Abstract: In this lab, the experimental procedure for determining the melt flow index for a material will be explained and exemplified. A material will begin in solid state, be melted, then the flow index will be measured using a scale and an extrusion plastometer.
Introduction: The melt flow index of a material is comparable to testing the viscosity of a liquid. At a certain temperature, a material is melted and forced through an extrusion plastometer. The time it takes for a certain amount of a melted material to drain through an orifice is measured by performing the following test. The information obtained in this lab and ones similar to it is important for knowing flow rates in various type of molding, including extrusion dies.
The American Society for Testing on Materials (ASTM) covers the requirements for performing this test. This test is the ASTM 1238. Various materials have different standard test conditions. The material being tested in this lab is polypropylene. It has two standards. First, it needs to be at two hundred and thirty degrees Celsius, with a tolerance of plus or minus 0.2 degrees. The other standard is that a weight of two thousand one hundred and sixty grams of weight be used on the extrusion plastometer. The standard sample weight for polypropylene is four to eight grams. .
Problem Statement: The information acquired in the following experiment will allow the melt flow index of polypropylene to be calculated. The specimens are small, clear beads probably about two or three millimeters in diameter. They are going to be melted and run through the extrusion plastometer. The process will be timed for later calculations. .
Theory: The theory behind this lab is that certain processes require a material to have a certain melt flow index. If the time should arrive when this number is needed to be calculated, the following procedure is the correct way of finding it.