Editing Dynamic mechanical analysis (section)

===Polymer composition===

Varying the composition of monomers and [[cross-link]]ing can add or change the functionality of a polymer that can alter the results obtained from DMA.  An example of such changes can be seen by blending ethylene propylene diene monomer (EPDM) with [[styrene-butadiene rubber]] (SBR) and different cross-linking or curing systems.  Nair ''et al.'' abbreviate blends as E<sub>0</sub>S,  E<sub>20</sub>S, etc., where E<sub>0</sub>S equals the weight percent of EPDM in the blend and S denotes sulfur as the curing agent.<ref name="Nair">{{cite journal|last=Nair|first=T.M.|author2=Kumaran, M.G. |author3=Unnikrishnan, G. |author4= Pillai, V.B. |year=2009|title=Dynamic Mechanical Analysis of Ethylene-Propylene-Diene Monomer Rubber and Styrene-Butadiene Rubber Blends|journal=Journal of Applied Polymer Science|volume=112|pages=72–81|doi = 10.1002/app.29367}}</ref>

Increasing the amount of SBR in the blend decreased the storage modulus due to [[intermolecular]] and [[Intramolecular force|intramolecular]] interactions that can alter the physical state of the polymer.  Within the glassy region, EPDM shows the highest storage modulus due to stronger intermolecular interactions (SBR has more [[steric]] hindrance that makes it less crystalline).  In the rubbery region, SBR shows the highest storage modulus resulting from its ability to resist intermolecular slippage.<ref name="Nair" />

When compared to sulfur, the higher storage modulus occurred for blends cured with dicumyl peroxide (DCP) because of the relative strengths of C-C and C-S bonds.

Incorporation of reinforcing fillers into the polymer blends also increases the storage modulus at an expense of limiting the loss tangent peak height.

DMA can also be used to effectively evaluate the miscibility of polymers.  The E<sub>40</sub>S blend had a much broader transition with a shoulder instead of a steep drop-off in a storage modulus plot of varying blend ratios, indicating that there are areas that are not homogeneous.<ref name="Nair" />