Study of the abnormal late co-elution phenomenon of low density polyethylene in size exclusion chromatography using high temperature size exclusion chromatography and high temperature asymmetrical flow field-flow fractionation

Size-exclusion chromatography of perfluorosulfonated ionomers

“…The chromatograms of samples diluted directly also exhibited abnormal late elution [18][19][20] with the light scattering detector measuring large molecules at longer than expected retention volumes. Examples of DRI and LS chromatograms for autoclaved and non-autoclaved Nafion with EW = 950 are shown in Fig.…”

Field Flow Fractionation for the Size, Molar Mass, and Gel Content Analysis of Emulsion Polymers for Water‐Based Coatings

“…It has to be noted that the MALLS signal intensity is low in the region after 29 min which could also result in inaccurate molar mass readings. In previous work, multiple fractionations of the late eluting SEC fractions of branched polyolefins and polybutadienes have been performed and were characterized by AF4 . The authors proved that high molar mass species are present after fractionation by SEC followed by reinjection into AF4.…”

“…In AF4 the true upper molar mass is presented in a more accurate way compared to SEC where the resolution of the upper molar masses is determined by the pore size of the selected column set . The MMD of the filtered sample was marginally lower at the high molar mass end compared to the unfiltered measurements.…”

“…Typically, the calculated molar masses will be lower than the true molar masses. Emulsion polymers may also contain ultrahigh molar mass fractions which might be shear‐degraded in the SEC column by the pores of the stationary phase or the column frits . This will also result in inaccurate molar mass analyses.…”

Describing and quantifying the chemical composition distribution in unimodal and multimodal ZN‐polyethylene using CRYSTAF

“…Therefore it is crucial to be able to characterize the microstructures of ethylene and α‐olefins copolymers in details. Polymer fractionation techniques enable the separation fractionation of polyolefins according to specific characteristics of their microstructures as defined by their distributions of molecular weight, chemical composition, tacticity, and long‐chain branching, resulting in gathering of significant information of the polymer structure. The most widely used technique to determine the MWD of polyolefins is high temperature gel permeation chromatography (HT‐GPC), while the CCD characterization of PE can be done by Crystallization Analysis Fractionation (Crystaf), analytical—Temperature Rising Elution Fractionation (a‐TREF) and since recently also by Liquid Adsorption Chromatography (LAC) …”