Extrusion plastometer

Flowability MFI melt flow index, ASTM D 1238 Procedure A Extrusion plastometer... 

Figure 5.5 shows a schematic diagram of a melt indexer (which is also sometimes referred to as an extrusion plastometer). To determine the melt flow rate of a polymer resin, we place a suitable mass of it into the barrel, which is pre-heated to a standard temperature appropriate to the polymer. We then place a weighted piston on top of the sample. After allowing the polymer to reach the temperature of the barrel we allow it to extrude from the capillary orifice. The melt flow rate is the mass of polymer in grams that extrudes in ten minutes. 

ASTM D1238-04c Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer, Book of Standards Vol. 08.011, ASTM International (formerly known as American Society for Testing and Materials), West Conshohocken, PA, USA. 

ASTM D1238-04c, Standard Test Method for Flow Rates of Thermoplastics by Extrusion Plastometer, (2004)... 

In 83) the authors studied the flow of polypropylene and polyethylene with the help of a constant-velocity viscosimeter developed on the basis of a standard extrusion plastometer for measurement of the melt flow index (MFI) to the stem of which acoustic vibration was applied. 

Figure 2.45 Schematic diagram of an extrusion plastometer used to measure the melt flow index.

The melt flow indexer. The melt flow indexer is often used in industry to characterize a polymer melt and as a simple and quick means of quality control. It takes a single point measurement using standard testing conditions specific to each polymer class on a ram type extruder or extrusion plastometer as shown in Fig. 2.45. 

Some of the test methods being used to measure the processing stability of polypropylene include melt flow drift measurements at elevated temperatures using an extrusion plastometer (melt indexer), melt viscosity retention measurements using a torque rheometer, retention of melt flow after repeated extrusions, and injection molded spiral test measured by the flow in inches at various temperatures and the retention of melt flow of the injected spirals. The nine commercial resins were evaluated by these methods. 

Melt index of polyethylene may be measured on an instrument called an extrusion plastometer. (Photo courtesy of Tinius Olsen.)... 

A simpler version of a capillary rheometer is known as melt indexer, or an extrusion plastometer. 

Figure 6.7 A melt indexer,also known as an extrusion plastometer...

The amount in grams of a thermoplastic resin forced through a 2.10 mm (0.0825 in. orifice when subjected to the prescribed force, e.g., 2.16 kg force during 10 min at the prescribed temperature (°C) using an extrusion plastometer (ASTM D1238). It is customary to refer to the flow rate of polyethylene as melt index. However, for all other materials, the term melt flow rate should be used. 

Extrusion plastometer (melt-indexer) ru A simple viscometer consisting of a heated vertical cylinder with two bores, a central one that contains a close-fitting piston and a recess for an orifice block, the other, nearby, for a thermoswitch. The orifice is 2.1 nun in diameter and 8 mm long. Plastic particles are loaded into the bore, allowed to heat for 6-8 min, then the weighted piston is released, and the extrudate is collected for a measured time internal. The melt-flow index (MFI) is stated as the rate of extrusion in grams/10 min. The instrument and its use are described in ASTM D 1238. Originally developed in 1953 for low-density polyethylene, the melt-indexer is now used with many other polymers with specific temperatures and piston weights. It... 

Melt viscosity, or flow, is typically measured using extrusion plas-tometers (or melt indexers), capillary rheometers, and parallel plate rheometers. The extrusion plastometer measures the flow of a polymer melt under conditions specified by ASTM standard D 1238. This test yields a single, low-shear-rate value which is typically used to specify resins. Capillary rheometers determine viscosity over a range of shear rates in channel flow. While they are subject to error, these rheometers are still the only means of measuring viscosity at high shear rates (typically -y > 1000 s i). Parallel-plate rheometers also measure viscosity over a range of shear rates, but the maximum allowable shear rate is about 100 s i. 

D1238, flow rate (melt index) by extrusion plastometer D569, flow properties D1525, Vicat softening point D746, brittleness temperature Analytical tests... 

The melt flow index test method is used to monitor the quality of plastie materials. The quality of the material is indicated in this test by melt flow rate through a specified die under preseribed conditions of temperature, load, and piston position in the barrel as timed measurement is being made. The melt flow rate through a specified capillary die is inversely proportional to the melt viscosity of the material if the melt flow rate is measured under constant load and temperature. The melt viseosity of the material or MFR is related to the moleeular weight of the material if the molecular structures are the same. The extrusion plastometer as specified in... 

ASTM Method 1238, Standard Test Method for Flow Rates of Thermoplastics by Extrusion Plastometer [6], completely defines the melt index, both the instrument and the experimental procedure. Temperatures and instrument configurations for common materials are given along with recommended calibration procedures and round-robin results. This method must be strictly followed if consistent melt index results are to be obtained. A melt index measurement is performed at low stress levels compared to capillary rheometers measurements (typical weights are in the range of 1.2-21.6 kg) and is sensitive to variations in operating procedure, instrument cleanliness (between tests), and operator bias (items such as packing and sample preparation). 

Melt flow measurements were performed according to ASTM D-1238-86 with an extrusion plastometer Davenport model 3. 

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