Occluded volume

While the occluded volume mechanism holds considerable attraction, it is by no means established that this is indeed the sole or even the major cause of the large t]r of polymers filled with highly reinforcing carbon... 

The structural class can be divided into 10 groups, based on particular approach to the problem as, for example, hydrodynamic theories. They belong models of Guth and Gold and Smallwood, but some authors include also the occluded volume theory of Medalia and theories of filler and bonded rubber compact spheres of Brennan and Jermyn and some others. The groups can be described as ... 

Recalling the assumptions involved in deriving Equation (8.8), it may be concluded that when the occluded volume correction is made as suggested by Medalia [16], the sphere model for an isolated filler particle is a good approximation this conclusion is valid only at a low loading, where the modulus is practically independent of strain amplitude, and only binary interaction between particles needs to be considered. 

Viscosity. Because a clump of particles contains occluded Hquid, the effective volume fraction of a suspension of clumps is larger than the volume fraction of the individual particles that is, there is less free Hquid available to faciHtate the flow than if the clumps were deagglomerated. The viscosity of a suspension containing clumps decreases as the system becomes deagglomerated. This method is not very sensitive in the final stages of deagglomeration when there are only a few small clumps left. 

Sediment Volume. If the dispersion is unstable, the sediment bed will be quite deep and sedimenting particles will stick together where they first strike the sediment bed, thus forming an open stmcture with considerable occluded Hquid. If the dispersion is stable to reagglomeration, the particles will move freely past one another to avoid contact as long as possible. The result is a thin sediment bed with maximum soHds packing and minimum occluded hquid (12). Since dispersed particles setde more slowly than docs, centrifugation maybe needed to force sedimentation of small particles within a reasonable analysis time. 

Aldehydes are usually most easily separated from the essential oils in which they occur, by means of acid sodium sulphite. The oil—or the suitable fraction thereof— is well shaken for a time varying according to the nature of the aldehyde, with an equal volume of a saturated solution of sodium bisulphite, with a little ether added, in order to hinder the non-aldehydic portion of the oil from becoming occluded in the crystals of the bisulphite compound of the aldehyde. These crystals are separated and washed well with ether They are then decomposed by warming with a solution of sodium carbonate, and the regenerated aldehyde is extracted by means of ether. 

A piperidene-based intermediate was found to crystallize as either an anhydrate or a hydrate, but the impurity profile of the crystallized solids differed substantially [26], Considerations of molecular packing led to the deduction that there was more void volume in the anhydrate crystal structure than in that of the hydrate form, thereby facilitating more clathration in the anhydrate than in the hydrate phase. This phenomenon was led to a decision to crystallize the hydrate form, since lower levels of the undesired impurity could be occluded and greater compound purity could be achieved in the crystallization step. 

The difference between the eluted volume found with p-xylene (Veiutedpxylene) and TIPCyC6 (VeiutedTIPCyC6) allows to evaluate the occluded mesopores volume (Vocduded) as ... 

Here, rqtz is the rate of quartz precipitation (mol s-1 from a kg of water) and My is the mineral s molar volume (22.7 cm3 mol-1). Figure 26.4 shows the resulting sealing rates calculated for several traversal times. For a At of one year, for example, we expect the fracture to become occluded near its high-temperature end over a time scale of about 10 000 years. 

The recoverability of hydrocarbon from the subsurface refers to the amount of mobile hydrocarbon available. Hydrocarbon that is retained in the unsaturated zone is not typically recoverable by conventional means. Additional amounts of hydrocarbon that are unrecoverable by conventional methods include the immobile hydrocarbons associated with the water table capillary zone. Residual hydrocarbon is pellicular or insular, and is retained in the aquifer matrix. With respect to recoverability, residual hydrocarbon entrapment can result in volume estimate discrepancies as well as decreases in recovery efficiency. With increasing water saturation, such as when the water table rises via recharge or product removal, hydrocarbons essentially become occluded by a continuous water phase. This results in a reduction of LNAPL and product thickness as measured in the well at constant volume. When water saturation is decreased by lowering the water table (as during recovery operations), trapped hydrocarbons can remobilize, leading to increased recoverability. 

