Loss in strength

Aluminum and aluminum alloys are employed in many appHcations because of the abiHty to resist corrosion. Corrosion resistance is attributable to the tightly adherent, protective oxide film present on the surface of the products. This film is 5 —10 nm thick when formed in air if dismpted it begins to form immediately in most environments. The weathering characteristics of several common aluminum alloy sheet products used for architectural appHcations are shown in Eigure 30. The loss in strength as a result of atmospheric weathering and corrosion is small, and the rate decreases with time. The amount of... 

With respect to the action of the enzyme itself, a loss of weight on account of cellulose hydrolysis, as well as loss in strength properties, occurs. Therefore, control of concentrations, temperature, and other processing conditions is important to achieve a product having the proper balance of properties. 

Chain scission—resulting in a loss in strength and toughness. 

One method of overcoming some of the instability and loss in strength of oxychloride cements when exposed to water has been to modify them by impregnation with sulphur (Beaudoin, Ramachandran Feldman, 1977). The resulting material appears to be a composite in which the respective components complement each other. The magnesium oxychloride part has relatively poor resistance to water as initially formed, whereas the sulphur is difficult to wet and is completely insoluble in water. 

Coating thickness should be chosen to optimize the benefit in toughness and minimize the loss in strength and some other properties. As a rule of thumb, the thickness of the coating should be kept minimum compared to the fiber diameter in order to eliminate any reductions of composite stiffness and strength in both... 

Other alkali-free accelerators used include aluminum hydroxide or a combination of this material with aluminum sulfate. They develop early strength even in low amounts (4%) and there is no decrease in later strengths up to 8%. However, a significant loss in strength has been observed with... 

Elastomers and, to a lesser extent, plastics tend to swell in the presence of solvents. Frequently, this swelling is accompanied by a loss in strength. In addition, some plastics are dissolved by certain solvents, and all-polymeric materials may be chemically destroyed. It is in the areas of solvent and chemical resistance that most problems are encountered in the laboratory. 

Sample description and citation Exposure conditions Exposure timeb Loss in strength [%]... 

The presence of S02 caused additional loss in strength over that caused by light exposure alone. Using copper number and carboxyl content as measure of degradation it appeared that the properties of samples exposed to light and S02 differed from that of acid hydrolyzed counterparts which had suffered similar losses in strength. 

Arsenic-based antioxidants, such as arsenic pentoxide and arsenic thioarsenate, had been used extensively in the past to retard oxidation. In a polyimide adhesive formulation, for example, arsenic compounds were found to improve thermal resistance. At 315°C no loss in strength was exhibited after 1000 h and substantial strength (1300 psi) was retained after 2000-h exposure. Without the arsenic additive there was marked reduction after only 200 h at 315°C. 

Air pollutants can cause damage to rayons. Artificial weathering tests have indicated that as the strength of the rayon decreases, its fluidity and reducing power as determined by copper number increase, but the carboxyl content decreases (62). When these tests were made with air contaminated with 0.1 ppm sulfur dioxide, an additional loss in strength was found over that caused when the weathering tests were made in pure air (62). 

Reports on long-term performance of man-made fibers are few. However, an analysis has been made of 20 nylon climbing ropes that had been used for up to 18 years, and it was found that significant deterioration had occurred. Note, however, that the deterioration was related to the amount and type of use and not to age. Loss in strength was a result primarily of fiber abrasion of the rope surface, and there was no evidence of significant light degradation (92). 

A linear regression of the strengths listed in Table I and shown in Figure 3 gives the least-squares equation for the loss in strength as a function of heating time... 

Part of the loss in strength properties of formaldehyde may come from hydrolysis of cellulose by the strong acid catalyst. 

Preparation of reagent Even in the absence of water a reagent consisting of iodine, sulfur dioxide, pyridine, and methanol undergoes rapid initial loss in strength, followed by slower change. The reactions involve the formation of quaternary pyridinium salts and pyridinium iodide, for example,... 

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