Computerised Melt Flow Index Tester Melt Flow Rates of Thermoplastics 550× 430× 730mm

Melt Flow Index Tester MFR MVR thermoplastics ISO1133 ASTM D1238 comparison MFI452
 
Function
The melt mass-flow rate (MFR) and the melt volume-flow rate (MVR) are determined by extruding molten
material from the barrel of a plastometer under preset conditions of temperature and load. For melt mass-flow rate, timed segments of the extrudate are weighed and the extrudate rate is calculated in g/10 min and
recorded. For melt volume-flow rate, the distance that the piston moves in a specified time or the time required for the piston to move a specified distance is measured to generate data in cm3/10 min. Melt volume-flow rate may be converted to melt mass-flow rate, or vice-versa, if the density of the material is known under the conditions of the test.
 
Standard: ASTM D1238
 

ASTM D 1238 - 04
Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer 
This test method covers measurement of the rate of extrusion of molten resins through a die of a specified length and diameter under prescribed conditions of temperature, load, and piston position in the barrel as the timed measurement is being made.

Procedure A is a manual cutoff operation based on time used for materials having flow rates that fall generally between 0.15 and 50 g/10 min. Procedure B is an automatically timed flow rate measurement used for materials having flows from 0.50 to 900 g/10 min. By both procedures, the piston travel is generally the same during the timed measurement; the piston foot is about 46 and 20.6 mm above the die. Comparable flow rates have been obtained by these procedures in interlaboratory round-robin easurements of several materials described in.

Provision is made for calculation of melt volume-flow rate as well as melt mass-flow rate.
 
Referenced Documents
2.1 ASTM Standards: 2
D 618 Practice for Conditioning Plastics for Testing
D 883 Terminology Relating to Plastics
E 691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
2.2 ANSI Standard:
B46.1 on Surface Texture
2.3 ISO Standard:
ISO 1133-1991 Determination of the Melt-Mass Flow Rate (MFR) and the Melt Volume-Flow Rate (MVR) of Thermoplastics
 
Apparatus
Plastometer:
The apparatus shall be a dead-weight piston plastometer consisting of a thermostatically controlled heated steel cylinder with a die at the lower end and a weighted piston operating within the cylinder. The essential features of the plastometer, illustrated in Figs. 1 and 2, are described in 5.2-5.8. All dimensional measurements shall be made when the article being measured is at 23 6 5°C.
 
Relatively minor changes in the design and arrangement of the component parts have been shown to cause differences in results among laboratories. It is important, therefore, for the best interlaboratory agreement that the design adhere closely to the description herein; otherwise, it should be determined that modifications do not influence the results.
 
Cylinder-The steel cylinder shall be 50.8 mm in diameter, 162 mm in length with a smooth, straight hole 9.5504 6 0.0076 mm in diameter, displaced 4.8 mm from the cylinder axis. Wells for a thermal sensor (thermoregulator,thermistor, etc.) and  3.2-mm plate shall be attached to the bottom of the cylinder to retain the die. A hole in this plate, centered under the die and countersunk from below, allows free passage of the
extrudate. The cylinder may be supported by at least two 6.4-mm high-strength screws at the top (radially positioned at right angles to the applied load) or by at least two 10-mm diameter rods screwed into the side of the cylinder for attaching to a vertical support. The essential dimensions of a satisfactory cylinder of this type are shown in Fig. 1 (Note 4). The cylinder bore should be finished by techniques known to produce approximately 12 rms or better in accordance with ANSI B46.1.

NOTE -Cylinders made of SAE 52100 or other equivalent steel heat-hardened to 60-65 Rockwell Hardness Scale C give good service when used at temperatures below 200°C. Cylinder liners of cobaltchromium-
tungsten alloy are also satisfactory to 300°C.

Die-The outside of the steel die shall be such diameter that it will fall freely to the bottom of the 9.5504 6 0.0076 mm diameter hole in the cylinder (Note 5). The die shall have a smooth straight bore 2.0955 6 0.0051 mm in diameter and shall be 8.000 6 0.025 mm in length. The bore and its finish are critical. It shall have no visible drill or other tool marks and no detectable eccentricity. The die bore shall be finished by techniques known to produce approximately 12 rms or better in accordance with ANSI B46.1.

NOTE -Recommended die material is tungsten carbide. Also satisfactory are steel, synthetic sapphire, and cobalt-chromium-tungsten alloy.
 
Piston:
The piston shall be made of steel with an insulating bushing at the top as a barrier to heat transfer from the piston to the weight. The land of the piston shall be 9.4742± 0.0076mm in diameter and 6.35 6 0.13 mm in length. The piston design may incorporate means for land replacement, for example, having threads and flats immediately above the land. Above the land, the piston shall be no larger than 8.915 mm in diameter (Note 6). The finish of the piston foot shall be 12 rms in accordance with ANSI B46.1. If wear or corrosion is a problem, the piston should be of stainless steel and equipped with a detachable foot for ease of replacement.
NOTE -To improve standardization it is preferable that the piston be guided with a loose-fitting metal sleeve at the top of the cylinder.
NOTE -Pistons of SAE 52100 steel with the bottom 25 mm, including the foot, hardened to a Rockwell hardness, C scale, of 55 to 59 have been found to give good service when used at temperatures below 200°C.
The piston shall be scribed with two reference marks 4 mm apart in such fashion that when the lower mark coincides with the top of the cylinder or other suitable reference point, the bottom of the piston is 48 mm above the top of the die. The combined weight of piston and load shall be within a tolerance of 60.5 % of the selected load.
 
Heater:
The equipment must have a heater capable of heating the apparatus so that the temperature at 10 mm above the die can be maintained within 60.2°C of the desired temperature during the test. The temperature of the barrel, from 10 mm to 75 mm above the top of the die, must be maintained within 61 % of the set temperature (°C).
 
Temperature Controller-The type of controller and sensor must be capable of meeting the required control tolerance.
Thermometer- Thermometers having a range of 4°C graduated in 0.2°C divisions may be used to indicate temperature. The temperature at this point may not necessarily be the temperature of the material 10 mm above the die. The thermometer may be used to monitor indirectly the temperature of the material 10 mm above the die and may be calibrated by reference to a thermocouple or platinum resistance temperature
sensor inserted in the material 10 mm above the die. For a description of a method for measuring temperature. Warning-Caution should be observed with the use of a mercury-filled thermometer. Mercury  aporization occurs if the thermometer is broken. Mercury thermometers are not to be used at or above the boiling point of mercury, which is 357°C.