Vapor development

VaporSep A family of separation processes, based on membranes which are selectively permeable to organic vapors. Developed by Membrane Technology Research, CA, in the... 

Two rabbits which survived 118 periods of exposure to 0.36 ppm (15 mg/m3) of endrin vapors developed a granulomatous pneumonitis (Treon et al. 1955). The pneumonitis was not observed in cats, guinea pigs, hamsters, rats, or mice, but the small number of animals tested limits the usefulness of this study. 

Figure 17. Effect of beam current (dose rate) on the vapor development of poly (2-methyl-1 -pentene sulfone).

A chemical worker accidentally exposed to an unknown concentration of the vapor developed giddiness, diarrhea, sleepiness, and irritability, with recovery in a week when reexposed 3 months later, he experienced drowsiness, vomiting, pallor, incoordination, slurred speech, muscular twitching, oliguria, coma, and death. At autopsy there were bronchopneumonia and pulmonary hemorrhages, with accumulation of combined iodine in the brain. 

These apparent contradictions can be rationalized in terms of a model which incorporates plasma-induced polymerization along with depolymerization. PBS has long been known to exhibit a marked temperature-dependent etch rate in a variety of plasmas. This is clearly seen in the previously published Arrhenius plots (3,7) for two different plasma conditions (Figure 1). This dependence is characteristic of an etch rate that is dominated by an activated material loss as would occur with polymer depolymerization. The latter also greatly accelerates the rate of material loss from the film. Bowmer et al. (10-13) have shown in fact that poly(butene-l sulfone) is thermally unstable and degrades by a depolymerization pathway. A similar mechanism had been proposed by Bowden and Thompson (1) to explain dry-development (also called vapor-development) under electron-beam irradiation. 

The first example of formation of a resist relief image in the absence of a wet developing step was reported by Bowden and Thompson in 1974 (131). They reported that exposure of certain poly(olefin sulfones) to electron beam radiation resulted in spontaneous relief image formation. When the films were cast thin enough and the substrates were heated above 90 C, clean images were produced in the resist film by exposure alone. They termed this phenomenon vapor development . 

Two types of commercial TSP vaporizers were used, i.e., the capillary vaporizers developed by Vestal and coworkers [64-65] and commercially available from Vestec, and the flexible capillary vaporizers introduced by Fiimigan MAT [66]. Problems with clogging of the Vestec type vaporizers were reported frequently. Replacement of the complete vaporizer is the final but expensive solution to clogging. With the Fiimigan MAT type of vaporizer, the tip must be slightly squeezed to ensure the formation of a sufficiently stable liquid jet at a particular flow-rate, which inevitably leads to poor reproducibility between vaporizers. 

This was verified in a subsequent study by NARCO [25] in which a more detailed explanation of the mechanism of frost formation was given. It is well known that silica bricks exposed to soda vapor develop a liquid phase at around 1450°F. The amount of liquid in the brick will increase as the amount of flux is increased. The liquid thus formed is gradually absorbed into the interior of the brick until the voids are filled. On the... 

Flash point Criterion for flammability of combustible liquids with subdivision into hazard categories. The flash point is the lowest temperature at which vapor develops from a liquid to such an extent that an inflamable vapor-air-mixture results, for example, hazard categories for adhesives or solvents ... 

Figure 1. Effect of postexposure baking on vapor development rate for single pass and multiple pass exposures.

Figure 11. Vapor development curves for PMPS in 20 PMPS/80 novolac composite film (lower curve postexposure baked at 130 °C for 2 h). Key , 1298 cm-1 ...

PMPS has been shown elsewhere to be vapor developable, which means that the polymer is vaporized and removed during electron beam exposure(13). The vapor development characteristics of PMPS are shown here in Figure 1. PMPS was not completely removed by a dose of 2xl0-5 C/cm2 at 15kV. Therefore, a resin suitable to NPR should show a large solubility increase with a decrease in its concentration in NPR. 

Figure 1. Exposure characteristics of PMPS prepared by vapor development (a) at 15kV (b) at 30kV.

Several studies that examined kidney toxicity of jet fuels other than JP-8 were described in the 1996 report (Parker et al. 1981 Bogo et al. 1983 MacEwen and Vernot 1985 Bruner et al. 1993). The results of those studies were consistent with the results of the Mattie et al. (1991) study. Male rats exposed to JP-4, JP-5, or DFM vapors developed kidney lesions consistent with hyaline droplet degeneration and resembling what is known as alpha 2u-globulin nephropathy. The mechanisms that underlie the development of that lesion are believed to occur only to male rats. The 1996 subcommittee concluded that the lesion is not expected to occur in humans. 

While this project is relatively new, significant progress has been made regarding the component design and modeling, sorbent and catalyst development and microchannel system development tasks. We will continue to focus on these tasks and microcombustor/vaporizer development. In addition, methods will be demonstrated to integrate catalysts into the micro-reactors. 

Liquids are necessarily more complicated than gases. To start with, they have much greater cohesiveness than gases for example, a liquid equilibrated with its gaseous vapor develops a meniscus. This boundary has a measurable surface tension caused by the asymmetry of particle interactions in the liquid and minimal interaction of particles in the gas phase above it. Hence a liquid must have significant interaction... 

M.J. Bowden and L.F. Thompson, Effect of olefin structure on the vapor development of poly (olefin sulfones) under electron irradiation, Polym. Eng. Sci. 17, 269 (1977). 

DTBP is slightly toxic by inhalation and in general exhibits low to very low toxicity by other routes. However, toxic effects are observed only at very high concentrations. Rats exposed to 4103-ppm vapor developed head and neck tremor after 10 minutes of exposure (Floyd and Stockinger 1958). Other symptoms were weakness, hyperactivity, and labored breathing. However, the animals recovered fully in 1 hour. 

The gravimetric, the bithermal, and the method based on the interpolation of weight changes are the best known, but of these the gravimetric method is the most widespread. This method is described here in detail references are provided for the others [8-10,29]. Constant vapor pressure is maintained by means of an acid or salt solution of a specified concentration. It is known that the moisture content of wet air, in equilibrium with an add or salt solution of known concentration, is constant at a given temperature. Partial pressures of water vapor developed with the use of solutions of sulfuric acid can be determined, as shown in Figure 2.1. The relative vapor pressure above an aqueous solution of sulfuric acid as a function of concentration and temperature can be calculated by the correlation [2]... 

FIGURE 2.1 Partial pressures of water vapor developed with the use of solutions of sulfuric acid. 

Additively colored single crystals heated in the presence of water vapor developed a colorless region around the surface of the crystal. This bleaching effect was explained by a model in which water diffused into the crystal and reacted with excess K to form a colorless photochemically-sensitive reaction product. Using this model, the diffusion coefficient of water in colored KCl was ... 

At first, Meyer was not convinced that a toxic compound had been formed, wondering whether or not his assistant had just been overreacting— or, less charitably, the apprentice had some sort of mental problem. To learn more, Meyer sent the product to a medical college, where his substance was applied to rabbits. The animals, when exposed to the vapors, developed conjunctivitis (irritation of the inner eyelid and outer eye membranes) and then died. Burns on rabbit skin produced by the chemical resembled those that developed on Meyer s hapless assistant. Meyer subsequently wrote ... 

Conduct an inventory and control of all materials used, stored, or generated Provide adequate space and equipment for handling and storing hazardous materials Monitor and document correct disposal of hazardous gases and vapors Develop work area and emergency response procedures to address specific hazards Use protective equipment when responding to hazardous materials spills or releases Maintain hazardous wastes manifests, permits, and licenses Ensure proper labeling of all hazardous materials and wastes... 

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