Term Durability

The long-term durability of an adhesively bonded connection, i.e. its ability to function effectively throughout its design life, is a vital prerequisite for the successful use of adhesives. Tests and experience are important to evaluate the long-term durability of a correctly bonded adhesive joint. 

Elastic adhesives are organic products and as such, are subject to ageing. The design of the adhesive joint has to take into account this complex process. Various factors have a long-term impact on ageing and are listed in Fig. 21. 

Adhesive joints are exposed to attack from many different chemical products. In most cases this means short to medium-term contact with water, aqueous solutions of chemicals or fuels. 

Exposure to water, especially when water penetrates into the interface between the cured adhesive and the substrate is very harmful for adhesion. Water behaves like a plasticizer and can react with the chemical groups responsible for adhesion and therefore may reduce the bonding. Intermolecular forces between the substrate 

High internal stress of thermoplastics ( stress cracking) 

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The required extent of durabiUty depends on the use of the treated article. For example, an antistatic finish that is removed after several launderings would be termed nondurable for blankets to be used in hospitals and motels where static protection through over fifty launderings is desirable. However, the same finish appHed to blankets for household use which would be laundered once or twice per year could be termed durable. Antistatic finishes have been widely reviewed (73—75,77,86,90—95). 

Durability. The term "durable" has several meanings, but in the present context it is used to describe an asphalt that possesses the necessary chemical and physical properties required for the specified pavement performance, being resistant to change during the in-service conditions that are prevalent during the life of the pavement. 

The demands on the PSA performance for these types of applications can be very high, especially in the areas of creep, shear resistance and long-term durability. For these reasons, crosslinked acrylics and stabilized block copolymer adhesives have become the main PSA material choices. 

This method is generally not capable of achieving a uniform standard of cleanliness on structural steel. It is not effective in removing intact mill scale or corrosion products from pitted surfaces. The durability of subsequent coats is therefore variable and unpredictable, and depends on the thoroughness of the operation and the exact nature of the contaminants left on the surface. The method should be confined to non-aggressive environments or where short-term durability is economically acceptable. 

Researchers are facing difficulties in improving the properties and response rates of chemomechanical andelectrochemomechanical systems based on polymer gels or proteins that are intended to be used as actuators in robotics. Lack of mechanical toughness and long-term durability are other problems to be solved. A basic improvement in the low efficiency... 

Effects of Time, Temperature, and Fluids on the Long-Term Durability of Elastomers... 

Liu, X., Chen, J., Liu, G., Zhang, L., Zhang, H., and Yi, B. (2010) Enhanced long-term durability of proton exchange membrane fuel cell cathode by employing Pt/Ti02/C catalysts. Journal of Power Sources, 195 (13), 4098-4103. 

Although considerable research has been conducted with Pd-alloy foils, tubes, and thinner composite membranes, long-term durability and stability need to be further demonstrated, especially in the fuel reforming or WGS operating conditions, for acceptance of this technology in a commercial sector. Furthermore, mass-scale and cost-effective production of industrial-scale Pd-alloy thin-film composite membranes need to be demonstrated to be competitive in the hydrogen production and purification market. 

Figure 4.23 Solar cells are efficiently isolated with a vapour-deposited ORMOSIL layer that ensures long-term durability of commercial photovoltaic modules. (Reproduced from ref. 18, with permission.)...

The films must be stable for long periods. Some materials, particularly those with a low glass transition temperature (Tg) may crystallize over time [22,23], Crystallization may be accelerated when the temperature of the thin film is raised during device operation [24-26]. Therefore, a high Ts is often desirable for the long-term durability of the OLED, e.g., rg>85°C. 

The persistence of polymers in the environments is useful for long term durability of structures such as buildings, vehicles, docks, boats and navigation aids. Unfortunately, when the polymers are unintentional byproducts of recreational or commercial activities, collateral wildlife loss may result from entanglement in packaging materials, lost nets, lines and ropes. These wildlife losses due to litter have received significant public visibility. The critical degradation to address this... 

Requires little maintenance, while providing long-term durability. Crash beams have a slower response time (normally 9.5-15.3 seconds, but can be reduced to 7-10 seconds in emergency situations) than do other types of active security barriers, such as wedge barriers. Because emergency activation of the barrier causes more wear and tear on the system than does normal activation, it is recommended for use only in true emergency situations. 

Building and automotive wiring is lightweight, mass-produced and cheap with fair electrical and mechanical performances and long-term durability. 

The stability of electrocatalysts for PEMFCs is increasingly a key topic as commercial applications become nearer. The DoE has set challenging near-term durability targets for fuel cell technology (automotive 5,000 h by 2010 stationary 40,000 h by 2011) and has detailed the contribution of the (cathode) catalyst to these. In particular, for automotive systems as well as steady-state stability, activity after simulated drive cycles and start-stop transients has been considered. In practice, both these treatments have been found to lead to severe degradation of the standard state-of-the-art Pt/C catalyst, as detailed next. 

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