Final particle diameter

Submicrometer uniform crystalline spheres of silver-doped zinc sulfide (ZnS Ag) were prepared by aging 0.04 mol dm-3 Zn(N03)2 and 2.80 X 10-6 to l. 68 X 10-5 mol dm-3 AgN03 with 0.4 mol dm-3 TAA for up to 100 min at initial pH 1.52 and 73°C (15). The authors found that the final particle density decreased with increasing content of silver ions, whereas the total reaction rate was virtually unaffected by the significant difference in the total surface area of the particle. In fact, the final particle diameter increased from 0.3 to 1.1 pm with increase in the content of silver ions from 5.6 to 16.8 pmol dm-3, as shown in Figure 3.1.5. Figure 3.1.6 shows the time evolutions of [Zn2+] and [Ag+] in the solution phase. 

The nucleation mechanism of dispersion polymerization of low molecular weight monomers in the presence of classical stabilizers was investigated in detail by several groups [2,6,7]. It was, for example, reported that the particle size increased with increasing amount of water in the continuous phase (water/eth-anol), the final latex radius in their dispersion system being inversely proportional to the solubility parameter of the medium [8]. In contrast, Paine et al.[7] reported that the final particle diameter showed a maximum when Hansen polarity and the hydrogen-bonding term in the solubility parameter were close to those of steric stabilizer. 

The estimated data (using Paine s model) were found to be in good agreement with experimental measurements obtained in St/PVPo and St/PEO-MA systems. However, in the case of MMA/PVPo, the model (e.g., Df - the final particle diameter) deviates strongly from experimental data. The deviations were discussed in terms of partitioning of the stabilizer (conventional, grafted stabilizer) between the particle surface and the serum and the efficiency of the graft stabilizer which depends on ... 

Thu.s for panicle volume-controlled growth, the final particle diameter is proportional to the initial diameter. For volume-controlled growth, the initial polydispersity is carried through to the hnal size distribution. This result is quite different from that of diffusion in the free molecule regime for which the Rnal panicle diameter is independent of the initial diameter. 

Calculate the total time that will be required for reaction and the final particle diameter. [Data kp at 60°C = 515 L mol s . Density monomer 0.9 g/cm polymer 1.2 g/cm . Dynamic solubility of monomer in polymer = 0.5 g monomer per gram polymer.]... 

Rate constant for initial increase in hydrolyzed aUcoxide concentration. For reactions containing TEOT, k2 is large and not easily measured. For these reactions, k2 is an estimate. Measured final particle diameter. 

The base case corresponds to an initial monomer concentration of 3.1 mol L" and a pressure of 20.4 MPa, respectively. The fitting to the experimental data in order to estimate the three adjustable parameters was done in terms of conversion versus time (Fig. 6.8) and MWD versus conversion (Fig. 6.9). Inspection of the results depicted in the two figures shows that the agreement is remarkably good, and the final values of the adjustable parameters are given in Table 6.3. Note that a value of 0.25 m g was used for the specific surface area. This value corresponds to a final particle diameter of around 10 pm, which is reasonable for the system under examination. 

Fitch and Tsai describe the preparation of monodisperse, emulsifier-free latexes made from methyl methacrylate and stabilized solely by end-groups [1]. The initiator system was persulfate-bisulfite-iron ((R-3) and (R-4)) and the temperature was always 30 °C. At a constant rate of initiation they found that the number of particles, N, was independent of the initial monomer concentration over the range 0.00380 to 0.0951 molar, while the particle diameter increased from 35.4 to 105.4 nm. In another experiment at a lower R , they obtained a final particle diameter of 172 nm and JV=1.1 X 10 1 , compared to Z)=68.7 nm and JV = 1.8x 10 1 at the same monomer concentration (0.035 M) but higher R,-. They estimated in the former case that each ionic group occupied 24.7 nm at the point when self-stabilization by... 

In order to obtain the desired final particle diameters, a number of parameters were varied, such as the capillary diameter (from 0.5 to 3.5 mm) and the type, molecular weight and concentration of the organic additive. 

The monomeric and low molecular weight species in the original silicate had polymerized onto the higher molecular weight polysilicate or colloid fraction, which has been shown to consist of particles about 1.0-1.5 nm in diameter, so that the final particle diameter in the ester is somewhat larger. 

Figure 9 Variation of total surface area, particle diameter, and percent surface coverage for 2.6% and 4.3% sodium lauryl sulfate with percent conversion for a 28 72 styrene-water ratio and final particle diameter 0.05um calculated assuming the number of particles is constant after 10% conversion, the monomer-polymer ratio is 50 50, all of the emulsifier is adsorbed on the latex garticles, and the molecular area of sodium lauryl sulfate is 45 A. ...

The final particle diameter when condensation is complete and all solute molecules have precipitated, Dp,f, can be calculated by equating the mass of solute in the metastable phase at initial time to the mass of the particles when condensation is complete ... 

Figure 12 Our two-step model for nucleation and condensation can be used to examine the effects of chemical potential difference and interfacial tension on final particle diameter and processing times.

Fig. 9.8 Contour plot of the experimental final particle diameter [pm], for initial mannitol mass fraction versus initial droplet size (Reprinted with permission from [34] Elsevier)...

Flow rate of monomer (gs ) Initial particle diameter (nm) (about 5% solids content) Final particle diameter (nm) (about 20% solids content) Gel effect... 

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