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PKG829 Packaging Plastics Laboratory

Objectives. To get familiar with the test procedure for measuring the melt flow index of plastic packaging materials;To determine the melt flow index of selected polymer samples by the Extrusion Plastometer technique.. Some Background Info.. Melt Flow Index (MFI)Definition:

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PKG829 Packaging Plastics Laboratory

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    1. PKG829 Packaging Plastics Laboratory Lab 2 Determination of Melt Flow Index by Extrusion Plastometer Li Xiong Fall 2004

    2. Objectives To get familiar with the test procedure for measuring the melt flow index of plastic packaging materials; To determine the melt flow index of selected polymer samples by the Extrusion Plastometer technique.

    3. Some Background Info. Melt Flow Index (MFI) Definition: “the rate of extrusion of a thermoplastic material through an orifice of specific length and diameter under prescribed conditions of temperature and pressure” V. Shah, 1984

    4. Significance Measure the flow rate of the material Distinguish different grades of a polymer Quality control Determine the extent of degradation Predict MW, MWD and molecular architecture Higher MW, Lower MFI For the same MW, narrower the MWD, lower MFI For the same MW/MWD, linear polymer has lower MFI

    5. Cautions Correlation of MFI and processability does not necessarily exist The effect of additives is not observed in the melt flow test The factors affecting the rheological properties of polymer melts might vary dramatically between melt flow test and large-scale processes

    6. Equipment Ray-Ran Melt Flow Indexer MK II Digital Model 2 “A” The plastometer is mainly consisted of: Cylinder Piston Heater Die See section 5 in ASTM D1238-99 for detailed apparatus info.

    7. Test Specimen (section 6 in ASTM D1238-99) “any form that can be introduced into the bore of the cylinder” Powder Granules Strips of film Molded slugs Pellets

    8. Conditioning (see section 7 in ASTM D1238-99) Most thermoplastic materials do not need conditioning process Exception is for those contain volatiles, are chemically reactive, or have special characteristics requiring conditioning process Moisture issue Affect reproducibility of MFI measurement Accelerate degradation

    9. Test Conditions See section 8.2 and table 1 in ASTM D1238-99 Test conditions are shown as: Condition __/__ For example, “Condition: 190/2.16 Temperature = 190oC Total Load (including piston) = 2.16 kg Suggested sample mass, testing time under standard test conditions Table 2 in ASTM D1238-99

    10. Test Procedure (see section 9 and 10 in ASTM D1238-99)

    11. Procedure A (Manual) (see section 9 in ASTM D1238-99)

    12. Procedure B (Automatic) (see section 10 in ASTM D1238-99) Select travel distance for the piston to either 6.35 mm (0.25 in) or 25.4 mm (1 in) See section 10.2.8 and table 3 in ASTM D1238-99) Choose 6.35 mm for material with MFI < 10 g/10 min or 25.4 mm for material with MFI ? 10 g/10 min

    13. Procedure B (con’t)

    14. Calculation for Procedure B

    15. B-1 to Calculate density d Based on the article by Paul Zoller “The pressure volume temperature properties of polyolefins”, Journal of Applied Polymer Science, p.1051, vol. 23, 1979.

    16. B-2 to calculate density d

    17. Report Nature and physical form of the test specimen Test conditions in standard form Test procedure used Original recorded data for each procedure Detailed MFI calculation for each procedure Show the detailed calculation to get the number “426” in the equation used to calculate MFI in procedure B, and what is the unit of 426? Why? And where does number “600” come from? (see figure 2 “Details of extrusion plastometer” in ASTM D1238-99)

    18. Discussion The MFI values (average) found in procedure A and B Comparison of MFI values (average) found in procedure A and B Discussion of the accuracy of each procedure (manual procedure A, auto procedure B-1, and auto procedure B-2) A detailed discussion of the relationship between MFI and the MW, MWD and molecular architecture of the two test resins List at least 3 factors affecting the result of MFI test

    19. Questions? Lab report is due by 5pm on Oct. 12, 2004 My office hour is 4-5pm on Monday or by appointment

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