Trapped moisture

An important property of a PVAc film is its permeabiUty to water vapor. The permeabiUty to saturated water vapor at 40°C is 2.1 g/(h-m ) for a film 0.025-mm thick. This allows the film to be laid down on a damp surface with trapped moisture gradually passiug through the film without lifting or blistering it. 

For large motors, the practice is to wind the stator with formed coils (Figure 9.2). The coils are pre-formed and cured before insertion into the stator slots. They are insulated with resin-rich glass and mica paper tapes. The process of impregnation is therefore termed resin-rich insulation. The completed formed wound stator is then heated to remove trapped moisture and finally impregnated in varnish class F or H as required, under vacuum and pressure. The stator is then cured in an oven as described above. The process of insulation and curing conforms to powerhouse insulation requirements. This practice facili-... 

It is essential to dry passivated surfaces promptly to protect them from moisture and atmospheric contamination. The drying may be carried out by blowing compressed air, which is easier and more economical, or by placing in the same oven as for the paint. Special care need be taken with hidden surfaces, such as in corners, bends and crevices, to ensure that there is no trapped moisture. 

The second unusual feature is that it has frequently been observed that the rubbers soften or reverse when subjected to high temperatures in a confined space. This is believed to be due to the presence of trapped moisture which, when not able to escape, causes hydrolysis of the polymer. 

Yencho then constructed the initial version of the machine and explored the parameters necessary to successfully form flaw-free parts. A key finding concerned the effects of trapped moisture. Despite the generally hydrophobic nature of PEEK, it was found that small amounts of moisture absorbed by the Gr/PEEK laminates subsequent to their manufacture converted into steam during the forming operation and caused extensive delamination. This was in... 

Exemplary materials for the waterproofing of masonry surfaces are waterproof membranes such as poly(vinyl chloride), PE, butyl rubber, and sealants such as tar, asphalt, paints, poly(urethane), epoxy or mastics. While these waterproofing agents can offer excellent resistance to water penetration and other contaminants, they can alter the appearance of the masonry surface, e.g., they may change the color of the surface or leave it with a shine. Waterproofing treatments can also trap moisture within the masonry surface and promote spalling. 

Exemplary water-repellent treatments for masonry surfaces include metal stearates, oils, waxes, acrylates (both polymers and monomers), silicones (solvent-based and emulsion), siliconates, silanes and, fluorochemicals. In contrast, to waterproofing coatings, water-repellent coatings, because they are permeable to water vapor, do not trap moisture and, therefore they can reduce spalling. In addition most water-repellent coatings do not alter the appearance of a porous masonry. 

Frequently, adhesion promoters are used. The substrates are primed or coated with a thin layer of an adhesion promoter, typically HMDS, prior to spin coating with resist (18). Possibly, the primary action of HMDS is to negate hydrophilic sites such as SiOH and trapped moisture on the substrate surface that would otherwise repel the photoresist. HMDS is applied by dipping, vapor priming in special chambers, or spin coating. Spin coating is most often accomplished with the same equipment that is used to coat resists. No high-temperature bake other than the resist prebake is required. 

The traditional view of moisturizers is that they increase the moisture content of the skin by forming an occlusive, hydrophobic film on the surface of the SC, thereby trapping moisture in the underlying tissue. However, restoration of barrier function after disruption can be accelerated by the application of lipids, like free fatty acids, cholesterol, and nonphysiological lipids like the complex hydrocarbon mixture petrolatum.4 Barrier repair can be measured within an hour after barrier disruption and leads to normalization of barrier function within hours to days, depending on the initial insult. 

The suction cup of the clingfish serves more than one purpose. Not only does it enable the fish to hang on, but it also holds water when conditions are dry. After the tide goes out, the water level in a tide pool can fall dangerously low. If this happens, the fish uses the moisture held within the suction cup to breathe. Sheltered beneath a rock or within the crevice of a rock, it takes in oxygen from the trapped moisture and waits until the tide rolls back in with a fresh supply of water, oxygen, and nutrients. 

The proper corrosion maintenance program should prevent or eliminate the conditions favoring corrosion (i) trapped moisture (ii) wet insulation blankets (iii) plugged drain holes and passages (iv) chipped or missing paint (v) loss of protective finish (vi) corrosive cargo. 

Carbon monoxide (CO) is a deadly gas that can form from a reaction between trapped moisture (for example, in the furnace insulation) and carbon. The source of carbon may be the graphite used in some furnaces for heating elements or in graphite-felt insulation. Problems can be avoided by ensuring that the furnace is kept dry. Domestic CO alarms can be installed in the laboratory area as an added precaution. 

External parameters such as relative humidity also play a very important role in void content in the laminate. Generally, epoxy resin tends to absorb moisture in the air and the trapped moisture is very difficult to remove under VBO processing. Influence of relative humidity on void content of VBO processed laminate has been systematically studied by Nutt et alJ Cure cycle recommendations from the manufacturer for the curing of Cycom 5320 are ... 

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