An Improved Method of Moments as a More Reliable Alternative for Prediction of Average Molecular Weights of Irreversible Non-Linear Polymerizations and Reversible Polycondensations

摘要

Mass balance equations of polymer species in ideal reactors yield first-order partial differential equations in terms of generating functions when dealing with homogeneous non-linear irreversible polymerizations, as also do simple linear reversible poly condensations. Their numerical solution using the method of characteristics is often plagued by problems of numerical sensitivity, which only recently could be reliably overcome. Besides allowing prediction of chain length distributions (not here discussed) an efficient prediction of average molecular weights even in the presence of gel is possible. Free-radical polymerization with transfer to polymer and vinyl/divinyl metallocene catalyzed copolymerization are discussed. Inherent weaknesses of "numerical fractionation" are unveiled through comparison with these results.