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  • latex  (3)
  • kinetics  (2)
  • CR: G1.8  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Approximation by finite differences of the propagation of acoustic waves in stratified media (1989)
    Springer
    Numerische Mathematik 54 (1989), S. 655-702 
    Details
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N05 ; CR: G1.8
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary In this paper, we analyze the approximation of acoustic waves in a two layered media by a finite diffrences variational scheme. We examine in particular the approximation of the guided waves. We point out the existence of purely numerical parasitic phenomena and quantify the numerical dispersion relative to guided waves.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01396488
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  • 2
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Key words Characterization ; particle size distribution ; multi-sized ; latex ; centrifuge ; quasielastic light scattering
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003960050176
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  • 3
    Digitale Medien
    Digitale Medien
    Polystyrene(1)/poly(butyl acrylate-methacrylic acid)(2) core-shell emulsion polymers. Part I. Synthesis and colloidal characterization (1991)
    Springer
    Colloid & polymer science 269 (1991), S. 812-824 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Polystyrene seed ; poly(butyl acrylate-methacrylic acid) shell ; particle mophology ; location of carboxylic groups ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Polystyrene (PS) (1)/Poly(n-butyl acrylate (BA)-methacrylic acid (MAA)) (2) structured particle latexes were prepared by emulsion polymerization using monodisperse polystyrene latex seed (118 nm) and different BA/MAA ratios. Three main aspects have been investigated: i) the polymerization kinetics; ii) the particle morphology as a function of reaction time; iii) the distribution of MAA units between the water phase and the polymer particles. The amount of MAA in the shell copolymer was found to be the main factor controlling the particle shape and morphology. The shape of the structured particles was, generally, non-spherical, and the shape irregularities increased as a particles was, generally, non-spherical, and the shape irregularities increased as a function of reaction time. At the beginning of the second stage reaction, new small particles were observed, which coalesced onto the PS seed as the polymerization proceeded. The distribution of the MAA groups in the latex particles and the serum was analyzed by alkali/back-acid titration, using ionic exchanged latexes. No MAA groups were detected in the latex serum. Due to the lowTg of the BA-MAA copolymers, alkali conductimetric titrations accounted for all the MAA groups on and within the polymer particles. Therefore, for these systems, this method is not only limited to a thin surface layer, as it is often assumed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00657448
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  • 4
    Digitale Medien
    Digitale Medien
    Rheology of concentrated multi-sized poly(St/BA/MMA) latices (1998)
    Springer
    Colloid & polymer science 276 (1998), S. 305-312 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Key words Rheology ; multi-sized ; high solid content ; latex
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003960050244
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  • 5
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): emulsion polymerization ; reaction calorimetry ; chain transfer agents ; kinetics ; radical desorption ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 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
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): 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
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: 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.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/polb.1995.090331101
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