PROCESSABILITY OF POLYETHYLENE HOMOPOLYMERS AND COPOLYMERS WITH RESPECT TO THEIR MOLECULAR STRUCTURE

Kim YS; Chung CI; Lai SY; Hyun KS

Korean Journal of Chemical Engineering, Vol.13, No.3, 294-303, May, 1996

The processability of commercial polyethylene homopolymers and copolymers, including both high and low density polyethylenes, was evaluated with respect to their molecular structure by measuring their melt rheological and thermodynamic properties. Short chain branching(SCB) mainly controls the density and thermodynamic properties, but it has little effect on the melt rheological properties. LCB increases the pseudoplasticity and the flow activation energy, reducing the viscosity in processing and thus improving the processability. Very small amounts of LCB in metallocene type low density polyethylenes very effectively reduce the viscosity and improve the flow stability in processing.

Keywords:Metallocene Polyolefin;Processability;Shear Sensitivity;Flow Stability

[References]

ASTM Standards, Part 27, Method D-1238
Boghetich L, Kratz RF, Trans. Soc. Rheol., 9, 255 (1965)
Brandrup J, Immergut ED, "Polymer Handbook," Interscience, VI, 41 (1966)
Bueche F, J. Chem. Phys., 25, 599 (1956)
Bueche F, J. Chem. Phys., 20(12), 1959 (1952)
Christensen RE, Cheng CY, Plast. Eng., 47(6), 31 (1991)
Chum PS, Kao CI, Knight GW, Plast. Eng., 51(6), 21 (1995)
Chung CI, Clark JC, Westerman L, "The Effects of Molecular Structure on the Melt Rheology of Low Density Polyethylene," Advances in Polymer Science and Engineering, Pae, K.D., et al. eds., Plenum Pub., 249 (1972)
Graessley WW, J. Chem. Phys., 47(6), 1942 (1967)
Kim YS, Chung CI, Lai SY, Hyun KS, J. Appl. Polym. Sci., 59(1), 125 (1996)
Kroschwitz JI, ed.-in-chief, Encyclopedia of Polym. Sci. Eng., Wiley, 4, 487 (1985)
Lai SY, Plumley TA, Butler TI, Knight GW, Kao CI, "Dow Rheology Index (DRI) for Insite Technology Polyolefins (ITP): Unique Structure-Processing Relationships," SPE-ANTEC Technical Papers, 2, 1814 (1994)
Mendelson RA, Bowles WA, Finger FL, J. Polym. Sci. A: Polym. Chem., 2(8), 105 (1970)
Speed CS, Trudell BC, Mehta AK, Stehling FC, "Structure/Property Relationships in EXPOL Polymers," SPE-RETEC Technical Papers on Polyolefins International Conference, 45 (1991)
Tung LH, J. Polym. Sci., 46, 409 (1960)

[1] ASTM Standards, Part 27, Method D-1238

[2] Boghetich L, Kratz RF, Trans. Soc. Rheol., 9, 255 (1965)

[3] Brandrup J, Immergut ED, "Polymer Handbook," Interscience, VI, 41 (1966)

[4] Bueche F, J. Chem. Phys., 25, 599 (1956)

[5] Bueche F, J. Chem. Phys., 20(12), 1959 (1952)

[6] Christensen RE, Cheng CY, Plast. Eng., 47(6), 31 (1991)

[7] Chum PS, Kao CI, Knight GW, Plast. Eng., 51(6), 21 (1995)

[8] Chung CI, Clark JC, Westerman L, "The Effects of Molecular Structure on the Melt Rheology of Low Density Polyethylene," Advances in Polymer Science and Engineering, Pae, K.D., et al. eds., Plenum Pub., 249 (1972)

[9] Graessley WW, J. Chem. Phys., 47(6), 1942 (1967)

[10] Kim YS, Chung CI, Lai SY, Hyun KS, J. Appl. Polym. Sci., 59(1), 125 (1996)

[11] Kroschwitz JI, ed.-in-chief, Encyclopedia of Polym. Sci. Eng., Wiley, 4, 487 (1985)

[12] Lai SY, Plumley TA, Butler TI, Knight GW, Kao CI, "Dow Rheology Index (DRI) for Insite Technology Polyolefins (ITP): Unique Structure-Processing Relationships," SPE-ANTEC Technical Papers, 2, 1814 (1994)

[13] Mendelson RA, Bowles WA, Finger FL, J. Polym. Sci. A: Polym. Chem., 2(8), 105 (1970)

[14] Speed CS, Trudell BC, Mehta AK, Stehling FC, "Structure/Property Relationships in EXPOL Polymers," SPE-RETEC Technical Papers on Polyolefins International Conference, 45 (1991)

[15] Tung LH, J. Polym. Sci., 46, 409 (1960)