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Melt Flow Indexer

Qty Product
Melt Flow Indexer
  • Price:
    $819115110111114112113121311171
Product Code
IDM-M0004-M1
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Melt Flow Indexer
The Melt Flow Indexer is a dead-weight extrusion plastometer which determines the melt flow rate (MFR). It consists of a thermostatically controlled melting chamber (the barrel) in which the polymer under test is heated and from which it is extruded through a standard die under standard conditions of load, which is, of course, made up of the combined weights of the extrusion piston and the loose weight both of which are carefully calibrated to well within the most stringent limits.
The instrument is used to determine the melt flow rate (MFR) of a thermoplastic material. The units of measure are grams of material/10 minutes (g/10 min). It is based on the measurement of the mass of material that extrudes from the die over a given period of time. It is generally used for materials having melt flow rates that fall between 0.15 and 50 g/10 min.  The Melt Flow Indexer has been designed and manufactured with reference to ASTM D1238- Procedure A standard. It is manufactured to determine the rate of extrusion of molten resins through a die of a specified length and a diameter under prescribed conditions of temperature, load, and piston position in the barrel as is it timed.

Melt Flow Indexer Apparatus

The Melt Flow Indexer is a dead-weight extrusion plastometer consisting of a thermostatically controlled melting chamber (the barrel), in which the polymer under test is heated and from which it is extruded through a standard die (sometimes referred as the `jet’ or `orifice’) under standard conditions of load, which is, of course, made up of the combined weights of the `extrusion piston’ and the `loose weight’ both of which are carefully calibrated to well within the most stringent limits called for in any published standard.

a) The Barrel (or Cylinder)

The Barrel is a steel cylinder, 50.8 mm in diameter and 162 mm long, through which a smooth straight hole, 9.55 mm. in diameter has been bored 4.8 mm (centre to centre) from the axis of the cylinder. Two further holes are provided, spaced equidistantly from the bore, to contain, respectively, K type thermocouple located in relation to the bore and its charge and the extrusion die.

b) The Heater

The heater is designed to give the most even temperature distribution that can be achieved, having in mind the differential thermal geometry of the cylinder and its pattern of heat loss. As a result the test temperature is maintained as accurately as possible along the full working length of the bore.

c) The Temperature Controller

The temperature of the barrel is controlled by the Digital Temperature Controller to select any temperature in the standard operating range of 100 - 300C ± 0.2°C.

d) The Timer

The Timer is used for timing the test procedure as certain steps need to be taken when the tests start. The Timer is started and stopped by pushing the Red Start / Stop Button and the Timer can be reset by pushing the Reset button.

e) The Die

Dies are made of Carbide, and conform precisely to the standard dimensions: 8° mm long, 9.47 mm overall diameter, internal diameter 2.096 mm. The bore is very highly finished and polished and is carefully tested to tolerance well inside the closest that are called for in any published standard, particularly with regard to any tendency to bell-mouthing.

f) The Die Plate

The extrusion die is retained in the bore by means of a die-plate, which is fitted to the bottom of the cylinder. It is held in place by two socket-headed screws. The `standard’ die-plate supplied is fitted with PTFE insulating disc - which also assists to some extent in making a clean extrudate cut-off.

g) The Piston

The solid steel piston has a head with a diameter of 9.47 mm and a length of 6.35 mm. The shank has a diameter of 8.89 mm and terminates with a portion of further reduced diameter, which is covered by an insulating, heat-resistant sleeve, forming a `spigot’ upon which the loading weights are placed. The purpose of this sleeve is to reduce as far as practicable, the heat-sink effect of the weights. The complete piston assembly weighs approx. 100 gm and the `loose weights’ are tared so as to account for this.

The shank of the piston is marked with two circumferential grooves, so positioned that the lower will be exactly coincident with the top of the cylinder when the face of the piston head is precisely 20 mm from the top of the die, whilst the distance between the two grooves themselves is 30 mm. The purpose of these grooves is explained in the description of the test itself.

