Latexes electron micrographs

Fig. 2. Didisperse acrylic latex. Electron micrograph, 18200 magnification...

Figure 6.9. PVC/P (B-co-AN) finished latex. Electron micrograph of Os04-stained particles.

As shown in Fig. 2a, the size of PVAc particles was found to have a range of approximately 0.1-1.0 /u,m from electron micrograph of the crack surface of the latex... 

From the electron micrographs, assuming that PVAc particles in the latex are the same size, the formation model of the porous film from the latex film can be illustrated as in Fig. 3 [19]. When the latex forms a dried film over minimum film-forming temperature, it is concluded that PVA coexisted in the latex and is not excluded to the outside of the film during filming, but is kept in spaces produced by the close-packed structure of PVAc particles. 

Figure 19 The scanning electron micrographs of the polystyrene seed latex and the copolymer latices carrying carboxyl, hydroxyl and amine functional groups, (a) PS/PAA, (b) PS HEMA, (c) PS/PDMAEM. The original SEM photographs were taken with 10,000 x magnification and reduced at a proper ratio to place the figure. (From Ref. 93. Reproduced with the permission of John Wiley Sons, Inc.)...

Figure 10. Electron micrograph of composite silica-polystyrene latex system,SPL(-), prepared by using bare silica particles as the seed.

Crosslinked polyacrylamide latexes encapsulating microparticles of silica and alumina have also been prepared by this method [179], Three steps are involved a) formation of a stable colloidal dispersion of the inorganic particles in an aqueous solution containing acrylamide, crosslinker, dispersant, and initiator b) HIPE preparation with this aqueous solution as the dispersed phase and c) polymerisation. The latex particles are polyhedral in shape, shown clearly by excellent scanning electron micrographs, and have sizes of between 1 and 5 pm. 

Figure 1.8 shows an electron micrograph of latex particles made from polystyrene cross-linked with divinylbenzene. Note that these latex particles are not the same as simple polystyrene molecules in a true solution. The particles shown in the figure display a remarkable degree of homogeneity with respect to particle size. Such a sample is said to be monodisperse (in size), in contrast to polydisperse systems, which contain a variety of particle sizes. We have a good... 

FIG. 1.8 Electron micrograph of cross-linked monodisperse polystyrene latex particles. The latex is a commercial product (d = 0.500 jun) sold as a calibration standard. (Photograph courtesy of R. S. Daniel and L. X. Oakford, California State Polytechnic University, Pomona, CA.)... 

Monodisperse spheres are not only uniquely easy to characterize, but also very rarely encountered. Polymerization under carefully controlled conditions allows the preparation of the polystyrene latex shown in Figure 1.8. Latexes of this sort are used as standards for the size calibration of optical and electron micrographs (also see Section 1.5a.3). However, in the majority of colloidal systems, the particles are neither spherical nor monodisperse, but it is often useful to define convenient effective linear dimensions that are representative of the sizes and shapes of the particles. There are many ways of doing this, and whether they are appropriate or not depends on the use of such dimensions in practice. There are excellent books devoted to this topic (see, for example, Allen 1990) and, therefore, we consider only a few examples here for the purpose of illustration. 

Lucovyl H 4010 is a copolymer obtained by chemical polymerization of a mixture of (principally) butadiene and acrylonitrile on a PVC latex. The mean particle diameter of the resin obtained is very small (less than 0.1 pm). Its refractive index is close to that of PVC, and its compatibility with PVC is excellent. This polymer disperses well in the PVC matrix to give a two-phase system as shown on the electron micrograph in Fig-... 

Figure 3.2 Electron micrographs, (a) Shadowed polystyrene latex particles (x 50 000), (b) Shadowed silver chloride particles i x 15 000)... 

Figure 15. Scanning electron micrograph illustrating the heterocoagulation of cationic latex particles (diameter = 0.43 fj/n) onto a negatively charged latex particle (diameter = 2.14 pm)...

The diameter of latex particles was measured from their transmission electron micrographs which were obtained by use of a Hitachi electron microscope HU-12AF. The uniformity ratio of particle size (U) was calculated from eq. 2 ... 

The total conversion where the latex particles came to appear first on the electron micrographs were more than 20 % for the copolymerization at f = 0.5, 12 % at f = 0.4, ca. 3 % at f = 0.3, and less than 1.2 % at f = 0.2. A common fact in four copolymerizations is that the AA fraction in instantaneously-formed polymer drops below 0.60 - 0.65 at the presented conversions. The fraction continues to decrease further to less than 0.05. 

Transmission electron microscopy (TEM) analysis (6-8) was used also to characterize the latexes in this particle growth monitoring study. The electron micrographs were taken at a magnification of 30.000X. 

Figure 4. Electron-micrograph of grafted latex ABS polymer by the osmium tetroxide technique...

Figure 44 presents a scanning electron micrograph of a capsule in which alumina particles are encapsulated in crosslinked polyacrylamide. Table 20 lists under PLA1 the amounts of the components involved in the preparation of these capsules. The capsules have a polyhedral shape and their sizes are larger (around 5 pm) and more uniform than the polymer latexes free of solid particles. Some of the cells of the gel coalesce during polymerization, forming bulk phases. As a result, some unencapsulated solid particles were also observed. 

Figure 1. Electron micrograph of 360-A rubber particles in Run 8B latex (22,160 X)...

Figure 3. Electron micrograph (4000 X) of typical latex section (top) ana latex dispersity graph (bottom). 5000-A latex characterization (Run A-32).

Electron micrographs of the latex particles were obtained in the usual way. 

Fig. 5 gives electron micrographs of latexes prepared with AIBN as initiator from emulsions with a constant styreneiHoO weight ratio = 1 3, a constant amount of OPB and with HD 0PB molar ratios of 0, 1 1,... 

Figure 8. Electron micrographs of monomer emulsion (A) and final latex (B) when benzoyl peroxide was used as the oil soluble initiator. Styrene = 166.7 g, HtO — 500 g, HD-.OVB == 4 1, OPB = 2.0 g/drrd H O. Temp. = 60°C. BP =- 2.0 g in...

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