Deterioration natural

Causes of Deterioration of Brick Masonry. Repeated natural destructive forces, nuld though they may be, break down hard rock into clay. These same forces act on clay bricks, fired tile, and fired terra cotta to cause deterioration. Natural stones and the binding mortars of masonry construction are similarly affected. In addition, airborne chemicals in industrial atmospheres and pollutants from internal-combustion engines contribute greatly to rapid soiling and chemical destruction of these binding materials and masonry units. 

Thousands of miles of new natural gas pipelines are put in-service each year, while thousands of miles more of deteriorated natural gas pipelines are replaced. It is estimated that between 2001 and 2010,... 

The properties of straight run diesel fuels depend on both nature of the crude oil and selected distillation range. Thus the paraffinic crudes give cuts of satisfactory cetane number but poorer cold characteristics the opposite will be observed with naphthenic or aromatic crudes. The increasing demand for diesel fuel could lead the refiner to increase the distillation end point, but that will result in a deterioration of the cloud point. It is generally accepted that a weight gain in yield of 0.5% could increase the cloud point by 1°C. The compromise between quantity and quality is particularly difficult to reconcile. 

Possible negative environmental effects of fertilizer use are the subject of iatensive evaluation and much discussion. The foUowiag negative effects of fertilizer usage have been variously suggested (113) a deterioration of food quaUty the destmction of natural soil fertility the promotion of gastroiatestiaal cancer the pollution of ground and surface water and contributions toward the destmction of the ozone layer ia the stratosphere. 

Deteriora.tlon. An important source of damage to stone objects is mechanical in nature. Both breakage and abrasion account for much of the losses on objects made of this relatively fragile material. More difficulties are offered by the processes of a chemical nature which play a role in stone deterioration (132—134). 

Deterioration. The causes of degradation phenomena in textiles (155—158, 164) are many and include pollution, bleaches, acids, alkaUes, and, of course, wear. The single most important effect, however, is that of photodegradation. Both ceUulosic and proteinaceous fibers are highly photosensitive. The natural sensitivity of the fibers are enhanced by impurities, remainders of finishing processes, and mordants for dyes. Depolymerization and oxidation lead to decreased fiber strength and to embrittlement. 

Elastomeric materials, which provide relatively low practical static deflections and have relatively high natural frequencies, are used only to isolate higher frequencies. The volume compressibiUty of elastomeric materials is relatively low, therefore the shape of the elastomeric isolator must be taken into account, and space must be provided for lateral expansion. Because of their inherent resistance to chemical and environmental deterioration, neoprene and other synthetic materials often can be used in severe environments where natural materials would deteriorate. 

Ton-exchange resins are used repeatedly in a cyclic manner over many years, and deterioration of both physical and chemical properties can be anticipated. Comparison of the properties of used resin with those of new resin is helpfiil to learning more about the nature and cause of deterioration (12). Corrective action frequendy extends the life of the resin. Comparison of properties must always be made with the resin in the same ionic form. 

In general, one day of oven aging at 70°C corresponds to one year of natural or shelf aging (a minimum requirement for mbber products), whereas the oxygen and air bomb methods are more drastic. By varyiag the amounts and types or combiaations of antioxidants the relative effectiveness of these materials against normal oxygen deterioration can be determined. 

Many instant coffee producers in the United States incorporate natural coffee aroma in coffee oil into the powder. These highly volatile and chemically unstable flavor components necessitate inert-gas packing to prevent aroma deterioration and stating from exposure to oxygen. 

During storage, natural pigments often deteriorate with time because of exposure to light, heat, air, and moisture or because of interaction of the components of the food with each other or with the packaging material. The color of maraschino cherries, for example, fares so poorly with storage that they are routinely bleached then artificially colored. 

As with c -polyisoprene, the gutta molecule may be hydrogenated, hydro-chlorinated and vulcanised with sulphur. Ozone will cause rapid degradation. It is also seriously affected by both air (oxygen) and light and is therefore stored under water. Antioxidants such as those used in natural rubber retard oxidative deterioration. If the material is subjected to heat and mechanical working when dry, there is additional deterioration so that it is important to maintain a minimum moisture content of 1%. (It is not usual to vulcanise the polymer.)... 

Resistance to penetration by micro-organisms is covered by EN 374-2 and protection from low temperatures in EN 511. Careful handling and regular inspection are essential since chemicals and abrasion will eventually cause deterioration of gloves. Rinsing in clean water and drying naturally will prolong their life. 

Textiles (natural/synthetic) Reduced tensile strength, deterioration... 

Ductility. A load-bearing device or component must not distort so much under the action of the service stresses that its function is impaired, nor must it fail by rupture, though local yielding may be tolerable. Therefore, high modulus and high strength, with ductility, is the desired combination of attributes. However, the inherent nature of plastics is such that high modulus tends to be associated with low ductility and steps that are taken to improve the one cause the other to deteriorate. The major effects are summarised in Table 1.6. Thus it may be seen that there is an almost inescapable rule by which increased modulus is accompanied by decreased ductility and vice versa. 

Marking products has its limitations as it may damage the product, be removed, or deteriorate during subsequent processing. If applied directly to the product, the location and nature of identification should be specified in the product drawings or referenced process specifications. If applied to labels which themselves are permanently secured to the product, the identification needs to be visible when the product is installed so as to facilitate checks without its removal. 

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