Tan delta represents the ratio of the viscous to elastic response of a viscoelastic material or in another word the energy dissipation potential of the material. To make it simple, assume that you apply a load to a polymer, some part of the applied load is dissipated by the energy dissipation mechanisms ( such as segmental motions) in the bulk of polymer , and other part of the load is stored in the material and will be release upon removal of the load (such as the elastic response of a spring!). Back to your question, increasing Tan delta indicates that your material has more energy dissipation potential so the greater the Tan delta, the more dissipative your material is. On the other hand, decreasing Tan delta means that your material acts more elastic now and by applying a load, it has more potential to store the load rather than dissipating it! For example, in case of nano-composites ( and filled polymers), increasing the nano-particle content diminishes the value of Tan delta as nano-particles impose restrictions against molecular motion of polymer chains ( due to the adsorption of polymer chain on the surface of the particles) resulting in more elastic response of the material.

Could you please include the thermograph?

Tan delta represents the ratio of the viscous to elastic response of a viscoelastic material or in another word the energy dissipation potential of the material. To make it simple, assume that you apply a load to a polymer, some part of the applied load is dissipated by the energy dissipation mechanisms ( such as segmental motions) in the bulk of polymer , and other part of the load is stored in the material and will be release upon removal of the load (such as the elastic response of a spring!). Back to your question, increasing Tan delta indicates that your material has more energy dissipation potential so the greater the Tan delta, the more dissipative your material is. On the other hand, decreasing Tan delta means that your material acts more elastic now and by applying a load, it has more potential to store the load rather than dissipating it! For example, in case of nano-composites ( and filled polymers), increasing the nano-particle content diminishes the value of Tan delta as nano-particles impose restrictions against molecular motion of polymer chains ( due to the adsorption of polymer chain on the surface of the particles) resulting in more elastic response of the material.

Victor H and Ebrhim thank you for your comment , please find attached thermograph

Besides the great explanation of Ebrahim Jalali Dil, viscous modulus is translated "as a rule of thumb" as the plastic phase, meanwhile the elastic modulus is translated as the "elastic phase". I have seen at your file that you have only the Storage Modulus (Elastic Modulus). As the temperature increases, the energy release (Dampening) happens for each sample. It's up to you to decide if the dampening maximum is more convenient at higher or lower temperatures. Good Luck!!

Increasing the height of tanδ peak represents higher damping for the nanocomposites.

Thanks alot

 I have impressed by Ebrahim 's answer . So lucid explanation. I had doubts on tan delta curve but today cleared.

Thanks ResearchGate & Ebrahim.

Please see my attached paper about the tan delta peak height in particle-reinforced polymers.  The stiffer the rubbery modulus, the lower the peak height due to general viscoelastic effect.  The loss modulus peak (E" or G") should be used for discussion of glass transition behavior not the tan delta peak.  I hope this is helpful (although I realize that my answer is very late because I just found this question accidentally now). Best, Chris

Hi Basheer,

from in the graph you attached the tandelta behavior for PE and its nano-composites is quite strange at those temperatures. 

Can you supply the graph with both the storage modulus and tan delta?