双子表面活性剂为乳化剂时PS乳液的制备与形貌研究

以双子表面活性剂[磺酸盐型双子表面活性剂(GS)、磺酸型双子表面活性剂(GSA)]、单子表面活性剂[十二烷基硫酸钠(SDS)、十二烷基苯磺酸钠(SDBS)]作为乳化剂,采用透射电镜(TEM)、凝胶渗透色谱(GPC)等方法重点研究了GS对苯乙烯(St)乳液聚合反应、聚苯乙烯(PS)乳胶粒子的形状、尺寸大小及其分布等影响。结果表明:当m(St)∶m(GS)=5:1、乳液聚合温度为80℃时,PS乳胶粒子的平均粒径为27.92 nm,粒径分布系数为0.154;与传统单子表面活性剂相比,以双子表面活性剂为乳化剂时,所得PS乳液的粒子尺寸更小、尺寸分布更窄以及相对分子质量更高,并且乳液中出现了异形乳胶粒子。     

以单一非离子型乳化剂制备氧化聚乙烯蜡微乳液

采用高压乳化法,以氧化聚乙烯(OPE)蜡为原料用单一乳化剂制备了淡黄色、半透明的非离子型OPE蜡微乳液.考察了非离子型乳化剂的用量和乳化压力对OPE蜡微乳液的乳胶粒子粒径和粒径分布的影响.结果表明:增加乳化剂用量或增加乳化压力均有利于降低水的表面张力,形成粒径更小的OPE乳胶粒子.在乳化剂用量为OPE蜡的25％、助剂用量为乳化剂的5％,乳化时压力为(8.5±0.5)MPa时,可获得性能良好的非离子型OPE微乳液.     

细乳液聚合制备二氧化钛/聚苯乙烯复合微球及其形貌分析

采用细乳液聚合法,以γ-甲基丙烯酰氧基丙基三甲基硅烷改性的TiO2粒子为核,制备了核壳结构的TiO2/聚苯乙烯(PS)复合微球。研究了超声细乳化时间、乳化剂十二烷基硫酸钠(SDS)的浓度、TiO2用量对细乳液粒径及其分布的影响。通过纳米粒度与Zeta电位分析仪、红外光谱、透射电镜等分析手段对产物进行了表征。结果表明,随着超声细乳化时间的增加,初始液滴的粒径变小。聚合后的乳胶粒粒径随着SDS浓度的增大而减小;TiO2用量不足导致乳胶粒粒径分布变宽,且出现双峰;制备所得的TiO2/PS复合微球粒度分布较为均匀,平均直径为176.5 nm,球形规整度较好。     

聚甲基丙烯酸甲酯共聚物微乳液粒径控制研究

本文对聚甲基丙烯酸甲酯共聚物微乳液聚合工艺、单体用量、反应型乳化剂、阴离子乳化剂用量及配比对粒子大小及分布的影响进行了研究。结果表明,通过半连续滴加聚合工艺制备的微乳液乳胶粒粒径小,分布窄;随着混合单体用量的增加,乳胶粒呈现粒径逐渐变大,分布逐渐变宽趋势;随着乳化剂用量的增加,乳胶粒径呈现不断减小的趋势;随着AA用量的增加,乳液的粒径及其分布呈增大的趋势。通过采用半连续滴加法获得了粒径大小可控(42.6~51.9 nm)的聚甲基丙烯酸甲酯共聚物微乳液。     

无醇微乳化柴油的研究

采用无醇复配乳化剂,在常温下制备油包水(W/O)型微乳化柴油,并绘制柴油-乳化剂-水的拟三元相图,通过对拟三元相图分析,考察亲水亲油平衡(HLB)值对无醇微乳化剂增溶性的影响;对微乳液中的水滴粒径、表面张力进行测试,考察HLB值与掺水量对微乳液水滴粒径、表面张力的影响,并对微乳液的稳定性进行分析。结果表明:无醇复配乳化剂微乳化性能较好,乳化剂用量为10.2%时,微乳体系的增溶水量为22.1%;当复配乳化剂的HLB=7.5时,体系拟三元相图的面积最大,且制得微乳液的水滴平均粒径与表面张力最小;当乳化剂用量为5%时,含水量为12%的微乳液能保持180 d外观透明。     

