Latex charged

A double shielded Faraday cage was used by Tardos et. al. (1984) for sampling 1.049 pm aerosol of polystyrene latex. Charge and current magnitudes were of the order 10 17 C per particle and 10 I3A respectively. They find that the particle charge Q is related to the current I by the relation... 

The emulsion process can be modified for the continuous production of latex. One such process (68) uses two stirred-tank reactors in series, followed by insulated hold-tanks. During continuous operation, 60% of the monomers are continuously charged to the first reactor with the remainder going into the second reactor. Surfactant is added only to the first reactor. The residence time is 2.5 h for the first reactor where the temperature is maintained at 65°C for 92% conversion. The second reactor is held at 68°C for a residence time of 2 h and conversion of 95%. 

Electroultrafiltration (EUF) combines forced-flow electrophoresis (see Electroseparations,electrophoresis) with ultrafiltration to control or eliminate the gel-polarization layer (45—47). Suspended colloidal particles have electrophoretic mobilities measured by a zeta potential (see Colloids Elotation). Most naturally occurring suspensoids (eg, clay, PVC latex, and biological systems), emulsions, and protein solutes are negatively charged. Placing an electric field across an ultrafiltration membrane faciUtates transport of retained species away from the membrane surface. Thus, the retention of partially rejected solutes can be dramatically improved (see Electrodialysis). 

The aqueous emulsion polymerization can be conducted by a batch, semibatch, or continuous process (Fig. 5). In a simple batch process, all the ingredients are charged to the reactor, the temperature is raised, and the polymerization is mn to completion. In a semibatch process, all ingredients are charged except the monomers. The monomers are then added continuously to maintain a constant pressure. Once the desired soflds level of the latex is reached (typically 20—40% soflds) the monomer stream is halted, excess monomer is recovered and the latex is isolated. In a continuous process (37), feeding of the ingredients and removal of the polymer latex is continuous through a pressure control or rehef valve. 

Synthetic rubber latex was made by a process with a large and hazardous inventory of butadiene and styrene. In a modified process, the reactor has an initial charge of water and emulsifier. Also, the monomers are added to the reactor as one premixed stream and the emulsified aqueous sodium persulfate is added as the other stream. The improved scheme, discussed by Englund (1991a) contains less hazardous material and at a lower, more controllable temperature. It illustrates that large and established processes may be made safer by applying inherent safety. 

There are three important processes for preparing PVAc latexes in the presence of PVA as a protective colloid batch, semi-continuous, and delayed addition of monomer [10]. In this Chapter, the effects of the addition of VAc and initiators on the properties of PVAc latexes are discussed using the three methods under the same charge of ingredients for polymerization as shown in Fig. 1 [1,11]. 

Ny lon-6 (108 g) carpet backed with calcium-carbonate-filled latex and polypropylene was charged to a 1000-mL three-neck round-bottom flask (equipped with a condenser) with 6 mL of 85% phosphoric acid. Superheated steam was injected continuously during a 45-min period. The vapor temperature of the reaction medium was 250-300°C. The volume of distillate collected was 1065 mL. The distillate contained 1.9% e-caprolactam (as determined by GC), which corresponded to a crude yield of 37.5%. The distillate was fractionated in a distillation column and the nonaqueous phase removed. The remaining aqueous phase was treated with 2% potassium permanganate at 40-50°C for 2 h. Evaporation of... 

Garda-Salinas M. J., Romero-Cano M. S., de las Nieves F. J.. Zeta potential study of a polystyrene latex with variable surface charge influence on the electroviscous coefficient. Progr Colloid Polym Sci (2000) 115 112-116. 

The most widely used model of adsorption is Langmuir s equation for reversible molecular adsorption [163]. However, this is inappropriate for charged latex particles, because... 

Fulda and coworkers [92,93], Bliznyuk and Tsukruk [94], and Serizawa and coworkers [95-97] were the first who tried to use this technique for the preparation of ordered bi- and multilayer assemblies of oppositely charged latex particles. The structure was investigated using scanning force microscopy (SFM) and SEM. In a further publication, Kampes and Tieke [98] studied the influence of the preparation conditions on the state of order of the monolayers. In the following section, the recent studies are more extensively reviewed. 

The foregoing examples show that hollow polymer capsules with varying composition and sizes of ca. 2-20 micrometers can be produced, either by templating charged (latex particles and biocrystals) or uncharged (organic microcrystals), and that different core removal procedures can be employed. Nanometer-size polymer capsules have also been produced by employing smaller particle templates [107]. 

Using this photon force measurement technique, radiation pressure induced by a focused laser beam and an evanescent field [12, 14, 19, 20] was investigated for polymer latexes and metallic particles. Electrostatic forces of charged particles in... 

If only electrostatic effects are responsible for polymer adsorption and flocculation, our results can be explained according to the same scheme as that used by Furusawa et Al.(20) to interprete the destabilization of negatively charged latex by a cationic polymer. In a first step, the adsorption of the polymer leads to the neutralization of the particles which are no more stabilized by electrostatic repulsions and there is flocculation (we have not studied this step since in our experiments polymer was always in large excess with respect to Al(0H)3). In a second step the adsorption inverses the charge and (we have indeed measured by... 

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