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  • 1
    Electronic Resource
    Electronic Resource
    Surfactants with transfer agent properties (transurfs) in styrene emulsion polymerization (1995)
    Springer
    Colloid & polymer science 273 (1995), S. 999-1007 
    Details
    ISSN: 1435-1536
    Keywords: Surfactants ; polystyrene ; emulsion polymerization ; amphiphilic thiol ; transfer agents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Styrene emulsion polymerization has been carried out at 70°C using 2–2′ Azobis (2 methyl, N-(2 hydroxyethyl) propionamide as initiator and thiol-ended surfactants (I) HS-C11 H22- (OCH2 CH2) n OH withn from 17 to 90 units. The kinetics of monomer conversion, the evolution of particle size, particle size distribution, molecular weight, and molecular weight distribution have been studied. After washing the final latex, the incorporation yield of the surfactant moieties in the particles has been measured. Most of the experiments have been carried out in batch; complementary experiments used semi batch or seeded process. In some experiments the two functions of transfer agent and surfactants have been decoupled using either dodecylmercaptan (oil soluble) or thioglycolic acid (water soluble) as transfer agent and the bromine ended precursor of (I) as surfactant. The discussion of the results is chiefly oriented towards both the molecular weight distribution and the incorporation of the surfactant to the latex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00657666
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of particle size and size distribution of multi-sized polymer lattices by centrifugation plus quasielastic light scattering (1997)
    Springer
    Colloid & polymer science 275 (1997), S. 986-991 
    Details
    ISSN: 1435-1536
    Keywords: Key words Characterization ; particle size distribution ; multi-sized ; latex ; centrifuge ; quasielastic light scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050176
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  • 3
    Electronic Resource
    Electronic Resource
    Rheology of concentrated multi-sized poly(St/BA/MMA) latices (1998)
    Springer
    Colloid & polymer science 276 (1998), S. 305-312 
    Details
    ISSN: 1435-1536
    Keywords: Key words Rheology ; multi-sized ; high solid content ; latex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050244
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  • 4
    Electronic Resource
    Electronic Resource
    Efficiency of mercaptan chain transfer agents in emulsion copolymerizations. I. Influence on kinetics and microstructure. Modeling of radical desorption (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 157-168 
    Details
    ISSN: 0887-624X
    Keywords: emulsion polymerization ; reaction calorimetry ; chain transfer agents ; kinetics ; radical desorption ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of chain transfer agents (CTA) on the emulsion copolymerization of styrene and butyl acrylate was studied in a bench scale 7 L reactor. On-line estimates of conversion were obtained through the joint use of calorimetric measurements and fast gravimetric data. Off-line measurements of partial conversions, molecular weight distribution (MWD), glass transition temperature (Tg), and particle diameter were also performed in order to investigate the effect of two mercaptans (tert-butanethiol and n-dodecanethiol) on both the kinetics of the polymerization process and the microstructure-dependent properties of the copolymer. The obtained experimental results were interpreted in terms of radical desorption and diffusive limitations of the CTA between the oil droplets and the particles. A model has been derived to compute the kinetic constants, the number of radicals per particle, and both the GPC/SEC diagrams and DSC thermograms related to MWD and Tg measurements, respectively. Several batch and semibatch examples are proposed to show that these important variables are satisfactorily fit by the model. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 157-168, 1998
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Steric stabilization of polystyrene colloids using thiol-ended polyethylene oxide (1995)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 6 (1995), S. 473-479 
    Details
    ISSN: 1042-7147
    Keywords: emulsion polymerization ; steric stabilization ; polymeric transfer agent ; redox system ; polystyrene colloids ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Thiol-ended polyethylene oxide (I) has been prepared from the esterification of thioglycolic acid with monomethylether of polyoxyethylene glycol. Emulsion polymerization of styrene (and, in a few cases, methylmethacrylate as comonomer) was carried out in the presence of I using either water-soluble azo initiator or t-butylhydroperoxide. In the former case, bimodal particle size distribution was obtained while monodisperse latexes could be prepared in the latter case. Then a redox system was formed from I and t-BuOOH so that I was both an initiator and a transfer agent. Good steric stabilization of the latexes was observed. The polyethylene oxide sequence of I was partly incorporated at the surface of the latex particles, but the incorporation yield remained limited (between 7 and 18%). Most of the resdue of I remained in the serum.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1995.220060708
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  • 6
    Electronic Resource
    Electronic Resource
    Polystyrene (1)/poly(butyl acrylate/amide type functional monomer) (2) two-stage emulsion polymers. Synthesis and thermomechanical properties of latex films (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1559-1572 
    Details
    ISSN: 0887-6266
    Keywords: core-shell ; N-methylol acrylamide ; N-methylol methacrylamide ; N-isobutoxy methyl acrylamide ; butyl acrylate ; polystyrene seed ; latex ; emulsion polymerization ; structured particles ; particle morphology ; functional monomers ; latex films ; phase arrangement ; mechanical properties ; film forming ; scanning electron microscopy ; annealing ; percolation ; coalescence ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polystyrene (PS) (1)/Poly (n-butyl acrylate (BA)/amide type functional monomer) (2) structured latex particles were prepared through emulsion polymerization varying the hydrophilicity of the functional monomer employed. The second-stage polymerization kinetics, the size and morphology of latex particles, and the location of the functional groups in the final latexes were studied, in order to relate them to the thermomechanical properties of films cast from these latexes. It has been shown that, as expected, increasing the hydrophobicity leads to a better homogeneity in the copolymer formed during the second-stage polymerization, while the more hydrophilic functional monomer partly homopolymerizes in a separate phase. However, the functionalization by all the monomers used in this work, prevents the PS seed particles to form a continuous skeleton (percolated network). Further heat treatments at 140°C do not lead to the formation of a continuous PS phase as for pure BA/pure PS two-stage particles. In addition, some thermally induced crosslinking effects are discussed in relation with the functional monomer location within the particles. © 1995 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090331101
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