PSt乳胶纳米粒子的制备

采用乳液原子转移自由基聚合法,成功制备出了聚合物乳胶纳米粒子。用光子相关光谱(PCS)和透射电子显微镜(TEM)对聚合物乳胶粒子的形貌、粒径和粒径分布进行了表征,结果表明:聚合物乳胶粒子的粒径小于100nm。研究了乳化剂的用量对乳胶粒子粒径大小的影响,研究发现:聚合物乳胶粒子的粒径随乳化剂用量的增大而减小。     

反相细乳液液滴界面聚合法制备酚醛树脂多孔微球

以热固性酚醛树脂为基体,Span-80为乳化剂,通过两步反应法--反相细乳液液滴界面聚合和热固化反应制得多孔酚醛树脂微球材料.研究了实验参数对微球粒径及形貌的影响.随着乳化剂用量增加,微球的平均粒径减小,在乳化剂用量大于1%(质量分数)后,粒径变化并不明显.采用滴加固化法可有效避免直接固化法制得的微球粒子间粘连严重、球形度不好的缺点,随着滴加时间的延长,制得的微球粒径分布变宽;使用油溶性引发剂过氧化苯甲酰(BPO)可使致孔模板单体丙烯酸(AA)在连续相和反相细乳液液滴界面间发生聚合;通过调控AA的用量,能得到表面多孔结构的酚醛树脂微球.     

无皂乳液聚合法制备亚微米级单分散聚苯乙烯微球

采用无皂乳液聚合法制备了亚微米级聚苯乙烯(PS)微球,考察了苯乙烯(St)单体浓度、引发剂过硫酸钾(K2S2O8)浓度、离子强度(氯化钠浓度)与PS微球粒径及其分布的关系。然后通过加入微量乳化剂或β-环糊精对无皂乳液聚合法进行改进,研究了改进效果。结果表明,PS微球的粒径随St单体浓度和氯化钠浓度的增加而增加、随K2S2O8浓度的增加而减小,通过调节这3种原料的浓度,可制得粒径在450~1000 nm且单分散系数小于0.08的PS微球,但产品收率较低,仅为30%左右。在相同的合成条件下,加入微量乳化剂可制得粒径在100~350 nm且单分散系数小于0.05的PS微球,产品收率提高到75%左右;加入微量β-环糊精可制得粒径在300 nm左右且单分散系数小于0.08的PS微球,产品收率可达80%且反应时间大幅缩短,由原来的12 h缩减到5 h。     

反应型乳化剂对醋-丙微皂乳液聚合及性能的影响

以醋酸乙烯酯,丙烯酸丁酯和甲基丙烯酸甲酯为原料,采用反应型乳化剂SVS与传统乳化剂（SDS,OP-10）复配,制备了具有核壳结构的醋-丙微皂乳液,讨论了软硬单体的选择,乳化剂选择及用量对乳液及涂膜性能的影响,并采用DSC,TEM等对共聚物的结构和乳液的性能进行表征。结果表明,通过半连续核壳乳液聚合方式,采用合适的反应型乳化剂复配体系,可用于制备综合性能优异,乳胶粒子粒径在80-100nm的醋-丙微皂乳液。     

核壳结构聚硅氧烷/丙烯酸酯复合乳液(Ⅰ)乳化剂对乳液聚合过程及粒径分布和粒子形态的影响

采用种子乳液半连续法合成了具有高有机硅含量的聚硅氧烷/丙烯酸酯核壳结构复合乳液,研究乳化剂的种类、复配比例及质量浓度对有机硅／丙烯酸酯壳核乳液性能与乳胶粒径、分布和结构的影响.结果表明：阴离子乳化剂十二烷基硫酸钠(SDS)、十二烷基磺酸钠(SDS-2)、十二烷基苯磺酸钠(SDBS)所合成的乳胶粒子粒径依次增大,SDS与非离子型乳化剂OP-10复配使用时,随OP-10质量分数的增加,聚合速率和转化率降低,化学稳定性增加,乳胶粒子粒径增大,分布变宽,确定了复合乳化剂的最佳配比.随复合乳化剂浓度的增加,聚合速率加快、转化率增加,乳胶粒子粒径减小而分布加宽.通过改变乳化剂加入方式可减小乳胶粒子的粒径分布.为减少壳层聚合物新粒子的产生,需严格控制乳化剂的浓度,使加入的壳层单体处于“饥饿”状态,在乳胶粒子表面富集、引发聚合,形成表层“过渡层”,最终形成核壳结构复合粒子.     

