Compatibilizer functionalized polymers

Keywords blend, block copolymer, compatibilizer, functionalized polymer, graft copol)mer, polyethylene, recycle. 

However, often it is difficult to produce suitable graft or block copolymers for important commercial applications. Alternatively, these compatibilizing copolymers can be generated in situ during the blend preparation through polymer-polymer grafting reactions using functionalized polymers (38). 

Chain functionalized polymers or graft copolymers are of great technological importance. They are used as compatibilizing agents for immiscible polymer blends (8) and adhesive layers between polymer-polymer co-extruded surfaces (8). Currently, of all polymers sold, about 30% are in the form of compatibilized immiscible blends (9-12). Next we discuss a few examples of chain functionalization. 

Although a sizable number of books on polyolefins and general polymer blends are available, only a few chapters address polyolefin blends. Currently, there is no single book that focuses exclusively on the fundamental aspects and applications of polyolefin blends. This is the primary source of motivation behind this book. The second motivation stems from the fact that new research trends in polyolefin blends such as in situ reactor blending and compatibilization/functionalization in the melt have emerged that need to be covered in a book format. 

In addition, there has been an increasing interest in new synthetic methods for the preparation of well-defined polymers with controlled chain-end functional groups [23], such as telechelic polymers, which are characterized by the presence of reactive functional groups placed at both chain ends. These materials can then be used as precursors in the synthesis of block copolymers, as modifiers of the thermal and mechanical properties of condensation polymers, as precursors in the preparation of polymer networks, and as compatibilizers in polymer blends [24]. 

The desired compatibilization can be obtained by different methods such as the addition of a third component (copolymer or functional polymer) or by inducing in situ chemical reactions (reactive blending) among blend components, leading to the modification of the polymer interfaces and tailoring the blend phase structure and the final properties. The final properties of a blend will be determined not only by the components properties but also by the phase morphology and the interface adhesion, both of which determine the stress transfer within the blend and its end-use applications. 

Polymers can also be compatibilized by the use of functionalized polymers. Thus polymers can be post-reacted with a reactive monomer to form functional groups that react with a second polymer to form grafts in a blend, e.g., EPDM-g-maleic anhydride/nylon-6,6 blends are produced by grafting maleic anhydride onto EPDM, followed by blending with nylon-6,6. The grafted maleic anhydride reacts with the terminal—NH2 groups of the nylon to form the following copolymer ... 

In the last decade, considerable progress was observed in the field of PO/compatibil-izer (predominantly on the base of PO-g-MA)/organo-surface-modified clay nanocomposites. Polyethylene (PE), polypropylene (PP), and ethylene-propylene (EP) rubber are one of the most widely used POs as matrix polymers in the preparation of nanocomposites [3,4,6,30-52]. The PO silicate/silica (other clay minerals, metal oxides, carbon nanotubes, or other nanoparticles) nanocomposite and nanohybrid materials, prepared using intercalation/exfoliation of functionalized polymers in situ processing and reactive extrusion systems, have attracted the interest of many academic and industrial researchers because they frequently exhibit unexpected hybrid properties synergisti-cally derived from the two components [9,12,38-43]. One of most promising composite systems are nanocomposites based on organic polymers (thermoplastics and thermosets). 

It has been generally assessed that the mechanism of interaction among the components of PO/day nanocomposites involves the functionalities of the functional polymer used as matrix or compatibilizer. The most frequent explanation is related to the hydrophilic/ hydrophobic balance of components involving some kind of undefined polar interaction between the silicate layers and the functional polymer (Alexandre and Dubois 2000, Sinha Ray and Okamoto 2003, Pavlidou and Papaspyrides 2008). The direct intercalation/interac-tion of a wide numbers of MAH-grafted low-molecular-weight compounds with layered silicates has been studied suggesting that the anhydride can promote the intercalation even if this is not a modeling of polymer intercalation (Sibold et al. 2007). 

The effect of the degree of nanoclay dispersion and pol5uner-filler interaction on the mechanical properties was also studied by Bilotti et al. [11-16]. Figure 12.25 shows the Young s modulus, yield stress, and strain at break of PP/sepiolite nanocomposites compati-bilized by different functionalized polymers (Section 12.4.1). The results are also compared with a PP nanocomposite reinforced by an alkyl silane-coated sepiolite (Sep-sil), without any compatibilizers. 

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