Interpenetrating Polymer Networks (IPN's) are composite materials in a special way.  A very general, simplistic definition of an IPN is a material with two co-continuous phases or a material with 2 parts intertwined throughout.  For a detailed website describing IPN's, please visit DM's IPN's.  The main goal of an IPN is to trap 2 polymer phases in each other thus causing a possible synergistic behavior or an addition of properties as opposed to a compromise of properties is the scenario which typically results in most composites.

        It is understood by many that a polymer can absorb or dissipate energy best when it is in its glass transition state (Tg).  Many polymer composites and blends are combinations of 2 polymeric materials which in conjunction with each other, alter the Tg, but do not broaden the temperature range.  If two materials can be blended together in a manner in which their properties are maintained and the glass transition temperatures of the 2 combine to broaden the temperature range in order to absorb energy at many applicable thermal stages, then you got something.  Depicted below are two Dynamic Mechanical spectra (DMA) which show the Tg's of blends and IPN's.  As you can see, the IPN displays a much broader glass transition than the blends.
 

      The following analysis techniques are very instrumental in characterizing IPN's, both their mechanical properties and their morphology.
 

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