Blend phase-separation mechanisms

Figure 3.1 Phase diagram illustrating the phase separation mechanisms of thermoplastic/thermoset blends at constant cure temperature...

This interpretation shows that the viscoelastic measurements can characterize the phase-separation mechanism in TP-modified epoxy systems. If we apply the Flory-Huggins theory to this pseudobinary blend (20), the calculated phase diagrams are in very good agreement with the morphologies encoun-... 

While miscible blends have attracted considerable interest due to the thermodynamic implications and commercial relevance, phase separated blends have had a prominent role in polymer blend technology. While mechanical compatibility is assured in miscible blends, phase separated blends can often achieve property advantages not capable with single phase blends. (Mechanical... 

Zhang, R. Y., H. Cheng, C. G. Zhang, T. C. Sun, X. Dong, and C. C. Han. 2008. Phase separation mechanism of polybutadiene/polyisoprene blends under oscillatory shear flow. Macromolecules 41 6818-6829. 

In the following sections a polymer-polymer-solvent blend phase separation is investigated, with the respect to self-assembly on a heterogeneously functionalized substrate. The evolutionary mechanisms were studied by measuring the characteristic length, and the influence of different compositions was examined. The effects of a heterogeneously functionalized substrate were studied, and a discrete cosine transform spectral method was employed to solve the nonlinear partial differential equation. A semi-implidt method was used in the time evolution this method was found to be efficient and unconditionally stable over large time steps [40] (see Section 15.1.4). 

PVC PPC PPC = poly(propylene carbonate) PVC/PPC blends phase separated NBR-g-PPC provided compatibUization and improved mechanical properties 868... 

The Spinodal Decomposition, also named reaction-induced [29] and also polymerization-induced phase separation [30], is the phase separation mechanism most observed on thermoset/thermoplastic blends, commonly initially miscible. In this mechanism the second-phase grows spontaneously, without a thermodynamic or energetic barrier, leading the blend to a immiscible region [27]. 

Boyard N, Vayer M, Sintnrel C, Seifert S, Eire R. Investigation of phase separation mechanisms of thermoset polymer blends by time-resolved SAXS. EurPolym J 2005 41 1333-41. 

Meier R, Ruderer MA, Diethert A, Kaune G, Kbrstgens V, Roth SV, et al. Influence of film thickness on the phase separation mechanism in nltrathin conducting polymer blend films. J Phys Chem B 2011 115 2899-909. 

From the above, we can see that the mechanism of morphology formation is quite different from that of traditional polymer solution organic-inorganic nanocomposites. For traditional polymer solution systems, the phase separation mechanism is similar to that of polymer blends, i.e., nucleation and growth mechanism and spinodal decomposition mechanism.Generally, the component with higher content is apt to form the continuous phase and the other the dispersed phase. However, for the PEA/bentonite emulsion system, whether PEA can be continuous or not depends mainly on whether the PEA latex particles are in close contact before the complete volatilization of water. Instead, it depends on whether the content of PEA is larger than that of bentonite. 

In considering the process of cellulose acetate dissolution in chloroform during experimental investigation of polymer dissolution in low-molecular solvents, Papkov et al. [126] were the first to distinguish several states of the phase structure formation in polymer systems with limited compatibility and some low-molecular blends. The solution was transparent at the selected initial temperature and concentration. However, if the temperature goes below the critical point (its position depends on concentration) the system shows turbidity phase disintegration (transition, separation) occurs. In this case an emulsion is formed. It is characterized by the number and size distribution of constituent particles which depends on phase separation mechanism, temperature decrease rate and etc. 

Block copolymers are closer to blends of homopolymers in properties, but without the latter s tendency to undergo phase separation. As a matter of fact, diblock copolymers can be used as surfactants to bind immiscible homopolymer blends together and thus improve their mechanical properties. Block copolymers are generally prepared by sequential addition of monomers to living polymers, rather than by depending on the improbable rjr2 > 1 criterion in monomers. 

Polymer alloys are generally named polymer blends within the polymer community. In a recent overview of such blends, Robeson (1994) points out that the primary reason for the surge of academic and industrial interest in polymer blends is directly related to their potential for meeting end-use requirements . He points out that, in general, miscible polymer pairs confer better properties, mechanical ones in particular, than do phase-separated pairs. For instance, the first commercial... 

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