I recently stumbled upon the concept of viscoelasticity. Not being a chemist, but being interested in the topic, I started to read the wikipedia article.

The main thing I extracted from it is:
Solids are elastic, fluids are viscous, viscoelastics materials are both viscous and elastic.

I didn't get it, maybe due to my poor background. Is viscoelasticity a state of matter or just a property of materials? In the latter case, can we talk about viscoelastic solid and viscoelastic fluids?
I know the state of matter isn't an element nor compound or material property but it changes as temeprature and pressure change. The strength of the bonds between atoms/molecules and the "value" of their kinetic/vibrational energy is what determines how we see them.

Anyway, I couldn't really fit viscoelastic material in my chemistry mental scheme, so I'm here in search of some clarifications.

  • 1
    $\begingroup$ Would you consider a semi-crystalline polymer between its glass transition and its melting point a solid or a liquid? Above its melting point it would be considered a liquid, but would still exhibit viscoelastic behavior. $\endgroup$ – Chet Miller Apr 6 '18 at 17:00

Viscoelastic materials are generally considered solids, but often are noncrystalline (like the vinyl in records). The 'visco' property is akin to ductility in metals, that a slowly deformed piece of material cannot be made to relax to its original shape.

Presumably, some near-neighbor bonds (hydrogen bonds?) reform in relatively short times when strained.

The vinyl record will hold its shape indefinitely under small forces, but if you bend it, the large force applied causes internal strain only for a short time, the strain relaxes and the material permanently takes the as-bent shape. Rapid bending (slap the record) will shatter it. Silly putty, if you are familiar with that material, is also viscoelastic, but won't hold its shape indefinitely, and should be considered a very viscous liquid, except that rapid bending will break it (in propogating-crack fashion).


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