Filled Porous Systems

In most of the two-component systems discussed so far, such as rubber-reinforced polyblends, the density or specific volume is approximately an average of the values for each component. There may be some exceptions to this generalization for example, if the smaller component fills free volume available in the major phase (Chander, 1971 Harmer, 1962 Huang and Kanitz, 1969). A similar but more important phenomenon exists when the volume available for filling by a monomer comprises not only free volume elements, but also gross pores, which may range in size from tens of angstroms to the order of micrometers or more. Examples of matrices may include partially sintered polymers, ceramics or metals, cement, concrete, minerals and rocks, paper, and wood (American Chemical Society, 1973). Clearly such systems tend to be complex even the matrix itself is often a multiphase material. 

The properties of filled porous systems must, for a given matrix type, depend on several factors (1) the degree of porosity, (2) the nature of the porosity (size, degree of pore connectivity, shape, and distribution of sizes), (3) the properties of the polymeric filler, including its state, and (4) the nature of the filler-matrix interface. 

Rationalization and prediction of behavior will, of course, depend on the classification that applies, e.g., interpenetrating networks or discontinuous phases in a matrix (American Concrete Institute, 1973u Krock, 1966). The classification itself must be general, and not specific to polymers, metals, or ceramics. When porosity is negligible, models such as those discussed in Chapter 12 may be appropriate otherwise the effects of porosity and of changes in porosity must be taken into account. 

In general, because of the strong interest in the practical behavior of this class of two-component materials, technology tends to have advanced more rapidly than fundamental understanding. The discussion that follows summarizes our state of knowledge about the preparation and behavior of 

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In this chapter, a number of transport phenomena with entirely different natures are compared for liquids filling porous systems. Here transport can refer to flow, diffusion, electric current or heat transport. Corresponding NMR measuring techniques will be described. Applications to porous model objects will be juxtaposed to computational fluid dynamics simulations. 

All of the examples of PEMs discussed within Section 3.3 unhl now have been composed of only one polymer system without any other compounds present—be they small molecules, polymers, or solid-state materials. A wide variety of different polymer blend and composite PEMs has been made. However, in this section, only a brief overview highlighting some of the more interesting examples that have been reported in the literature will be presented. Eor discussion, these types of PEMs have been divided into three categories polymer blends, ionomer-filled porous substrates and reinforced PEMs, and composite PEMs for high-temperature operation and alternative proton conductors. 

The adsorption of vapors in complex porous systems takes place approximately as follows [1-3] at first, micropore filling occurs, where the adsorption behavior is dominated nearly completely by the interactions of the adsorbate and the pore wall after this, at higher pressures, external surface coverage occurs, consisting of monolayer and multilayer adsorption on the walls of mesopores and open macropores, and, at last, capillary condensation occurs in the mesopores. 

Abstract Porous copolymers have been prepared by suspension-emulsion polymerization of divinylbenzene with styrene or some methacrylic monomers di(methacryloyloxymethyl)naphthalene, methacrylic ester of p,p -dihydroxy-diphenylpropane diglycidyl ether, and dimethacrylglycolethylene in the presence and absence of chemically modified fillers (fumed silicas with grafted methyl and silicon hydride groups). The results of investigations of the unfilled and filled polymeric systems by IR and 13C NMR spectroscopies combined with AFM are presented. 

We will now consider gas-filled polymeric systems as bodies composed of a very large number of individual particles containing spaces. In general these spaces may be either void or filled with gas or liquid. For simplicity, the particles themselves will be assumed to be non-porous. 

Let a sufficiently portion of the porous system have a net volume of which is composed of the volume of the substance (the solid phase) V, and the total volume of all voids V. The gas filling G will then be given by the ratio of V, to the total of the system ... 

What is actually the meaning of the parameters G and U with respect to probability The value U is the probability of the filling of a finite volume of an addition system by the elements of a porous system or, alternatively, the probability of encountering individual elements within a given volume. Accordingly, G is the probability of the recurrence of voids in a system. It is extremely important that, as might be expected for dimensionless probability parameters, neither G nor U depend on the nature of the elements or the absolute geometrical dimensions of the latter... 

Eq. (12) has commonly been used, e.g. in the analysis of mass and gas transfer in gas-filled systems. From this relationship it may be deduced that varies from 0 to 00 and that = 1 when G = 0.5. Systems for which G 4 0.5 are poorly gas-filled ( low-porous ) and those with G > 0.5 are highly gas-filled . The rule of reciprocals ( reversal rule ) facilitates the analysis of gas-filled structures such as foamed plastics by enabling the use of the so-called complementary gas-filled (porous, cellular) systems. The complementary systems relate to each other as a mold and casting or negative and positive . 

Parra, J.O., 1991. Analysis of elastic wave propagation in stratified fluid-filled porous media for interwell systemic applications, Journal of the Acoustic Society of America 90 pp. 2557-2575. 

One of the ways of improving wear resistance and reliability of sealing elements is filling of porous semis by components able to form a secondary porous system [146]. For example, a blank of a polyurethane foam is impregnated with a mixture of dispersed PE with an inhibited lubricant. The formation of a gel under certain temperature regimes is accompanied by phase distribution within the material. The contact surface of the blank is cleaned by acetone to remove the lubricant. As the acetone evaporates, the prepared zones are zinc-plated and pores freed from the lubricant become filled with zinc. This makes the coating adhere strongly to the surface and allows zinc to penetrate to a depth acceptable for wear limits. 

The capillary and porous system of the body exists in vascular tissue and intercellular spaces. Xylem forms an open conduit of relatively low hydraulic resistance that is filled with diluted mineral solution. Phloem exists in cells with a width ranging from 10 to 70 pm and a length from 100 to 500 pm in dicotyledons [4]. Their turgor is around 2 MPa (beetroot is 1.83 MPa) with a pressure gradient of 0.02-0.03 MPa/m [5,6]. As phloem transports substances of very different molecular weight, shape, charge, and surface activity along with water, it is presumed that the mechanism is an osmotically driven solution flow [6]. 

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