In Rocks.—In a state of "occlusion, or molecular condensation, hydrogen is to be found in most igneous rocks in association with other gases, the total volume of occluded gases being on the average about 4 5 times the volume of the rock. 

An examination of a defective Admiralty bronze casting showed that there was an appreciable quantity of occluded gas in it, containing 7 6 per cent of hydrogen by volume ... 

The densities of polymers can be determined by the pyknometer technique or by the flotation method. In the pyknometer technique the liquid volume displaced by the polymer sample is determined by weighing. Most polymers have a density larger than that of water, which can, therefore, be used as the liquid. Polymers in the form of powders or pressed discs tend to adsorb or occlude air bubbles, which can lead to serious errors. This can be largely prevented by careful degassing of the pyknometer and polymer sample under vacuum before filling with liquid, and/or by addition of a small amount (0.1%) of commercial detergent to lower the surface tension of the water. 

Another coke formed in a FCC unit is occluded or residual coke. In a commercial unit this coke corresponds to coke formed on catalyst porosity and its content depends on textural properties of the catalyst (pore volume and pore size distribution) and the stripping system capacity in the reaction section. Finally on the FCC catalyst rests some high-molecular weight of nonvaporized hydrocarbons. These molecules do not vaporize or react at the reactor conditions and accumulate in the catalyst pores like a soft carbonaceous residue with high hydrogen content. 

Occluded coke is a function of the operating conditions of the FCCU stripper, of catalyst pore volume and pore size distribution. This coke that has the higher content of hydrogen is the lowest refractory between the different kinds of coke produced in the FCC process. Althongh in this study it was not directly evalnated, it may be associated with the peak A at the lowest temperature ( 500°C-550°C). So once the... 

Neon was discovered by Ramsay and Travers in 1898.1ts name comes from the Greek word neos, which means new. It is present in the atmosphere at a concentration of 0.00182% by volume (dry atmosphere). This element also is found in stars and interstellar gas clouds. Earth s earliest crust probably contained neon occluded in minerals. The gas later escaped into the atmosphere. 

The NMR chemical shift of I29xe adsorbed on molecular sieves reflects all the interactions between the electron cloud of the xenon atoms and their environment in the intracrystalline void volume [1]. This nucleus therefore proved to be an ideal probe for investigating various zeolitic properties such as pore dimensions [2, 3], location of the countercations [4, 5], distribution of adsorbed or occluded phases [6-8] and framework polarisability [8, 9]. 

Water and organic molecules occluded during the synthesis were removed from the intracrystalline volume as follows. The solids were slowly heated (5°C/min) in a N2 flow up to 550°C and held at this temperature for 2h. The coke deposit resulting from the non-oxidative degradation of the organics was then... 

Occluded IV catheter. Disconnect IV tubing from catheter attach a 1 -ml TB syringe with 5,000 U urokinase to catheter inject urokinase slowly (equal to volume of catheter). Connect empty 5-ml syringe aspirate residual clot. When patency is restored, irrigate with 0.9% NaCl reconnect IV tubing to catheter. 

The value of j8 for most solids lies in the range 10" to 10" dynes" Vcm" or about 10 to 10" psia" This implies that a sample with a volume of about 1 cm will be compressed by one millionth to one ten-millionth of a cubic centimeter for each pound of applied pressure. Therefore, at pressures as high as 60 000 psia the sample will compress by only 0.006 to 0.06 cm. However, some softer plastics and other materials may have greater compressibilities for which corrections should be made. Some materials have occluded pores without access to the surface and can collapse on pressurization. Figure 11.6 illustrates an intrusion-extrusion curve accompanied by compression and decompression curves for a sample of porous material. 

---