Ethylene/1‐heptene copolymers as interesting alternatives to 1‐octene‐based LLDPE: Molecular structure and physical properties

Abstract

Classical linear low density polyethylenes (LLDPEs) are copolymers of ethylene and 1-octene or 1-hexene, respectively. In the past, other 1-olefins have been tested as comonomers but the resulting LLDPEs were never commercialized as large scale products. The present study focuses on the use of 1-heptene as an interesting comonomer for the synthesis of LLDPE. For a comparison of the molecular structure and the physical properties of 1-heptene-and 1-octene-based LLDPEs, five Ziegler-Natta LLDPEs of varying comonomer contents based on 1-heptene and 1-octene, respectively, were acquired and analysed using advanced methods. The comonomer contents of the resins were between 0.35 and 6.4 mol %. Crystallization-based techniques revealed similar bimodal distributions that are due to the formation of copolymer and polyethylene homopolymer fractions. The compositional distribution of the copolymers was studied by high-temperature (HT) HPLC and HT-2D-LC. The analytical results indicate similar chemical heterogeneities and molar mass distributions of the two sets of LLDPE up to a comonomer content of 3 mol %. Similar to the molecular structure, the physical properties of the materials are quite similar. At comonomer contents of 3 mol % differences between the two sets of samples are seen that are attributed to differences in the abilities of 1-heptene and 1-octene in disrupting the crystal arrangements of the polymer chains in solid state. V C 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 962-975

Chemical Composition Fractionation of Olefin Plastomers/Elastomers by Solvent and Thermal Gradient Interaction Chromatography

“…[11] The authors used a solvent gradient tech nique (solvent gradient interaction chromatography, SGIC) that is based on adsorptive interactions and it has been demonstrated later that the method can be applied to olefin homopolymers, copolymers, and blends. [10,[12][13][14][15][16][17][18][19] The technique has the draw back that for 1D separations only the evaporative light scattering detector (ELSD) can be used, which needs to be calibrated versus several polymer features to enable quantification.…”

Deformulation of commercial linear low‐density polyethylene resins by advanced fractionation and analysis

“…Alternatively, high‐temperature HPLC (HT‐HPLC) is able to fractionate polyolefins according to their chemical composition irrespective of crystallizability. Accordingly, this technique is a selective fractionation technique for both crystalline and non‐crystalline materials . A more comprehensive approach for evaluating molecular heterogeneity in terms of CCD and MMD in complex polymer systems is to perform preparative fractionations as in preparative temperature rising elution fractionation (pTREF), solvent gradient fractionation and preparative molar mass fractionation (pMMF) .…”

Comprehensive branching analysis of polyethylene by combined fractionation and thermal analysis

“…High‐temperature high performance liquid chromatography (HT‐HPLC) is able to fractionate polyolefins according to their chemical composition or branching irrespective of crystallizability. Accordingly, this technique is a selective fractionation technique for both crystalline and non‐crystalline materials …”

“…Accordingly, this technique is a selective fractionation technique for both crystalline and non-crystalline materials. 1,12,23,24 The bulk analysis of branched PE compared to linear PE is schematically presented in Fig. 1.…”