Durability specifications

SAE J2722 Recommended Practice for the Durability Testing ofPEM Fuel Cell Stacks, Scope This recommended practice is intended to serve as a procedure to verify the durability specifications or vender claims of any PEM... 

The combination of durability and clarity and the ability to tailor molecules relatively easily to specific applications have made acryflc esters prime candidates for numerous and diverse applications. At normal temperatures the polyacrylates are soft polymers and therefore tend to find use in applications that require flexibility or extensibility. However, the ease of copolymerizing the softer acrylates with the harder methacrylates, styrene, acrylonitrile, and vinyl acetate, allows the manufacture of products that range from soft mbbers to hard nonfilm-forming polymers. 

Several types of wax and wax—metal emulsions are water repeUents (30,31). Among these are wax dispersions without metal salts and wax dispersions containing aluminum or zirconium salts. The products that do not contain metal salts are anionic emulsions of wax, used alone or in combination with durable-press resins. Specific compositions are proprietary. Their chief use is on nylon, polyester, and acetate fabrics. 

The role played by the various ingredients in the composition of sealant, and in particular on the durability of adhesion has been discussed recently [77]. Inert plasticizers, such as trimethylsilyl-endblocked-PDMS, are typically added to silicone sealant compositions in order to adjust the rheology of the uncured sealant. They result in a reduction of the modulus and hardness of the cured sealant. Differences in the durability of silicone sealants are found to be due to differences in their cure chemistry, and more specifically to the nature and... 

The chemical process industries (CPI), petroleum and allied industries apply physical as well as chemical methods to the conversion of raw feedstock materials into salable products. Because of the diversity of products, process conditions and requirements, equipment design is often unique, or case specific. The prime requirement of any piece of equipment is that it performs the function for which it was designed under the intended process operating conditions, and do so in a continuous and reliable manner. Equipment must have mechanical reliability, which is characterized by strength, rigidness, steadiness, durability and tightness. Any one or combination of these characteristics may be needed for a particular piece of equipment. 

Well cementing materials vary from basic Portland cement used in civil engineering construction of all types, to highly sophisticated special-purpose resin-based or latex cements. The purpose of all of these cementing materials is to provide the well driller with a fluid state slurry of cement, water and additives that can be pumped to specific locations within the well. Once the slurry has reached its intended location in the well and a setup time has elapsed, the slurry material can become a nearly impermeable, durable solid material capable of bonding to rock and steel casing. 

Diagnosis of defects by inspection of visible causes or more sophisticated means (tracer-dye inundation to find sources and routes of leaks, infrared photography, etc.) is a prerequisite for correct repair specification. Greater skill in detailing and specifying suitable materials and methods are required in the design of flat roofs and the same applies to repairs. Here, too, durability and effectiveness are, to some extent, cost related. 

A primer, as its name implies, is the first coat of a system. Its principal functions are to provide adhesion and good protection to the substrate. The manner in which these properties are obtained will vary with the substrate, but frequently involves the use of a large proportion of a specific pigment. This may impose a restriction on the colour and gloss, and probably on other desirable properties such as durability. 

After special pretreatments, specific grades of plastics can be put through electroplating processes similar to those used in the plating of metals. Electroplated plastic products are very durable and provide... 

With such a broad subject area, to meet the objectives of the present publication, the general approach for this chapter has been to cover as wide a range as feasible with, where possible, emphasis made on relationships of specific effects with actual service applications. The chapter illustrates various effects of time, temperature, and fluids on long-term service durability of a range of elastomers, mainly by employing various data obtained by Materials Engineering Research Laboratories (MERE) personnel over recent years. 

Painting is generally performed by a contractor on a bid basis. Unless another agreement is made, a contractor will furnish the lowest priced paint that will do an acceptable job, even though it may have inferior durability. To avoid this, the contract should be very specific with regard to the type of paint to be used. It may even specify a certain brand. 

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