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Melt Index

Melt Index

Information

Melt index test method

 

Melt Mass Flow Rate (MFR)

Melt Volume Rate (MVR)

This test is to determine the Melt Volume Rate (MVR) of the thermoplastic sample under certain conditions.

This test is suitable for thermoplastic material.
 

1 Definition

MVR is defined as the weight of the material passing through a standard exit every 10 minutes, under a set temperature and pressure.

 

2 Sample and Process

2.1 Shape of Sample Pellets, Powder, Chips, or other shapes.

2.2 Pre=Drying Moisture-absorbing samples must be pre-dryed accordingly.

 

3 Apparatus

Testing apparatus is as shown below.

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Actual testing apparatus is as shown below.

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3.1.1  Hopper

Round hopper is made of steel (hardness >300Hv). Inner Diameter (9.550±0.025mm), Length (150-180mm), Inside Wall Cleanliness >▽8.

3.1.2 Stopper

Hardness of the stopper should be slightly less than that of the Hopper. Length of it should be longer than hopper length. Stopper diameter is 9mm, Head of the stopper is 6.35±0.10mm, with a diameter smaller than that of the hopper by 0.075±0.015mm. Inside Wall Cleanliness >▽8. The inverted angle at the bottom of the stopper should have diameter of 0.4mm, and the upon edge should be smoothed.

3.1.3 Standard Exit

Exit should be made from carbonized Tungsten, paired with the Hopper to creat room. Acceptable diameter includes 2.095±0.005mm and 1.180±0.010mm. Inside Wall Cleanliness >▽8, and height is 8.000±0.025mm.

3.1.4 Weight pressure

Weight pressure is the total of the Weight, the Tray and the Stopper, with the overall accuracy at ±0.5%.

3.1.5 Temperature Control Device

Apparatus has a temperature measuring device to ensure temperature fluctuationg at ±0.5℃. Oven temperature is measured 10.0mm from Exit.

 

3.2 Other Devices

3.2.1 Cutting tools such as scrappers, or flexible steel plate.

3.2.2 Weigh with sensitivity of 0.001g

3.2.3 Timer accuracy to 0.1s.

 

4 Temperature Standardization

Temperature device must be tuned before every tests, and before every temperature change. First, adjust the heat control system until the desired temperature is reached. Meanwhile, the thermometer is inserted into the hopper until temperature is reached. Then, take out the thermometer and put the sample material into the hopper and pressed firm, inserting the thermometer again. After the material is melted, thermometer is again inserted into the melted material 10mm from the exit. After 4 minutes, standardize the 2 thermometers.

5 Testing Conditions

 

 
 
Number Standard Exit (inner diameter mm) Testing Temperature Exit Weight
1 1.180 190 46.6 2.160
2 2.095 190 70 0.325
3 2.095 190 464 2.160
4 2.095 190 1073 5.000
5 2.095 190 2146 10.000
6 2.095 190 4635 21.600
7 2.095 200 1073 5.000
8 2.095 200 2146 10.00
9 2.095 220 2146 10.00
10 2.095 230 70 0.325
11 2.095 230 258 1.200
12 2.095 230 464 2.160
13 2.095 230 815 3.800
14 2.095 230 1073 5.000
15 2.095 275 70 0.325
16 2.095 300 258 1.20

* Load unit N,1kgf=9.8N.


MVR Testing Condition for various material
 

 
 
material condition(℃/kg)
Polyoxymethylene(POM) 190/2.16 190/1.05
Acrylic 230/1.2 230/3.8
Acrylonitrile Butadiene Styrene(ABS ) 200/5 230/3.8 220/10
PC/ABS alloy 260/5 260/2.16 260/3.8 240/5 230/3.8
Nylon(PA) 275/0.325 235/1.0 235/2.16
235/5.0 275/5.0
Polyethylene(PE) 125/0.325 125/2.16 2.5/1.2
190/0.325 190/2.16 190/21.6
190/10 310/12.5
Polycarbonate(PC) 300/1.2
Polypropylene(PP) 230/2.16 190/5.0
Polystyrene(PS) 200/5 230/1.2 230/3.8 190/5.0
Polyparaben 250/2.16 210/2.16 285/2.16
Polyphenylene sulfide(PPS) 315/5
SAN 220/10 230/10 230/3.8
Thermoplastic elastomer(TEO/TPO) 230/2.16
Polyethylene terephthalate(PBT) 250/2.16 210/2.16


6 Testing Procedure

 

6.1 Pre-dying the sample material

6.2 Set the apparatus at level.

6.3 Put the standard exit into the hopper, insert the stopper and start the heating until desired temperature is reached. Maintain temperature for at least 15 minutes

6.4 Put the material into the hopper accordingly to the below table


Time elapsed between material insert and testing
 

 
 
MVR (g/10min) Material Weight (g) Elapsed Time (s)
0.1~0.5 3~4 120~240
>0.5~1.0 3~4 60~120
>1.0~3.5 4~5 30~60
>3.5~10 6~8 10~30
>10~25 6~8 5~10


After material is inserted, stopper is put in to close. Within 1 minute, add weigh according to the pre-selected testing condition.

Note: if MVR is higher than 10g/10min, then pre-heating will cause material loss. Under this circumstance, pre-heat can be done with little or no weigh. Weigh can be introduced when pre-heating is done.


6.5 After 4 minutes of pre-heaing, when temperature is back to normal, stopper should be pushed by hand to the lower circle mark 5-10mm from the exit. This should take no longer than 1 minute. When stopper is lowered to the mark, the excess material should be cut from the sample, according to the time interval set in the above table. Keep 3 consecutive bubbles-free sample. Stop when the stopper is level to exit.

Note:① For material susceptible to oxidation, nitrogen can be used to clean the hopper.

② For material with MVR at 25g/100min or above, may use an exit with a smaller diameter

③ Sample plate should be cut between 10-20mm, but the specified elapsed time should be made priority.


6.6 After sample is cooled, it should be placed on the weigh for measuring

6.7 After each testing, the mold surface, hopper and stopper should be wiped clean. Holes should be cleaned with the proper copper wire or nails, and then cleaned with clothes.

 

7 Calculation

① The melt (mass) flow rate is calculated according to the formula:

formula:

MFR —— The melt flow rate,g/10min;

m —— The arithmetic mean of the quality of cut samples,g;

t —— Bar time interval, s The sample result shall be two significant digits.

② Melt (volume) flow rate is calculated according to formula:

img

formula:

MVR —— melt flow rate, cm3/10min;

The result of the sample is two significant digits.

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