MELT MASS- FLOW RATE

TEST STANDARD

Melt flow index test (DIN ISO 1133)

MFI measures the rate of extrusion of a thermoplastic material through a orifice of specific length and diameter upon the application of load at prescribed temperature condition for the specific material. The reported melt index values help to distinguish between the different grades of a polymerMaterials with high molecular weights have higher viscosity means higher resistance to the flow which leads to the lower MFI values whereas the materials with lower molecular weight have higher MFI values.

Upon the basis of these MFI values one can predict the process ability of that specific polymeric material.

Test Conditions for different materials Sr. No Material Condition Designation

1 Acetals (copolymer and homopolymer) 190/2.16 190/1.05

2 Acrylics 230/1.2 230/3.8

3 Acrylonitrile-butadiene-styrene 200/5.0 230/3.84 Polyethylene 125/0.3255 Polypropylene 230/2.166 Polystyrene 200/5.0 230/1.2

Test Conditions for Load and Temperature against the condition designation

Sr. NoCondition

DesignationTemperature

(ºC)

Total Load Including Piston

(kg)

Approximate Pressure

kPa psi

1 125/0.325 125 .325 44.8 6.5

2 125/2.16 125 2.16 298.2 43.25

3 150/2.16 150 2.16 298.2 43.254 190/0.325 190 .325 44.8 6.55 190/2.16 190 2.16 298.2 43.25

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LAB REPORT

6 200/5.0 200 5.0 689.5 100.0

Test Procedures

The melt index apparatus is preheated to 200 C˚ temperatureMaterial is weighted using weight balance The material is loaded into the cylinder from the top A specified weight is placed on a piston. The material is allowed to flow through the die. The initial extrudate is discarded because it may contain some air bubbles and contaminants.Depending on the material or its flow rate, cuts for the test are taken at different time intervals.The extrudate is weighed and melt index values are calculated in grams per 10 min.Diameter of the extrudate is measured for analysis and discussion.

Results and discussion

Test ParametersSample No 1

Material Polystyrol 168 NWeight of the SAMPLE 4.04 grams

Temperature 200 C˚Load Applied 5 Kg

Cut off Time interval 60 sec (1Min)

Sr. No Samples Weight (grams) Average Wt (grams)

MFI (grams/10 min)

Diameter of extrudate (mm)

1 1 0.18

0.9

1.90 (grams/10 min)1.53 cm³/10min

1.5 cm³/10min (as per campus data )

2.68

2 2 0.193 3 0.164 4 0.195 5 0.186 6 0.197 7 0.198 8 0.199 9 0.19

10 10 0.2211 11 0.19

Test ParametersSample No 2

Material Polystyrol 143 EWeight of the SAMPLE 4.20 grams

Temperature 200 C˚Load Applied 5 Kg

Cut off Time interval 15 sec

Sr. No Samples Weight (grams) Average Wt (grams) MFI Diameter of extrudate

(mm)1 1 0.41

0.38

15.26 gram/10min9.6 cm³/10min

10.0 cm³/10min (as per campus data)

3.02

2 2 0.393 3 0.374 4 0.385 5 0.326 6 0.397 7 0.4189

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Test ParametersSample No 2

Material Polystyrol 168 NWeight of the SAMPLE 4.04 grams

Temperature 200 C˚Load Applied 10 Kg

Cut off Time interval 15 sec

Sr.No Samples Weight (grams) Average Wt (grams) MFI Diameter of extrudate (mm)

1 1 0.26

0.23

9.20 gram/10min

6.13 cm³/10min

3.05

2 2 0.233 3 0.24 4 0.185 5 0.266 6 0.247 7 0.28 8 0.239 9 0.2310 10 0.2311 11 0.23

Answer 2

The values calculated by us in the MFI experiment are having units of gram per 10min whereas the values used in the campus data are cm³ /10 min.

According to ISO 1133 , the MFI is the weight of polymer melt flowing out from a standard die (2.095 x 8 mm) at a given temperature and with a standard weight applied to the piston, which pushing the sample.

ISO 1133 specifies two methods for testing: Procedure A is a manual mass-measurement method, in which timed segments of the extrudate are weighed with a balance after the test to determine the melt mass-flow rate (MFR). This is expressed in g/10 min. Procedure B is a displacement-measurement method, based on the measure of the piston displacement by means of an encoder. The result is the melt volume-flow (MVR) rate.

Flow rate = (426 × L × d)/t

Where

L = length of calibrated piston travel (cm)

d = density of resin at test temperature (g/cm³)

t = time of piston travel for length L (sec)

Converting MFR TO MVR

SAMPLE 1 Polystyrol 168 N @ 5kg load application

Flow rate = (426 × 2.54 × .936)/660 = 1.53 cm³/10min

SAMPLE 1 Polystyrol 143 E @5 kg load application

Flow rate = (426 × 2.54 × .936)/105 = 9.6 cm³/10min

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SAMPLE 1 Polystyrol 168 N @ 10kg load application

Flow rate = (426 × 2.54 × .936)/165= 6.13 cm³/10min

Comparison on MVF values

Sr.No

Material LoadMVF Value

Our result Campus Data1 Polystyrol 168 N 5kg 1.53 cm³/10min 1.5 cm³/10min

2 Polystyrol 143 E 5 kg 9.6 cm³/10min 10.0 cm³/10min

3 Polystyrol 168 N 10kg 6.13 cm³/10min

n/a

Above test results shows that there is slight error in our result but overall the values are ver closeto the campus data values. This possible error can be following The possible error sources come from

poor packing dirty barrel worn die uneven test temperature

Answer 3

load applied 5kg load applied 10kg

MFI cm³/10min

1.53 MFIcm³/10min

6.13

Test conducted at higher wt (10 Kg) gives us very high values of the MFI.It indicates that flow is enhanced upon increase in load. As the load was increased it

caused more shear stress and forced the molten polymer to extrudate more.

Answer 4

2.095mm is the standard diameter of the MFI Tester orifice. But if we take a look of the values obtained one can conclude that the phenomena of die swell is clearly responsible of these higher values of extrudate diameter.

What is die swell?

When the melt is sheared through the die, the molecules become extended with the greatest orientation near the die wall. As they leave the die the molecules tend to coil up and thus contract in the flow direction and expand in the direction perpendicular to the flow.

Bonus

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Material Load DiameterPolystyrol 143 E 5 kg 3.02 mmPolystyrol 168 N 5 kg 2.68 mmPolystyrol 168 N 10 kg 3.05 mm

As described in Campus Data the Polystyrol 168 N is high molecular polymer which suggest us that Polystyrol 168N will have low values of MFI.We know that melt index is an inverse measure of molecular weight. Since flow characteristics are inversely proportional to the molecular weight, a High-molecular-weight polymer will have a low melt index value and vice versa.

Another factor which effects the flow properties is long chain branching. Long branched molecules are more compact and tend to entangle less with other molecules resulting in lower melt viscosities as compared to with un branched polymers.

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