Cocontinuous Structures

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... 

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). 

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. 

Effect of different components in multicomponent blends based on polyamide 6 (PA 6) and styrenic polymers. Addition of a reactive compatibilizer maleic anhydride grafted styrene acrylonitrile (SANMA) changed the matrix-dispersed particle structure of PA6/styrene acrylonitrile (SAN) to a cocontinuous one. Replacement of part of SAN by polybutadiene particles led to a coarse cocontinuous structure (PA6/acrylobutadiene styrene [ABS]), which was refined after compatibUizer addition. SEM of cut surfaces etched in different solvents. (A) PA6/SAN = 50/50 wt%, SAN etched in tetrahydrofurane (B) PA6/ABS = 50/50 wt%, PA6 etched in formic add (C) PA6/ABS = 50/50 wt%, SAN etched in tetrahydrofurane (D) PA6/SAN+SANMA, PA6 etched in formic add (E) PA6/ABS+ SANMA, PA6 etched in formic add and (F) PA6/ABS = 50/50 wt%, PA6 etched in formic add. (From S. H. Jafari, P. Potschke, M. Stephan, G. Pompe, H. Warth, and H. Alberts, Polymer 43,6985-6922,2002. With permission.)... 

Nowadays, PS/PLA blends with a cocontinuous structure are one of the most attractive blends for generating biodegradable controlled release devices and tissue engineering scaffolds, since after selective removal of the PS phase from the blends, highly structured and completely interconnected porous PLA structures are obtained [32, 39-41]. The pore... 

Generally, the range of cocontinuity is dependent on the viscosity (torque) ratio. In blends with a viscosity ratio near unity, a fully cocontinuous structure appears around 50 50 composition otherwise, the component vhth a lower viscosity tends to form a continuous phase and the range of cocontinuity is shifted to the lower amounts of less-viscous component (Figure 3.11). A second important parameter determining the formation of cocontinuous structure is the interfacial tension. With increasing interfacial tension, the minor phase forms more spherical... 

In the present chapter, the morphology development of immiscible binary polymer blends is discussed. First, morphology development in droplet-matrix structures is described. Subsequently, the dynamics of fibrillar structures is reviewed and finally cocontinuous structures are briefly discussed. Although the main aspects of polymer blending are well established and polymer blends are already widely used in commercial products, recent novel insights in the areas of miniaturization and particle stabilization have opened new research topics in the area of polymer blending. In the last part of this chapter, these recent advances in polymer blend systems are briefly discussed. 

Figure 19.14 Transition from droplet-matrix structure to cocontinuous structure (a) Neat 60/40 PPS/PA66 blend. Zou et al. [193], Reproduced with permission of Elsevier, (b) 60/40 PPS/PA66 blend with 0,3 phr multiwall carbon nanotubes. Zou et al. [193]. Reproduced with permission of Elsevier, (c) Schematic representation of percolated particle network in a cocontinuous structure.

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