Five regions of viscoelastic behavior

Five regions of viscoelastic behavior - Five regions of...

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Five regions of viscoelastic behavior: Viscoelastic materials simultaneously exhibit a combination of elastic and viscous behavior. Generally, viscoelasticity refers to both time and temperature dependence of mechanical behavior. Figure 1: Five regions of viscoelastic behavior for a linear, amorphous polymer. 1) The glassy region: From fig.1 in region 1 the polymer is glassy and frequently brittle. Young`s modulus for glassy polymers just below the glass transition temperature is surprisingly constant over a wide range of polymers having the value approximately 3× 10 10 dynes/cm 2 . Here the molecular motions are largely restricted to vibrations and short range rotational motions. The bulk modulus (B) = 8.04 (CED) = 8.04 δ 2 , where CED is cohesive energy density. 2) The glass transition region:
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Region 2 in fig.1 is the glass transition region. Typically the modulus drops a factor of about 1000 in a 20 to 30 range. The behavior of polymers in this
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