Effect of moisture

The presence of water has considerable influence on the lubrication properties of molybdenum disulphide, and their interaction has been studied in some detail. Nevertheless there is still conflict and confusion about this aspect of behaviour, as about many others. 

Molybdenum disulphide has been shown to adsorb or chemisorb water, but 

The presence of moisture induces oxidation even at room temperature in long storage . The ultimate product of this oxidation is almost certainly molybdenum trioxide, but it has been suggested that the primary product at elevated temperatures in the absence of air is an oxysulphide MoOS, with the release of gaseous hydrogen. 

According to this work no hydrogen sulphide is formed at any stage, but at temperatures above 300°C sulphur dioxide is released. Such a process requires the release of considerable amounts of gaseous hydrogen if we assume that the second stage is on the following lines - 

The liberation of gaseous hydrogen was shown by Kalamazov to occur when water vapour was dissociated on the surface of molybdenum disulphide at 700°C. It has also been shown that hydrogen sulphide was produced during sliding of molybdenum disulphide in moist nitrogen, presumably by the reaction 

The presence of moisture does have a noticeable effect on the rate of the low-temperature oxidation of coal. Thus, if the coal is thoroughly dried, the rate of oxidation decreases (see, for example, Ogunsola and Mikula, 1992), but other factors may play a role in this otherwise simple observation. For example, water is a product of the oxidation reaction and if the rate of the oxidation appears to increase with time it may be that the water that is formed as a reaction product actually causes the 

FIGURE 12.3 Aerial oxidation of subbituminous coal at various temperatures. (From Jensen, E.J. et al., Advances in Chemistry Series No. 55, American Chemical Society, Washington, DC, 1966, p. 621.) 

Care should be taken to achieve a balance and uniformity in the moisture content of the polymer. Bone dry resin requires higher processing temperatures, which are likewise harmful, while moist resin rapidly reduces the molecular weight during processing. So, the level of moisture content in the resin should be kept constant during the mn to ensure uniform properties throughout 

Components may be subjected to conditions of high relative humidity or directly exposed to, or immersed in, fresh or sea water and so take up moisture. In desert conditions, the converse would apply as the relative humidity would be very low and so moisture might well be given off. The rate of water uptake (or release) and its equilibrium concentration as well as its influence on properties, could therefore be of concern. 

Tests in boiling water are often used as a simple way to accelerate the effect of water immersion and give an indication of the worst effects likely to occur. 

The water absorption uptake of both pure resin and laminate is very dependent upon temperature. The higher the temperature the quicker the plateau value is reached. At temperatures around the glass transition temperature of the matrix (74°C), there appears to be a further uptake in water absorption possibly balancing the loss of organic material by leaching. 

The diffusivity is greater in the pure than the reinforced resin. The results have been analysed in terms of Pick s Law and the activation energies for the water uptake and desorption of various materials are compared in Table 9.1. 

Pritchard, G. and Speake, S.D. (1987) The use of water absorption kinetic data to predict laminate property charges. Composites 18, 227-32. 

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Moisture pickup and freeze—thaw resistance of various insulations and the effect of moisture on the thermal performance of these insulations has been reported (207). In protected membrane roofing appHcations the order of preference for minimizing moisture pickup is... 

Its influence appears to result primarily from suppression of the embrittling effects of moisture in air (75). The role of chromium, on the other hand, is to reduce the embrittling effects of oxygen at temperatures above about 500°C (76). 

Fig. 3. The effects of moisture on the desorption of -xylene from a clay soil at 150°C where ) represents dry clay (-...

L. I. Knab, D. R. Jenkins, and R. G. Mathey, "The Effect of Moisture on the Thermal Conductance of Roofing Systems," NBS Building Science Series 123, National Bureau of Standards, U.S. Dept, of Commerce, Washington, D.C., Apr. 1980. 

Fig. 5. Typical effect of moisture on PVB adhesion A, pummel data (—20°C) from Monsanto Co. B, compressive shear data from Du Pont Co. To...

Fig. 3. Effect of moisture content on bending strength of stmctural lumber, MOR = modulus of mpture.

Table 6. The Effect of Moisture Content on the Physical Properties of Wool Fibers at 25°C ...

Tile is based mainly on vinyl chloride and vinyl acetate copolymers. Some polypropylene tile systems have recendy been iatroduced. A petroleum resia is usually employed as an extender and processiag aid conventional vinyl plasticizers and stabilizers also are iacorporated. Reinforcing fibers and limestone constitute the remainder of the tile composition the fibers contribute hot strength for processiag and dimensional stabiHty ia the finished tile, limestone suppHes bulk at an economical cost. Stable pigments are also iacorporated. Siace tile is iastalled oa and below grade level, it is important that the finished product be resistant to the effects of moisture and alkaH. 

