Partial miscibility

We can classify blends into three categories miscible, partially miscible, and immiscible. Miscibility can be defined in thermodynamic terms. For a binary blend to be miscible the following two conditions should be satisfied ... 

Miscibility means how complete two or more liquids dissolve in each other. It is a qualitative rather than quantitative observation—miscible, partially miscible, not miscible. (To state exactly how miscible two liquids were, a scientist would use the larger coiKept of solubility, usually in a specific weight or volume per liter of solution.) Two ccmpletely miscible liquids will form a homogeneous (uniform) solution in any amount. Water and ethyl alcohol, for example, are ccmpletely miscible whether the solution is 1% water and 99% ethyl alcohol, 50% of both, or 1% ethyl alcohol and 99% water. When first mixed, miscible liquids often ow oily bands— called striaticns—in the bulk of the solution these disappear when mixing is complete. 

Drug substance and carrier can be both in the glassy state. Total miscibility, partial miscibility, or total immiscibility has been observed. This type of system is very sensitive to temperature and moisture... 

A fundamental question, which has to be addressed first about any blend system of interest, is of course whether the components are miscible or not. Polymer mixtures of chemically dissimilar polymers can be divided on the basis of the miscibility of their components being miscible, partially miscible or fully immiscible. 

A large number of polymer blends contain one or two crystallizable components. The crystallization behavior of a polymer component in a blend is expected to be altered by the presence of the second blend component, whether both are completely miscible, partially miscible or totally immiscible. Therefore, a profound scien-... 

ABS/PC Styrolution Sabic Bayer Daicel Polymer Novodur Cycoloy Bayblend Novolly S Partial miscibility Partial miscibility Amorphous/ amorphous... 

Three types of binary liquid mixtures are possible namely - completely miscible, partially miscible and completely immiscible liquid pairs. 

Because polymer-polymer miscibility depends on a balance between AH and AS and because AS , is molecular weight dependent, any statement as to miscibility, partial miscibility or immiscibility should be qualified by the molecular weights of the polymers involved. A system which is partially miscible for one pair of molecular weights may become miscible for mixtures of lower molecular weight species or immiscible if the molecular weight of one or both components is increased. 

Several polymer blends that are commercial products in the industry are partially miscible. Partially miscible polymer blends are those that exhibit some shift from their pure component glass transition temperatures. Thus, a binary miscible polymer blend will exhibit one glass transition temperature and a partially miscible polymer blend will exhibit two distinct glass transition temperatures different from their pure component glass transition temperatures. Some experimental systems that have been reported as partially miscible polymer blends are PET and poly(hydroxy butyrate) (PHB) and PC/SAN. Later on, in a separate chapter, a mathematical framework... 

Polymer blending has attracted the attention of researchers because polymers with extraordinaiy properties obtained by chemical synthesis are more expensive than existing polymers and blending operations. Furthermore, a wise choice and combination of the polymeric materials in specific amounts may lead to the fabrication of blend materials with desirable properties. There are various numbers of polymers that can be combined to form blends with different physical properties. The characteristics of the polymeric blend are influenced by the nature of the dispersed and dispersion phases, the volume ratio of the phases, the sizes and size distributions of the particles of the dispersed phase and interfacial adhesion. One of the popular questions being addressed regarding the polymer blend is the miscibility between the components. The blends formed can be miscible, partially miscible or fully immiscible. The miscible polymer blend is formed by choosing polymers with compatible chemical structures which are capable of specific interactions. ... 

Evaporation into Vacuous Space.—When two volatile liquids—miscible, partially miscible or non-miscible—are placed together in a vacuous space, such as that over the mercury in a barometer tube, evaporation takes place, and, as a rule, the composition of the residual liquid differs from that of the vapour. It is only when the liquids form a mixture of maximum or minimum vapour pressure—and therefore of constant boiling point—and when it is this particular mixture that is introduced into the vacuous space, that the composition of the vapour is the same as that of the liquid. In all other cases the vapour is richer in the more volatile of the two components into which the mixture tends to separate when distilled, these components being either the original substances from which the mixture was formed, or one of these substances and a mixture of the two which has a higher or lower boiling point than that of either of the original constituents. 

In all cases, miscible, partially miscible, or immiscible, fugacity should be used instead of partial pressure and vapor pressure if the pressures are such that deviations from perfect-gas law are significant. 

Since, ultimately, the properties of a polymer blend will depend on the final morphology, various research groups have recently undertaken extensive studies of the miscibility and phase behavior of polymer blends. In practice, the physical properties of interest are found either by miscible pairs or by a heterogeneous system, depending on the type of application. Generally, polymer blends can be completely miscible, partially miscible or immiscible, depending on the value of AG [4]. 

The physical state of mixing which is present in polymer blends can be categorized in three ways miscible, partially miscible or immiscible. A miscible polymer blend is a homogeneous, single-phase material. In many respects, a miscible blend behaves as if it is a single polymer. K the two components in the blend are miscible only within a certain composition range, the polymers are deemed partially miscible. An immiscible blend contains two distinct phases and is heterogeneous in nature. 

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