Definition of Solubility Parameters

As noted earlier, compatibility of two elastomers is defined as when the polymers are immiscible but if in combination provide properties or show characteristics that are more useful than the properties of the original polymers 2]. Incompatible polymers when blended will show a dual 7. As discussed earlier, miscible blends are obtained when, at the molecular level, the two polymers are compatible. For example, blends of two highly polar polymers such as PVC and NBR are truly miscible. Polymer compatibility is governed by three parameters  

1) Thermodynamics microdomain formation is achieved by surface energy reduction (i.e., use of processing aids) and vulcanization. 

2) Viscosity oil/filler levels in dissimilar elastomers can be adjusted in mixing. 

3) Cure rate NR/EPDM and NR/IIR or NR/HIIR systems where the respective polymers are significantly different. 

Polymer compatibilization can therefore be achieved either by reduction of interfadal energy, improvement of dispersion during mixing, stabilization of the polymers to prevent phase separation after mixing, or improvement of interfacial or interdomain adhesion. This can be achieved as follows  

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This is the so-called one-component solubility parameter or also Hildebrand solubility parameter [29,30]. Other definitions of solubility parameters extend this concept and include the various contributions to intermolecular interactions in multicomponent polar and nonpolar liquids. Expressed in the experimentally... 

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