Testing Applications 

The Melt Flow Rate (M.F.R.) of a thermoplastics material is the measured gravimetric flow rate of the sample melt extruded from a die of specified length and diameter, under prescribed conditions of temperature and pressure. The die is often referred to as a jet or orifice. Different standardised combinations of extrusion temperature and pressure are used for different types of polymer, but, for purpose of comparison, different samples of the same polymer type should be tested under precisely similar conditions. The Melt Flow Rate Apparatus may be regarded as a simple thermometer operating at conditions of low shear. Although the shear stresses applied and the resultant shear rates are much lower than those used in most fabricating processes, the results obtained do provide a useful indication of the relative ease with which different samples will flow when they are fabricated. Hence, 
since higher M.F.R. values indicate easier melt flow, a grade of polymer with a high M.F.R. is generally chosen when the fabricational process envisaged involves relatively high rates of shear (for example, injection moulding).
M.F.R. is also a measure of the average molecular weight of the sample and is, therefore, indicative of the mechanical strength of the material. Average molecular weight and M.F.R. are indirectly proportional, so that, although a sample of high M.F.R. will almost certainly process readily, its strength is likely to be poor.
In addition to M.F.R. determinations, the apparatus can be used to measure several other properties, providing useful knowledge of polymer behaviour. Thus, by determining the M.F.R. under two or more different loads, much very useful information about the rheological properties of the material is revealed. It can, for instance, be quite wrongly assumed that two polymer samples having the same M.F.R. when tested under the same conditions, will behave in the same way, with respect to output (shear-rate), when subjected to the much higher pressures (shear-resistances) used in fabrication processes. If the samples have different molecular weight distributions (M.W.D.), the increase in shear-rate resulting from an identical increase in shear-stress will be different as well as general, larger M.W.D.’s correspond with greater shear sensitivity, i.e. a higher rate of change in shear-rate per unit increase in shear-stress. A most useful measure of the shear-stress/shear-rate relationship (FLOW PARAMETER) can be made by measuring the sample’s M.F.R. at the standard and at a higher load. 
For instance, increasing the test load (for polyethylene) from the standard 2.16 Kg to 21.6 Kg increases the level of shear-rate by a factor of from 50 : to 100:1, depending upon the M.W.D. of the sample and the simple arithmetic ratio; (M.F.R. 21.6 Kg/(M.F.R. 2.16 Kg) gives an excellent measure of flow parameter. Depending on the M.F.R.’s at 2.16 Kg load, the values at 21.6 Kg load can be equivalent to shear rates of more than 100 secs, thus coming into the range of extrusion processes, at least. Not to be forgotten, also, is the facility for measuring flow parameter at different temperatures, so gaining an insight into the temperature sensitivity of the sample, another important characteristic.
The extrudate itself, as generated by the apparatus during routine M.F.R. measurements, can also be used to determine several other important properties. Its particular usefulness derives from the fact that its history is quite precisely known. Thus, its temperature and diameter on emerging from the die are known and its rate of cooling from the test temperature - because it is extruded directly into a reasonably constant ambient environment - is automatically `controlled’ and thus highly repeatable. Two very important properties can be measured more conveniently and with greater precision on the extrudate from the Melt Flow Indexer, than with commercial processing machinery. These are `DIE SWELL’ and `DRAW DOWN’.
Die-swell, sometimes referred to as `Swelling Ratio’, is simply the arithmetic ratio of the extrudate diameter, when it has cooled to ambient temperature  and the diameter of the die and is an important factor in many processing situations, e.g. pipe extrusion and the production of parisons for blow-moulding, to name two.
Draw-down is the tendency of the polymer extrudate to be extended by the tensile force of its own weight as the extrudate lengthens. It is of particular importance in the case of blow-moulding parisons and good draw-down characteristics are prerequisites of polymers intended for this application. Draw-down is measured in the Melt Indexer extrudate as a change in diameter of the extruded strand along its length. Because both die-swell and draw-down depend upon the accurate measurement of extrudate diameter, it is necessary to endure that the extrudate cross-section shall be as nearly circular as possible. Since the most common cause of irregularity of cross-section is a draught, causing asymmetric cooling, precautions against this must be taken. The article referred to in Note 1 below illustrates a suitable `Draught-Excluder Pot’ for this purpose.
Since the thermal history of the extrudate can be so precisely controlled, it is an ideal test specimen for determining the density of a partially crystalline material.
Finally, it must not be forgotten that the melt indexer, used in conjunction with a Flow Rate Timer, which enables both volumetric and gravimetric flow rates to be determined simultaneously, thereby providing a quick, convenient and reasonably precise means of determining polymer melt density.

