CoContinuity

The component with the lower viscosity tends to encapsulate the more viscous (or more elastic) component (207) during mixing, because this reduces the rate of energy dissipation. Thus the viscosities may be used to offset the effect of the proportions of the components to control which phase is continuous (2,209). Frequently, there is an intermediate situation where a cocontinuous or interpenetrating network of phases can be generated by careflil control of composition, microrheology, and processing conditions. Rubbery thermoplastic blends have been produced by this route (212). 

See also Carbon monoxide (CO) Cocondensation resins, 15 778-780 Cocontinuous morphology, in polymer blends, 20 329-330... 

Structural steels, tellurium in, 24 425 Structure(s), see also Chain structure Chemical structures Cocontinuous structures Controlled structure Crystal structure Molecular structure Morphology Phase structure of carbon fibers, 26 737-739 detersive systems for, 8 413t HDPE, 20 157-162 LLDPE, 20 182-184, 203-205 polyesterether elastomer, 20 72-73 polyester fiber, 20 21 polyether antibiotics, 20 137-139 polyimide, 20 276-278 polymer, 20 395-405 protein, 20 449 PTT, 20 68t... 

Lavorgna, M., Mensitieri, G., Scherillo, G., Shaw, M. T., Swier, S. and Weiss, R. A. 2007. Polymer blend for fuel cells based on SPEKK Effect of cocontinuous morphology on water sorption and proton conductivity. Journal of Polymer Science Part B Polymer Physics 45 395-404. 

Fig. 1 Development of morphology in a thermoplastic vulcanizate from cocontinuous (left) to dispersed phase (right) [14]...

Transmission electron microscopy measurements reveal that the nanotubes are selectively located in the PA-6 phase. The selectively filled PA-6/ABS blends show a highly irregular, cocontinuous morphology. 

The structure and mechanical properties of ASA and blends of ASA and poly(butylene terephthalate) (PBT) have been studied. 40/60 and 60/40 blends of ASA/PBT are composed of two phases, thus are dispersed, while a 50/50 blend shows a cocontinuous structure. With increasing processing temperature, the mechanical properties decrease, probably due to the degradation of PBT in the course of processing. The mechanical properties do not as much decrease for blends with a continuous structure (24). 

At the recent European Symposium on Polymer Blends [59] about half of the contributions dealt with thermodynamic effects on molecular architecture, on polymer morphology, and on processing and performance of polymer blend materials. Although some attention has been focused mainly on the interface (material) in heterogeneous blends, in general most thermodynamic studies of such heterogeneous blends deal with two- or more bulk phases. Essential morphological features such as droplet size, cocontinuous phases, micellar or... 

Steinmann S, Gronski W, Friedrich C (2001) Cocontinuous polymer blends influence of viscosity and elasticity ratios of the constituent polymers on phase inversion. Polymer 42 6619-6629... 

Galloway, J. A., Montminy, M. D. and Macosko, C. W. (2002) Image analysis for interfacial area and cocontinuity detection in polymer blends. Polymer, 43,4715-22. 

At some volume fraction, mostly around

phase inversion occurs around this value, A and B are both continuous. This may, however, also happen at other values of (p, depending on the rheological behaviour of the components. Moreover, cocontinuity is possible at any volume fraction (see in 9.1.4 the remark on SBS). For the properties of a co-continuous two-phase system an expression has been derived by Nielsen ... 

Fig. 4 Isothermal FIPI paths for the inversion of (A-in-B) or (B-in-A) emulsions through a cocontinuous unstable emulsion phase (AB). TSV, thermodynamic state variable DSV, deformation state variable. (View this art in color at WWW. dekker. com.)...

Fig. 6. Scanning electron micrographs of various morphologies produced with tailor-made thermoplastics toughened epoxy resins (A) homogeneous, (B) particulate, (C) phase inverted, (D) and (E) cocontinu-ous. (From Flamerton, L, Ed. Chemistry and Technology of Cyanate Ester Resins, Blackie Academic and Professional Glasgow, 1994.)...

Shortly thereafter, Yeo, et al. (7.8) showed that the domain size depended quantitatively on the crosslink density, the interfacial surface tension, and the temperature. For many compositions involving non-polar polymer pairs and moderate crosslinking levels, domain sizes of the order of 50-100 nm were predicted. While the theory was developed for spheres for simplicity, it was already known that both phases tended to be cocontinuous, especially for midrange compostions... 

Harrats C, Blacher S, Fayt R, Jerome R, Teyssie Ph. Molecular design of multicomponent polymer systems. XIX. Stability and cocontinuous phase morphologies in low density polyethylene/polystyrene blends emulsified by block copolymers. J Polymer Sci Part B Polym Phys 1995 33 801-811. 

It has been reported that the onset of cocontinuity occurs at an average volume fraction, onset = 0-19 0.09. In many branches of physics, the concept of percolation has been found useful. For example, when the concentration of conductive spheres in non-conductive medium exceeds the percolation threshold volume fraction, there is a sudden increase of electrical conductivity. For a three-dimensional case, 3D, the theory predicts that (b = 0.156, for ID it is 6 =0.019. 

Co-continuous morpholoey A different type of morphological structure, cocontinuity of the phases, can prove beneficial by drawing on properties of both constituents stiffness from a rigid polymer and high strain at break from a ductile one. This is illustrated by Kyu et al. (1991) who studied the toughness enhancement of PC/PMMA blends. The blends were prepared using three different procedures ... 

The three components of the normal vector cannot be computed from 2D micrographs without previous knowledge (or assumption) of the interface shape. For simple shapes with axial symmetry that can be described with simple functions, such as ellipsoidal droplets and cylindrical threads, analytical expressions for (and qy) have been obtained from 2D images [193-195]. However, for complex interfaces (e.g., cocontinuous structures), which are not axisymmetric and cannot be described by any analytical equation, this approach is not applicable. 

Figure 20.4 (a) 3D-rendered interface of 50/50 PS/SAN cocontinuous blend. The color in... 

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