Effect of humidity

Permeability coefficient of oxygen in nylon 6 as a function of water activity at 23°C [3] 

Permeability coefficients of oxygen in amorphous nylon as a function of relative humidity [2] 

The determination of the concentrations of compounds by PTR-MS can be affected by humidity. The humidity effect derives from the increase in the quantity of hydrated hydro-nium clusters, H30+(H20) , within the drift tube as the humidity of the analyte gas increases. Some compounds undergo slower proton transfer from hydrated hydronium clusters when compared with H3O +, while some will not react at all (see Section 2.2A.2). Raising the E/N of the drift tube can reduce the proportion of hydrated hydronium clusters but there are limits as to how far this can be pushed before other, unwanted, fragmentation effects occur. Raising the E/N excessively is also undesirable from the point of view of detection sensitivity, since it reduces the reaction time for the analyte gas in the drift tube. 

Sample humidity will affect those compounds that do not react with H30+(H20). An illustration of this has been provided by Warneke et al, who used benzene and toluene as the target compounds [6]. Both benzene and toluene will accept a proton from H3O+ but proton transfer from H3O+ (H2O) is thermodynamically forbidden. The sensitivity towards these compounds declined at a fixed E/N (106 Td in this specific case) as the relative humidity was increased from 20% to 100%. This occurs because more of the H30 is tied up in the form of unreactive H3O+(H2O) clusters as the humidity is increased. Deduction of the H3O+/H3O + (H20) abundance ratio, which can be used to assess the impact of 

The effect of humidity on the determination of concentrations is compound specific. To incorporate the humidity factor into the calibration process de Gouw and co-workers [10] have suggested that the ratio 

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Thundat T, Warmack R J, Allison D P, Bottomley L A, Lourenco A J and Ferrell T L 1992 Atomic force microscopy of deoxyribonucleic acid strands adsorbed on mica the effect of humidity on apparent width and image contrast J. Vac. Sol. Technol. A 10 630... 

The greater the degree of crystallinity the less the water absorption and hence the less will be the effect of humidity on the properties of the polymer. The degree of crystallinity also has an effect on electrical and mechanical properties. In particular high crystallinity leads to high abrasion resistance. 

Figure 19.8. Effect of humidity, time and temperature on the water absorption of acetal homopolymer resin (Delrin). (Du Pont Trade Literature).

Thus the total mass flows tn= m, + m,) differ in different cases. Water vapor flow th, is obtained by multiplying the dry air mass flow by the corresponding humidity x (Eq. 4.93). As a basic quantity in humid air mass and energy balance calculations, we use dry air mass flow m and the effect of humidity on the energy balance is noted in the enthalpy h, (Eq. 4.87). 

R.H. Weldon J.R. Bentley, The Effect of Humid Storage on the Burning Properties of a Delay Composition Using Manganese as a Fuel , Australian Weapons Research Establishment, TM CPD 127 (1968) 22) P.J. Humphris ... 

The cure kinetics will depend on the initial isocyanate to hydroxy ratio and on the humidity. Assuming that the concentration of water in the coating is constant during cure, it is possible to define the following parameter which determines the effect of humidity on cure ... 

Humidity. There are two conceivable effects of humidity. Particularly with respect to agricultural products the moisture content can influence the hardness and elasticity. For example, Segler (1951) observed that dry peas are more sensitive to breakage than wet ones. Moreover, Wyszynski and Bridgwater (1993) have reported that a lubricating layer of moisture on the particle surface can reduce the particle degradation. 

Figure 8.4. Effect of humidity on the dielectric constant of polyetherketones 3-7.

The effect of humidity on combustibility of various mixtures of organic matter and sodium chlorate was studied. Addition of a proportion of hygroscopic material (calcium or magnesium chlorides) effectively reduces the hazard. Similar effects were found for sodium dichromate and barium chlorate. 

Akitsu, H., Norimoto, M., Morooka, T. and Rowell, R.M. (1993a). Effect of humidity on vibrational properties of chemically modified wood. Wood and Fiber Science, 25(3), 250-260. 

Armstrong J, Armstrong W, Beckett PM, Haider JE, Lythe S, Holt S, Sinclair A. 1996. Pathways of aeration and the mechanisms and beneficial effects of humidity- and Venturi-induced convections in Phragmites australis (Cav.) Trin. ex Steud. Aquatic Botany 54 177-198. 

