Self-compatibilization

Figure 5.15. MFC can be obtained from incompatible polymer blends by extrusion and orientation (the fibrillization step) followed by thermal treatment at a temperature between the melting points of the two components at constant strain (the isotropization step). The block copolymers formed during the isotropization (in the case of condensation polymers) play the role of a self-compatibilizer. Prolonged annealing transforms the matrix into a block and thereafter into a random copolymer (a) an MFC on the macro level, (b) an MFC on the micro (molecular) level (Fakirov Evstatiev, 1994).

S-MMAIPC blend. This blend (Novacor SD-9101) was reported to have better flow, surface finish and scratch resistance than PC/polyester blends and an equivalent level of impact toughness (Table 15.24). It is believed that these formulations also include some acrylic rubber (core-shell type) for impact modification. One would expect a sufficient level of partial miscibility for self-compatibilization between the styrene-methyl methacrylate copolymer (S-MMA) and the polycarbonate especially at high MMA content of the copolymer, since the binary blends of PMMA... 

PET/PTMG-PET Invista PET bottle producers Oxyclear Self- compatibilized ... 

Partial miscibility between the components leads to self-compatibilization even though these systems are phase separated. Experimentally, these blends exhibit two Tg s, but different from each of the pure components due to a small amount of mutual miscibility Grafting involves direct chemical reaction between the components during melt mixing, generating a graft copolymer as the compatibilizer... 

As polymerized reactor copolymer, obtained by in-reactor grafting, polymerization technology is a two-phase rigid copolymer, which combines the best attributes of semicrystalline polypropylene with those of amorphous polystyrene. In the process, the compatibilizer PP-g-PS and the nonolefinic polymer component PS are simultaneously generated from the monomer styrene. This styrenic Hival-loy (Hivalloy is a trademark of Montell USA, Inc.) system can be regarded as self-compatibilized, with a reactor product composition of about 70% PP, 20%... 

No.22,15th Nov.1999, p.4233-40 SELF-COMPATIBILIZATION OF POLYMER BLENDS PREPARED VIA FUNCTIONALIZED CONCENTRATED EMULSION POLYMERIZATION Hangquan Li Haohao Hiang Ruckenstein E Beijing,University of Chentical Technology Buffalo,State University of New York... 

The described peculiarities of MFCs can be expected and realized when the blend partners are condensation polymers or, at least, functionalized polyolefins. The latter restriction however, concerns only the self-compatibilization effect but by no means the basic principles of MFC manufacturing, i.e., MFCs can be prepared also from polyolefin partners provided the basic temperature requirements for their preparation are satisfied. 

These reactions result in the formation of a copolymeric layer at the interface, playing the role of a compatibilizer, i.e., one deals with a self-compatibilization effect in that there is no need to introduce an extra synthesized copolymer of the blend components, as in the common approach [5]. Compatibilization can be effective only in the initial stages of chemical interaction. During prolonged thermal treatment, the reaction goes to completion and finally involves the entire amount of the molten blend components in the formation of block copolymers, thus transforming the homopolymeric (molten) blend into copolymers. 

Block copolymers in selective solvents exhibit a remarkable capacity to self-assemble into a great variety of micellar structures. The final morphology depends on the molecular architecture, tlie block composition, and the affinity of the solvent for the different blocks. The solvophobic blocks constitute the core of the micelles, while the soluble blocks form a soft and deformable corona (Fig. Id). Because of this architecture, micelles are partially Impenetrable, just like colloids, but at the same time inherently soft and deformable like polymers. Most of their properties result from this subtle interplay between colloid-like and polymer-like features. In applications, micelles are used to solubilize in solvents otherwise insoluble compounds, to compatibilize polymer blends, to stabilize colloidal particles, and to control tire rheology of complex fluids in various formulations. A rich literature describes the phase behavior, the structure, the dynamics, and the applications of block-copolymer micelles both in aqueous and organic solvents [65-67],... 

The same group used analytical arguments and numerical self-consistent field calculations to compare the interfacial tensions for a system of A and B homopolymers, immiscible with each other, having AB diblocks and comb copolymers localized at the interface [330,331]. In this case the overall molecular weight of the compatibilizer molecule was kept constant and the architecture was varied. At fixed N and > as the number of teeth increased the comb becomes less efficient at reducing the interfacial tension as compared to the diblock. At high values of N and x> the difference between the architectures becomes more pronounced. The diblock produces the lowest interfacial tension at the lowest concentrations. On the other hand, long combs with multiple teeth were found to be more efficient compatibilizers than short diblocks. 

Advancements in synthetic polymer chemistry have allowed a remarkable range of new nonlinear block copolymer architectures to be synthesized. The result is a wide variety of new materials with the capacity to form self-assembled phases in bulk and in solution. At present our synthetic capabilities exceed our understanding, both theoretical and experimental, of the properties of such macro-molecular systems. We anticipate that a better understanding of structure-property relationships for these materials will lead to impressive new polymers with applications such as structural plastics, elastomers, membranes, controlled release agents, compatibilizers, and surface active agents. From the synthetic standpoint it seems likely that recent advances in living free radical polymerization will make the syntheses of many non-linear block copolymers more commercially appealing. 

The major use of Heveaplus MG is in adhesives. It gives good bond strength for natural rubber to PVC and therefore, it is particularly useful in shoe manufacturing. It is used as a compatibilizer in plastic-rubber blends. It is also used in applications such as automobile bumpers due to its self-reinforcing nature. 

First, the compatibDizing copolymer is automatically formed at the interface between the two immiscible polymers where it is needed to stabilize morphology. In contrast, when a compatibilizing copolymer is added as a separate entity to a polymer blend, it must diffuse to the polymer-polymer interface to be effective for promoting morphology stabilization and interfacial adhesion between dispersed and continuous phases. However, that added copolymer may prefer to self-associate in micelles and form a separate phase that is useless for compatibilization. 

---