Humidity/temperature exposure

A laboratory test must be designed and performed so that the most important parameters from an atmospheric corrosion perspective are controlled. Reproducibility and the ability to mimic the atmospheric corrosion in different ambient environments are other important criteria of a laboratory test. Parameters to consider in accelerated tests are sample preparations prior to exposure, relative humidity, temperature, exposure time, corrodents, and corrodent delivery rate [1]. 

Often, water reacts with the polymer matrix and causes irreversible chemical changes and diminishes performance. The process of moisture absorption and desorption on the surface layers takes place almost immediately on contact with the environment, but moisture diffusion into the bulk material is usually a slow process. It takes weeks to months for a substantial amount of moisture to be absorbed by the composite and long time (i.e., 1-2 years) before the material reaches saturation. The rate of moisture uptake by a composite laminate depends on the relative humidity, temperature, exposure time and mechanical load. Elevated temperatures accelerate the rate of moisture uptake and material degradation. Similarly, tensile loads accelerates moisture uptake by opening existing internal cavities or voids, and by micro-crack formation. The effect of moismre on polymer composites is potentially... 

Colorants must provide colorfastness under the required exposure conditions of light, temperature, humidity, chemical exposure, and so on, but without reducing other desirable properties such as flow during... 

Exposure conditions appear to play the most important role in the induction and elicitation of contact hypersensitivity. These conditions involve factors inherent to the individual, including thickness of the exposed skin and skin condition at the exposure site. External factors including the vehicle, occlusive or non-occlusive conditions, temperature and humidity, and exposure to sunlight may also influence the development of contact allergy. 

For example, amorphous clarithromycin was prepared by grind and spray-drying processes, and XRPD was used to follow changes in crystallinity upon exposure to elevated temperature and relative humidity [59]. Exposure of either substance to a 40°C/82% RH environment for seven days led to the formation of the crystalline form, but the spray-dried material yielded more crystalline product than did the ground material. This finding, when supported with thermal analysis studies, led to the conclusion that the amorphous substances produced by the different processing methods were not equivalent. 

In point of fact, when considering the weathering performance of plastic materials, there exists even more interplay between weathering factors than the factors noted above, such as the ambient temperature, temperature of the actual specimens under exposure and the humidity during exposure of the materials. If the... 

The relative aggressiveness of the environments proved to be consistent for all substrates, with the room temperature control the least hostile (virtually no loss of adhesion), and the cycle tests the most aggressive (up to 100% loss of adhesion within 60 days). Humidity cabinet exposure and 60°C water immersion yielded very similar values. As a result, for reasons of clarity, only water immersion data is actually presented here. Joint strength data obtained from either the Ford APG or Fisher Body Cycle Tests were identical, and were therefore also represented by one set of data points. The relative aggressiveness of the host environments toward... 

Such a method is detailed in ISO 252833 and ASTM E9634 for sheet materials in general. To avoid leaks, the wax seal must be applied very carefully using the templates specified, and the temperature and humidity during exposure of the sealed dishes must be controlled closely. The test must be continued until the increase in weight is substantially linear with time, i.e. equilibrium has been reached. 

Once a chemical enters the body of animal or human, it undergoes metabolic reaction. A host of factors modulate the reaction rate and the induction of toxicological effects. These factors have been termed intrinsic factors and include animal species, gender, age, nutritional status, pregnancy, other health status, and circadian rhythms. In addition, there are certain extrinsic factors (e.g., physicochemical properties of chemicals, solvent or vehicle, route of exposure, temperature, and humidity) during exposure to chemicals that also influence the effect of a test chemical. We shall discuss these factors in greater detail. 

The time has come for the sensors to be taken from the well-controlled environment of the research laboratory and applied to real conditions. This means that the sensors must be robust and able to stand rough conditions in terms of, for example, humidity, temperature, and exposure to organic solvents. When applying the sensors in direct contact with biological fluids biocompatibility will be a major problem. 

The surface chemical structure of several thin polyimide films formed by curing of polyamic acid resins was studied using X-ray photoelectron spectroscopy (ESCA or XPS). The surface modifications of one of the polymer systems after exposure to KOH, after exposure to temperature and humidity, after exposure to boiling water, and after exposure to O2 and 02/CF plasmas were also evaluated. The results showed imide bond formation for all cured polyimide systems. It was found that (a) K on the surface of the polyamic acid alters the "normal" imidization process, (b) cured polyimide surfaces are not invarient after T H and boiling water exposures, and (c) extensive modifications of cured polyimide surfaces occur after exposures to plasma environments. Very complex surfaces for these polymer films were illustrated by the C Is, 0 Is, N Is and F Is line characteristics. 

Gelatin is hydrolyzed by most of the proteolytic systems to yield amino components. Further, it reacts with acids and bases, aldehydes and aldehydic sugars, anionic and cationic polymers, electrolytes, metal ions, plasticizers, preservatives, and surfactants. Even, exposure to stress conditions of humidity, temperature, and/or light leads to perceptible changes. 

Reactor Relative Humidity Temperature Pressure (mm Accumulated Radiation Exposure During 40 yr... 

Moisture Sorption Isotherms. Green wood loses moisture to the atmosphere and approaches a moisture content designated as the equilibrium moisture content (EMC) for the particular atmospheric conditions. The EMC is a function of relative humidity, temperature, previous exposure history (hysteresis), species, and other miscellaneous factors. 

Finally, environmental conditions such as incubation time, temperature, exposure to light, humidity, and so forth may affect some steps of the immunoassay and therefore the overall performance. 

All previously described analytical tools and specifications are used to describe the quality of a biopharmaceutical. In terms of use, it is important to know how stable the product itself and its formulation are, and which specific handling conditions or precautions must be estabhshed. Stabihty studies are conducted to generate the corresponding data [26]. These studies address (apart from temperature and humidity) light exposure, interaction with the container/closure system (e.g., vials or ready-to-use syringes) and also in-use stability, for examples in case of dissolved lyo-philisates. 

Relative Humidity, Temperature, and Exposure Time The air is typically humidified at a constant relative humidity within the range from 50 to 95% and the variation in relative humidity should be kept within 3% of the desired value. In order to avoid water droplets or aerosols. 

Silver-filled epoxies and other electrically conductive adhesives are widely used to electrically connect chip devices or packaged components to interconnect substrates or printed-circuit boards. Chip capacitors, resistors, transistors, diodes, and magnetic components may be attached with silver-filled epoxies whose volume resistivities range from 1 x 10 " to 3 x 10 " ohm-cm or with gold-filled epoxies whose volume resistivities are approximately 8 x 10 ohm-cm. Conductive adhesives are also finding use as replacements for solder balls in flip-chip devices. In all cases, to achieve reliable connections, initially low-contact resistances or volume resistivities must remain low on aging and on exposure to operational stress conditions, such as humidity, temperature, vibration, shock, and power. 

Lastly, FTIR can be used to study the kinetics of degradation of cured adhesives on exposure to various conditions such as temperature, time, radiation, humidity, or exposure to chemicals. 

The environments in northerly and southerly latitudes change in temperature, relative humidity and exposure condition so separating out temperature effects is difficult. A full discussion of all transport mechanisms is given in Kropp and Hilsdorf (1995). 

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