Elastomer blends, immiscible compatibilization

Since most polymers, including elastomers, are immiscible with each other, their blends undergo phase separation with poor adhesion between the matrix and dispersed phase. The properties of such blends are often poorer than the individual components. At the same time, it is often desired to combine the process and performance characteristics of two or more polymers, to develop industrially useful products. This is accomplished by compatibilizing the blend, either by adding a third component, called compatibilizer, or by chemically or mechanically enhancing the interaction of the two-component polymers. The ultimate objective is to develop a morphology that will allow smooth stress transfer from one phase to the other and allow the product to resist failure under multiple stresses. In case of elastomer blends, compatibilization is especially useful to aid uniform distribution of fillers, curatives, and plasticizers to obtain a morphologically and mechanically sound product. Compatibilization of elastomeric blends is accomplished in two ways, mechanically and chemically. 

The sampUng of polymer blends in Polymeric Compatibilizers by S. Datta and D. J. Lohse, Hanser-Gardner, 1996, that >93% of polymer blends are combinations of thermoplastic and elastomers. However, automotive tires (5000kt/yr in 1995), a blend of elastomers, are the largest application for any immiscible polymer blend. 

There are many similarities between ABS/PVC and ABS/PC blends. Both are immiscible, having three distinct phases of PVC or PC, SAN, and an elastomer [Suarez and Barlow, 1984]. The blends are compatibilized by the dipole-dipole interactions between PC and SAN, particularly evident... 

Interfacially active graft or block copolymers of the t5 pe A-B or A-C may compatibilize the immiscible polymers A and B provided that C is also miscible or capable of strong interactions with B. Poly(ethylene-co-propylene) elastomer (EPR) or poly(ethylene-co-propylene-co-diene) (EPDM) is an example of such nonreactive compatibilizer for polyethylene/polypropylene (PE/PP) blends. 

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