The number of structural units or mers in the average polymer molecule in a particular sample. In most plastics the DP must reach several thousand if worthwhile physical properties are to be had.
The average number of repeating units in the individual macromolecules in a polymer. Note: In general, this average will depend on the basis on which it is calculated, which should be stated. For example, it may be based upon a mass (weight) or a number average.
The degree of polymerization, or DP, is the number of repeat units in an average polymer chain at time t in a polymerization reaction. The length is in monomer units. The degree of polymerization is a measure of molecular weight.