Polymer particle formation

The occurrence of coagulative nucleation does not alter the -power dependence of N on R,. However, the coagulative nucleation mechanism indicates a more complex dependence of N on S. The exponent of S decreases monotonically from 1.2 to 0.4 with increasing S. The concentration of polymer particles is higher and the nucleation time is longer for systems with high surfactant concentrations. Polymer particle formation becomes less efficient at longer... 

Static and Dynamic Light Scattering Test of Polymer Particles Formation Process in Supercritical Fluid... 

The Mechanism of Polymer Particle Formation in Polymer Polyols Synthesis by Radical Polymerisation [19]... 

The practical technique to obtain polymer polyols by radical polymerisation is to add an homogeneous mixture of vinylic monomer, initiator, chain transfer agent and a part of polyether polyol, to the rest of polyether polyol containing the NAD (macromer or nonreactive NAD), at 115-125 °C. The mechanism of solid polymer particle formation during radical polymerisation of vinylic monomers in liquid polyethers, in the presence of a nonreactive NAD, in the form of very stable dispersions, is described next. 

Equations 10.1 and 10.4 show that the number of polymer particles is crucial in determining both the rate and degree of polymerization. The mechanism of polymer particle formation indicates clearly that the number of polymer particles will depend on the emulsifier, its initial concentration (which determines the number of micelles), and the rate of generation of primary radicals. Smith and Ewart have shown that... 

For homogeneous catalysts, the process of polymer particle formation generally leads to porous, low-density polymer particles, which can cause significant increase in slurry viscosity and reactor fouling, leading to inadequate reactor temperature control. Additionally, polymer particles with poor powder properties are undesirable for postreactor polymer processing. These problems must be addressed before using soluble metallocene catalysts for industrial production of polyolefins. 

Fig. 2. The micellar model for the polymer particle formation (where MD denotes monomer droplet, MP monomer-polymer particle, Mic micelle, and E emulsifier) [49],...

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