Block copolymers compatibilizers

Numerous reports of comparable levels of success in correlating adhesion performance with the Scatchard-Hildebrand solubility parameters can be found in the literature [116,120-127], but failures of this approach have also been documented [128-132J. Particularly revealing are cases in which failure was attributed to the inability of the Scatchard-Hildebrand solubility parameter to adequately account for donor-acceptor (acid-base) interactions [130,132]. Useful reviews of the use of solubility parameters for choosing block copolymer compatibilizers have been prepared by Ohm [133] and by Gaylord [134]. General reviews of the use of solubility parameters in polymer science have been given by Barton [135], Van Krevelen [114], and Hansen [136]. 

Marie M, Macosko CW (2002) Block copolymer compatibilizers for polystyr-ene/poly(dimethylsiloxane) blends. J Polym Sci Part B Polym Phys 40(4) 346-357... 

The importance of these block copolymers is realized when they are used as minor components with normally immiscible homopolymers (each having the composition of one of the blocks). In the absence of the block copolymer (compatibilizer), the resulting two-phase system might not be of practical usefulness. The often high interfacial tension between the two phases results in poor dispersion of the minor phase in the other, continuous phase. On processing, this will lead to macroscopic separation, so the result is a crumbly, useless material. The presence of a minor third component, the block copolymer, can enhance adhesion between the two components and so stabilize the morphology of the system. This process is discussed in more detail later. 

The concept of the solubility parameter (Section 1.3.1) leads to the conclusion that the ideal block-copolymer compatibilizer would have components that were identical to the two phases that were to be stabilized. Ideally, the chain length of each block would also match that of the corresponding phase, so ensuring total interpenetration of the copolymer block into each homopolymer. However, it has been demonstrated (Boimer and Hope, 1993) that this is not required and practical considerations dominate, such as... 

PA-6 (80) / PS (10-16) / SMA (2% MA) (4-10) internal mixer at 240°C / torque rheometry / SEM / selective solvent extraction / DSC / morphological stability to annealing / lap shear adhesion / comparison to PA-PS block copolymer compatibilized blends Park et at., 1992... 

Compatibilizer, block copolymer Compatibilizer, copolymer Compatibilizer, co-solvent Compatibilizer, graft copolymer Compatibilizer, ionic/ionomeric... 

One can also prepare the block copolymer compatibilizer from two functionalized polymers that do not react with each other. In such instances two functionalized polymers are melt mixed with a bifunctional bridging compound that will react with both the groups (Scheme 3.7). 

Galloway Jeffrey, Jeon Hyun, Bell Joel, and Macosko Christopher. Block copolymer compatibilization of cocontinuous polymer blends. Polymer. 46 no. 1 (2005) 183-191. 

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

The preceding examples show that many of the successful block copolymer compatibilizers are of the type, where block A is identical with phase A, whereas block C is different than phase B but is miscible or at least practically compatible with it. Further extension of this principle leads to the assumption that successful compatibilizers might also include block copolymers of the type C-D, where C is different from phase A but is miscible or at least compatible with it, and where D is different from phase B but is miscible or at least compatible with it. A number of experimental studies have demonstrated that this is often successful and practical. 

Block copolymers have become commercially valuable commodities because of their unique stmcture—property relationships. They are best described in terms of their appHcations such as thermoplastic elastomers (TPE), elastomeric fibers, toughened thermoplastic resins, compatibilizers, surfactants, and adhesives (see Elastot rs, synthetic—thermoplastic). 

Frounchi and Burford [37] studied the effect of styrene block copolymer as a compatibilizer in isotactic PP-ABS blends. It was found hat in PP-rich blends a marginal improvement in mechanical properties was obtained. However, in acrylo nitrile butadiene styrene (ABS) rich blends no improvement was obtained. The effects of four different block copolymers, SBS, SIS,... 

Compatibility and various other properties such as morphology, crystalline behavior, structure, mechanical properties of natural rubber-polyethylene blends were investigated by Qin et al. [39]. Polyethylene-b-polyiso-prene acts as a successful compatibilizer here. Mechanical properties of the blends were improved upon the addition of the block copolymer (Table 12). The copolymer locates at the interface, and, thus, reduces the interfacial tension that is reflected in the mechanical properties. As the amount of graft copolymer increases, tensile strength and elongation at break increase and reach a leveling off. 

Blends based on polyolefins have been compatibilized by reactive extrusion where functionalized polyolefins are used to form copolymers that bridge the phases. Maleic anhydride modified polyolefins and acrylic acid modified polyolefins are the commonly used modified polymers used as the compatibilizer in polyolefin-polyamide systems. The chemical reaction involved in the formation of block copolymers by the reaction of the amine end group on nylon and anhydride groups or carboxylic groups on modified polyolefins is shown in Scheme 1. 

The applicability of Noolandi and Hong s theory of compatibilization of immiscible blends using block copolymers has been extended to the reactive compatibilization technique by Thomas and coworkers [75,76]. According to Noolandi and Hong [77], the interfacial tension is expected to decrease linearly with the addition... 

Polyarylate (PAR)-b-PSt and PAR-b-PMMA for compatibiiizers are described 135,39,40). The addition of PAR-b-PSt (1-10 parts) to 100 parts of a blend of PAR-PSt (7w-3w) resulted in improvement of the tensile and flexural modulus (Fig. 4), and PSt dispersed particles were diminished from 1-5 microns to an order that is undetectable by SEM, indicating the excellent, compatibilizing effect of the block copolymer. The alloy thus formed exert the characteristic of PAR, an engineering plastic, as well as easy processability of PSt. Addition of PAR-b-PMMA (3 or 8 parts) to 100 parts of a blend of PAR-polyvinylidenefluoride (PVDF) (7w-3w) resulted in improved microdispersed state of PVDF due to compatibility of PMMA with PVDF, while segregation of PVDF onto the surface was controlled. 

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