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Environmental Stress Cracking (ESC) is one of the most common causes of unexpected brittle failure of thermoplastic (especially amorphous) polymers known at present. According to ASTM D883, stress cracking is defined as "an external or internal crack in a plastic caused by tensile stresses less than its short-term mechanical strength".
Failure in polymer components can occur at relatively low stress levels, far below the tensile strength because of four major reasons: long term stress or creep rupture, cyclic stresses or fatigue, the presence of structural flaws and stress-cracking agents. Formations of submicroscopic cracks in polymers under load have been studied by x ray ...
Polymers are susceptible to environmental stress cracking where attacking agents do not necessarily degrade the materials chemically. Nylon is sensitive to degradation by acids, a process known as hydrolysis , and nylon mouldings will crack when attacked by strong acids.
Stress corrosion cracking is a phenomenon where a synergistic action of corrosion and tensile stress leads to brittle fracture of normally ductile materials at generally lower stress levels. During stress corrosion cracking, the material is relatively unattacked by the corrosive agent (no general corrosion, only localized corrosion), but fine ...
The left section depicts a polymer sample under stress, while the right section provides a detailed view of craze development at the crack tip. Crazes in polymers are typically load-bearing and expand in width and area until a region within the craze breaks down, forming a large void. With further stress or over time, this void can develop into ...
Solvent stress cracking is a significant polymer embrittlement mechanism. It occurs when liquids or gasses are absorbed into the polymer, ultimately swelling the system. The polymer swelling results in less shear flow and an increase in crazing susceptibility.
However, product design is important in maximising the strength of the product, especially in eliminating sharp corners and other stress concentrations. Injection molding must ensure that moldings are stress-free. Like most other amorphous thermoplastics, Noryl is sensitive to environmental stress cracking when in contact with many organic liquids.
Stress cracking may refer to: Environmental stress cracking; Stress corrosion cracking; Sulfide stress cracking This page was last edited on 30 ...