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Polyolefin elastomer (POE) has very weak crystalline ability, consequently, applying the conventional preparative temperature‐rising elution fractionation (P‐TREF) to separate is challenging. Here, a unique, home‐built P‐TREF apparatus with an extensive range of temperatures from −80°C to 150°C is applied to first fractionate POE depending on its crystallizability. The main fractions are eluted at 0°C, 8°C, 15°C, 20°C, 25°C, 30°C, and 35°C. The corresponding weight percentages of fractions are 8.31, 13.38, 15.59, 12.05, 13.39, 17.30, and 10.53 wt%, respectively. The chain structures of fractions are further analyzed by high‐temperature gel permeation chromatography (HT‐GPC), 13C‐nuclear magnetic resonance spectroscopy (13C‐NMR), differential scanning calorimetry (DSC), and successive self‐nucleation and annealing (SSA). The crystallinity of the fraction grows continually as the elution temperature rises. The 1‐octene comonomer concentrations within the fractions decreases from 13.8 to 7.9 mol% when the elution temperature rises from −10°C to 40°C. These findings enable for the detailed recognition of the chain microstructure of POE resin and the extension of the TREF approach to POE resins. This lays the groundwork for fundamental studies and practical uses in industry. [ABSTRACT FROM AUTHOR]

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 (Lw: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. [ABSTRACT FROM AUTHOR]

TREF (temperature rising elution fractionation) is a method to separate resins based on crystallizability. The influence of TREF cooling rate (V0) on the fractionation process is still unclear. Herein, a poly(1‐butene‐co‐ethylene) resin is fractionated by the TREF method at three different cooling rates (1, 2, and 4 °C h−1), and then the fractions are analyzed by high‐temperature gel permeation chromatography (HT‐GPC), differential scanning calorimetry (DSC), and 13C‐nuclear magnetic resonance spectroscopy (13C‐NMR). The cooling rate V0 affects the crystallization process of the PB‐1 resin, resulting in different fraction contents at the same elution temperature. Furthermore, the cooling rate also affects the chain microstructure of fractions obtained from the same elution temperatures, i.e., the content of 1‐butene and ethylene monomer units, average sequence length and isotacticity. The lower cooling rate is beneficial to the effective separation of the fractions with weak crystallizability. These results have important guidance for optimizing fractionation conditions and obtaining different narrow distribution fractions of poly(1‐butene) (PB‐1) resin. [ABSTRACT FROM AUTHOR]

It is crucial to establish a relationship between chain microstructure and mechanical performance for the ultimate applications of impact polypropylene. Here, two in-reactor alloy impact polypropylene resins (samples A and B) with same stiffness and different toughness are fractionated into nine fractions (at 35, 80, 100, 105, 110, 115, 120, 125, 140 °C, respectively) using preparative temperature rising elution fractionation (P-TREF). These fractions are characterized with high-temperature gel permeation chromatography (HT-GPC), Fourier transform infrared (FTIR) spectrometer, 13C nuclear magnetic resonance (13C NMR) spectrometer, differential scanning calorimetry (DSC), and thermal fractionation. It is found that both samples are primarily made up of isotactic polypropylene homopolymer, ethylene-propylene rubber (EPR), ethylene-propylene segmented and blocky copolymers. The content and Mw of ethylene-propylene rubber in sample A (16.90 wt%, 500.0k) are higher than those (15.78 wt%, 385.4k) of sample B. Thus, sample A shows better toughness. The crystallinities of the fractions 4–9 in sample A (50.5, 51.0, 60.8, 52.7, 47.2, 48.5%) are higher than the corresponding fractions of sample B (47.8, 49.0, 51.0, 49.1, 46.6, 41.6%). Particularly, the content of high-temperature fractions (115–140 °C, i.e. fractions 6–9) is slightly higher than those of the fractions in sample B, but their molecular weights of the corresponding fractions are lower. Finally, the comprehensive effect leads to the same stiffness of the two samples. Definitely, the above results provide guidance on chain structure for improving mechanical properties of polypropylene with excellent stiff-tough balance. [ABSTRACT FROM AUTHOR]