磺化超细聚苯乙烯树脂的制备

采用微乳液聚合方法合成了纳米聚苯乙烯(PS)粒子,利用H_2SO_4和有机溶剂成功地对PS微乳液进行破乳。通过固相磺化反应,得到了超细聚苯乙烯阳离子交换树脂(SSPS)。通过测量和观察SSPS的粒径分布、微观形貌,以及利用红外光谱法测定树脂的磺化度,结果表明:SSPS树脂没有发生团聚,粒径控制在2μm以内,SSPS树脂的磺化度约为83%。     

Model filled rubber. VI: Dynamic property dependence on filler particle size of rubber compounds during curing

The effect of particle size on curing kinetics and dynamic properties was examined with model filled rubber compounds containing monodisperse size crosslinked polystyrene (PS) particles synthesized from emulsifier‐free emulsion polymerization. In the process of curing, the magnitude of the dynamic moduli increased and the gelation time (GP) decreased as PS particle diameter decreased from 1.25 to 0.315 μm. GP was 5.5 hours for the pure matrix, 13 minutes for the composite containing 0.315 μ.m particles, 1.4 hours for 0.688 μm particles and more than 2 hours for 1.25 μm particles. We propose that in PS particle filled systems, the ability to form clusters was due to interparticle dispersive interactions which increase with decreasing particle size. The particle clusters function as physical crosslinks, so that the overall crosslink density was significantly enhanced. Rheologically, the dynamic moduli and gelation rate were increased with decreasing particle diameter.     

核壳型复合聚合物乳液合成工艺研究

以乳化单体加料的种子聚合技术,合成了聚丙烯酸乙酯/聚苯乙烯核壳型复合聚合物乳液.确定了种子聚合过程中乳化剂补加量与聚合单体量之间的定量关系和合理的单体加料速率.该体系所得聚台物乳液的乳胶粒是“翻转型”的核壳结构.     

Toughening modification of PS with n‐BA/MMA/styrene core–shell structured copolymer from emulsifier‐free emulsion polymerization

Core–shell structured particles, which comprise the rubbery core and glassy layers, were prepared by emulsifier‐free emulsion polymerization of poly(n‐butyl acrylate/methyl methacrylate)/polystyrene [P(n‐BA/MMA)/PS]. The particle diameter was about 0.22 μm, and the rubbery core was uncrosslinked and lightly crosslinked, respectively. The smaller core–shell structured particle–toughened PS blends were investigated in detail. The dynamic mechanical behavior and observation by scanning electron microscopy of the modified blend system with core–shell structured particles indicated good compatibility between PS and the particles, which is the necessary qualification for an effective toughening modifier. Notched‐impact strength and related mechanical properties were measured for further evaluation of the toughening efficiency. The notched‐impact strength of the toughened PS blends with uncrosslinked particles reached almost sixfold higher than that of the untoughened PS when 15 phr of the core–shell structured particles was added. For the crosslinked particles the toughening effect for PS was not obvious. The toughening mechanism for these smaller particles also is discussed in this article. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1290–1297, 2003     

Microemulsion polymerization of styrene using developed redox initiation system and study of rheological properties of obtained latices

Microemulsion polymerization of styrene was kinetically studied using a potassium persulfate (KPS)/P‐methyl benzaldehyde sodium bisulfite (MeBSBS) adduct as the developed redox pair initiation system. The rate of microemulsion polymerization of styrene was found to be dependent on the initiator, emulsifier, and monomer to the powers of 1.4, −0.77, and 0.83, respectively. The apparent Arrhenius activation energy (E_a) estimated for the microemulsion polymerization system was 6.5 × 10⁴ J/mol. Also, the morphological parameters were studied at different initiator concentrations. The rheological measurements for the prepared microemulsions were carried out to investigate the effect of the preparation parameters on the rheological behavior of the polystyrene microemulsions. The rheological flow curves of the polystyrene microemulsion latices prepared at different temperatures were carried out, and we found that the plastic viscosity and Bingham yield values of the flow curves increased with an increasing reaction temperature. That may be due to the cage effect of the prepared polymer particles, which trapped the medium molecules. The plastic viscosity increased with increasing emulsifier concentration while the Bingham yield value decreased. For the polystyrene microemulsion prepared in the presence of different initiator concentrations, the plastic viscosity and Bingham yield increased with increasing initiator concentration. This trend was found to be the same for the microemulsion latices prepared in the presence of different monomer concentrations. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1240–1249, 2000     

