Does a higher Tan delta value for a vsico-elastic polymer lead to an increased cold creep?
Does a higher Tan delta value for a vsico-elastic polymer lead to an increased cold creep?
You ask an essential question in materials science. I will show you the main directions to follow to answer them. If you want more details, let me know. I will send you in a few days a link to a site that develops them into a formation. It helps to avoid blocking points on the subject of creep and more generally of all damage. It is preferable to reason separately with the imaginary part and with the real part of the polarization or of a mechanical modulus, which must be analyzed in very large stress and temperature scales. The two components correspond to different energy processes. While strains and damages are attributed to the applied stress, it is not dissociable from the internal stress. It is therefore necessary to separate what is due to the internal stress and what is due to the applied stress, which supposes studying the processes of multiplication of defects and localization of energy. The next point is to study the nature of internal energy, which has an elastic component and an entropic component. Creep begins with the aging of the material and ends with its explosion. If you are doing a thesis in material sciences or if you are in contact with industrial problems, you will not regret following these directions. Sincerely.
claude
When properly measured in the linear viscoelasticity region, Tan Delta provides indication on mechanical energy dissipation in the material under cycling deformation. Being ratio of Loss/Viscous modulus over Storage/Elastic modulus (G"/G') Tan Delta grows with G" increase, indicating higher viscous contribution in the overall viscoelasticity. That is, higher Tan Delta indicates higher ability of polymer chains (or chain segments) to plastic (rather than elastic) deformation, which indeed may indicate higher propensity of the material to deform under constant stress (creep behavior). Alternatively, Tan Delta also grows with G' decrease, indicating lower elastic contribution and lower instant creep modulus, that is higher instant creep deformation. Anyway, while increasing molecular mobility or lowering structure rigidity indeed may lead to higher creep, higher Tan Delta does not "lead", but indicates higher tendency of the polymer to deform plastically.
I started from the fact that the term viscoelasticity is an oxymoron masking that energy has two terms, one represents mechanical energy which by definition is elastic, i.e. reversible, and the other which has both properties to be able to remain stored and relaxe with temperature jump. To say "properly measured" introduces an assumption contrary to reality. Loss and viscous mean the same thing and G"/G' is difficult to interpret because both vary in different ways depending on the transformation. You say the classic things very clearly. Only this vision does not lead to a equation of state and does not explain the mechanisms of damage By comparing all the observations made under various stresses, we understand the effects of losses on instabilities, we discover the factors that result from this and enter into an equation of state. Experimental techniques are very different from real practices. I cannot go into more detailed explanations. If you are interested in exploring these comments in more detail, I would link you to a site that develops them.
Good day
Claude
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