Fractionation of Polyethylene Wax by Multistage Molecular Distillation: From Carbon-Number Distribution to Fraction Properties

Polyethylene wax (PEW) often carries a broad carbon-number distribution (CND) that limits its use in grades with controlled melting point, viscosity, and hardness. This study examines how multistage molecular distillation reshapes PEW composition and how the resulting compositional change is transmitted to fraction properties. An industrial PEW was processed through a wiped-film light-removal step and three short-path distillation stages, yielding five fractions whose normalized yields were 4.03% (PEW-40), 12.16% (PEW-70), 22.26% (PEW-80), 30.33% (PEW-90) and 30.71% (PEW-105). The peak carbon number migrated stepwise from C42 in the feedstock to C21, C37, C42, C50 and C68 in the fractions, and basic wax properties, DSC transition temperatures and TGA mass-loss temperatures moved consistently with the compositional shift. Weighted mean carbon number correlated with drop melting point (R2 = 0.938), kinematic viscosity at 100 °C (R2 = 0.951), penetration (R2 = 0.780) and oil content (R2 = 0.798), and the second-heating melting peak correlated with the 50% mass-loss temperature (R2 = 0.992). These results support a three-level correspondence connecting distillation operation, CND reshaping and fraction properties, and position molecular distillation as a grade-oriented physical process for by-product PEW.