Molecular-Weight Multimodality of Multiple Flory Distributions

It is well-known that the final end-use properties of polymer resins depend on the shape of the molecular-weight distribution (MWD) very strongly. Particularly, polymer resins with bimodal MWDs are required for certain special applications, as they may simultaneously present enhanced mechanical and flow properties. A theoretical framework for the characterization of bimodality (or multimodality) of MWDs of polymers produced through linear polymerizations at steady-state or quasi-steady-state conditions is developed and presented here. Conditions for the development of bimodality in generalized NS-Schulz–Flory distributions are characterized for different forms of presentation of the MWDs. It is shown that the bimodal character of the MWD depends on the particular form used to represent it, which can then be used to generate an index of bimodality of the MWD. The theoretical results are finally used to compute the index of bimodality of actual polymer materials obtained at plant site.