Microstructure characterization of a complex branched low-density polyethylene

Xue, Yanhu; Fan, Yandi; Bo, Shuhui; Ji, Xiangling

doi:10.1007/s10118-015-1609-z

Cited by 12 publications

(1 citation statement)

References 43 publications

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“…The branching factors of linear SRM1475 are both close to 1; whereas, those of SRM1476 gradually decline as its molecular weight approaches the critical molecular weight. A series of branching parameters can be calculated as described in another literature [42]. For SRM1476, the mean R g is 11.9 nm, and the average branching factors g and g′ are 0.71 and 0.58, respectively.…”

Section: Resultsmentioning

confidence: 99%

Molecular chain heterogeneity of a branched polyethylene resin using cross-fractionation techniques

Xue

2015

J Polym Res

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The typical standard long chain branching (LCB) polyethylene (PE) SRM1476 is issued by the American National Bureau of Standards, which is widely used as a standard reference material in chromatographic experiments. Although some works have been reported in literatures, they are not consistent, such as the data about its molecular weight and molecular weight distribution. Therefore, it is necessary to further investigate the microstructure features of SRM1476 in order to better serve as a reference object in comparison with other unknown resins. In this study, the molecular chain heterogeneity of SRM1476 is investigated extensively and compared with the linear PE SRM1475. Based on the characterization of the original sample, SRM1476 actually has both LCB and short chain branching (SCB) structures, as well as the SCB content is more than LCB content in 13 C-NMR results. After successive self-nucleation and annealing (SSA) thermal fractionation, SRM1476 shows a broad-range endotherm with multiple melting peaks (more than eight peaks), which proves the molecular chain heterogeneity in SRM1476. SRM1476 is fractionated into nine fractions by preparative temperature rising elution fractionation (TREF). At the high elution temperature region, the amounts of fractions are more than 90 %, and their molecular weights are higher. At the low elution temperature region below 50°C, molecular weights of fractions are lower and their amounts are less than 5 %. Differential scanning calorimetry (DSC) melting curves of TREF fractions with higher elution temperatures shift toward higher temperature with sharper melting peaks. In the results of TREF-SSA cross-fractionation, each fraction shows a broadrange endotherm with multiple melting peaks that shift toward the high elution temperature region with the elution temperature. The arithmetic mean methylene sequence lengths of TREF fractions gradually increase from 33 to 105 as elution temperature increases. Results from TREF-DSC and TREF-SSA cross-fractionations indicate that SRM1476 and its TREF fractions have both intramolecular and intermolecular heterogeneity.

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Section: Resultsmentioning

confidence: 99%