As of my knowledge cutoff in September 2021, the ASTM method for melt flow rate, also known as melt index, is governed by ASTM D1238. ASTM D1238 is the standard test method for determining the flow rates of thermoplastics by extrusion plastometer. This method is commonly used to measure the melt flow properties of plastics, which is an important parameter in the processing and quality control of thermoplastic materials.

The ASTM D1238 test involves extruding a molten plastic sample through a standardized die under specific conditions of temperature and pressure. The rate at which the molten plastic flows through the die is then measured and reported as the melt flow rate (MFR) or melt index (MI) in grams per 10 minutes (g/10 min) or grams per minute (g/min). The test conditions, such as temperature and applied load, can vary depending on the type of material being tested.

It's important to note that standards and methods may be updated or revised over time. Therefore, I recommend checking the latest version of the ASTM D1238 standard or consulting the ASTM website for the most up-to-date information on the melt flow rate test method.