Environmental Stress Cracking ESC

Of course, to understand a previously unknown mechanism and evaluate corrective measures, we had to develop unique tests that did not exist before. These are accelerated in vivo tests, since ESC has not yet been exactly duplicated in vitro (Fig. 3). We now know that ESC is a four-factor interaction, all four of which 

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Resistance to Chemical Environments and Solubility. As a rule, amorphous plastics are susceptible, to various degrees, to cracking by certain chemical environments when the plastic material is placed under stress. The phenomenon is referred to as environmental stress cracking (ESC) and the resistance of the polymer to failure by this mode is known as environmental stress cracking resistance (ESCR). The tendency of a polymer to undergo ESC depends on several factors, the most important of which are appHed stress, temperature, and the concentration of the aggressive species. 

All polyethylenes are soft, flexible and resistant to acids and alkalis up to 60°C. They retain this flexibility down to —40°C. Hence they have good resistance to impact even at low temperatures. However, unless correctly formulated they can suffer from environmental stress cracking (ESC), poor adhesion and UV degradation. ESC is the phenomenon which occurs when a thermoplastic is put under stress, e.g. bent, in a particular environment and prematurely cracks or crazes. Alcohol and detergent are examples of agents that can cause ESC in polyethylenes. 

ISO 4599, Plastics - Determination of resistance to environmental stress cracking (ESC) - Bent strip method, 1986. 

When a plastic exposed to air is subjected to a stress or a strain below its yield point, cracking can occur after a very long duration. The simultaneous exposure to a chemical environment under the same stress or strain can lead to a spectacular reduction of the failure time. The accelerated cracking in this way corresponds to environmental stress cracking (ESC). 

Liner types available are suitable for a wide variety of chemical services, including acids, alkalies, and various solvents. All liners are permeable to some degree, and manufacturers use various methods to vent gas out of the interspace between the liner and casing. All plastics are subject to environmental stress cracking (ESC). ESC can occur even when the liner is chemically resistant to the service. Lined pipe manufacturers should always be consulted regarding liner selections and service apph-cations. Also consult manufacturers regarding vacuum service limits. 

Environmental stress cracking (ESC), usually associated with SCG accelerated by surfactants or other aggressive media, is also of considerable interest in its own right, since pipe materials are often intended for service in contact with water or other industrial fluids. Oxidative degradation is another important concern, particularly at high temperatures, and stabilisers are often added specifically to retard SCG and catastrophic failure [65, 66, 67, 68], the stabiliser type and concentration being critical at very low SCG rates, even where they have little effect on rapid fracture [69]. 

The environment also plays a role in some environments brittle crack failure is strongly promoted. For example, detergents such as synthetic soaps can decrease the time to brittle failure of PE by a factor between 10 and 50 (see Figure 7.21). This phenomenon is known as stress corrosion or environmental stress cracking (ESC) (see further 8.5). 

Chemical resistance test for rubber linings by Atlas blind flange test Determination of effects of liquid chemicals on plastics Determination of environmental stress cracking (ESC) by the bent strip method... 

Determination of environmental stress cracking (ESC) by the ball or pin impression method... 

Kawaguchi T, Nishimura H (2003) Environmental stress cracking (ESC) of plastics caused by non-ionic surfactants. Polym Eng Sci 43(2) 419-430... 

Environmental Stress Cracking (ESC), Thermoplastic Elastomer (TPE), Creep, Time-to-Failure, Hydrolysis, Co-poly(ester ester), Poly(butylene terephthalate), Poly(butylene adipate). 

The Environmental Stress Cracking (ESC) of polymer materials can be can give rise to the sudden and unpredicted failure of constructions. The chance of ESC occuring can easily be overlooked because neither loading nor the environment factor in isolation can be termed damaging to the material, but the two in combination is fatal. Knowledge of ESC mechanisms is important if one is to succesfully prevent premature failure and economic loss. 

Environmental stress crack (ESC) resistance. Simulate end-use conditions (ideal), ASTM D1693, (Ethylene Plastics), ISO 4600, ISO 6252, ISO 4599... 

Environmental stress cracking (ESC) can be induced by cleaning a rigid plastic with a low boiling point solvent. Acetone has been applied to the polystyrene jewel case shown here, resulting in the formation of opaque areas. 

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