Compatibilizer effects

The ductility of HISPS is remarkably improved by the addition of a small amount of PPO and MA-g-SEBS. The following toughening mechanism is proposed (a) PPO dissolves into the amorphous phase of the SPS matrix to reinforce the matrix, and (b) MA-g-SEBS is localized in the interface between SEBS domains and the SPS matrix to increase the adhesive force. 

If mechanism (b) is vahd, it is necessary for MA-g-SEBS to be partially miscible with both SEBS and SPS. That is to say, the interaction between styrene and ethylenebutylene block chains should be reduced by the modihca-tion with maleic anhydride (compatibiUzer effect). 

The interaction parameter % introduced by Flory is obtained experimentally with the SAXS [6], and the % parameter for the interaction of styrene and modified EB is compared to that between styrene and unmodified EB. 

The enhancement of the partial miscibility of the elastomer domains and the SPS matrix causes the reduction of the domain size and the thickening of the interface (compatibilizer effect). 

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Asaletha and coworkers [12,22] further studied the compatibilizing effect of NR-g-PS in NR-PS blends. NR-PS blend is incompatible and immiscible and its compatibility can be improved by the addition of the... 

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. 

The infrared spectra demonstrate that there is a strong interaction between CR and the PS segment of SBS and between SBS and BR. Scanning electron micrographs of the fracture surfaces further support the conclusion. The fracture surface of 70 30 BR/CR shows layer-shaped morphology and 30 70 blends show hillock-shaped protmsions. Addition of 5% SBS reduces the particle size, makes the particles more spherical, and enhances uniform distribution. This provides further evidence of the compatibilizing effect of SBS. 

The higher amounts of bound rubber for all samples filled with plasma-treated silica demonstrate an improved filler-polymer interaction between the plasma-treated silica and the polymers in the blend compared to untreated and silane-treated silica. The highest filler-polymer interaction for the PPy-silica can be due to the best compatibilization effect of PPy-silica with both polymers in the blend, as... 

This exponential dependence leads to the dramatic compatibilization effect of block copolymers in immiscible polymer blends. Leibler (1988) noted that for strongly incompatible systems, the exponential increase of Ay with h only occurs for small c. At larger copolymer content, the reduction in interfacial area per block causes a slower increase in Ay (i.e. reduction in y). 

The compatibilizing effect of poly(ethylene-g-vinyl chloride), the characteristic constituent of these VC/PE graft copolymers, may be shown by electron photomicrographs of films consisting of a PVC-PE/50-50 mixture on the one hand, and of a VC/PE (50-50) graft copolymer containing about 50 of poly(ethylene-g-vinyl chloride), 25 of polyethylene and 25 of polyvinyl chloride on the other hand (see Figure 8). The films were obtained from a solution in o-dichlorobenzene. In the first case, the polyvinyl chloride and polyethylene phases are clearly separated in the second case, they interpenetrate closely. 

Figure 8. Electron photomicrographs showing the compatibilizing effect of poly(ethylene-g-vinyl chloride)...

S. H. Anastasiades, I. Ganattz, and J. T. Koberstein, Compatibilizing Effect of Block Copolymers Added to the Polymer/polymer Interface, Macromolecules, 22, 1449-1453 (1989). 

In an assessment of the relative importance of the block-copolymer architecture, the compatibilizer effectiveness was ranked in the following order ... 

Enhanced interphase interactions, deduced from thermal and dynamic mechanical properties and morphology observed by SEM, demonstrate the efficient compatibilizing effect of iPS-fo-iPP copolymer on iPS-iPP blends. Each sequence of the iPS-fc-iPP diblock copolymer can probably penetrate or easily anchor its homopolymer phase and provide important entanglements, improving the miscibility and interaction between the iPS and iPP phases. This is in good agreement with what is inferred from the mechanical properties of the iPS-fo-iPP-iPS-iPP polyblends. 

In contrast to the situation found for dilute solutions, the behavior of nonlinear block copolymers in the solid state seems to have attracted great attention. Many theoretical publications appeared in recent years, dealing mainly with the phase behavior of star-block, simple graft and comb copolymers. Issues like the nature of the phase diagram and the order-disorder transition have been studied in considerable detail. The compatibilizing effects of complex copolymers, in comparison to simple diblock copolymers, were also investigated. 

Similar polymer compatibilization effects were observed by Wellons and co-workers (19) on radiation graft copolymers of cellulose acetate and polystyrene and by Riess and his colleagues (20) on various block copolymers. Hughes and Brown (21) also reported some evidence of compatibilization in a... 

Compatibihzation enhances dispersion, increases the total apparent volume of the dispersed phase, rigidifies the interface, and increases interactions not only between the two phases, but also between the dispersed drops. These changes usually increase the blends viscosity, elasticity and the yield stress. The compatibilizer effects are especially evident at low frequencies. There are two mechanisms that may further affect these behaviors (i) the... 

Effective compatibilization of binary polymer blends by addition of a copolymer reduces the dispersed particles size and Vj [Anastasiadis et al, 1987 Wu, 1987 Patterson et ai, 1971]. An illustration is shown on Figure 4.15. The effect of compatibilizer addition is similar to the emulsification of the classical emulsions. In the former systems, the compatibilizer effect on the drop size and Vj follows the same behavior as the emulsion drop size reduction upon addition of a surfactant. The latter behavior is usually described as the titration curve that characterizes the surfactant efficiency. The shape of the titration curve depends on the type of emulsifier and the emulsification process, e.g., mixing time and equipment. However, the amount of emulsifier to saturate the interface also depends on the affinity of emulsifier to the dispersed phase, the size of the dispersion, the orientation of the emulsifier at the interface and its ability to prevent flocculation and coalescence [Djakovic et al., 1987]. A similar behavior is to be expected for polymer blends upon addition of a compatibilizer. 

Flow of emulsions provides the best model for polymer blends, where the viscosity of both polymers is comparable. The microrheology of emulsions provides the best, predictive approach to morphological changes that take place during flow of polymer blends. The effect of emulsifiers on the drop size and its stability in emulsions has direct equivalence in the compatibilization effects in polymer blends. 

This brief summary of compatibilizer effects on the flow behavior of polymer blends substantiate that many aspects of the behavior remain unclear. For example, the effects of limited miscibihty of copolymer, the copolymer structure and molecular weight, micelle formations and inter-particle interactions are still beyond the capability of the proposed models. Similarly, little information has been published on copolymer/homopolymer blends. 

Compatibilizing effects of interfacial agents such as block or graft copolymers that reduce the interfacial tension, stabilize the morphology, and strengthen adhesion at the interface. 

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