Aging and durability

The minimum thickness specification for an FML top liner covered with a layer of soil is 0.75 mm for an FML without a soil cover layer, the specification is 1.14 mm. An FML in a composite bottom liner system must be at least 0.75 mm thick. Even though these FML thicknesses meet U.S. EPA specifications, 0.75mm is not a suitable thickness for all FML materials. In fact, most FML materials installed at landfills are in the range of 1.50-2.50 mm in thickness. Other key factors affecting the selection of FML materials include chemical compatibility with waste leachate, aging and durability characteristics, stress and strain characteristics, ease of installation, and water vapor/ chemical permeation. 

Once the application performance and degradation requirements are understood, the next step is to review available information or conduct tests to screen product options to determine the most likely products that will meet application expectations. Weathering, aging and durability testing of polymers have been used extensively for years to qualify durable polymers for specific applications. Since the mid 1980s, new standard tests have been developed for degradable polymers [2],... 

Why Do We Need to Know This Material The d-block metals are the workhorse elements of the periodic table. Iron and copper helped civilization rise from the Stone Age and are still our most important industrial metals. Other members of the block include the metals of new technologies, such as titanium for the aerospace industry and vanadium for catalysts in the petrochemical industry. The precious metals—silver, platinum, and gold—are prized as much for their appearance, rarity, and durability as for their usefulness. Compounds of d-block metals give color to paint, turn sunlight into electricity, serve as powerful oxidizing agents, and form the basis of some cancer treatments. 

The method of placement makes shoterete potentially more variable and more anisotropic than normal concrete. Consequently, the development of the physical and mechanical properties such as strength, shrinkage, permeability and durability is drastically different from those of normal concrete. The effects are particularly noticeable during the very early and later ages [107, 109, 117]. 

From a practical point of view, the main consequence of physical ageing by structural relaxation is embrittlement (decrease in fracture resistance Chapter 12). For the other aspects of mechanical behavior, ageing has either no effect or a favourable effect (increase of relaxation times, leading to a decrease of creep or relaxation rates). This is the reason why, in most thermoset applications, the knowledge of short-term properties is considered to be sufficient for engineering design, as far as fracture and durability are not concerned. 

T or many years scientists and engineers have attempted to modify the properties of sulfur so that it might be of value as a construction material, but until recently these random efforts lacked direction. Frequently the objectives of work described in many published papers could not be reconciled with the experimental design. For example, authors cited availability, low cost, and low toxicity as reasons for evaluating sulfur as a construction material. The same authors would then proceed to modify sulfur with additives which were in short supply, expensive, and highly toxic. The aging characteristics of sulfur concretes beyond a 28-day period were never examined, and durability outside the laboratory environment was seldom considered. With these limitations, the data were of little value to the construction industry. 

Another important attribute of vegetable fibers is that they are subject to biological decay. Most vegetable fibers darken and weaken with age and exposure to light. They are not as durable as synthetic polymeric fibers. All of them get easily attacked by a variety of organisms, at high humidity and temperature, leading to rot and mildew. 

A considerable number of ALL cases occur in patients older than age 60 years, but no specific treatment recommendations can be made. The response to therapy and durability of response seem less than in younger adults or children. Older patients have a higher incidence of Ph+ ALL compared to younger patients, and a lower occurrence of T-ceU ALL. Based on data demonstrating excellent responses in CML, the addition of imatinib to conventional chemotherapy in Ph+ ALL patients is an increasingly common approach. Whether this leads to any increase in EPS or overall survival (OS) remains to be seen. In general, older patients have a lower CR rate, and when achieved, the duration of remission is shorter than with younger patients. 

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