GPC-VIS-MALS study of EVA copolymers: Quantification and interactions of SCB and LCB |
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| Institution: | 1. Instituto de Desarrollo Tecnológico para la Industria Química (INTEC, UNL-CONICET), Güemes 3450, 3000 Santa Fe, Argentina;2. Facultad Regional Santa Fe, Universidad Tecnológica Nacional, Lavaise 610, 3000 Santa Fe, Argentina;3. Polymer Institute, Slovak Academy of Science, Dúbravská cesta 9, 84541 Bratislava, Slovakia;1. Department of Chemical Sciences, Tezpur University, Assam, India;2. Department of Physics, Tezpur University, Assam, India;3. Faculty of Science, Department of Chemical Sciences, Tezpur University, Assam 784028, India;1. Freiburg Materials Research Center FMF, Stefan-Meier-Str. 21, D-79104 Freiburg, Germany;2. Institute for Macromolecular Chemistry of the University of Freiburg, Stefan-Meier-Str. 31, D-79104 Freiburg, Germany;1. Fraunhofer Institute for Structural Durability and System Reliability LBF, Division Plastics, Group Material Analysis, Schlossgartenstrasse 6, 64289, Darmstadt, Germany;2. SABIC Technology & Innovation, STC Geleen, P.O. Box 319, 6160, AH, Geleen, the Netherlands |
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| Abstract: | Long-chain branching (LCB) is a structural phenomenon that affects important properties in polyethylene (PE) and some copolymers. Quantification of LCB frequency (λ) can be carried out by gel permeation chromatography dotted with detector for viscosity (GPC-VIS) or light scattering (GPC-MALS) by calculating branching indexes against a linear reference. In copolymers, interactions between LCB and SCB (short chain branching) have been described and lead to errors in quantification.In this work, ethyl vinyl acetate (EVA) copolymers of composition ranging 3–20 wt% VA have been studied. A numerical method, developed for the reduction of GPC-VIS and GPC-MALS data of PE, was used for quantifying molecular weights, intrinsic viscosities and gyration radius, as well as the confident ranges. Reliable results were obtained despite the low LCB determined values.A low density polyethylene was also included and compared. Discrepancies in the scaling laws for gyration radius and intrinsic viscosity reveal a strong effect of SCB which was confirmed by the structure factor and its dependence on molecular weight and comonomer content. However, the recently designed gpcBR index revealed to be nearly independent on the short chain branching and allowed detecting differences between apparently similar samples. |
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| Keywords: | EVA copolymers Multi angle light scattering (MALS) Intrinsic viscosity Long chain branching (LCB) Branching index Data analysis |
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