ASTM D2839 Standard Practice for Use of a Melt Index Strand for Determining Density of Polyethylene

Get Certified ASTM D2839 Polyethylene Density Testing

The ASTM D2839 test is designed to calculate polyethylene density from a strand of polyethylene melt for manufacturers, polymer processors, and others who use the polymer. The strand is melted under controlled melt index conditions to obtain a representative sample, which is weighed and measured to determine the strand density. Engineers can then compare the various grades of polyethylene, production batches, formulations, and processing conditions. Consistent results depend on proper specimen preparation and measurement.

• Polyethylene: Laboratories determine the density of applicable polyethylene materials.
• Melt Index Strand: Technicians use the strand produced during melt index testing as the density specimen.
• Density Determination: Laboratories measure the relevant specimen characteristics to determine density.
• Material Comparison: Engineers compare polyethylene grades and production batches using density results.
• Quality Control: Manufacturers use density measurements to monitor material consistency.
• Processing Evaluation: Engineers can evaluate differences associated with material processing and formulation.

What are the uses of ASTM D2839 testing?

ASTM D2839 testing provides useful density information for polyethylene characterization and quality evaluation. Manufacturers and engineers can use the results to compare materials and identify variations between production conditions. ASTM D2839 test standard-

• Determines polyethylene density using a melt index strand.
• Supports polyethylene material characterization.
• Helps compare different polyethylene grades.
• Supports quality control between production batches.
• Helps identify material variations.
• Supports research and development activities.
• Provides density information for material selection.
• Helps evaluate processing and formulation differences.

Which materials can be tested according to ASTM D2839?

ASTM D2839 applies to polyethylene for which a suitable melt index strand can be obtained. Laboratories should confirm what the material is and the specimen requirements before testing.

• Polyethylene Materials: Determines density from a melt index strand.
• Polyethylene Grades: Allows engineers to compare density characteristics among applicable grades.
• Processed Polyethylene: Supports evaluation of material obtained through controlled melt index testing.
• Different Formulations: Helps compare density differences associated with polyethylene formulations.
• Production Batches: Supports consistency checks between batches of polyethylene material.

Why is ASTM D2839 testing important?

Density provides important information about polyethylene structure and material characteristics. Property variations depend on differences in density, for example, stiffness, strength, flexibility, and processing behavior. ASTM D2839 offers a practical method for measuring polyethylene density from a strand of the melt index. The strand from the melt index test can aid in sample preparation and in material comparison and quality control.

• Melt Indexer: Produces the polyethylene strand used for density determination.
• Analytical Balance: Measures the mass of the prepared strand specimen.
• Micrometer or Dimensional Measuring Device: Measures the relevant specimen dimensions.
• Specimen Cutting Tool: Allows technicians to prepare a suitable section of the melt index strand.
• Calibrated Measuring Equipment: Supports accurate dimensional and mass measurements.

How is density determined in ASTM D2839?

To determine density, the mass of the specimen is measured and compared to the volume calculated using the dimensions of the specimen. 

Density = Mass ÷ Volume

The laboratory reports the density in an appropriate unit (e.g., g/cm³) as required by the reporting procedures.

ASTM D2839 Equipment and Sample Preparation Guide

To obtain reliable density results, technicians must have appropriate melt index equipment and accurate measuring devices. They produce and carefully measure a representative strand of melt and determine the specimen density.

This practice covers other tests such as ASTM D1505 and D1238. The ASTM D2839 testing procedure is as follows.

ASTM D2839 Testing Process and Data Collection

Technicians begin by identifying the polyethylene sample and preparing the melt index test. The melt indexer produces the strand under the specified testing conditions. The technician then selects a representative strand section and measures its mass and relevant dimensions. The laboratory uses these measurements to determine the specimen volume and calculate density. Technicians record the density result along with material identification, specimen information, measurement data, and relevant observations. Accurate measurements help engineers compare polyethylene materials and production batches.

Common Challenges and Troubleshooting

There are a number of factors that may impact ASTM D2839 density results. These include changes in melt index, strand deformation, incorrect dimensional readings, balance performance, contamination, and inconsistent specimen preparation. Take representative samples and use calibrated measurement instruments. Technicians should also not bend the strand before taking the measurement. The laboratory should investigate the following if the results are significantly different between specimens: specimen preparation, strand quality, dimensional measurement, balance performance, and other factors that may affect the tests.

• ASTM D2839 produces a density result rather than a collection of different property-specific test values.
• Laboratories typically report polyethylene density in an applicable unit such as g/cm³, along with the measured specimen mass, dimensions, calculated volume, and relevant material information.
• Consistent melt index strand preparation, accurate mass and dimensional measurements, suitable equipment, and controlled test conditions help laboratories produce reliable density results.
• Engineers can use these results to compare polyethylene grades, formulations, production batches, and processing conditions. They should interpret density values alongside relevant material and testing information.

Link to ASTM D2839