Entrapment cross-section

CaC03 precipitation is clearly visible in Figure 14.14, which is a TEM image of halloysite cross-sections. Halloysite has >90% of the tubular form with outer diameter 50 5nm and inner diameter of the lumen 15 nm. The length of the initial halloysite is less than 1 micron, which results in a substantially short diffusion path length. The calculated value of the free inner space indicates the ability to load a maximum 14 3 % of the total volume ofthe halloysite. The entrapment efficiency of 5 % by volume was estimated. 

Fig. 8 Preparation of biodegradable microspheres entrapping proteins using amphiphilic PDP-b-PLA block copolymers as biodegradable polymeric surfactants, and SEM images of their cross-sections. Reprinted from [182] with permission...

FIGURE 24.10 Schematic cross section of the polypyrrole/polycarhonate/polypyrrole sandwich membrane with the epoenzyme entrapped in the pores. The membrane is drawn as coming out of the plane of the paper. The various components are not drawn to scale. (From Lakshmi, B.B. and Martin, C.R., Nature, 388, 758, 1997. With permission.)... 

Fig. 27 Cross-sectional view of a bioresponsive insulin delivery system, a feedback-regulated drug delivery system, showing the glucose oxidase-entrapped hydrogel membrane constructed from amine-containing hydrophilic pol5mier. The mechanism of insulin release, in response to the influx of glucose, is also illustrated. (From Ref. l)...

First, a bundle of fibers will entrap air both between the fibers and also on the fiber surfaces, since we are not dealing with cylindrical specimens but with fibers which may-have very complex cross-sectional shapes and helices. If all this entrapped air is not displaced and remains trapped by the fiber, the liquid displacement will be too high (i.e., the assumed fiber volume will be too high) and the calculated density will as a consequence be too low. 

The existance of non-wetting phase(s) oil or gas, in a water-wet system reduces the total cross-sectional area available for polymer solution flow. Therefore, the role of mechanical entrapment increases. 

Typically, a fiber bundle has hundreds to thousands of fibers in an elliptical cross-section with a width of a few nuflimeters. Considering that a glass or carbon fiber has a diameter of 10 microns approximately, and if all the fibers are densely packed in a bundle, the gap between the fibers is only in the order of microns (i.e., 10 m). This is much smaller empty space than the empty space between the fiber bundles which is typically of the order of millimeters (i.e., 10 m). These two types of empty spaces give rise to two scales of permeabilities encountered by the resin flow, and they may result in microvoid entrapment inside the fiber bundles. 

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