Janus-like polymer particles prepared via internal phase separation from emulsified polymer/oil droplets

Poly(methylmethacrylate) (PMMA) and polystyrene(PS)/PMMA particles with Janus-like morphology were prepared via the internal phase separation followed by extraction of hexadecane (HD) template. The internal phase separation was triggered by evaporation of dichloromethane (DCM) from the polymer/HD/DCM-in-water emulsion droplets, which led to the formation of HD/PMMA or HD/PMMA/PS microparticles. After extraction of HD with hexane, PMMA or PS/PMMA particles with different morphologies were produced. Poly(vinyl pyrrolidone) (PVP), sodium dodecyl sulfonate (SDS) or sodium dodecyl benzylsulfate (SDBS) was chosen as the emulsifier. The morphology depended on the HD/polymer ratio and the interfacial tensions, which were adjusted by changing the type of the emulsifier and its concentration. With poly(vinyl pyrrolidone) (PVP) emulsifier, PMMA hollow spheres were observed; while with SDS emulsifier, the particles changed from bowl-like particles to hemispheres and truncated spheres with the increase of SDS content. The morphology of PS/PMMA composite particles depended on the ratio of the two polymers. Scanning electron microscopy observation, selective etching and X-ray photoelectron spectroscopy results confirmed that PMMA tended to engulf PS component. With the increase of PMMA/PS ratio, the particles changed the morphology from capped acorn to ‘ball in bowl’ morphology. Furthermore, the particle morphology was simulated via a theoretical model based on the minimum interfacial energy of the system. The simulation results agreed with the experimental observations. Our results indicate that internal phase separation is an effective method to obtain Janus-like microparticles. Via adjusting the composition of the system and the corresponding interfacial tensions, we could tailor the polymer particles with different morphologies.     

Entry in emulsion polymerization using a mixture of sodium polystyrene sulfonate and sodium dodecyl sulfate as the surfactant

A mixture of sodium polystyrene sulfonate (NaPSS) and anionic surfactant, sodium dodecyl sulfate (SDS), was used as the emulsifier in the emulsion polymerization of styrene at 60 °C. The latexes prepared were stable, bearing the better resistance to the addition of electrolyte, and have the larger values in particle size and the higher polymerization rates than those counterparts prepared using SDS only. The NaPSS was prepared by a series of process: a concentrated cyclohexane solution of an anionically polymerized polystyrene (PS) was sulfonated with sulfuric acid at 80 °C, and then neutralized and purified through dialysis. The data of average polymer number per particle (n_p) were found useful in investigating the surfactant content effect on the entry of radicals into particles, where the latex particle size plays an important role.     

Synthesis of polystyrene/poly(butyl acrylate) core–shell latex and its surface morphology

A polystyrene (PS)/poly(butyl acrylate) (PBA) composite emulsion was produced by seeded emulsion polymerization of butyl acrylate (BA) with PS seed particles which were prepared by emulsifier‐free polymerization of styrene with potassium persulfate (KPS) under a nitrogen atmosphere at 70°C for 24 h with stirring at 60 rpm and swelled with the BA monomer in an ethanol/water medium. The structure of the PS/PBA composite particles was confirmed by the presence of the characteristic absorption band attributed to PS and PBA from FTIR spectra. The particles for pure PS and PS/PBA with a low content of the BA monomer were almost spherical and regular. As the BA monomer content was increased, the particle size of the PS/PBA composite particles became larger, and more golf ball‐like particles were produced. The surface morphology of the PS/PBA composite particles was investigated by AFM and SEM. The T_g's attributed to PS and PBA in the PS/PBA composite particles were found at 110 and ?49°C, respectively. The thermal degradation of the pure PS and PS/PBA composite particles occurred in one and two steps, respectively. With an increasing amount of PBA, the initial thermal decomposition temperature increased. On the contrary the residual weight at 450°C decreased with an increasing amount of PBA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 595–601, 2003