Immiscible polymer blends INDEX

One can assume that blends of polymers will be more difficult to color than any component by themselves. DiflPuse reflection can increase due to internal light reflection or scattering at phase interfaces if the polymers are at least partially immiscible or their refractive indexes are significantly different. Blends of translucent polymers are typically more opaque than either resin alone. Furthermore, colorant stability (thermal or chemical) can be adversely affected by the presence of the other polymer(s). As in the case of neat polymers, both circumstances will result in a restricted achievable color gamut for the polymer blend. An example of a prominent polymer blend is GEs Noryl (PS/PPO) which certainly colors much differently than the polystyrene component by itself... 

The miscibility of a polymer blend is usually ascertained by studying the optical, morphological, and glass transition behavior of the blend. When two amorphous polymers with different refractive indices mix intimately to form a miscible blend, the refractive index of the blend is uniform, and the blend appears transparent. On the other hand, when the two polymers do not mix intimately, the resulting blend is opaque. It must be cautioned that a two-phase immiscible blend may appear transparent if the refractive indices of the two polymers are closely matched or the domain size is smaller than the wavelength of the visible light. For a blend containing a crystallizable polymer, the blend may appear opaque even when the amorphous phases of the two polymers mix intimately. 

The simplest method for preparation of polymer blends involves finding a mutual solvent. If the polymer blend is highly immiscible in the solid state, it will often show phase separation in solution with a common solvent with two layers observed (if densities of the solvent-polymer phases are different). If phase separation occurs in solution, the agitated solution will appear turbid or opaque if sufficient refractive index contrast is present. Observation of... 

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