Most polyolefin products are produced with incorporation of comonomers to reduce crystallinity and to extend the range of product performance. To define these copolymers, a chemical composition or comonomer incorporation parameter is required in addition to the molar mass distribution.

This is the case for instance of Linear Low Density Polyethylene (LLDPE), Low Density Polyethylene (LDPE) or Polypropylene (PP), where the incorporation of comonomers such as Butene, Pentene, Hexene or Octene results in short-chain branches or small amounts of Ethylene in the case of PP, that influence the crystallinity, final density and performance of the resin.

Chemical Composition Distribution curve (CCD) can be obtained by Crystallization Analysis Fractionation (CRYSTAF), Temperature Rising Elution Fractionation (TREF) or Crystallization Elution Fractionation (CEF).