If you remember from the last post, the degree of crosslinking plays a large role in determining the magnitude of the loss and storage moduli in the rubbery region (see also top figure on left). In the figure above, the storage modulus drops dramatically at the Tg and then as the temperature continues to increase during the DMA scan, the chemical crosslinking reaction causes an increase in the storage modulus. The additional crosslinking triggered by heating above the Tg caused the crosslink density to increase thus increasing the modulus. At higher temperatures, the storage modulus achieves a plateau suggesting the completion of the crosslinking reaction. Note that the storage moduli and tan delta peak are frequency dependent. Tan delta curve has the typical peak at Tg and also has a second peak due to the additional crosslinking reaction