Natural Durability

Inhalation of certain durable natural mineral fibers of amphibole asbestos, such as amosite and crocido-lite, can lead to the development of inflammation, fibroproliferation, pulmonary neoplasms, and cancer of the serosal lining of the body cavities or mesothelioma. Administration of fibrous particles to laboratory animals has included, in addition to inhalation, intratracheal instillation and intracavitary implantation and instillation. Inhalation studies are difficult to conduct due to the problems associated with the generation and characterization of the fibers during all phases of the assay. 

Because of the popcorn, clinker-like low durability nature of some BA particles, BA has been used more frequently in base courses than wearing surfaces. Boiler slag has been used in wearing surfaces, base courses and asphalt surface treatment or seal coat applications... 

Electrode Walls. Development of durable electrode wads, one of the most critical issues for MHD generators, has proceeded in two basic directions ceramic electrodes operating at very high surface temperatures (>2000 K) for use in channels operating with clean fuels such as natural gas, and cooled metal electrodes with surface temperatures in the range 500—800 K for channels operating with slag or ash-laden flows. 

Synthetic polymers have become extremely important as materials over the past 50 years and have replaced other materials because they possess high strength-to-weight ratios, easy processabiUty, and other desirable features. Used in appHcations previously dominated by metals, ceramics, and natural fibers, polymers make up much of the sales in the automotive, durables, and clothing markets. In these appHcations, polymers possess desired attributes, often at a much lower cost than the materials they replace. The emphasis in research has shifted from developing new synthetic macromolecules toward preparation of cost-effective multicomponent systems (ie, copolymers, polymer blends, and composites) rather than preparation of new and frequendy more expensive homopolymers. These multicomponent systems can be "tuned" to achieve the desired properties (within limits, of course) much easier than through the total synthesis of new macromolecules. 

W. M. Burkmyre, W. E. Liss, and M. Church, Natural Gas Converter Peformance and Durability, SAE 930222, Society of Automotive Engineers, Warrendale, Pa., 1993. 

Plasticised PVC, referred to below as PPVC, is used in a wide variety of applications. Originally a substitute for natural rubber when the latter material became difficult to obtain during World War II, it is frequently the first material to consider where a flexible, even moderately rubbery, material is desired. This arises from the low cost of the compounds, their extreme processing versatility, their toughness and their durability. 

The adhesion of metal and ink to polymers, and the adhesion of paint and other coatings to metal, are of vital importance in several technologies. Aluminum-to-alu-minum adhesion is employed in the aircraft industry. The strength and durability of an adhesive bond are completely dependent on the manner in which the adhesive compound interacts with the surfaces to which it is supposed to adhere this, in turn, often involves pretreatment of the surfaces to render them more reactive. The nature and extent of this reactivity are functions of the chemical states of the adhering surfaces, states that can be monitored by XPS. 

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... 

As polymer chemistry advanced in the 1930s and 1940s, stronger and more durable synthetic adhesives such as early phenol, resorcinol and urea formaldehydes began to supplant natural glues in wood aircraft manufacture. Around this time however, metal began to replace wood as the dominant material for aircraft manufacture. Aerospace adhesives research and development moved on to focus on metals, primarily aluminum, as the substrates of interest. 

The durability of a building (i.e. its life expectancy and its resistance to deterioration) is determined by deliberate design decisions relating to stmcture and choice of materials as much as to the natural or precipitate process of ageing. Within certain limits, the design of an industrial building can and should take into account the predicted use or lifespan of the process or method of operation which it is to accommodate. To aim at durability beyond that has ascertainable cost implications. These may be acceptable if the building is to serve future known or even unpredictable purposes. 

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. 

By the use of many commercial abrasive processes, the corrosion resistance of magnesium alloys can be reduced to such an extent that samples of metal that may lie quiescent in salt water for many hours will, after shot blasting, evolve hydrogen vigorously, and the corrosion rate, as measured by loss of weight, will be found to have increased many hundred-fold. The effect in normal atmospheres is naturally much less, yet the activation of the surface is an added hazard and is the opposite of passivation which is essential if later-applied paint finishes are to have proper durability. 

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