Polyethylene is characterized by molecular weight (MW), molecular weight distribution (MWD), and density. Melt index (MI2) is measured in the quality control (QC) lab and is used as an indication of resin MW. Melt flow ratio (MFR or MI20/MI2) is a calculated QC lab number, which is used as an indication of MWD. Density is a measure of crystallinity. This article shows that a capillary rheometer can provide a fast and reliable method on a production line to control MW and MWD by predicting MI2 and MI20 for a resin within specific ranges of density, melt index and equipment/catalysts.
ASTM D1238-04c. (2004). Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer , American Society for Testing and Materials (ASTM International), 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, USA.
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ASTM D3835-02. (2002). Standard Test Method for determination of Properties of Polymeric Materials by Means of a Capillary Rheometer, American Society for Testing and Materials, West Conshohocken, PA.
ASTM D3123-98. (2004). Standard Test Method for Spiral Flow of Low-Pressure Thermosetting Molding Compounds , American Society for Testing and Materials (ASTM International), 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, USA.
