Compatibilizing efficiency

AMPS-containing, 23 722 block, 7 645-650 characterization, 7 655-659 classification in terms of monomer sequence distribution, 7 608t compatibilization efficiency of, 20 335-336 graft, 7 650-654 in high bulk yarns, 11 213 hyperbranched, 7 654-655 IUPAC source-based classification, 7 698t... 

Grading systems, for flax fiber, 77 617 Gradual failures, 26 981 Graduate students, role in facilitating research partnerships, 24 383 Graft copolymerization, 20 327. See also Graft polymerization Graft copolymers, 7 650-654 20 391 compatibilization efficiency of, 20 338 formation of, 23 395 in polymer blends, 20 324—325 in reactive compatibilization,... 

Styrene-butadiene copolymer(s) (latex), 23 367, 389-390 from butadiene, 4 375, 383, 384t compatibilization efficiency of, 20 336 Styrene-butadiene copolymerization, 14 256... 

The dependence of the components molar mass and of the mixing conditions on the compatibilizing efficiency of PE-g-SBH copolymers has also been studied (21). The results indicate that the PE-g-SBH copolymers do, in fact, compatibilize the HDPE/SBH blends and that the effect is more pronounced with the lower molar mass PE matrix and with the SBH sample having lower viscosity. Moreover, the compatibilizing ability of the graft copolymer is improved, if the latter is first blended with either of the two main components (21). 

Figure 2. Plot of compatibilizing efficiency as a function of sequence distribution fora linear copolymer.

Ray, S. S. and Bousmina, M. 2005. Effect of organic modification on the compatibilization efficiency of clay in an immiscible polymer blend. 

Song et al. (2012a) prepared blends of PMMA with various functionalized poly (propylene-ethylene) copolymers. Blends were characterized by mechanical, morphological, and adhesion tests. Compatibihty was found to increase in the order of unfunctionalized poly(propylene-ethylene), MA-grafted poly (propylene-ethylene), hydroxy-grafted poly(propylene-ethylene), and secondary amine-grafted poly (propylene-ethylene) which latter species exhibited the best compatibilization efficiency. 

The consequences of Eq. (2.5) are displayed in Figure 2.2. Independently of the compatibilizer efficiency, the postulated parallel concentration dependence of dz and Vi2 is observed. The rheological outcome of compatibilization is related to the increased volume fraction ofthe dispersed phase and enhanced interactions between particles, which often lead to the appearance of yield stress in a compatibilized blend (usually yield stress is absent in non-compatibilized blends). 

Various reports [19-25, 32-41] on the effects of the copolymer molecular weight and molecular architecture on its compatibilization efficiency for polymer blends rank in the order tapered diblock > conventional diblock > triblock and smaller molecular weight > higher molecular weight... 

Mechanical properties that are sensitive to stress transfer (impact strength, tensile strength, elongation) are usually considered as criteria of compatibilization efficiency because they indirectly characterize interface adhesion (1,7,45). Morphological characteristics, such as particle size of the dispersed phase, structure homogeneity, character of interfacial layer, existence of micelles, or mesophases, also give evidence on the compatibilization efficiency (25,29,40-44). 

Effect of the Compatibilizer Architecture. Compatibilization efficiency of various copolymers follows from their thermodynamic and microrheological effects. It has been generally accepted that the total molecular weight of the copolymer, molecular weight of its blocks and their nnmber are the main structnral compatibilizer characteristics affecting the phase strncture of the final blend. 

Contradictory results have been published on the effect of block copolymers with different numbers of blocks. In some papers, diblock copolymers have been found more efficient compatibilizers than triblock copolymers (51,154,155), whereas in several other studies, the opposite results have been obtained (156-158). Still others state that there is no difference between diblocks and triblocks (159). Some more recent articles show the compatibilizing efficiency of multiblock (tetrablock, pentablock, heptablock) copolsrmers (160-162), which seems to be supported also by some theoretical studies (163,164). 

Cavanaugh and co-workers (166) have studied the compatibilization efficiency of various styrene-butadiene copolymers in polystyrene (PS, Mw = 202,000)/polybutadiene (PB, Mw = 320,000) blends. The most effective compat-ibilizer proved to be a long, asymmetric diblock (M = 182,000 PS content 30%), which could entangle in both homopolymer phases. Short diblock copolymers and most of the random copolymers were inadequate as interfacial agents. Moderate improvement in impact strength was observed for a S-B multiblock. 

In the PS/EPR blends, Radonjic and co-workers (179) found the S-B-S triblock copolymer with Mn of the PS blocks of 7,000, to be localized at the PS/EPR interface. The compatibilization efficiency of this block copolymer was further confirmed by finer dispersion in the resulting PS/EPR/S-B-S blends, as well as by improved PS/EPR adhesion. This short triblock copolymer appears to be a good compatibilizer also in iPP/aPS blends. According to mit and Radonjic (180), S-B-S forms an interfacial layer between dispersed honeycomb-like PS/S-B-S particles and PP matrix and influences also crystallization in iPP. 

Hence, the compatibilization efficiency of block and graft copolymers is influenced by many factors, such as their chemical composition with respect to the character of the corresponding blend components, the number of the blocks, their molecular weights, and consequently, the total molecular weight. Also, in blends where one block of a compatibilizer is not miscible, but only compatible with, the corresponding blend component, achievement of thermodynamic equilibrium can be difficult, as it depends on the processing conditions. However, it seems that triblock copolymers can be considered the most efficient compatibiUzers for most of the blends studied. 

Effect of Compatibilizer Concentration. The compatibilizing efficiency of the copolymers is, besides the architecture, a function of their concentration. The effect of a compatibilizer concentration has been quantitatively characterized by the emulsification curve—the dependence of the average particle diameter of the minor dispersed phase on copolymer concentration (70). The particle diameter decreases with increase of copolymer concentration until a constant value is obtained. For most systems, this value is achieved if the copol5uner amount is 15—25% of the dispersed phase. There are systems where saturation was detected only at substantially higher concentration of a copolymer (181). 

Chatreenuwat B, Nithitanakul M and Grady B P (2007) The effect of zinc oxide addition on the compatibilization efficiency of maleic anhydride grafted HDPE compatibilizer for HDPE/PA6 blends, J Appl Polym Sci 103 3871-3881. 

S. Sinha Ray and M. Bousmina, Compatibilization efficiency of organoclay in an immiscible polycarbonate/poly(methyl methacrylate) blend. Macromolecular Rapid Communications, 26 (2005), 450-55. 

At this point, more experiments are needed to know how the distribution of the reactive groups along multifunctional chains affects the compatibilization efficiency of the copolymer formed at the interface. 

Figure 6.7 Compatibilizing efficiency of premade and reactively formed styrene-methyl methacrylate P(S-b-MMA) diblock copolymers for the PS/PMMA (70/30) blend in terms of the dispersed phase diameter as a function of mixing time. After Nakayama et al. [30]...

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