Melting Index Tester

Melt flow testing is vital for producers, processors and converters in their understanding plastic materials and their melt characteristics. It is used by professionals in the field for consistently producing the quality production of materials. Melting index testers test the melt flow resistance/ melt viscosity of a number of polymers/materials in a typically 10-minute standardize test.

Melt flow rate is an indirect measure of molecular weight; high melt flow rate corresponds to low molecular weight of the particular thermoplastic material(s), while the opposite remains true (low melt flow rate = high molecular weight). The growth in use of melting index testers come as more plastic manufacturers and processors are complying with industry standards for quality management and for firms evaluating finished materials and products. Increased efficiency via automized testing machines has come along with tech advances and the computer era, generating more accurate results, minimizing operator error.

Technologies

The MFI (Melt Flow Index) is the measurements of the flow of melted thermoplastic polymer. The Melt Flow Index is standardly tested by weighing the mass of a polymer (in grams) through a specific diameter to the desire of the tester for 10 minutes. Melt Flow Indexers are used to test melt flow resistance, or MFR.

Determining melting flow index involves using up to 5 grams of the test polymer and applies pressure through a piston to push the test polymer through a thin crevice known as a Die. A heated barrel, heated to the desired temperature, surrounds the test sample. The weight the piston is applied coupled with the heated barrel causes the production of a melted polymer referred to as a resin through the die. MFI is expressed as the grams of melted polymer or resin during the 10-minute test.

There are two technically equivalent but slightly different procedures that have been standardized, the ASTM 1238 and ISO 1133. The Standard ISO 1133-1 directs the procedure for the measurement of the flow rate. The first standardized test called ASTM 1238 involves making cuts of the test material at scheduled intervals as it exits the extrusion die at its defined temperature and test load. The cuts are weighed, and the average mass which is induced to the total mass at the end of the 10 minute test.

The ISO 1133 test is simple as there is no cutting or weighing procedure as the volume of the testing material is obtained from the barrel and distance of the piston over a measured period of time, determining the melt volume rate (MVR) over a 10 minute period. The volume of the resin is hence calculated automatically as its not exposed to the impurities or user interference that may exist while cutting such as an air bubble, making the ISO 1133 melting index test generally more accurate and reproducible.

Melt Flow Indexer technologies feature precision measurement tools to ensure accurate results. Tri-Zone Barrel Heating and control: Ensures accurate and stable temperatures are maintained throughout the barrel in compliance with international standards. This form of temperature control and monitoring guarantees that every test is made to exact temperature specifications. The sensor in the piston accurately reports the flow rate of the polymer during the course of the test. Any discrepancy in desired temperatures and actual testing temperatures can be identified quickly and in turn, tuning to the barrel can be swift. Nearly 80 percent of current melting index testers have temperature variations ranging up to 68 degrees Fahrenheit (20 degrees Celsius) and as a result lead to inaccurate conclusions drawn from such testing. In addition, the computerization of melt index testing has minimized the possibility of human error, increasing the accuracy and hence the quality of the tests.

Features

GAOTek offers high quality yet cost efficient Melting Index Testers that conform to all of the industry’s international standards and regulations regarding the practice including BS EN ISO 1133 and ASTM D 1238.

Currently, GAOTek produces the Melting Index Tester with Intelligent Temperature Control. Temperature control is one of the most important factors when conduction melt index testing, and GAOTek has accounted for the issue by introducing a testing equipment that controls and maintains the temperature throughout the process. Some of the features and specifications include:

·       Intelligent temperature control with four pairs of significant temperature setting control; PID parameters can be automatically set with precision up to± 0.1 (0.01 degrees Fahrenheit)

·       Temperature range of experiments start between 176 degrees Fahrenheit and 752 degrees Fahrenheit (between 80 and 400 degrees Celsius)

·       Barrel parameters Inner holeф9.55±0.025mm with weight accuracy ±0.5

Applications

Melting Index Testers are used as a common quality control and process in laboratories used for a number of reasons. Among them are:

·       Quality checking and verification of the Melt Flow Index (MFI) of various in house materials

·       Evaluation of new materials and material suppliers, and comparing new materials in the product development stages

·       Examining and hypothesizing about how a given polymer will behave under processing techniques

A plastics engineer would work with melting index testers so as to find the right balance of a polymer that is strong enough for its desired functional use, yet easy for molding purposes.

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