Understanding Melt Flow Measurement

A Melt Flow Indexer is a laboratory tool that gives a measurement of melting plastics by keeping a particular temperature range, whilst using a target load on the plastic specimen.

This creates a flowing material which can be calculated in grams per ten minutes (as per the ASTM D1238/ISO 1133 standard) supplying crucial material characteristics for applications in the plastic extrusion process.

Dynisco LMI5000 Series Laboratory Melt Flow Indexer

The Dynisco LMI5000 series laboratory Melt Flow Indexereither meets, or surpasses both relevant ISO and ASTM standards. The ASTM/ISO standard decides the apparatus guidelines, and the actual test procedures for testing the melt flow indexer of 90% of the polymers which are known to exist.

By employing the tables shown in the standards, the melt flow indexer can be used to either qualify resins that are bought by outside vendors or to publish melt flow rates on resins being manufactured. The most frequent is test method “A” per the ASMT D1238, in which the user will provide a particular amount of material (Pellet/Powder/or Flake) and charge the barrel.

Measurement of Melt Flow

A weight load and temperature are chosen that conforms with the tables provided in the standard, and the material is exposed to this temperature for a specified “melt period,” this is usually around 360 seconds. After the melt time is over, the target weight load linked with the polymer family is administered to the specimen in the barrel using a piston assembly.

The piston descent is followed by the user as the test proceeds, until the target travel has finished (this is marked by scribe lines on the piston itself). The specimen is gathered over one minute, and then the weight of the melted polymer is collected by utilizing a balance.

To calculate the melt flow index expressed in grams per ten minutes, the resulting value is then multiplied by ten. Melt Flow Rate will help establish the temperature and force required in the process to keep a consistent product quality, without generating waste material.

This information has been sourced, reviewed and adapted from materials provided by Dynisco.

For more information on this source, please visit Dynisco.


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