Embrittlement environmental stress cracking

Environmental stress cracking (ESC) is the premature cracking of a polymer due to the combined action of a stress and a fluid. It is associated with the phenomenon of crazing and solvent plasticization of the polymer. The embrittlement by oxidative or other chemical degradation is not included under ESC, but is classed as corrosion stress cracking (CSC). 

The manner in which small amounts of colloidal filler destroy the cohesion of low-molecular-weigiht polyethylenes was thought by Kendall and Sherliker [61] to be similar to the phenomenon of environmental stress cracking, in which minor amounts of detergents or alcohol produce inordinate embrittlement of polymers, especially of low molecular weight [63]. In order to check their hypothesis, a drop of isopropanol was placed at die tip of the tear, and the fall in force at constant speed was measured. The results were plotted as a function of... 

Environmental stress cracking plastics may be embrittled by exposure to water, light, temperature and oxygen as well as chemical attack. 

Rockwell C 22 is the commonly selected limit above which sulfide embrittlement and resultant sulfide stress cracking become problems. The change, however, is not that abrupt but the critical "gray band" is about C 20 to 25, with the point of change affected by mechanical, physical and chemical environmental factors. 

The total cost of material fracture is about 4% of gross domestic product in the United States and Europe (88,89). Fracture modes included in the cost estimates were stress-induced failures (tension, compression, flexure, and shear), overload, deformation, and time-dependent modes, such as fatigue, creep, SCC, and embrittlement. The environmentally assisted corrosion problem is very much involved in the maintenance of the safety and reliability of potentially dangerous engineering systems, such as nuclear power plants, fossil fuel power plants, oil and gas pipelines, oil production platforms, aircraft and aerospace technologies, chemical plants, and so on. Losses because of environmentally assisted cracking (EAC) of materials amount to many billions of dollars annually and is on the increase globally (87). 

Thermoplastic cracking develops under certain conditions of stress and environment, sometimes on a microscale. Because there are no fibrils to connect surfaces in the fracture plane (except possibly at the crack tip), cracks do not transmit stress across their plane. Cracks result from embrittlement, which is promoted by sustained elevated temperatures and ultraviolet, thermal, and chemical environments existing in the presence of stress or strain. There appears to be no practical definition that can sufficiently distinguish between environmental and other stress cracking, although the micromechanics of the two types of cracking may be quite different. 

Severe loss of ductility of a metal (or alloy) loss of load carrying capacity of a metal or alloy the severe loss of ductility or toughness or both, of a material, usually a metal or alloy. Many forms of embrittlement can lead to brittle fracture and many can occur during thermal treatment or elevated-temperature service (thermally induced embrittlement). Some of these forms of embrittlement, which affect steels, include blue brittleness, 885 °F (475 °C) embrittlement, quench-age embrittlement, sigma-phase embrittlement, strain-age embrittlement, temper embrittlement, tempered martensite embrittlement, and thermal embrittlement. In addition, steels and other metals and alloys can be embrittled by environmental conditions (environmentally assisted embrittlement). Forms of environmental embrittlement include acid embrittlement, caustic embrittlement, corrosion embrittlement, creep-rupture embrittlement, hydrogen embrittlement, bquid metal embrittlement, neutron embrittlement, solder embrittlement, sobd metal embrittlement, and stress-corrosion cracking. 

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