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1.
Series of styrene-methyl methacrylate and styrene-methacrylic acid copolymer latices have been prepared by emulsion polymerisation using polyoxyethylene nonyl phenyl ether as emulsifier and potassium persulphate as initiator. the effects of surfactant concentration and monomer composition on the ultimate particle size and conversion were investigated. The ultimate particle diameters decreased with increasing surfactant concentration, while the conversions were found to be almost independent of surfactant concentration. The ultimate particle diameters were notably decreased by increasing the content of methacrylic acid. Trace carboxyl groups were detected both in polystyrene latex and styrene-methyl methacrylate copolymer latices. The number of sulphate groups on the polystyrene latex surface was about five times that of carboxyl groups. 相似文献
2.
Ronald H. Ottewill Rajasingham Satgurunathan Frederick A. Waite Margaret J. Westby 《Polymer International》1987,19(5):435-440
Colloidally stable non-ionic polystyrene latices were prepared in aqueous media, with a narrow distribution of particle sizes, using a nonyl phenol polyethylene glycol condensate as the surface-active agent, methoxy polyethylene glycol methacrylate as the comonomer-stabiliser and ascorbic acid-hydrogen peroxide as the initiator system. For comparison, a typical charge-stabilised polystyrene latex was also prepared using an anionic surface-active agent and potassium persulphate as the initiator. These latices were characterised using transmission electron microscopy, conductometric titration and microelectrophoresis. The stability of the latices to the addition of electrolyte was examined and also the stability to freeze-thaw conditions. The glass transition temperatures of the latices were also determined. 相似文献
3.
Siti Hajjar Che Man Azanam S. Hashim Hazizan Md. Akil 《Journal of Polymer Research》2008,15(5):357-364
The graft copolymerization of styrene/methyl methacrylate (MMA) onto deproteinized natural rubber (DPNR) latex was carried
out using ammonium peroxy disulfate (N2H8O8S2) as the initiator. The presence of the grafted polystyrene (PS) and polymethyl methacrylate (PMMA) on the rubber backbone
was confirmed by FTIR spectroscopy. The effects of monomer concentrations on curing characteristics and mechanical properties
were studied. It was found that the cure time and scorch time were increased with increasing monomer concentration whereas
the torquemax–min value was slightly decreased. It was also noted that the increase in the monomer concentration resulted in stiffer rubber
with increased modulus and reduced elongation at break. 相似文献
4.
Styrene — acrylonitrile copolymer latices were prepared by emulsion polymerisation using sodium lauryl sulphate as emulsifier and potassium persulphate as initiator. The effect of sodium lauryl sulphate on the stability of these copolymer latices has been investigated using magnesium chloride as flocculating agent by measuring the rates of flocculation in the presence of various concentrations of surfactant. The values of the critical coagulation concentration (ccc) were found to increase with increasing sufactant concentration for all latices. The rates of increase in ccc with increasing surfactant concentrations were found to be almost independent of the content of acrylonitrile in the latex particles. The electrophoretic behaviour of these latices in the presence of the ionic surfactant has also been studied. The values of mobilities at ccc were found to decrease slightly with increase in the concentration of the ionic surfactant. 相似文献
5.
Nicoleta Preda Elena Matei Monica Enculescu Edina Rusen Alexandra Mocanu Bogdan Marculescu Ionut Enculescu 《Journal of Polymer Research》2011,18(1):25-30
Surfactant-free emulsion copolymerization was used to prepare methyl methacrylate-hydroxyethyl methacrylate (MMA-HEA) and
methyl methacrylate-hydroxypropyl methacrylate (MMA-HPMA) latex particles. Also, glycidyl methacrylate (GMA) was grafted onto
the surface of the preformed MMA-HPMA latex particles by seeded surfactant-free emulsion copolymerization. The copolymerization
reactions were conducted at 75 °C using a water-soluble initiator, potassium persulfate (KPS). The morphologies of copolymer
latex particles were observed using Scanning electron microscopy (SEM). The influence of different reactions parameters (the
MMA saturation concentration (Sr), the KPS concentration and the aqueous solubility of the comonomers (HEA or HPMA)) on the
particles average diameter and particles size dispersity was investigated. The experimental results showed that the increase
of initiator concentration induces in all investigated cases the increase of particles average diameter, while the presence
of HEA or HPMA as comonomers in the copolymerization reaction of MMA (1,000% Sr) lead to a decrease of particles average diameter.
