Volatile vapors

With a sufficiently long press cycle, a state of complete cure is reached. At this point, the laminate is cooled in the press, under pressure, and removed for finishing operations. If the press is opened at a temperature above the boiling point of trapped volatiles, vaporization occurs causing interlaminar blistering which mins the laminate. 

When sihca volatilizes, vapors condense on cooler areas to form a white bloom that can be removed by heat or dilute hydrofluoric acid. Because dilute hydrofluoric acid also attacks the substrate, a mild, careful treatment is required. To minimize volatilization, the temperature should be as low as possible. 

Figure 8-2 illustrates a typical normal volatility vapor-liquid equilibrium curve for a particular component of interest in a distillation separation, usually for the more volatile of the binary mixture, or the one where separation is important in a multicomponent mixture. 

Most batch distillations/separations are assumed to follow the constant relative volatility vapor-liquid equilibrium curve of... 

The diffusion system. Figure 8.31(B), is a useful and simple apparatus for preparing mixtures of volatile and moderately volatile vapors in a gas stream [388]. The method is based on the constant diffusion of a vapor from a tube of accurately known dimensions, producing a gas phase concentration described by equation (8.12). 

Substances with high vapor pressure evaporate rapidly. Those with low vapor pressure evaporate slowly. The impact of vapor pressure on the rate of evaporation makes vapor pressure a very important property in considering the tactical use and duration of effectiveness of chemical agents. A potential chemical agent is valuable for employment when it has a reasonable vapor pressure. One with exceptionally high vapor pressure is of limited use. It vaporizes and dissipates too quickly. Examples are arsine and carbon monoxide. On the other hand, mechanical or thermal means may effectively aerosolize and disseminate solid and liquid agents of very low vapor pressure. Vapor pressure and volatility are related. Translated into volatility, vapor pressure is most understandable and useful. 

Dust evaluation calculations are performed in a manner identical to that used for volatile vapors. Instead of using ppm as a concentration unit, mg/m3 or mppcf (millions of particles per cubic foot) is more convenient. 

Figure 3-3 Mass balance for volatile vapor in an enclosure.

Consider the enclosed volume shown in Figure 3-3. This enclosure is ventilated by a constant volume airflow. Volatile vapors are evolved within the enclosure. An estimate of the concentration of volatile in the air is required. 

C be the concentration of volatile vapor in the enclosure (mass/volume),... 

It follows that rfVc is the volumetric rate of bulk vapor being displaced from the drum (vol-ume/time). Also, if pv is the density of the volatile vapor, rfVcpv is the mass rate of volatile displaced from the container (mass/time). Using the ideal gas law,... 

In the first reaction, pyrolysis, the dissociated and volatile components of the fuel are vaporized at temperatures as low as 600°C (1100°F). Included in the volatile vapors are hydrocarbon gases, hydrogen, carbon monoxide, carbon dioxide, tar, and water vapor. Because biomass fuels tend to have more volatile components (70 to 86% on a dry basis) than coal (30%), pyrolysis plays a larger role in biomass gasification than in coal gasification. 

R.G. Ewing and CJ. Miller, Detection of volatile vapors emitted from explosives with a handheld ion mobility spectrometer. Field Analytical Chemistry and Technology 5(5) (2001) 215—221. 

The condensation of low-volatility vapors on preexisting particles depends on a number of factors, including the rate of collisions of the gas with the surface, the probability of uptake per collision with the surface, i.e., the mass accommodation coefficient (see Chapter 5.E.1), the size of existing particles, and the difference in partial pressure of the condensing species between the air mass and the particle surface. While some of these parameters are reasonably well known, others are not. For example, mass accommodation coefficients for the complex surfaces found in the atmosphere are not well known. Indeed, the exact nature of the surfaces themselves, which determines the uptake and the partial pressures of gases at the surface, remains a research challenge. 

Inhalants of abuse are substances whose volatile vapors can... 

The second ramp portion of this cure cycle is critical from a void nucleation and growth standpoint. During this ramp, the temperature is high, the resin pressure can be near its minimum, and the volatile vapor pressure is high and rising with temperature. These are the ideal conditions for void formation and growth. 

An appreciation of the importance of hydrostatic resin pressure must be developed to understand void growth fully. Because of the load-carrying capability of the fiber bed in a composite layup, the hydrostatic resin pressure needed to suppress void formation and growth is typically only a fraction of the applied autoclave pressure. The hydrostatic resin pressure is critical because it is the pressure that helps to keep volatiles dissolved in solution. If the resin pressure drops below the volatile vapor pressure, then the volatiles will come out of solution and form voids. 

Void formation and growth in addition curing composite laminates is primarily due to entrapped volatiles. Higher temperatures result in higher volatile pressures. Void growth will potentially occur if the void pressure (i.e., the volatile vapor pressure) exceeds the actual pressure on the resin (i.e., the hydrostatic resin pressure) while the resin is a liquid (Fig. 10.9). The prevailing relationship, therefore, is ... 

INHALANTS Legal household, industrial, medical, and office products that are volatile (vaporize or evaporate easily), producing chemical vapors. Abusers inhale concentrated amounts of these vapors, by various means, to alter their consciousness. 

Synonyms ethanal, acetic aldehyde Formula CH3CHO MW 44.05 CAS [75-07-0] used in the production of acetic acid, acetic anhydride, and many synthetic derivatives found in water stored in plastic containers colorless mobil liquid fruity odor when diluted boils at 20.8°C solidifies at -121°C highly volatile vapor pressure 740 torr at 20°C density 0.78 g/mL at 20°C soluble in water, alcohol, acetone, ether, and benzene highly flammable... 

Because of high reactor temperatures, the hydrocarbon volatiles vaporize immediately, and are vented from the reactor to a quench tower (Item 3), where they are sprayed with cooled, recycled, heavy oil, and the larger molecules (molecules containing eight carbon atoms (C8) or more) are condensed. The condensate leaves from the bottom of the quench tower and is collected in the heavy oil receiver (Item 4). Compounds that are not condensed (i.e., light oil, C3-C7) in the quench tower enter a non-contact condenser that uses cold water The light oils, C3 to C7, are condensed and collected in the light oil receiver (Item 6). 

Flavor Extraction and Concentration. The apparatus used for the steam vacuum stripping consisted of a Nickerson-Likens extractor as modified by Schultz et al. (2). The sample/water slurry was maintained at a boil of 57-60°C (600-610 itm gauge pressure) for one hour. During this time, approximately 200 mL of water vapor and flavor volatiles vaporized, condensed, and were collected in the 250 mL flask. A needle-valve was attached to a glass tube in the second neck of the sample flask to admit a controlled stream of charcoal filtered air through the sample for even boiling under vacuum. 

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