investigating the Impact of Crystalline Structure on the Physical Properties of Polyethylene Using TREF Analysis

Abstract

The structure–property relationships of two linear low-density polyethylene (LLDPE) plastomers, ethylene/1-octene (PE1) and ethylene/1-hexene (PE2), were investigated using preparative temperature rising elution fractionation (TREF). Fractionated and bulk materials were characterized by differential scanning calorimetry (DSC), density-based crystallinity, and Vickers microhardness measurements. TREF revealed distinct elution behaviors, with PE2 exhibiting broader and higher-temperature fractions, indicating longer ethylene sequence lengths and enhanced crystallizability. DSC results showed consistently higher melting and crystallization temperatures for PE2, reflecting thicker and more perfect lamellae. Increasing short-chain branching was found to reduce melting temperature, crystallinity, and microhardness, confirming a strong dependence of thermal and mechanical properties on comonomer distribution. Fraction removal experiments further demonstrated that eliminating low-crystallinity fractions increases melting temperature and hardness, while removal of highly crystalline fractions leads to their reduction. These findings highlight the critical role of comonomer type and distribution in tailoring the thermal and mechanical performance of LLDPE plastomers.

Our findings demonstrate that strategic modification of polymer architecture at the molecular level can lead to significant improvements in performance, paving the way for the development of more efficient, durable, and application-specific polyethylene materials. This research contributes to the growing field of advanced polymer design and offers practical pathways for enhancing material performance through targeted structural engineering.