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Authors
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Khonakdar, H. A. ; Morsheidan, J.
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Title
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Influence of long-chain branching extent in polyethylenes on molecular weight and molecular weight distribution predicted via rheological analysis
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Date
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01.05.2015
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Number
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46032
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Abstract
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This work highlights the potential of rheological analysis as an alternative powerful tool for estimation of molecular weight (MW) and molecular weight distribution (MWD) in terms of long-chain branching (LCB) extent in polyethylenes (PE). Different PE samples with different branching structure (mLLDPE, mVLDPE, LDPE, LLDPE, and LDPE/LLDPE blends) were prepared and their viscoelastic behavior was studied. The results showed that in metallocene samples a suitable agreement existed between the MWDs determined both experimentally and also by rheological data evaluation, while in the rest of samples this agreement was not so good. It seems that the presence of branching in LDPE and LLDPE makes this difference significant, while the absence of branching in metallocene samples caused suitable agreement between the results of predictions and measurements. In blend samples, this significant difference was attributed to existence of branching and also to noncompatibility of polymer components in some blend ratios. The results showed that normalized relaxation time spectrum is a good measure for qualitative comparison of MWDs of various samples. Applying Thimm Kernel function and relaxation modulus data in generalized mixing rule, the calculated MW and MWD of PE samples (without LCB) showed good agreement with the experimental results with high accuracy.
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Publisher
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Polymer Bulletin
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Wikidata
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Citation
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Polymer Bulletin 72 (2015) 1217-1231
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DOI
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https://doi.org/10.1007/s00289-015-1334-3
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Tags
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thermoplastic resin microstructures rheological properties
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