The melt flow index is used to measure the ability or the ease of the flow rate of a polymer, often a thermoplastic. This is done using specific diameter capillaries at a specific length and at a temperature over a period of time.
The choice of a melt flow index tester can range from a relatively basic machine to one with additional functions and features. The choice of the equipment will largely be a factor of the type of testing required and the specific data that is required by the facility.
The Procedure
While there are some differences between different models of melt flow index tester systems, the general process is the same. This will include taking a small amount of the sample into the chamber and removing any air pockets. The chamber will have a die at the bottom that has a specific diameter opening.
A piston is placed over the sample and the sample is heated to a precise temperature and then a pre-set weight is applied to the top of the piston. The force of the weight on the melted sample causes it to move through the die. The material exiting from the die is collected after a specific amount of time has passed. This is weighed and is reported in grams per ten minutes to determine the melt flow index.
Features to Consider
While not a complex process, precision is critical with this testing method. The melt flow index tester selected needs to have precision features to enhance the accuracy of all test.
Look for a touch screen for easy operator control, dual heating elements for fast, even temperature control of the changer and a high-resolution pressure transducer to provide accurate volume output through the die.
Additionally, the option to use USB or LAN connection from the tester to a computer makes data recording simple, easy and effective and also cuts down on technician time in data entry in the lab.