A DMA graph of a thermoset polymer gives the storage modulus graph, loss modulus graph and a Tan (delta) graph. Tg of the polymer can be either Storage onset temperature or the Tan (delta) peak temperature in most cases.
In the case, the question is, how can we explain the relationship between half peak width (glass transition)of Tan(delta) and the network structure of the polymer. Can someone explain?
Width of glass transition is related to uniformity of network. (Mean) Network density on the other hand is related to rubbery plateau modulus.
Storage onset temperature can be determined from linear scaled modulus (as in DIN 65583) or from logarithmic scaled modulus (as in ASTM D7082). Logarithmic scale makes more sense.
I would say that width of Tan D peaks in DMA is related to distribution width of the associated relaxing elements. In the case of glass transition, relaxing elements are mobile chain segments in amorphous regions. The wider is the distribution of the segments in terms of their mobility (length, rigidity, packing density, free volume, intermolecular interactions etc.) the wider is the DMA peak. Accordingly, widening of the peak in crosslinked systems may indicate nonuniform crosslinking structure: presence of domains differing in the crosslinking density (length of the segments between the crosslinks).
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