This material characterization test measures the rate of extrusion (grams/10 minutes) of a thermoplastic material thorough an orifice of specific length and diameter under temperature and load. This test is primarily used to measure the uniformity of the flow rate of the material. The melt flow index values found from the test help determine the difference between different grades of the same material. A higher melt index value corresponds with a higher viscosity material.
D1238
This standard is conducted to determine the rate of extrusion of molten plastic. After a preheating time, the material is extruded through a die with a specified length and orifice diameter under a specified temperature and load. This standard is useful for quality control of thermoplastics and determine the uniformity of the flow rate of the polymer.
There are four test methods within this standard. Procedure A is used to find the melt flow rate of a thermoplastic material with a flow rate from 0.15 to 50 grams/10 mins. Procedure B is used to determine the melt flow rate and melt volume rate of thermoplastic materials that have a flow rate from 0.50 to 1500 grams/10 minutes. Procedure C is used to determine the melt flow rate of polyolefin materials that have a flow rate greater than 75 grams/10 minutes. Procedure D is used to find the flow rate ratio with two of three different test loads. The flow rate of the material should be less than 0.15 or greater than 900 grams/10 minutes.
