Comparison of chain structures between special polyethylene resins for natural gas pipes by preparative temperature rising elution fractionation and cross-fractionation

In general, natural gas pipes have the highest standard requirements of all pipes. Therefore, it is essential to establish the relationship between microstructure and properties. Two special polyethylene resins in the field were selected and researched in detail. Using the preparative temperature rising elution fractionation (P-TREF) method, both resins were separated across nine fractions. Following that, high temperature gel permeation chromatography (HT-GPC), differential scanning calorimetry (DSC), ¹³C-nuclear magnetic resonance spectroscopy (¹³C-NMR), and successive self-nucleation and annealing (SSA) thermal fractionation were used for analyzing the initial resins and respective fractions. For both samples, the major fractions were eluted between 85 °C and 98 °C. Sample B differed from Sample A in that it had a higher molecular weight, a longer average methylene sequence length (L_w:303.5), and more high-temperature fractions (over 100 °C). The chain structures and distribution of two typical resins were analyzed deeply, and the connection between chain architecture and property was investigated as well.