At small KPS concentration the latex is monodisperse, the increase of the initiator concentration leading to the formation
of polydisperse latex. In the case of grafting reaction of GMA onto the monodisperse preformed MMA-HEA latex particles, although
the average diameter of the final particles doubles the latex remains quasi-monodisperse. 相似文献
6.
Nanoparticles of methacrylate comonomers were obtained by microemulsion polymerization by using cetyltrimethylammonium bromide as the stabilizer. Stable and bluish transparent latexes were produced from these polymerizations in which potassium persulphate was used as the initiator. The viscosity average molecular weights were in between 6 × 105 and 1.25 × 106. The average diameters of the latex particles were in the range of 20–40 nm, which was obtained by scanning tunneling microscopy. The average particle diameter increased both with an increase in the relative amount of the comonomers and their type. The glass transition temperatures of these polymers obtained by DSC were in the range of 30–103°C, and decreased with the increase in the comonomer ratio. The comonomer ratios in the final copolymers were obtained from 1H‐NMR spectra, which were smaller than those ratios used in the original recipes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 569–575, 2000 相似文献
7.
8.
The emulsion polymerization of methyl methacrylate was studied in water using potassium persulphate as initiator and dedocyl–benzene sodium sulphonate as emulsifying agent at 85°C. The effect of Egyptian delta titano magnetite ore (EDTMO) upon the activation energy and on the mean average molecular weights of the obtained polymers was studied. It was found that the viscosity average molecular weights increase with decrease of reaction temperature and initiator concentration but increase with increase of monomer concentration in the reaction medium. Some of the polymer samples prepared in absence and in presence of some (EDTMO) were separated on tlc plates according to molecular weight in binary mixture, benzene:methanol (1:1.4 by volume) at 30°C. The tlc techniques were performed to give an idea about the molecular weight distribution of the polymer samples obtained. 相似文献
9.
This article describes the effect of various process variables in the semicontinuous emulsion polymerization of methyl methacrylate. A series of poly(methyl methacrylate) (PMMA) emulsions were prepared using ammonium persulphate as initiator in absence and presence of Dowfax 2AI as surfactant. The effect of process variables such as initiator concentration, monomer concentration (solid content), surfactant concentration, reaction temperature, monomer feeding time, and holding time were systematically studied on monomer conversion, particle size, gel content, and molecular weight using a two‐level fractional factorial experimental method. Analysis of fractional factorial design revealed that surfactant concentration, monomer concentration, initiator concentration, and monomer feeding time affect all the properties. However, the surfactant concentration and the interaction effect of initiator and monomer feeding time are the key variables influencing the properties of PMMA latex. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
10.
The effects of initiator concentration, ionic strength of polymerization medium, polymerization temperature, and monomer/water phase ratio on particle size, particle size distribution and molecular weight of the resulting polymers prepared by an emulsifier-free emulsion polymerization of styrene, methyl methacrylate and glycidyl methacrylate have been studied. Optimal conditions for preparation of uniformly sized polystyrene particles larger than 1 μm have been found. An attempt to synthesize monodisperse particles of similar size from methacrylate monomers and crosslinked particles has failed. It is shown that the swelling ability of “non-activated” latex particles does not exceed 70 fold increase in the volume and strongly depends on the size of the original particles. 相似文献
11.
