Dynamic mechanical analysis: Difference between revisions

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Revision as of 15:58, 6 January 2017

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===Viscoelastic properties of materials===

[[Image:Dynamic+Tests+Setup+Chem+538.jpg|thumb|325px|Figure 1. A typical DMA tester with grips to hold sample and environmental chamber to provide different temperature conditions. A sample is mounted on the grips and the environmental chamber can slide over to enclose the sample.]]

Polymers composed of long molecular chains have unique viscoelastic properties, which combine the characteristics of [[Elasticity (physics)|elastic solid]]s and [[Newtonian fluid]]s. The classical theory of elasticity describes the mechanical properties of elastic solid where stress is proportional to strain in small deformations. Such response of stress is independent of [[strain rate]]. The classical theory of hydrodynamics describes the properties of viscous fluid, for which the response of stress is dependent on strain rate.<ref name="Ferry1980">{{cite book|last=Ferry|first=J.D.|title=Viscoelastic properties of polymers|publisher=Wiley|year=1980|edition=3}}</ref> This solidlike and liquidlike behavior of polymerpolymers can be modeled mechanically with combinations of springs and dashpots.<ref name="Ferry1991">{{cite journal|last=Ferry|first=J.D|year=1991|title=Some reflections on the early development of polymer dynamics: Viscoelasticity, dielectric dispersion and self-diffusion|doi=10.1021/ma00019a001|journal=Macromolecules|volume=24|issue=19|pages=5237–5245|bibcode = 1991MaMol..24.5237F }}</ref>

===Dynamic moduli of polymers===