Estimations of fold surface densities using space‐filling models

Abstract

AbstractThe model of a tight‐fold adjacent reentry fold surface for polyethylene single crystals has been questioned, because it has been speculated that a tight‐fold surface should have a density approximating that of the unit cell (∼1.00 g/cm3). This would lead to an overall lamella density of close to unity. In contrast, the majority of measured values are in the range 0.96 to 0.97+ g/cm3. These lower values have been taken as evidence to disprove a tight‐fold–surface model. The present calculations made on space filling models of tight folds indicates a fold surface density on the order of 0.75 g/cm3. This produces no inconsistency between a tight‐fold model and accepted lamella density values. Further, calculated values of the weight fraction crystallinity of lamella, as a function of the number of carbons in the fold, limits this number to approximately 9 to 11 carbons per fold.