The final latex particle size is controlled by the concentration of polymerizable non-ionic surfactant NE-40 in the emulsion copolymerization of methyl methacrylate (MMA) and butyl acrylate (BA). The particle size decreases with increasing NE-40 concentration and increases with increasing persulphate initiator concentration. The dependence of particle size on the initiator concentration does not follow conventional Smith–Ewart theory, which is attributed to the bridging flocculation process during the particle nucleation period. The differences in the particle nucleation and growth stages and colloidal stability observed in the NE-40 and nonyl phenol-40 mol ethylene oxide adduct (NP-40) stabilized systems can be attributed to the different distribution patterns of surfactant molecules in the particles. Experimental data also indicate that the particle size decreases with increasing electrolyte concentration, or agitation speed. The total scrap, presumably caused by the bridging flocculation process, increases rapidly with increase in the NaCl concentration The amount of large flocs formed during polymerization is generally greater for the run operated at higher agitation speed. As expected, the latex products stabilized by non-ionic surfactants show excellent stability toward added sodium salt. 相似文献
12.
周应学 《化学推进剂与高分子材料》2009,7(3):46-48
由种子乳液聚合法制备了聚苯乙烯-聚甲基丙烯酸甲酯核-壳粒子。以过硫酸钾(KPS)为引发剂,分别以非离子型辛基酚聚氧乙烯醚(OP—10)和复合十二烷基硫酸钠(SDS)/OP—10(质量比为1:4)为乳化剂,合成了聚苯乙烯种子核。连续滴加甲基丙烯酸甲酯(MMA),以OP—10乳化的种子乳液可以制备粒径范围在0.16~0.67μm的核-壳粒子,当单体苯乙烯与甲基丙烯酸甲酯(St/MMA)的质量比为3:7时,所得粒径为0.18μm,粒径分散系数为0.012。而以OP-10/SDS质量比为4:1制备的种子乳液所得核壳粒子直径在毫米级。差示扫描量热研究显示,以OP-10乳化所得种子乳液制衢的复合粒子的玻璃化转变温度为97.2℃,峰形单一,表现山良好的热性能。 相似文献
13.
The influences of polymerization temperature, initiator and monomer concentrations, ionic strength of the aqueous phase, as well as ethylene glycol dimethacrylate (EGDM) co-monomer, on the kinetics of the emulsifier-free emulsion polymerization of methyl methacrylate (MMA) and on the properties of the resulting poly(methyl methacrylate) (PMMA) lattices were studied. The polymerizations were carried out using potassium persulfate (KPS) as the initiator. Monodisperse PMMA lattices with particle diameters varying between 0.14–0.37 μm and polymer molecular weights of the order 0.4 × 106 to 1.2 × 106 g/mol were prepared. The initial rate of polymerization increases with increasing temperature, KPS-MMA mole ratio, EGDM content, or with decreasing ionic strength of the aqueous phase. It was shown that the bead size can be limited by reducing the monomer concentration or by using the cross-linking agent EGDM. The ionic strength of the aqueous phase has a dominant effect on final particle diameter and polymer molecular weight. The uniformity of the latex particles increases as the temperature increases or as the initiator concentration decreases. The experimental results can be reasonably interpreted by the homogeneous nucleation mechanism of the emulsifier-free emulsion polymerization of MMA. © 1996 John Wiley & Sons, Inc. 相似文献
14.
采用苯乙烯(St)悬浮聚合过程滴加甲基丙烯酸甲酯(MMA)乳液聚合组分,进行悬浮-乳液耦合聚合(SECP), 制备大粒径聚苯乙烯-聚甲基丙烯酸甲酯(PS-PMMA)复合粒子.采用1H NMR分析方法,讨论了SECP动力学特征.St的SECP聚合速率和转化率与悬浮聚合一致;MMA聚合速率决定于乳胶粒子聚合速度和凝并在悬浮粒子表面的速度,聚合速率比常规乳液聚合速率低.由于凝并在悬浮粒子表面的PMMA乳胶粒子不再有乳液聚合特征,MMA在SECP中转化率低于同条件常规乳液聚合.分别得到乳化剂和引发剂浓度与SECP和普通乳液聚合恒速段聚合速率的关系. 相似文献
15.
