Melt flow index (MFI) : The determination of melt flow rate (MFR) and melt volume rate (MVR) is described in various international standards.
The most common ones are ISO 1133 and ASTM D1238. These two standards describe similar tests, but slightly different. This article aims to provide a brief overview and demonstrate the differences between them.
The ISO 1133:2005 has been split and replaced with ISO 1133-1:2011, which describes general testing methods. In addition, ISO 1133-2:2011 has been published for materials that are sensitive to time temperature history and/or humidity. According to the different testing materials, appropriate standards must be used.
ISO 1133-1 basically describes two different procedures.
In program A, the extruded wire is cut off according to the defined time steps during the measurement period. MFR is determined based on the weight of the wire section. In program B, measure the piston speed and calculate MVR based on it. The melt density can be used to convert between MVR and MFR. The measurement is always conducted within a measurement range of 50-20 millimeters in front of the capillary, with a melting time of 5 minutes. For low viscosity materials, a capillary tube of half size (half diameter, half length) can also be used. The determination of flow rate ratio (FRR) is also described in the standard.
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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 |