FIG. 27-20 Effect of moisture in coal on pulverizer capacity. Sufficient drying can be accomplished to restore capacity if air temperatures are high enough. [K = ( F -I- 459.7)/1.8] (Combustion Engineer, Combustion Engineeiing Inc., New York, 1966. )... 

Figure 22.6 Effect of moisture content, temperature and salt on the resistivity ot soil...

In addition to the great dependence of MIE on particle size distribution and the possible accumulation of additives, complicating factors in measuring and applying MIE data include the presence of flammable gas (6-1.3.1) plus the effects of moisture (6-1.6) and possibly increased temperature (6-1.5) relative to the test temperature. 

Figure 18.13. Effect of moisture content on the Young s modulus of nylon 66 and nylon 6...

Figure 18.15. Effect of moisture content on tKe volume resistivity of nylon 66...

Effect of moisture cure on properties of a urethane-based hot melt adhesive... 

Fig. 14. DSC evaluation of the effects of moisture content (by weight) on the reactivity of a PF film [160].

What is the effect of moisture on the flowability and feeding characteristics of dry bulk filter aids ... 

Dry bulb The air temperature recorded by a dry bulb thermometer, a sensory device excluding any effects of moisture or radiation. 

In our study, the effect of moisture over the nonneutral pH range of 3-11, direct sunlight, ozone at a concentration level of 6000 ppm, and the effects of loading stresses, were investigated for the three commercial sealants. A characteristic variation of crosslink density for the typical silicone sealants is shown in Fig. 29. This figure depicts the results for the coupons exposed to moisture and sunlight. Initially upon exposure, the crosslink density of the sealants exhibit an increase due to the availability of residual uncurred crosslink sites... 

This neglects the effect of moisture removal on molecular weight, assumes constant k and n values, and assumes the gas is cooled back to 95°F as it enters the second case. 

These results clearly demonstrate (a) the effect of moisture in increasing the corrosion rate six times in the rural areas compared with the arid areas... 

Of the numerous reasons for measuring and controlling the moisture content of dehydrated foods, one of the more important is the effect of moisture content on the stability of the food. The storage life of a food generally increases with decreasing amount of water and it is therefore customary to dehydrate the food to some safe moisture level which is determined empirically. 

Fig. 7-26 Example of the effects of moisture on the mechanical properties of an IM hygroscopic PET plastic.

Moisture Deteriorating effects of moisture are well known as reviewed early in this chapter (OTHER BEHAVIOR, Drying Plastic). Examples for high moisture applications include polyphenylene oxide, polysulfone, acrylic, butyrate, diallyl phthalate, glass-bonded mica, mineral-filled phenolic, chlorotrifluoroethylene, vinylidene, chlorinated polyether chloride, vinylidene fluoride, and fluorocarbon. Diallyl phthalate, polysulfone, and polyphenylene oxide have performed well with moisture/steam on one side and air on the other (a troublesome... 

Table VII. The Effect of Moisture on the Gas Permeation of Various Polymers...

Moisture. The effect of moisture on expls, propints and pyrots can be deleterious in terms of reliability, efficiency and safety. This unwanted ingrenlent can add uncertainty and possible hazard in the manuf, storage and eventual use of ammo. Moisture adds to the costs of ammo in many ways. These include less effective material being available per unit volume, with concomitant increases in malfunction rate, curtailed shelf life because of structural failures occasioned by moisture-generated chem reaction products and the cost of many investigations undertaken to understand and prevent effects (Expls Refs 6,8, 11, 12, 15,17,21,26, 28,31,34,35,39, 40,. 41, 43, 44, 46, 48, 52 54 Propints Refs 9, 13, 16, 19, 21, 23, 27, 29, 37 53 Pyrots Refs 5, 7,10, 14,18, 20, 23, 24, 28, 30 38)... 

Illustrations of the deleterious effects of moisture on the manuf, storage and performance of individual classes of energetic materials will now be considered... 

Effect of Moisture on Explosives Expls are the only energetic materials which can exist in useable form as a w slurry. These materials do not meet Mil specifications, however, they are commercially available and are used as gels in mining operations (Refs 35, 36, 43 44)... 

Effect of Moisture on Propellants. The effects of the addition of 0.1% moisture on the performance of small arms proplnt is shown below (Ref 13) ... 

Small arms ammo can be so severely affected by moisture that a special indicating lacquer was developed for 20mm rounds which changes color from grey to black on w exposure (Ref 59) Effect of Moisture on Pyrotechnics Pyrot formulations usually contain finely powdered metal fuels such as Mg, Al, Fe, Cu, etc, all of which can react with moisture to yield H2. This effect has been dubbed gassing in pyrot circles, and is the major problem associated with the storage of hermetically sealed ammo of this... 

Effect of Moisture On 80-20 Tritonal , PATR 1560 (1945) 13) Anon, Moisture Content... 

S.E. Smith, Effect of Moisture on the Gelation of Castable Plastic Bonded Explosives ,... 

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