Blends and Alloys
Mixing polymers is a cost-effective way to tailor properties of polymeric materials for specific applications. Being able to precisely predict properties is essential to design and application. The simple ideal is based on a simple average of individual polymer properties. An important feature is the homogeneity of the mixture. Ideally for compatible polymers the blend is a homogeneous mixture with no microstructure. In the other extreme, incompatible polymers form a microstructure, i.e. two or multiphase structures, dependent on compatibility and mixing techniques. A common distinction is the alloy which imply complete compatibility or solution behavior versus the blend which implies incompatibility and multiphase structure. In practice the terms alloys and blends are used interchangeably without little or any compatibility distinction. (RDC 3/28/2010) However for many properties such as elastic modulus, thermal conductivity and electrical conductivity, the microstructure of blend also affects properties and must be considered. For incompatible or partially compatible blends (A/B), the microstructure depends on composition ranging from a continous matrix (A) containing dispersed particles (B)for low concentrations of B or a continuous matrix (B) containing dispersed particles (A). As the concentraton of the minor component increases, the particles and aggregates grow until a continuous network forms, the percolation threshold. These particles continue to grow until two continous and symmetrical structures form (co-continous) at the phase inversion. Phase Inversion is the change from continous A/particle B to particle A in continuous B. Wang et al, Polymer Engineering & Science, 50, #4, p 643-651 (2010)
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Editor's Notes
As the literature is reviewed, and items of interest concerning this topic are found. These may be added in an abbreviated form with the reference. Readers and contributors are invited to add their own notes. Contributors may add them directly and other readers can simply send their notes to the editor, Roger Corneliussen at rcorneliussen@4spe.org. He may edit and add them to this page at his discretion.