Short-chain Branching in polyolefins: what causes short-chain branches and how to study them.
Polymer Char
by raquel
6M ago
  Polyolefin copolymer resins incorporate comonomers such as 1-butene, 1-hexene, or 1-octene, which results in short-chain branches irregularly added that influence the crystallinity and final density of the resin. Depending on their density, the resulting resins are classified as high-density polyethylene (HDPE), medium-density polyethylene (MDPE), linear low-density polyethylene (LLDPE), and very low-density polyethylene (VLDPE).   In the case of linear low-density polyethylene (LLDPE), the incorporation of the comonomer in the chains is not uniformly distributed in all the molecul ..read more
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Chemical Composition measurement in GPC/SEC analysis. Differentiating polyolefins with similar Molar Mass Distribution.
Polymer Char
by nuria
6M ago
  The simultaneous analysis of concentration and chemical composition in Gel Permeation Chromatography (GPC) or Size Exclusion Chromatography (SEC) is of significant interest for today’s complex polyolefin copolymers. In polyethylene and copolymers, chemical composition is centered around the study of short-chain branches, created by the incorporation of comonomers into the main chain. The measurement of short-chain branching adds a new dimension to the conventional GPC/SEC technique that may be critical when dealing with resins that have very similar Molar Mass Distribution (MMD) but dif ..read more
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Why it is important to analyze the Chemical Composition Distribution in polyolefins
Polymer Char
by raquel
6M ago
  Polyolefins with heterogeneous chemical composition are becoming prevalent in the industry. These resins are produced by incorporating comonomers into the main chain in order to reduce their crystallinity and extend the range of product performance. To define these copolymers, characterization by molar mass (the most popular characterization technique) will not tell us about the intermolecular distribution of comonomer into the linear chains. Instead, we need to find out about its chemical composition or comonomer incorporation parameter. To define the microstructure of heterogeneous re ..read more
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Advantages of Size Exclusion Chromatography (SEC/GPC) for polyolefins
Polymer Char
by Esther López
6M ago
Polyolefin resins have become complex polymers by design, achieved with multi-reactor processes and the incorporation of comonomers that improve their performance for the desired application. This design complexity requires advanced methods of analysis, as the average properties measured by melt index and density techniques are not enough to define the microstructure of these polymers.   Size Exclusion Chromatography (SEC) – also called Gel Permeation Chromatography (GPC) – offers a great advantage in this area, as separating the polyolefin by its molar mass allows the study of its distri ..read more
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Practical considerations in Gel Permeation Chromatography analysis of polyolefins
Polymer Char
by Esther López
6M ago
This guide covers some practical considerations regarding solvent, analysis conditions, and laboratory supplies needed for analyzing polyolefins by Gel Permeation Chromatography (GPC) or Size Exclusion Chromatography (SEC) technique.   The data and recommendations presented here have been derived from the day-to-day operation of the GPC-IR and GPC-QC instruments in Polymer Char’s laboratory.     Solvent Consumption and Analysis Time   In Gel Permeation Chromatography, solvent consumption and analysis time depend mainly on the vial size, the number and type of columns, and t ..read more
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How to choose the most appropriate combination of detectors for high temperature SEC/GPC analysis of polyolefins
Polymer Char
by raquel
6M ago
  High Temperature Size Exclusion Chromatography (SEC) – also called Gel Permeation Chromatography (GPC) – is the most widespread technique to characterize the microstructure of polymers. Different detector-configurations can be used with SEC instrumentation, each of them contributing to the resin’s characterization in a different manner. In this guide we will cover the industry’s most used detectors for the characterization of polyolefins by SEC/GPC technique: two types of concentration detectors (DRI and IR), capillary Viscometers, and static Light Scattering detectors. Single-detector ..read more
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Comparison of Infrared detectors for GPC/SEC analysis
Polymer Char
by raquel
6M ago
  By coupling GPC-IR and GPC-QC* with any of Polymer Char’s Infrared detectors – IR4, IR5, or IR6 – it is possible to obtain both molecular weight distribution and chemical composition information of polyolefin resins. Each IR detector was developed with a specific application in mind, and their capabilities vary from one another. The purpose of this guide is to help you choose the Infrared detector most suited to your polyolefin characterization needs.   IR4 Detector   IR4 is a dual-wavelength detector, which uses the principle of infrared absorption spectroscopy to measure the ..read more
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How to dry the resulting fractions obtained from a preparative fractionation system
Polymer Char
by Pilar del Hierro
6M ago
Preparative fractionation systems, like PREP mc2 and PREP C20, fractionate polymers by dissolving them in the appropriate solvent and then separating their molecules according to certain parameters, such as molecular weight and crystallinity. At the end of the process in the preparative system, the resulting polymer fractions are still mixed with the solvent, so we need to remove the solvent in order to obtain the dry polymer for each fraction. In this article, we will explain the steps and equipment needed to dry these fractions.     Step 1: Pre-treatment   To improve the preci ..read more
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How we make our GPC/SEC columns last longer (almost 2 years)
Polymer Char
by Esther López
6M ago
  As analysts in the Gel Permeation Chromatography (GPC) field, we know that picking the right columns and developing a stable analysis method is essential to delivering precise and accurate results. Even the most comprehensive analytical system will fail to provide the quality of data required if the columns perform a poor separation or if the analytical process is not stable.   GPC columns are at the core of GPC systems, which can be problematic due to their: short lifespan extreme sensitivity to changes in analytical conditions high cost This drives us, analysts, to take extra p ..read more
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Short-chain Branching in polyolefins: what causes short-chain branches and how to study them.
Polymer Char
by raquel
2y ago
  Polyolefin copolymer resins incorporate comonomers such as 1-butene, 1-hexene, or 1-octene, which results in short-chain branches irregularly added that influence the crystallinity and final density of the resin. Depending on their density, the resulting resins are classified as high-density polyethylene (HDPE), medium-density polyethylene (MDPE), linear low-density polyethylene (LLDPE), and very low-density polyethylene (VLDPE).   In the case of linear low-density polyethylene (LLDPE), the incorporation of the comonomer in the chains is not uniformly distributed in all the molecul ..read more
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