was inserted between the P（MMA-BA-MAA-EGDMA） core and the PSt shell, well designed soap-free hydrophilic-hydrophobic core-shell latex particles with 24 wt% MAA content in the core preparation were obtained.

小橡胶粒子对浓缩天然胶乳胶体性能的影响

基于鲜天然胶乳制备浓缩胶乳的过程中胶清未得到有效利用,同时小橡胶粒子有着自己的独特的性能。本文通过膏化法从胶清中获得小橡胶粒子,将小橡胶粒子胶乳(SRPL)与浓缩胶乳以不同质量比进行混合,对贮存过程中混合胶乳的胶体性能进行研究。结果表明,小橡胶粒子的相对分子质量较大,小橡胶粒子在浓缩胶乳中含量越多,混合胶乳的相对分子质量随之增大;随着小粒子含量的增加,浓缩胶乳样的平均粒径不断减少;随着贮存时间的增加,各胶乳样品中橡胶粒子的平均粒径变化不大;SRPL加入到浓缩胶乳中,对浓缩胶乳的黏度、机械稳定度、热稳定度都有影响,随着小橡胶粒子用量的增加,胶乳的黏度随之升高,胶乳的机械稳定度和热稳定性先下降,随后上升并趋于稳定。

不同附聚法聚丁二烯胶乳对ABS性能的影响

采用高分子附聚法和醋酸附聚法获得了大粒径聚丁二烯胶乳(PBL),然后与丙烯腈(AN)和苯乙烯(St)发生乳液接枝聚合反应,制得了丙烯腈-丁二烯-苯乙烯共聚物(ABS)高胶粉。将ABS高胶粉与丙烯腈-苯乙烯共聚物(SAN)共混挤出,制得了ABS树脂。研究了2种附聚法对PBL的粒子形态、粒径大小、粒径分布指数以及ABS树脂性能的影响。结果表明:与醋酸附聚法PBL相比,高分子附聚法PBL的粒径分布指数更大,普遍大于0.10,粒径均一性更差,且存在团聚现象;高分子附聚法PBL接枝后出现黏结现象;由高分子附聚法PBL所得ABS样条断面无明显的“海-岛”结构,抗冲击性能普遍较差。

纳米丁腈橡胶胶乳的制备与催化加氢

采用常规乳液聚合法结合低温间歇聚合工艺制备了丁腈橡胶胶乳,使用自制钌系催化剂对该胶乳进行乳液加氢,系统研究了催化剂用量和氢气压力对丁腈橡胶胶乳加氢效果的影响规律。结果表明,所制备丁腈橡胶胶乳的平均粒径为69.13 nm,加氢前后胶乳的粒径基本保持不变且胶乳稳定性良好;氢气压力越大催化加氢效果越好;当催化剂质量分数为0.017 5%时,可制得氢化度为99%以上且不含凝胶的产品。

阳离子淀粉/苯丙共聚物乳液乳胶粒形成过程的研究

本文以淀粉水解产物为乳化剂制备了纳米阳离子苯丙乳液,探讨了淀粉水解条件对乳液乳胶粒形成过程的影响,结果表明:所制备的共聚物乳液乳胶粒平均粒径在60-110 nm之间,且呈均匀、规整、球状颗粒。

600 nm粒径聚丁二烯胶乳的制备

以丁二烯为单体制备了小粒径聚丁二烯(PB)胶乳,并且用丙烯酸丁酯(BA)和甲基丙烯酸(MAA)制备了附聚剂。通过高分子附聚法附聚小粒径PB胶乳制备了600 nm大粒径PB胶乳,考察了附聚剂用量、电解质用量、附聚时间、附聚温度、搅拌速度等因素对大粒径PB胶乳的影响。结果表明:小粒径PB胶乳最佳粒径为100 nm,附聚剂中MAA适宜用量为20%,电解质用量为0.2%,适宜附聚时间为1~3 h,温度对附聚胶乳粒径的大小影响较小。

环氧树脂乳化剂的合成及其乳液的性能评价

以环氧树脂E-44为主要原料制备了水性环氧乳液。研究了乳化剂掺量对乳液粒径特征、贮存稳定性和离心稳定性的影响,并测试了最佳乳化剂掺量下乳液胶膜的基本性能。结果表明:随着乳化剂掺量的增加,乳液微粒逐渐向粒径更小的方向迁移,贮存稳定性与离心稳定性均逐渐提升。当乳化剂掺量大于18%时,乳液平均粒径减小幅度与稳定性提升幅度均放缓,推荐乳化剂掺量为18%~24%。乳化剂掺量为18%时的乳液胶膜固化后铅笔硬度为3 H,柔韧性为1 mm,附着力为1级,具有较好的耐水耐酸性。

种子乳液法聚氯乙烯糊树脂粒径的影响因素

探讨了种子乳液法聚氯乙烯糊树脂生产中乳化剂、引发剂、熟化温度及时间对胶乳粒径的影响,以及干燥温度和物料在干燥塔内的停留时间对二次粒子粒径的影响。

探究羧基含量对丁腈胶乳性能的影响

丁腈胶乳中引入羧基会对胶乳性能产生明显影响。探究不同羧基含量对胶乳粘度、粒径、结合腈含量、门尼粘度和物理机械性能的影响。实验结果表明,粒径和结合腈含量与羧基含量无关,粘度受羧基含量影响呈指数变化,门尼粘度和物理机械性能与羧基含量呈线性相关。

Synthesis of submicron-sized peanut-shaped poly(methyl methacrylate)/polystyrene particles by seeded soap-free emulsion polymerization

Submicron-sized peanut-shaped poly（methyl methacrylate）/polystyrene （PMMA/PS） particles were successfully synthesized by seeded soap-free emulsion polymerization of styrene on the spherical crosslinked PMMA seed particles. The obtained peanut- shaped particles showed a novel internal morphology： PS phase formed one domain which linked to the other domain having PMMA core encased by PS shell.