Characterisation of curing and cure state studies

DMA is an effective tool for investigating the cure of rubbers, because the cure state of a sample has an effect on both the tan 8 plot (reducing its height) and the final modulus value of the compoimd (increasing its value). It is, however, less sensitive than DSC (see Section 6.4.5), which measures the exotherm that results from a curing reaction. 

SchubneU and Schawe [39] used DMA to investigate the effect that differing degrees of cross-linking had on the viscoelastic properties of SBR rubbers that had been cured using 

With respect to the modulus, the degree of change moving from the uncured to cured state will be influenced by the composition of the rubber compound for example the amount of filler that is present, as this will have a significant influence on the modulus in itself. For a highly filled compound, the difference in modulus between a fuUy cured and uncured sample will be less than the difference observed for an unfilled rubber. These factors underline the fact that the data produced by DMA for this, and a number of other apphcations, are best used in a comparative way. 

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