Dispersed phase particles, soft

There are two main approaches for the numerical simulation of the gas-solid flow 1) Eulerian framework for the gas phase and Lagrangian framework for the dispersed phase (E-L) and 2) Eulerian framework for all phases (E-E). In the E-L approach, trajectories of dispersed phase particles are calculated by solving Newton s second law of motion for each dispersed particle, and the motion of the continuous phase (gas phase) is modeled using an Eulerian framework with the coupling of the particle-gas interaction force. This approach is also referred to as the distinct element method or discrete particle method when applied to a granular system. The fluid forces acting upon particles would include the drag force, lift force, virtual mass force, and Basset history force.Moreover, particle-wall and particle-particle collision models (such as hard sphere model, soft sphere model, or Monte Carlo techniques) are commonly employed for this approach. In the E-E approach, the particle cloud is treated as a continuum. Local mean... 

In contrast to the pearlite structure, which is lamellar (Figure 2.15), tempered martensite contains the carbide particles as a spheroidal dispersed phase. While the tempered martensite is soft and tough, the parent martensite is hard and abrasion resistant. 

Emulsion polymerization also has the advantages of good heat transfer and low viscosity, which follow from the presence of the aqueous phase. The resulting aqueous dispersion of polymer is called a latex. The polymer can be subsequently separated from the aqueous portion of the latex or the latter can be used directly in eventual appUcations. For example, in coatings applications-such as paints, paper coatings, floor pohshes-soft polymer particles coalesce into a continuous film with the evaporation of water after the latex has been applied to the substrate. 

PVA Particles. Dispersions were prepared in order to examine stabilization for a core polymer having a glass transition temperature below the dispersion polymerization temperature. PVA particles prepared with a block copolymer having M PS) x 10000 showed a tendency to flocculate at ambient temperature during redispersion cycles to remove excess block copolymer, particularly if the dispersion polymerization had not proceeded to 100 conversion of monomer. It is well documented that on mixing solutions of polystyrene and poly(vinyl acetate) homopolymers phase separation tends to occur (10,11), and solubility studies (12) of PS in n-heptane suggest that PS blocks with Mn(PS) 10000 will be close to dissolution when dispersion polymerizations are performed at 3 +3 K. Consequently, we may postulate that for soft polymer particles the block copolymer is rejected from the particle because of an incompatibility effect and is adsorbed at the particle surface. If the block copolymer desorbs from the particle surface, then particle agglomeration will occur unless rapid adsorption of other copolymer molecules occurs from a reservoir of excess block copolymer. 

Such materials essentially contain PS as the matrix polymer and uniformly dispersed in this matrix are elastomeric types of particles, which form the soft phase (3). The soft phase is essentially composed of poly(butadiene) or of block copolymers of butadiene and styrene. This soft phase can be also addressed as the impact modifier for PS. 

In order to explain such a microhardness depression, AH = Heal — Hexp (Table 5.4), it is convenient to consider the behaviour of the harder component dispersed in the liquid component (with zero hardness). It seems reasonable here to assume that the total microhardness of such a system will also depend on the viscosity of the soft component in which the particles of the harder component are floating . The deviation of Hexp from Hcai may actually reflect the viscosity of the soft-segment phase which also contributes to the resistance of the total system against the applied load. The viscosity of the soft phase introduces two important effects. 

In the intermittent contact mode phase images shown in Fig. 3.74 a clear contrast between the constituent phases can be observed both for the compression-molded hmsPP (panel a), as well as for the blown film (in the machine and transverse direction in panels band c, respectively). The soft EPR phase appears with dark phase contrast indicating that a substantial amount of energy is dissipated in this phase compared to the PP phase. The EPR particles measure 1 pm or smaller in diameter dispersed in the polypropylene matrix. The horizontal lines and the occasional vertical streaks in the images are artifacts of microtoming. 

Keywords Colloidal dispersions Colloidal glasses Dynamics Grafted particles Hairy particles Micelles Nanoparticle-polymer hybrids Phase diagrams Polymers Rheology Soft colloids- Softness Stars... 

Phase Behavior of Soft Particle Dispersions Suspensions and Glasses... 

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