Summary
A new method for determining the dominant termination mechanism in radical polymerization based on ultrasonic scission of
long chains is used to study the termination of polystyrene and polymethyl methacrylate. The method is extended to obtain
the disproportionation/combination ratio. Long dead polymer chains in solution were broken by ultrasound. The chain radicals
thus formed were then allowed to terminate in the presence and absence of a chain terminating agent (radical trap). The resulting
molecular weights are compared to find the dominant termination mechanism. It is found that the dominant mechanism in polystyrene
is combination and that in polymethyl methacrylate is disproportionation. These results are in accordance with those quoted
in the literature and obtained by other methods.The effectiveness of the radical trap used (2-chloroethyl benzene) was tested
by NMR and it was found that when the trapping agent is present it terminates 100% of the polymethyl methacrylate chains.
The time evolution of the degree of polymerization was compared to simulations based on Schmid's model. The disproportionation/combination
ratios were found for polymethyl methacrylate as 2 and for polystyrene as 1/7 respectively through simulation studies.
Received: 15 March 1999/Revised version: 12 June 1999/Accepted: 12 June 1999 相似文献
16.
用种子半连续法制备500nm的PMMA粒子 总被引:1,自引:0,他引:1
用种子半连续乳液聚合法,在油溶性氧化剂和水溶性还原剂引发剂体系中,辅以水相阻聚剂合成了粒径大于500nm的单分散聚甲基丙烯酸甲酯乳胶粒。 相似文献
17.
Styrene–acrylonitrile copolymer latices were prepared by emulsion polymerisation using sodium lauryl sulphate as emulsifier and potassium persulphate as initiator. The effect of polyoxyethylene nonyl phenyl ether on the stability of these copolymer latices has been investigated using magnesium chloride as a flocculating agent by measuring the rates of flocculation in the presence of various concentrations of surfactant. The values of the critical coagulation concentration (c.c.c.) were found to increase with increasing surfactant concentration for all latices. The rates of increase in c.c.c. with increasing surfactant concentrations were found to increase uniformly with increase in the content of acrylonitrile. The electrophoretic behaviour of these latices in the presence of surfactant has also been investigated. The values of mobilities at c.c.c. were found to decrease with increasein concentration of surfactant. 相似文献
18.
19.
Polymeric latex particles of uniform size in the range of 750 to 10 000 Å in diameter were prepared by emulsion copolymerization of methyl methacrylate, methacrylic acid, 2-hydroxyethyl methacrylate and ethylene glycol dimethacrylate, using sodium dodecylbenzene sulphonate as an emulsifier and ammonium persulphate as an initiator. With a fixed composition of monomers the carboxyl groups on the latex particles ranged from 5 × 103 to 180 × 103 per particle, but the average number per unit surface area remained within a limited variation. Human immunoglobulin G (IgG) was covalently bonded to the latex particles by either the carbodiimide or the cyanogen bromide method, taking advantage of carboxyl and hydroxyl groups, respectively. The resulting conjugates exhibited a specific agglutination with rabbit anti-human IgG and sera from rheumatoid arthritis (RA) patients. The immunolatex particles were found to be superior to those derived from nylon-6, which had been used in our previous work, and are expected to offer useful means in various immunological studies. 相似文献
20.
A facile emulsifier‐free emulsion polymerization approach was developed to fabricate highly monodisperse polystyrene (PS) spheres using potassium persulfate as the initiator and polyvinylpyrrolidone (PVP) as a stabilizer, respectively. It was found that the size of monodisperse PS spheres tends to decrease with increase of the PVP concentration, and the size of monodisperse PS spheres could be easily controlled in a wide range from 200 to 1500 nm simply by adjusting the concentration of PVP. The increase of monomer concentration led to the increase in size of monodisperse PS spheres. In contrast, the increase of initiator concentration resulted in the decrease in size of monodisperse PS spheres. These concentration changes, however, did not significantly affect the size distributions of PS spheres. It was also found that the size of monodisperse PS spheres obtained by adding the initiator at room temperature was larger than that by adding the initiator at 70°C, and the existence of inhibitor resulted in smaller PS spheres. The mechanisms in which the above factors influence the size and size distribution were discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献