Volume specific

Specific volume v J, thermal expansion coefficient, heat capacity at constant pressure (cj, heat capacity at constant volume (cj, enthalpy, entropy, and thermal conductivity (X) are thermal characteristics relevant for processing and applications. They depend on PE grade, temperature, pressure, average molecular weight, branching, crystallinity or density, stretching ratio, heating rate, spherulite size, and so on. 

Values of specific volume for different grades of PE at different temperatures and pressures are given in Table 3.5. 

Derksen (1935) measured the specific volume of a much more con- 

The decrease in apparent specific volume of gelatin accompanjdng gelation should result in a shift of the process toward gelation at high pressures. An effect of this sort has been observed by Marsland and Brown (1942), who found that the viscosity of a 4% solution increased by a factor of 10 when the confining pressure was increased to 8000 lbs. per sq. in. 

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Now using a hydrocarbon component, say ethane, as an example, let us consider the other parameter, volume, using a plot of pressure versus specific volume (i.e. volume per unit mass of the component, the inverse of the density). The process to be described could be performed physically by placing the liquid sample into a closed cell (PVT cell), and then reducing the pressure of the sample by withdrawing the piston of the cell and increasing the volume contained by the sample. 

Starting at condition A with the ethane in the liquid phase, and assuming isothermal depletion, then as the pressure is reduced so the specific volume increases as the molecules move further apart. The relationship between pressure and volume is governed by the compressibility of the liquid ethane. 

Because the neutron tool responds to hydrogen it can be used to differentiate between gas and liquids (oil or water) in the formation. A specific volume of gas will contain a lot fewer hydrogen atoms than the same volume of oil or water (at the same pressure), and therefore in a gas bearing reservoir the neutron porosity (which assumes the tool is... 

Now integrate the equation (5) taking into account the formulae for pi and pN. As a result we arrive to the specific volume flow rate in a film, referred to the unit of length for cross section ... 

Glassware designed to contain a specific volume of solution when filled to its calibration mark. 

Figure 4.1 Schematic illustration of possible changes in the specific volume of a polymer with temperature. See text for a description of the various lettered phenomena.

If the amorphous component contributes nothing to the measured property (as with heat of fusion), then Eq. (4.39) reduces to Eq. (4.37). Specific volume is an example of a property which has been extensively used in this way to evaluate 6. 

As noted above, not all techniques which provide information regarding crystallinity are useful to follow the rate of crystallization. In addition to sufficient sensitivity to monitor small changes, the method must be rapid and suitable for isothermal regulation, quite possibly over a range of different temperatures. Specific volume measurements are especially convenient for this purpose. We shall continue our discussion using specific volume as the experimental method. 

Although the extent of crystallinity is the variable under consideration, time is the experimental variable. Accordingly, what is done is to identify the specific volume of a sample at t = 0 (subscript 0) with V, the volume at t = °° (subscript °o) with and the volume at any intermediate time (subscript t) with the composite volume. On this basis, Eq. (4.39) becomes... 

In discussing Fig. 4.1 we noted that the apparent location of Tg is dependent on the time allowed for the specific volume measurements. Volume contractions occur for a long time below Tg The lower the temperature, the longer it takes to reach an equilibrium volume. It is the equilibrium volume which should be used in the representation summarized by Fig. 4.15. In actual practice, what is often done is to allow a convenient and standardized time between changing the temperature and reading the volume. Instead of directly tackling the rate of collapse of free volume, we shall approach this subject empirically, using a property which we have previously described in terms of free volume, namely, viscosity. 

Sephadex G-X Specific volume water mL/g dry gel Permeabihty, iC Operating pressure, kPa Flowrate water, mL/(cm h)... 

Polymeric materials are unique owing to the presence of a glass-transition temperature. At the glass-transition temperatures, the specific volume of the material and its rate of change changes, thus, affecting a multitude of physical properties. Numerous types of devices could be developed based on this type of stimuli—response behavior however, this technology is beyond the scope of this article. 

Enthalpy. Enthalpy is the thermodynamic property of a substance defined as the sum of its internal energy plus the quantity Pv//, where P = pressure of the substance, v = its specific volume, and J = the mechanical equivalent of heat. Enthalpy is also known as total heat and heat content. 

Pressure. Standard atmospheric pressure is defined to be the force exerted by a column of mercury 760-mm high at 0°C. This corresponds to 0.101325 MPa (14.695 psi). Reference or fixed points for pressure caUbration exist and are analogous to the temperature standards cited (23). These points are based on phase changes or resistance jumps in selected materials. For the highest pressures, the most rehable technique is the correlation of the wavelength shift, /SX with pressure of the mby, R, fluorescence line and is determined by simultaneous specific volume measurements on cubic metals... 

The free volume, T of a polymer is described by the equation where % = specific volume at a temperature t and V° = specific... 

Fig. 4. Specific volume vs temperature for a crystallizahle polymer. The dashed line represents amorphous material (6). Numbers refer to individual states.

The dielectric constants of amino acid solutions are very high. Thek ionic dipolar structures confer special vibrational spectra (Raman, k), as well as characteristic properties (specific volumes, specific heats, electrostriction) (34). 

Fig. 1. MoUier diagram for ammonia. Numbers on dashed lines represent specific volume values ia m /kg. To convert from kPa to psi, multiply by 0.145.

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