Ultra high molecular weight polyethylene fractions having narrow molecular weight distributions and methods of making and using the same

摘要

Polymer fractions such as polyethylene fractions can be produced that have a PDI less than about 2.3 and a M_w greater than about 1,000,000 g/mol, 3,000,000 g/mol, or 6,000,000 g/mol. Such polyethylene fractions are separated from a UHMWPE parent polymer by first dissolving the parent polymer in a relatively good solvent. The conditions employed for such dissolution are selected to reduce the degradation of the parent polymer. The resulting parent solution is transported into a fractionation column in which a support is disposed. The fractionation column is thereafter operated at conditions effective to form a precipitate on the support comprising the desired polyethylene fraction. The polyethylene fraction may then be recovered from the fractionation column by repeatedly displacing a solvent/non-solvent mixture into the column to dissolve the polyethylene fraction. The relative concentrations of the solvent and the non-solvent are based on a solvent gradient profile of the polyethylene parent polymer.