Heterogeneous polymer blends

Binary fluorides, methods of preparing noble-gas, 77 335-336 Binary heterogeneous polymer blends compliance of, 20 347-348 moduli of, 20 346-347 nonlinear viscoelastic behavior of, 20 348 yield and/or tensile strength of, 20 348-349... 

Binary plutonium halides, 79 689 Binary plutonium oxide, 79 688 Binary polymer blends, 20 330-334, 343. See also Binary heterogeneous polymer blends... 

Heterogeneous particle morphology, in polymer colloids, 20 387 Heterogeneous photocatalysis, 19 73, 103 principles of, 29 74-75 Heterogeneous polymer blends, 20 343. 

McPeters and Williams6 at Rohm and Haas (Spring House, PA, USA) used in-line transmission NIR to monitor the compositions of heterogeneous polymer blends and... 

REDOR was also applied to examine the structure and dynamics of interfaces of heterogeneous polymer blends. A heterogeneous blend was prepared from [carbonyl- C]polycarbonate and poly(p-fluorostyren-co-styrene) copolymer of p-fluorostylene. The blend was formed by coprecipitation from chloroform into methanol. A fluorine dephased REDOR signal indicates that the 1 polycarbonate chain in 20 exists at the interface, suggesting that the polycarbonate phase is embedded in a continuous polystyrene matrix which is 200 A thick or 400 A in diameter [54],... 

Table 11 compares the effectiveness of a synergistic UV stabilizer (BHBM-B + EBHPT-B) with some commercial stabilizing systems for ABS added conventionally. The exceptional activity of the polymer-bound system is believed to be due to the fact that it is confined to the rubber phase of the polyblend (18), which is known to be more sensitive than the thermoplastic phase to the effects of both heat and light (36). This finding, if confirmed in other multiphase systems, could be of considerable importance for the stabilization of heterogeneous polymer blends. 

Radioluminescence spectroscopy has been used to examine molecular motion, solubility, and morphology of heterogeneous polymer blends and block copolymers. The molecular processes involved in the origin of luminescence are described for simple blends and for complicated systems with interphases. A relatively miscible blend of polybutadiene (PBD) and poly(butadiene-co-styrene) and an immiscible blend of PBD and EPDM are examined. Selective tagging of one of the polymers with chromophores in combination with a spectral analysis of the light given off at the luminescence maxima gives quantitative information on the solubility of the blend components in each other. Finally, it is possible to substantiate the existence and to measure the volume contribution of an interphase in sty-rene-butadiene-styrene block copolymers. 

Figure 2. Ion recombination processes. Schematic of electron trapping in heterogeneous polymer blend near domain interface.

Fig. 12.5 Possible types of compatibiliser (a) diblock, (b) triblock, (c) multigraft and (d) single-graft copolymers at the interface of a heterogeneous polymer blend. A and B represent the two components of the blend O and represent the monomers of the blocks C and D, respectively, of the compatibilising molecules. (Adapted with permission of Elsevier Science.)...

We have recently shown that the presence of phase-separated structures in heterogeneous polymer-blend microparticles can be indicated qualitatively by a distortion in the two-dimensional diffraction pattern. The origin of fringe distortion from a multi-... 

The mechanical properties of the blends can be correlated with the morphology of the blends. The variation in morphology of heterogeneous polymer blends depends on composition of blend, melt viscosity of the individual polymers, and processing history [42]. When polymers with different viscosities are mixed to form blends, less viscous polymer will form the continuous phase [54]. The optical photomicrographs of PMMA/EMA blends are shown in Figures 5.11a through 5.11c, respectively. EMA is found to be... 

J.A. Barrie, K. Monday, Gas transport in heterogeneous polymer blends. Journal of Membrane Science 13 (1983) 175. 

More down-to-earth challenges do get attention from thermodynamics scientists such as supercritical polymerizations, energy storage via organic solar cells, copolymeric compatibilizers in the interphase of compressed heterogeneous polymer blends, membranes and monolayers. 

The morphology of heterogeneous polymer blends is controlled by interfacial tension. The interfacial tension, a, is intrinsically positive and can be defined as the change in the Gibbs free energy when the interfacial area A is reversibly increased at constant temperature and pressure at closed system (24). 

A direct comparison of the spatial resolution of XPS and transmission infrared spectroscopy imaging on heterogeneous polymer blends of poly(vinyl chloride)/PMMA was presented by Artyushkova et al. [226] The spatial resolution of the XPS and infrared instruments was 2-3 p,m and 7 p.m, respectively. The comparable resolution of the instrumentation allowed for images and spectra from the same areas of the samples to be directly compared (Fig. 32). 

Heterogeneous Polymer Blends from Plastics Recycling... 

An important criterion for the performance of blends is the specific surface of the disperse phases, i.e., the shape and size of the dispersed particles. In heterogeneous polymer blends, interactions are possible only through the interfaces. Besides the thermodynamic interactions, the specific surface determines the adhesion between the phases and therefore the properties of the blend. 

The phenomenon of carbon black (CB) particles gathering at the interface in binary heterogeneous polymer blends is not only of fundamental interest, but has a practical aspect as a method for improving the electric conductivity of composite polymer materials [1-12] and the mechanical properties of polymer blends with a low interfacial adhesion [13-15], The works examining the causes of this phenomenon are few in nmnber. Most of authors only note that some part of a filler tends to accmnulate at the interface. Contradictory assmnptions of the conditions necessary for such localization are made. 

It is known that carbon-black filled polymers conduct electric current only with the concentration of carbon black exceeding the threshold of percolation ((p ). In heterogeneous polymer blends carbon black is distributed nonuniformly between polymer phases. If the concentrations of carbon black in both phases of a blend are lower than (p, the blend can conduct electric current only subject to the condition that the part of carbon black is localized at the interface and its concentration here reaches the percolation threshold [12]. So if the concentration of carbon black in both phases of a blend is only slightly lower than (p, even a minor accumulation of carbon black at the interface confers conductivity on the polymer blend. This enables the extent of carbon black aggregation at the interface to be judged by the conductivity value. 

In both phases of a heterogenous polymer blend the shear stress is the same, so the same is the force of particle removal from the interface. Hence, the local equilibrium eoneentration of particles at the interface will be determined by their adhesion to a phase. In this case it is important to specify to what of two polymer phases the adhesion is considered. It is known [I] that the transfer of filler partieles from one phase of polymer blend to another is observed very rarely. Therefore, in most cases the particles of a filler after abstraction from the interfaee return back in that phase Irom which they came to the interface. Otherwise a fast transfer of a filler would be observed from a phase of lower wetting force to opposite polymer phase. So the force holding particles at the interface is a result of their adhesion to the unfilled polymer phase. Besides, this suggests... 

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