Single-phase blends

Alcryn (DuPont) Blend Chlorinated polyolefin Ethylene reactive blend Single phase, soft, oil resistant... 

The compatibility is also a very important fact. Good compatibility means that the two kinds of polymers in the blends are mixed at the molecular level to form an apparently single phase. This kind of blending system shows only one Tg. If the two polymers have only partial compatibility, the entire system will maintain two different TgS and TPU only serves as a modifier not a plasticizer. 

In a fundamental sense, the miscibility, adhesion, interfacial energies, and morphology developed are all thermodynamically interrelated in a complex way to the interaction forces between the polymers. Miscibility of a polymer blend containing two polymers depends on the mutual solubility of the polymeric components. The blend is termed compatible when the solubility parameter of the two components are close to each other and show a single-phase transition temperature. However, most polymer pairs tend to be immiscible due to differences in their viscoelastic properties, surface-tensions, and intermolecular interactions. According to the terminology, the polymer pairs are incompatible and show separate glass transitions. For many purposes, miscibility in polymer blends is neither required nor de-... 

Miscible Polymer Blends A subclass of polymer bends encompassing those blends that exhibit single-phase behavior. 

The mechanism of formation of morphology structures in iPP-E-plastomers blends via shear-dependent mixing and demixing was investigated by optical microscopy and electron microscopy. A single-phase stmcture is formed under high shear condition in injection machine after injection, namely under zero-shear environments, spinodal decomposition proceeds and leads to the formation of a bicontinuous phase stmcture. The velocity of spinodal decomposition and the phase separation depend on the molecular stmcture of iPP and E-plastomer components. 

The microstmcture appeared well mixed although co-continuity of the phases was not obvious. The blends appeared to have a continuous PP phase containing extended, yet isolated, SBR components as shown in Figure 11.17. It appeared to be similar to the microstmcture of the TPV-based on nylon and EPDM. The presence of entrapped air or mumal dissolution was not observed. As the fraction of PP increased, the microstmctures became clustered into larger PP and SBR single phases, with lower SBR-PP interface area. Both the materials were shear thinning. There is a large decrease in the viscosity of the composites at small shear rate. The viscosity values of the phases followed the equation... 

Polymer blend that is a single-phase structure. 

For blends consisting of components with sufficiently different glass transition temperatures, like PS/PPE (Tg(PS) = 105 °C, Tg(PPE) = 220 °C),two phases (two glass transition temperatures) can still be detected for the blended powder. However, the melt and the solid obtained from the melt are only composed of a single phase (with only one glass transition temperature, depending on the composition of the blend). 

Intermolecular forces also play an important role in determining the compatibility of two or more polymers in a polymer blend or polymer alloy. Although the distinction between a polymer blend and a polymer alloy is still the subject of some debate, we will use the convention that a polymer alloy is a single-phase, homogeneous material (much as for a metal), whereas a blend has two or more distinct phases as a result of polymer-polymer immiscibility (cf. Section 2.3.3). In general, polymers are... 

Figure 1 shows a typical PBI/polyimide solution blended phase diagram after solvent removal. It is clear that, in the absence of solvent, the single phase... 

PAr is soluble in similar polar organic solvents (e.g., NMP, DMAc, DMSO, etc.) which dissolve PBI. It was observed that miscible solution blends of PBI and PAr could be formed. For example, NMP dopes containing 10 wt % PBI and PAr are visually homogeneous and contain no insolubles as formed. After being kept at room temperature for a period of time (e.g., several days), a PBI-rich phase starts to form precipitate, but this polyphasic material can be easily redissolved into a single phase with a mild heating (i.e., 100 °C for 20 min). Based on the haze level, the stability of the PBI/PAr/NMP solutions appeared to increase with the increase of the relative PAr concentrations. 

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