Reactive Blends

The sales of plastics continue to increase in a large part due to technical and economic advancements of polymer blends. Reactive blending is a useful technique for elastomers but, it appears that chemistry could also play an important role in the correct microstructure adjustment of thermoplastic alloys. Interfacial reactivity should be the focal point in maintaining the expected structure during subsequent stages of manufacture. Besides industrial examples, various kinds of polymeric co-reacting systems are also presented in order to emphasise the key factors of reactive blending. 

Extrusion of Polymer-1 containing monomer of Polymer-2, followed by post reaction to Polymer 2 (polyimides, electrically conductive polymer blends, reactive blends, e.g., with crosslinked elastomers), etc. 

Immiscible polymer blends normally have a sea-island stmcture, where one polymer is dispersed as (normally spherical) particles in the other polymer, which forms the matrix, or a co-continuous structure, where both polymers are equally distributed in the blend without one polymer forming a continuous phase. For the blends to have good mechanical properties, it is also important that there is good interaction between the different components in the blend. To ensure this, researchers have tried a variety of methods to compatibilize the polymers in blends. The most used method is to add a third polymer, which interacts well with the other two polymers, into the blend. Reactive blending is another well-used method, and recently, a lot of investigation went into the use of (especially clay) nanoparticles to improve the interaction between the polymer components by locating themselves on the interfaces between the polymers. 

Y.-Y. Cui, B.-J. Dong, B.-L. Li, S.-C. Li, Properties of polypropylene/poly(ethylene terephthalate) thermostimulative shape memory blends reactively compatibilized by maleic anhydride grafted polyethylene-octene elastomer. Int. J. Polym. Mater. Polym. Biomater. 62, 671-677 (2013)... 

Ethylene-1-octene copolymer was also used as an amorphous blend partner of PA6 in PA6/ethylene-1-octene blend reactively compatibilized using PE-g-MA reactive copolymer (Sanchez et al. 2006). Because of the dispersed phase... 

Dow has prepared a compatibilized blend of PC and linear PE. The compati-bilizer used was EPDM grafted with SAN. The product has high impact strength and good melt processability. Polymer alloys with S-AMS copolymer and PP with styrene-grafted polyolefin copolymer have been reported. Triax 1000 of Monsanto is a blend of nylon and ABS compatibilized with styrene-acrylonitrile and glycidyl methacrylate terpolymer. The compatibilizer often improves the property balance of an immiscible blend. Reactive compatibilization is an emerging technique. 

The possibility of H-bonding or formation of donor-acceptor interactions between PHA and the other blend constituents helps improve blend miscibility and reduces the tendency of phase separation. To increase the compatibility and reduce the tendency of phase separation of the blends, reactive blending between the components has been developed. For instance, the components have been blended with peroxides. The latter decompose to form free radicals that cross-link the polymers " in the blend. 

The morphology development in the case of EPM/Nylon 6 blends, reactively compatibilized by EPM-g-MA, is reported to be extremely fast [59]. In this study the... 

Figure 8.26 Effect of blending reactive rubbers (m-EPR with or without the additional E-MAA, Zn ionomer) on the flexural modulus of PA6 [28]...

Extrusion, melting, mixing, polymer blends, reactive extrusion, viscosity, energy dissipation, phase inversion. 

---