LimsPulse
Materials & polymer testing

Melt flow indexer

Melts a thermoplastic in a heated barrel and pushes it through a small standard die under a fixed weight. The mass (or volume) of polymer that flows out in 10 minutes is the melt flow rate, a quick measure of how easily the polymer flows.

  • Polymers & plastics
  • Packaging
  • Pipes & fittings
  • Automotive
  • Recycling
  • Chemicals
Photo of a Melt flow indexer
Photo: Miladfarhani, CC BY-SA 3.0 (cropped), via Wikimedia Commons
Follow your site SOP
This is a typical operating sequence for learning. Your instrument model and approved SOP take precedence.
STAGE 1

Before you start

  1. 1Check the instrument is within its calibration due date for temperature, load and die dimensions.
  2. 2Select the test condition (temperature and load) from the material specification or ISO 1133 / ASTM D1238.
  3. 3Dry hygroscopic polymers (for example PET, PA, PC) as the material standard or supplier advises.
  4. 4Switch on and allow the barrel to stabilise at the test temperature, typically for at least 15 minutes.
  • The barrel, die and piston are at 190–300 °C. Use heat-resistant gloves and tongs.
STAGE 2

Charging and preheat

  1. 1Weigh the charge (typically 4–8 g, depending on the expected MFR) as the standard advises.
  2. 2Pour the granules into the barrel through a funnel in one go and compact with the packing rod.
  3. 3Insert the piston and start the preheat timer (typically 5 minutes from the end of charging).
  4. 4If the MFR is high, a support or small weight may be used to stop premature flow during preheat.
  • Charge within the time stated in the standard; slow charging lets the first granules degrade.
STAGE 3

Measurement

  1. 1At the end of the preheat, add the test weight and let the piston descend.
  2. 2Discard the extrudate until the lower reference mark on the piston reaches the top of the barrel.
  3. 3Take cut-offs at fixed time intervals chosen so each cut-off is a convenient length (often 10–20 mm).
  4. 4Stop measuring when the upper reference mark is reached; discard cut-offs with bubbles.
  5. 5Weigh at least three cut-offs to 1 mg once cool, and calculate the MFR.
  • Cut-off masses should agree closely; a trend up or down suggests degradation or a temperature problem.
STAGE 4

Cleaning and shutdown

  1. 1Push out the remaining melt while still hot.
  2. 2Remove the die and clean it with the die drill; clean the barrel with cotton patches on the cleaning rod.
  3. 3Clean the piston while hot with a soft cloth; do not scratch the bore or piston.
  4. 4Record results, the condition used and any observations in the log.
  • Never use abrasive cloths or steel brushes inside the barrel or die bore.
In LimsPulse · Calibration Management

Keep every MFI tester in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.

See how