Test Method

Although the various National and International Standard Test Methods so far published are in close general agreement, in particular with regard to the apparatus specifications, they do differ in certain methodological aspects. 

The test method described here is, in our own carefully considered opinion, the best way to use the apparatus to get the most consistent, reproducible and meaningful results.
Place the Charging Plate (white) on the top of the cylinder so that hole on the plate matches the position of the cylinder bore. The plate is used to ease charging of the test sample and prevent spillage around the cylinder and thermocouple bores. Charge the cylinder with the test sample, introducing it in several increments and tamping down each increment with the charging tool to exclude as much air as possible. Complete the charging operation in LESS THAN ONE MINUTE.
On completion of the charging operation, remove the Charging Plate, insert the piston into the barrel and place the Piston Support. Place the appropriate weight on the piston and manually force the test material through the die with reasonable force (less then 30kgf). Start the timer, stop it and reset it when the timer registers SEVEN MINUTES from the beginning of the charging operation; remove the Piston Support and watch the progress of the piston down the barrel. As soon as the lower circumferential ring on the piston enters the barrel, cut off and discard the extrudate and AT THE SAME TIME start timing the extrusion.
Cut off and retain, in order, specimens of the extrudate at a succession of as nearly identical time intervals as possible (usually 1 minute for material >3.5 to 10 g/10min). The time interval used should be chosen on the basis of the expected M.F. rate of the same but whenever possible, cut at least five samples making quite certain that they are ALL taken only during the period of piston travel when the lower groove is INSIDE the barrel and the upper one still OUTSIDE it. Keep in mind that time is related to expected M.F.R. equation below.
Melt Flow Indexer Apparatus

Optional Items 

1. Die

  • Tungsten Carbide: 8 mm long
  • 9.5504 mm overall diameter
  • 2.0955 mm internal diameter
  • The alternative Standard die in BS 2782method 1050 with a bore diameter of1.181 mm is also available on request.

2. Piston

  • Diameter: 9.47 mm
  • Weight - 100 gm

3. Calibration Certificate

4. Spare Die

Applications

  • Plastics

Features

  • BARREL: Precision ground and honed. Manufactured from high grade tool steel for longer life; 50.8 mm outside diameter; 9.55 mm inside diameter; 162 mm long.
  • TEMPERATURE: The temperature of the barrel is controlled by the Precision Digital Temperature Controller. Temperature Range: 100° - 300°C, ± 0.2°C; 100° - 400°C, ± 0.2°C
  • PISTON: Diameter: 9.47 mm; Weight - 100 gm.
  • PISTON WEIGHTS: 4.9 Kg weight (1); 2.06 Kg weight (1)
  • Sample Cut Off Knife (1)
  • Die Remover (1)
  • Die Cleaner (1)
  • Cleaning Tool (1)
  • Filler Tool (1)
  • Level (1)

Benefits

  • Easy to use
  • Fast results
  • Accurate

Standards

  • BS 2782 - Methods of testing plastics
  • ASTM D1238: Procedure A - Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer
  • ISO 1133 - Plastics — Determination of the melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastics — Part 1: Standard method

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Qty Product
Melt Flow Indexer
  • Price:
    $819115110111114112113121311171

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