What is the effect of time and temperatuure on the mechanical properties of polymers (in regards...

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Mechanical Engineering

What is the effect of time and temperatuure on the mechanicalproperties of polymers (in regards to polymer chains)?

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EFFECT OF TEMPERATUREWhen substances made of small molecules are heated they simplymelt and form a freeflowing liquid however with polymers theprocess is more complex When polymers are cooled they will oftenbecome very brittle When heated the polymers will first becomeflexible before melting The individual molecules that make uppolymeric materials are very large and have an extended chainlikeshape that results in an entangled structure This entanglement isbeneficial in some respects The relatively high levels ofelongation that most polymers exhibit without breaking are due inlarge part to chain entanglement However this entanglement alsorestricts the freedom required at a molecular level to organizeinto crystals Consequently no polymer under normal processingconditions is fully crystalline and some polymers do notcrystallize to any significant degreeThis is due to their structure In some polymers there areareas of crystalline and amorphous regions In the glassy statethe tangled polymer chains in the amorphous region become frozenwhich prevents easy movement of the chains relative to each otherIf the polymer is forced to change shape it does so by breakingWhen the glassy material is heated the polymer chains will reach atemperature at which they can move relative to See Answer

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