ISO 1133 and ASTM D1238 cover the determination of the Melt Mass-Flow Rate (MFR) and Melt Volume-Flow Rate (MVR) using easy and quick test procedures.

The ASTM D1238/ISO 1133 standards specify detailed test conditions, including pre-heating period, starting position, and measurement length/time.

However, fulfilling all standard specifications using a basic melt flow tester (extrusion plastometer) can be challenging, especially when testing some polymers and compounds.Results can be affected by poor repeatability.