Information on the most widely used ASTM standards within the materials testing industry
ISO 1133: Plastics -- Determination of the melt mass-flow rate (MFR) and the melt volume-flow rate (MVR) of thermoplastics.
ISO 1133 standard specifies two procedures for the determination of the melt mass-flow rate (MFR) and the melt volume-flow rate (MVR) of thermoplastic materials under specified conditions of temperature and load. One is a mass-measurement method. The other is a displacement-measurement method. Normally, the test conditions for measurement of melt flow rate are specified in the material standard with a reference to ISO 1133. The test conditions normally used for thermoplastics are listed in annexes.
There two accurate ISO tests, primarily used for quality control and performed under specified temperature conditions, can be described as:
Procedure A – a mass-measurement method Or MFR.
Procedure B – a displacement-measurement method. Or MVR.
Melt volume flow rate testing is particularly useful when inspecting materials of different filler content and when comparing filled, with unfilled, thermoplastics. Mass flow rate testing can be determined from melt volume flow rate testing measurements, or vice versa, provided the melt density at the test temperature is known.
The thermoplastics materials industry uses the Melt Flow Index (MFI) as a basic tool for quality control and acceptance of incoming products. The measure of the flow properties is contained on the identity card, and is used as a check to verify if the plastic's grade is within the required fluidity range. This is commonly used for polyolefins (polyethylene HDPE, LDPE, LLDPE, and polypropylene PP).
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The melt flow index (MFI) is a measure of the ease of flow of the melt of a thermoplastic polymer. It is defined as the mass of polymer, in grams, flowing in ten minutes through a capillary of a specific diameter and length by a pressure applied via prescribed alternative gravimetric weights for alternative prescribed temperatures.Polymer processors usually correlate the value of MFI with the polymer grade that they have to choose for different processes, and most often this value is not accompanied by the units, because it is taken for granted to be g/10min. Similarly, the test load conditions of MFI measurement is normally expressed in kilograms rather than any other units. Originally called Melt Flow Index or Melt Index (typically for polyethylene, but applied to a variety of materials), the standard designation today is Melt Mass-Flow Rate or MFR, which is a mass flow expressed in g/10min. An alternative quantity is the volume flow expressed in cm3/10min, called Melt Volume-Flow Rate or MVR. MVR multiplied by the melt density (i.e. density of the material in the melted state) gives MFR.
Melt flow rate is very commonly used for polyolefins, polyethylene being measured at 190 °C and polypropylene at 230 °C. The plastics engineer should choose a material with a melt index high enough that the molten polymer can be easily formed into the article intended, but low enough that the mechanical strength of the final article will be sufficient for its use.
Melt Flow Index is a very valuable test for quality assurance.
1, Raw material certification
2, Comparison of "good" and "bad" samples
3, Batch to batch comparisons
4, Grade differentiation of materials
5, Determination of the nature of material degradation (processing, transportation, storage, and drying conditions)
Common Melt Flow Rate Conditions by Material
| Material | Condition |
| PS | 200/5.00 |
| PE | 190/2.16 |
| 190/0.325 | |
| 190/21.60 | |
| 190/5.00 | |
| PP | 230/2.16 |
| ABS | 220/10.00 |
| PS-I | 200/5.00 |
| E/VAC | 150/2.16 |
| 190/2.16 | |
| 125/0.325 | |
| SAN | 220/10.00 |
| ASA, ACS, AES | 220/10.00 |
| PC | 300/1.20 |
| PMMA | 230/3.80 |
| PB | 190/2.16 |
| PB | 190/10.00 |
| POM | 190/2.16 |
| MABS | 220/10.00 |
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