High‐density polyethylene fractionation with supercritical propane

Stereochemical heterogeneity of biodegradable poly(L‐lactide) homopolymer as revealed by temperature rising elution fractionation and successive self‐nucleation/annealing thermal fractionation

“…Therefore, there is a need for accurate characterization of the stereodefect distribution in PLLA. Currently, temperature rising elution fractionation (TREF) makes it possible to determine a quantitative defect distribution for polymers of certain crystallizability, which has been applied mainly with polyolefin such as polyethylene (PE),17–19 ethylene copolymers,20–22 polypropylene (PP),23–25 and propylene copolymers,26–28 but also with random copolyester 29, 30. TREF involves two sequential stages: the sample is first crystallized on a column from a dilute solution under well‐controlled conditions by slowly decreasing the temperature, and then the precipitated sample is eluted at increasing temperatures (continuously or stepwise) 31.…”