Blending compatibilizing agents

TEMPO-modified poly(ethylene-co-propylene-g-maleic anhydride), (IV), and poly((ethylene-co-1 -decene)-g-alkylacrylates), (V), were prepared by Matsugi [3] and used as polymer blend compatibilizing agents. 

Blends with good mechanical properties can be made from DMPPO and polymers with which DMPPO is incompatible if an appropriate additive, compatibilizing agent, or treatment is used to increase the dispersion of the two phases. Such blends include mixtures of DMPPO with nylon, polycarbonate, polyester, ABS, and poly(phenylene sulfide). 

It has been found by Baird and others [74-77] that the presence of LCP may accelerate and presumably direct the crystallization of conventional polymers (PET, etc.). Porter [76] has shown that, by blending biphasic polymers such as the PET-poly HBA copolymers, miscibility may be achieved between the conventional phase of the biphasic polymer with another conventional polymer that component is miscible with, i.e., X7-G/PBT. The latter phenomena may offer direction in the search for useful compatibilizing agents for LCP/conven-tional polymer systems. 

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. 

In the blends discussed above, the interaction among the components and the compatibilizing agent is purely physical. However, to extend the range of possibilities for optimized blends preparation, reactive processing, where covalent chemical bonds are created between the partners, offers great potential. 

MAJOR PRODUCT APPLICATIONS purification agent, asbestos replacement, filler in plastics and mbber, adhesives, blend compatibilizer... 

The problems and challenges Inherent to developing useful materials with optimal morphologies and properties from an Immiscible or partially miscible polymer blend are not trivial and have spawned considerable Industrial and academic research. Work on polymer miscibility, compatibilizing agents, reactive systems, and the Influence of flow on the structure and properties of blends Is described in later chapters. 

One possible way of reducing interfacial tension and improving phase adhesion between PP-based blend phases is to use a selected copolymeric additive that has similar components to the blend, as a compatibilizer in the blend system. Well-chosen diblock copolymers, widely used as compatibilizing agents in PP-based blends, usually enhance interfacial interaction between phases of blends (15, 16), reduce the particle dimensions of the dispersed phase (16, 17), and stabilize phase dispersion against coalescence (16-18) through an emulsification effect, thus improving the mechanical properties (15-19). 

Intense commercial and academic interest in block copolymers developed during the 1960s and continues today. These materials attract the attention of industry because of their potential for application as thermoplastic elastomers, tough plastics, compatibilizing agents for polymer blends, agents for surface and interface mo dification, polymer micelles, etc. Academic interest arises, primarily, from the use of these materials as model copolymer systems where effects of thermodynamic incompatibility of the two (or more) components on properties in bulk and solution can be probed. The synthesis, characterization, and properties of classical linear block copolymers (AB diblocks, ABA triblocks, and segmented (AB)n systems) have been well documented in a number of books and reviews [1-7] and will not be discussed herein except for the sake of comparison. 

Modification of Melt and Solution Properties. In addition to modifying mechanical properties resulting from polymer blending in the presence of a suitable compatibilizing agent, the melt and solution viscosities of the com-patibilized blend differ from those of the blend in the absence of the agent because the compatibilized blend is not truly compatible it is only partially or marginally so. 

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