New particle formation

When an aqueous phase radical enters the polymer particles it becomes a polymer phase radical, which reacts with a monomer molecule starting a propagating polymer chain. This chain may be stopped by chain transfer to monomer, by chain transfer to agent or it may terminate by coupling. Small radicals in the particle may also desorb from or reenter the particle. In a batch reactor. Interval I indicates the new particle formation period, Interval II particle growth with no new particles, and Interval III the absence of monomer droplets. 

Data of Nomura and Funita (12). The predictive capabilities of EPM for copolymerizations are shown in Figures 8-9. Nomura has published a very extensive set of seeded experimental data for the system styrene-MMA. Figures 8 and 9 summarize the EPM calculations for two of these runs which were carried out in a batch reactor at 50 °C at an initiator concentration of 1.25 g dm 3 water. The concentration of the seeded particles was 6x10 dm 3 and the total mass of monomer was 200 g dm 3. The ratio of the mass of MMA to the total monomer was 0.5 and 0.1 in Figures 8 and 9 respectively. The agreement between the measured and predicted values of the total monomer conversion, the copolymer composition, and the concentration of the two monomers in the latex particles is excellent. The transition from Interval II to Interval III is predicted satisfactorily. In accordance with the experimental observations, EPM predicted no new particle formation under the conditions of this run. 

In addition to these nuclear reactions, myriads of other gas-phase transformations produce low-vapor pressure species, with the oxidation of SO2 and other reduced sulfur species dominating aerosol formation and growth. Oxidation of SO2 in the gas phase produces H2SO4, a readily condensable species that either combines with other molecules (new particle formation) or condenses on existing aerosols. 

Hoffmann, T R. Bandur, U. Marggraf, and M. Linscheid, Molecular Composition of Organic Aerosols Formed in a-Pinene/Oj Reaction Implications for New Particle Formation Processes, J. Geophys. Res., 103, 25569-25578 (1998). 

FIGURE 9.32 Some evidence from field studies along the coast of Washington State on April 22, 1991, both for new particle formation and for condensation on preexisting nuclei (a) particle surface area for particles with D > 0.02 p.m (b) ratio of number of particles with D 0.015 p.m to those with D > 0.015 p.m (c) number concentration with diameters 0.02-0.024 ju.ni (adapted from Covert el at., 1992). 

Hoppel, W. A., G. M. Frick, J. W. Fitzgerald, and R. E. Larson, Marine Boundary Layer Measurements of New Particle Formation and the Effects Nonprecipitating Clouds Have on Aerosol Size Distribution, J. Geophys. Res., 99, 14443-14459 (1994). 

O Dowd, C. D., M. Geever, M. K. Hill, M. H. Smith, and S. G. Jennings, New Particle Formation Nucleation Rates and Spatial Scales in the Clean Marine Coastal Environment, Geophys. Res. Lett., 25, 1661-1664 (1998). 

Towards a quantitative understanding of new particle formation in aircraft exhaust plumes, Nature, submitted (2000)., ... 

Cheung HC, Morawska L, Ristovski ZD (2011) Observation of new particle formation in subtropical urban environment. Atmos Chem Phys 11(8) 3823—3833... 

Utilizing the seed latex polymerization method to avoid the occurance of new particle formation, the kinetic treatment of an emulsion polymerization is quite straight forward. Assuming that all the particles are the same size, the rate of polymerization,... 

A and were subsequently swollen with monomer to the extent of 150-175 parts of monomer per hundred parts of polymer. The surfactant level was adjusted to 45% of saturation on the swollen particle surface so that each experiment was equivalent in surface density of surfactant at the start of the reaction. That maintained a stable latex throughout the polymerization and avoided new particle formation. 

In the present work the conditions used to obtain uniform growth of the seeded particles, in a single step, in the emulsion polymerization of VC, are reported (4), in particular, we show that limited emulsifier is not sufficient to prevent new particle formation. A qualitative interpretation of results is suggested. 

Molecular clusters can be considered to be the smallest size range of an aerosol particle size distribution. Nucleation from the gas phase to particles or droplets involves, in the initial stages, the formation of clusters. Research on clusters provides a valuable approach to understanding, on a molecular level, the details of the transfer of molecules from the gaseous to the condensed state by either new particle formation or heterogeneous processes including adsorption onto or dissolution into particles. 

Atmospheric particles influence the Earth climate indirectly by affecting cloud properties and precipitation [1,2], The indirect effect of aerosols on climate is currently a major source of uncertainties in the assessment of climate changes. New particle formation is an important source of atmospheric aerosols [3]. While the contribution of secondary particles to total mass of the particulate matter is insignificant, they usually dominate the particle number concentration of atmospheric aerosols and cloud condensation nuclei (CCN) [4]. Another important detail is that high concentrations of ultrafine particles associated with traffic observed on and near roadways [5-7] lead, according to a number of recent medical studies [8-11] to adverse health effects. 

Case B Radicals enter both micelles and polymer particles at rates that are proportional to their surface areas (collision theory), so that the rate of new particle formation is given by... 

Yu, F. (2006). Effect of ammonia on new particle formation A kinetic H2SO4-H2O-NH3 nucleation model constrained by laboratory measurements. J. Geophys Res. 111D01204, doi 01210.01029/ 02005JD005968. 

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