Void morphology

Youssef K. Hamidi, Levent Aktas, M. Cengiz Altan, Three-dimensional features of void morphology in resin transfer molded composites. Composites Science and Technology 65 (2005), pp. 1306-1320. 

Hamidi, Y.K. Altan, M.C. Spatial variation of void morphology in resin transfer molded e-glass/ epoxy composites. J. Mater. Sci. Lett. 2003, 22 (24), 1813-1816. 

The objective of this smdy is to be able to estimate the effective transport resistance of a porous medium by characterizing its void morphology by mercury porosimetry. A series of porous catalyst solids were obtained differing only in void morphology, overall porosity and pore sizes. We cahnilated the tortuosity by a dynamic experiment employing solid-gas chromato phy, SGC. Tortuosities of aU solids were very si ar, in the range of 5-25. Transport resistance is more easily related to overall volume porosity rather than specific network architectu features observable by porosimetry. 

For samples of intermediate porosity, produced by random agglomerative processes such as the selected solids used in this work, tortuosity is best estimated in the range of 10-20. This is considerably higher than l.S-2 which would be estimated assuming a void morphology of well packed microspheres. 

Since all solids were in the intermediate range of porosity (45-60% v/v), the measured transport might be less sensitivity to void morphology. Sensitivity to void architecture will be greater at extremes of porosity where percolation concepts might also be applicable. 

When monomers of drastically different solubiUty (39) or hydrophobicity are used or when staged polymerizations (40,41) are carried out, core—shell morphologies are possible. A wide variety of core—shell latices have found appHcation ia paints, impact modifiers, and as carriers for biomolecules. In staged polymerizations, spherical core—shell particles are made when polymer made from the first monomer is more hydrophobic than polymer made from the second monomer (42). When the first polymer made is less hydrophobic then the second, complex morphologies are possible including voids and half-moons (43), although spherical particles stiU occur (44). 

Impression Plasters. Impression plasters are prepared by mixing with water. Types I and II plasters are weaker than dental stone (types III and IV) because of particle morphology and void content. There are two factors that contribute to the weakness of plaster compared to that of dental stone. First, the porosity of the particles makes it necessary to use more water for a mix, and second, the irregular shapes of the particles prevent them from fitting together tightly. Thus, for equally pourable consistencies, less gypsum per unit volume is present in plaster than in dental stone, and the plaster is considerably weaker. 

CNT films are also of interest from morphological aspect because their structure provides nanoscale voids within the networks of CNTs. For example, composites with conducting polymers are very interesting both from scientific and technological interests, since we would expect CNTs to give a well-dispersed film. 

Morphology of the cured samples was analyzed by SEM of the fractured samples etched with tetrohydrofuran (THE), which is a solvent for the rubber. Figure 11.24 shows the fracture surfaces of the PWE and PNE specimens. Whereas the PWE fracture surface presents an essentially homogeneous surface with only a few small voids present, small yet uniformly distributed cavities are seen in PNE samples. The PWE morphology is consistent with the high degree of intermolecular link between rubber and epoxy macromolecules. The PNE morphology indicates incomplete reaction between epoxy and rubber. 

Figure 3. Schematic representation of the micro- and nanoscale morphology of gel-type (a) and macroreticular (b) resins [13], Level 1 is the representation of the dry materials. Level 2 is the representation of the microporous swollen materials at the same linear scale swelling involves the whole polymeric mass in the gel-type resin (2a) and the macropore walls in the macroreticular resin (2b). The morphology of the swollen polymer mass is similar in both gel-type and macroreticular resins (3a,b). Nanopores are actually formed by the void space surrounding the polymeric chains, as shown in level 4, and are a few nanometer wide. (Reprinted from Ref [12], 2003, with permission from Elsevier.)...

Macroporous substrates with interconnected voids can be used as platforms for biomacromolecule separation and enzyme immobilization. These assemblies are likely to find application in biocatalysis and bioassays. The inorganic framework can provide a robust substrate, while their large and abundant pores allow the transportation of biomolecules. The availability of various morphologies for macroporous materials provides another level of control over the function of the hybrids. 

Here, following the works of J.H. De Boer (Delft, The Netherlands, see elsewhere [1,2]), by texture one means the individual geometrical structure of catalysts, supports, and other porous systems (PSs) at the level of pores, particles and their ensembles (i.e., on a supramolecular level scale of 1 nm and larger). In a more complete interpretation, texture includes morphology of porous space and the skeleton of a condensed (solid or sometimes liquid) phase, the shape, size, interconnectivity, and distribution of individual supramolecular elements of the system particles and pores (or voids) between particles, various phases, etc. In turn, texturology also involves general laws of texture formation and methods for its characterization [3],... 

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