The protection of microelectronics from the effects of humidity and corrosive environments presents especially demanding requirements on protective coatings and encapsulants. Silicone polymers, epoxies, and imide resins are among the materials that have been used for the encapsulation of microelectronics. The physiological environment to which implanted medical electronic devices are exposed poses an especially challenging protection problem. In this volume, Troyk et al. outline the demands placed on such systems in medical applications, and discuss the properties of a variety of silicone-based encapsulants. 

To determine the effect of humidity on the stress, one sample (0% excess MDA) was placed in the oven with desiccant at 200°C for 6 hours, and the deflection was measured during that time span. The sample was next cooled to room temperature, weighed, and returned to the oven at 200°C the dish of desiccant was now replaced by a dish of water. The deflection as a function of time was again measured over a time span of 6 hours. The sample was cooled to room temperature and weighed again to determine percent weight gain. 

S. Kadir, N. Yata, M. Kawata and S. Goto, Effect of humidity aging on disintegration, dissolution and cumulative urinary excretion of p-aminosalicylate formulations. Chem. Pharm. Bull, 34 (1986) 5102. 

Inert Simulants for High Explosives. In certain physical tests on weapons explosives, eg the effects of humidity and temp cycling on the dimensional stability of the weapon, it is desirable to simulate the explosive filler by an inert filler. Many such inert simulants have been proposed and tested (Refs 1, 2 3). Simulants for Comp B TNT have been patented (Ref 4). The simulant for Comp B consists of a mixt of 30% of 1,2 hydroxystearic acid, 5% wood rosin 65% dead-burned gypsum. The simulant for TNT is a 40/60 mixt of hydroxystearic acid dead-burned gypsum... 

The effect of humidity on conductivity of thin films of poly(dG)-poly(dC) and poly(dA)-poly(dT) in air was also investigated. It was found that above 20% relative humidity (RH) the conductance increases exponentially with RH [68]. It was concluded that the resistance of the films is not determined by that of the DNA, but rather by conduction through the hydration layers surrounding the DNA molecules in the film [68]. 

The presence of gas-phase water is generally beneficial to the photocatalytic oxidation of aromatic contaminants. In continuous photoreactors, humidity appears to prolong catalyst activity and delay or prevent catalyst deactivation. The effects of humidity on reaction rates, however, appear to vary, depending on the aromatic contaminant concentration and the humidity level. For example. Petal and Ollis [18] examined the continuous photocatalytic oxidation of m-xylene in a powder-layer photoreactor at several different relative humidity levels. The m-xylene photo-oxidation reaction rate was observed to increase for gas-phase water concentrations up to 1000 mg/m (—7% relative humidity). Increasing the humidity level further (up to 5500 mg/m ) produced a gradual decrease in the observed reaction rate, possibly due to increased adsorption-site competition between xylene and water. The reported xylene removal rate for a water concentration of 5500 mg/m was approximately half that seen at 1000 mg/m. ... 

Effect of Humidity. Extensive data were not taken hy MSW on the effects of humidity. Instead they chose to control the RH. at approx 40% for all the tests. Since LA is not hygroscopic, no effects due to changes in surface conductivity would be anticipated for himities below 70% and this was shown to be true by the authors of Ref 35. Loeb (Ref I), however, pointed out that impurities in the ambient gas can strongly affect the nature... 

Chiou, C. T., and T. D. Shoup, Soil sorption of organic vapors and effects of humidity on sorptive mechanism and capacity , Environ. Sci. Technol., 19, 1196-1200 (1985). 

Goss, K.-U., and R. P. Schwarzenbach, Quantification of the effect of humidity on the gas-mineral oxide and gas-salt adsorption of organic compounds , Environ. Sci. Technol., 33, 4073-4078 (1999b). 

Effects of Humid Climates. The specimen is exposed to warm air saturated with water vapor, with or without intermittent cooling to room temperature. The test is very suitable for assessing the corrosion resistance of metals, protective coatings, and composite materials in buildings. For standards, see Table 1 ( Climates Containing evaporated water ). Apparatus Kesternich condensation equipment. 

EFFECT OF HUMIDITY ON SILANE/AOHESIVE JOINTS 8.1. Metal... 

Brittain, H.G., Ranadive, S.A., and Serajuddin, A.T.M. (1995). Effect of humidity-dependent changes in crystal structure on the solid-state uorescence properties of a new HMG-CoA reductase irffiftaton,... 

More detailed data concerning the effects of humidity, membrane area and lower helium concentrations in the feed stream on helium recovery must be obtained before a final design can be performed with confidence. 

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