Tensile properties, aging

Bele 21S Highdemperatuie tensile properties (aged at540 X)... 

Because of the simplicity of the first test method, most of the comparisons are made usiag this technique. The effects of the aging process are usually measured on tensile properties such as tensile strength, elongation, and stress (modulus) at 300% elongation (42). 

Table 24. Conductivity and Age Hardened Tensile Properties of Chromium—Copper Alloys...

Copper wrought alloy C180, properties of precipitation-hardened, 7 762t Copper wrought alloy C181, conductivity and age- hardened tensile properties, 7 761t... 

Copper wrought alloy C18135, conductivity and age- hardened tensile properties,... 

Aziridine. Propellants cured with MAPO have excellent processing characteristics and satisfactory uniaxial tensile properties over a wide range of temperatures. However, the problems associated with the aging behavior of these propellants have led to the use of other types of curing systems which do not contain the P—N bond. These latter materials are di- and trifunctional aziridines, such as those shown in Table IV, and provide satisfactory propellants in which the uniaxial tensile properties can be tailored to a desired modulus. Such mixed aziridine-cured systems give satisfactory initial properties, reduce the postcure behavior, and improve the storage characteristics of CTPB propellants. 

The actual exposure clearly requires a very specialised facility but the methods used to monitor changes are the same as for other ageing tests. For example, change in hardness and tensile properties would serve for general purpose evaluation and compression set and stress relaxation are relevant for seals. 

Tensile properties are used in the evaluation of batches of material as well as in determining the aging effects on polyurethane. Currently, the time taken for the preparation and stabilization of the samples does not make this test ideal for a batch-to-batch real-time quality control tool. Testing is normally carried out to one of the following standards ... 

The Arrhenius relationship of the property degradation rates of uncoated silk over a range of temperatures was determined. A temperature of 150°C was found to be inappropriate for the accelerated thermal aging of silk because of the large effect on the extrapolated reaction rate at 20°C for tensile properties and also because of the amount and hue of color developed. In addition, changes in the relative humidity affected the degradation rate of tensile properties and yellowing only above a level of 50%. 

Amines as Antioxidants or Antiozonants for Rubber (13). Oxidative degradation of vulcanized rubber is evaluated from the depression in the tensile properties during aging in the Geer oven. 

Reactivities of Amines in Homogeneous Systems (14, 17). The decrease in the tensile properties of the vulcanized rubber during aging may be attributed to the degradation of the rubber molecule by oxidation. This may be supported by the experimental result in the oxidation of rubber solution. 

Fig. 32. Tensile properties retention vs, aging time of HTI ( ) and HR (o). Conditions 170 °C in air...

ASTM D 3574 - Test K covers dry-heat aging of flexible cellular materials. This test consists in exposing foam samples in an air-circulating oven at 140°C for 22 hours. The specimens are then removed and conditioned for not less than 12 hours at 23°C and 50 percent RH. As with the Steam Autoclave Tests (Jj and J2) physical tests are carried out before and after agiqg. According to Shah (1) tensile properties are usually studied after dry-heat aging. 

An accelerator is a substance that speeds up the vulcanization of rubber or allows it to happen at a lower temperature. Accelerators may also enhance tensile properties and improve age resistance of the final product. 

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