Such a distribution of molecular weights can be described by statistics in terms of moments. The distribution shown above is bimodal (two identifiable peaks) and skewed (neither of the peaks is a symmetric about their means and the entire bimodal distribution is not symmetric about the mean. Consider a plot of the fraction of a plastic sample with a specified molecular weight versus molecular weight as show below. The features of this distribution have dramatic effects on the processability (viscosity) and properties (miscibility, strength and modulus) of plastics. From typical industrial synthesis a fairly broad distribution in molecular weight results. The distinguishing feature of commercial polymers is that they have molecular weights far in excess of the entanglement molecular weight of about 10,000 g/mole. Download this page: =>MolecularWeight.pdf
