Of a moderate environmental stress crack agent can result in an order of Reduces the energy required for disentanglement to occur. Polymer chains, allowing accelerated molecular disentanglement. The plastic, interfering with the intermolecular forces bonding the In environmental stressĬracking, the chemical agent permeates into the molecular structure of Stress concentration within the part, cyclic loading, fatigue, andĬontact with specific chemical agents (ESC). Several factors will accelerate the embrittlement processĪssociated with creep rupture, including an increase in temperature, Creep rupture is cracking within a plasticĬomponent that occurs as a response to stress that occurs throughĭisentanglement of the polymer chains by overcoming intermolecularįorces, such as Van der Waal's forces and hydrogen bonding, between Through extended exposure to levels of stress that are below the yield Under the influence of constant stress, and occurs as a function of time 32), creep is the tendency of a solid material to deform permanently This, environmental stress cracking and creep rupture are parallelĪs reviewed in the July/August 2015 issue of Plastics Engineering The chemical simply accelerates the stress cracking. Stress cracking in air, also known as creep rupture, given sufficient Significantly, in the absence of the chemical the plastic would undergo Molecular structure alteration or degradation does not occur. Through a chemical reaction between the polymer and the chemical agent. The ESC failure mechanism does not proceed It involves molecular degradation or chemical attack of the plastic Secondary chemical agents are far more common.Ī common misconception about environmental stress cracking is that Failures connected with primaryĬhemical agents are rare in service because the chemical compatibility This is in contrast to a primary chemical agent, where contact isĮxpected, such as gasoline with a small-engine fuel filter, or paint A secondary chemical agent is one that is notĪnticipated to contact the molded plastic part throughout its lifecycle. Mostįailures associated with ESC occur through contact with a secondaryĬhemical agent. Prevalent in manufacturing, commercial, and household settings. Plastic killer" (see, for example, Figure 7).Ī principal consideration in the relatively high failure rateĪssociated with environmental stress cracking is the widespread lack ofĪwareness and understanding of the interaction between plastic materialsĪnd chemicals, particularly organic-based chemicals, which are so Because of theįrequency and severity of ESC failure, it has been nicknamed "the Subsequent cracking of a plastic due to the simultaneous and synergisticĪction of stress and contact with a chemical agent. Retrieved from Įnvironmental stress cracking (ESC) is considered a leading cause
APA style: Plastic failure through environmental stress cracking: ESC, 'the plastic killer,' is a frequent cause of field failures.Plastic failure through environmental stress cracking: ESC, 'the plastic killer,' is a frequent cause of field failures." Retrieved from MLA style: "Plastic failure through environmental stress cracking: ESC, 'the plastic killer,' is a frequent cause of field failures." The Free Library.BSAC Technical courses are delivered via clubs, regional teams or at BSAC Technical Centres. Divers interested in technical training could if they wish contact BSAC Technical Instructors directly.Īctive BSAC Technical Instructors are listed in the tables below.
0 kommentar(er)
