The role of 1-hexene comonomer content in thermal behavior of medium density polyethylene (MDPE) synthesized using Phillips catalyst

Document Type: Original research


1 Iran Polymer and Petrochemical Institute, 14965-115, Tehran, Iran

2 Leibniz-Institut für Polymerforschung Dresden e.V., D-01069, Dresden, Germany


In this work, the role of comonomer content of 1-hexene-medium density polyethylene (MDPE) copolymer, synthesized using Phillips catalyst, on thermal behavior parameters such as: crystallization, melting temperature and thermal degradation was investigated in detail. The copolymer was fractionated to homogenous short-chain branching (SCB) fractions by "preparative temperature rising elution fractionation" (P-TREF) method and then it was subjected to thermal analyses. A broad chemical composition distribution (CCD) in terms of SCB content and molecular weight (Mw) was observed by P-TREF and gel permeation chromatography (GPC), respectively. Based on P-TREF results, a parabolic relationship between methylene sequence length (MSL) and elution temperature (ET) was presented. Differential scanning calorimetry (DSC) showed distinct, well-defined melting peaks over a 22 °C temperature range for SCB contents of about 3-12 (br/1000 C). The variations in physical characteristics such as melting temperature (Tm), crystallinity (Xc), crystallization temperature (Tc) and lamellae thickness (Lc) against SCB content were correlated. Thermogravimetric analysis (TGA) suggested linear relationships between the temperature at maximum degradation rate (Tmax) as well as the degradation initiation temperature (T5%) versus SCB content. Moreover, the TGA curves exhibited distinct differences at both initiation and propagation stages of thermal degradation at dissimilar comonomer contents.


Main Subjects

  1. Sacchi MC, Losio S, Stagnaro P, Mancini G, Boragno L, Menichetti S, Viglianisi C, Limbo S (2014) Macromolecular non-releasing additives for safer food packaging: application to ethylene/α-olefins and propylene based polymers. Polyolefin J 1: 1-15
  2. Zohuri GH, Damavandi S, Ahmadjo S, sandaroos R, Shamekhi M (2014) Synthesis of high molecular weight polyethylene using FI catalyst. Polyolefin J 1: 25-32
  3.  Jeon HJ,Kim MN (2014) Degradation of linear low density polyethylene (LLDPE) exposed to UV-irradiation. Eur Polym J 52: 146-153
  4. Benítez A, Sánchez JJ, Arnal ML, Müller AJ (2013) Monitoring abiotic degradation of branched polyethylenes formulated with pro-oxidants through different mechanical tests. Polyme Degrad Stabil 98: 1705-1716
  5. Morlat-Therias S, Fanton E, Gardette J-L, Dintcheva NT, La Mantia FP, Malatesta V (2008) Photochemical stabilization of linear low-density polyethylene/clay nanocomposites: Towards durable nanocomposites. Polym Degard Stabil 93: 1776-1780
  6. Peacock A (2000). Handbook of polyethylene: structures: properties, and applications CRC Press.
  7. Ko YS, Han TK, Sadatoshi H, Woo SI (1998) Analysis of microstructure of ethylene–1-hexene copolymer prepared over thermally pretreated MgCl2/THF/TiCl4bimetallic catalyst. J Polym Sci Part A: Polym Chem 36: 291-300
  8. Chu KJ, Soares JB, Penlidis A, Ihm SK (1999) The influence of the Ti3+ species on the microstructure of ethylene/1-hexene copolymers. Macromol Chem Phys 200: 1298-1305
  9. Czaja K,Białek M (2001) Microstructure of ethylene-1-hexene and ethylene-1-octene copolymers obtained over Ziegler–Natta catalysts supported on MgCl2(THF)2. Polymer 42: 2289- 2297
  10. Van Grieken R, Carrero A, Suarez I, Paredes B (2007) Effect of 1-hexene comonomer on polyethylene particle growth and kinetic profiles. Macromol Symp 259: 243-252
  11. Sarzotti DM, Soares JB, Penlidis A (2002) Ethylene/1-hexene copolymers synthesized with a single-site catalyst: Crystallization analysis fractionation, modeling, and reactivity ratio estimation. J Polym Sci Part B: Polym Phys 40: 2595-2611
  12. dos Santos JHZ, Larentis A, da Rosa MB, Krug C, Baumvol IJR, Dupont J, Stedile FC, de Camargo Forte M (1999) Optimization of a silica supported bis (butylcyclopentadienyl)-zirconium dichloride catalyst for ethylene polymerization. Macromol Chem Phys 200: 751-757
  13. Terano M, Soga K (1994). Catalyst Design for Tailor-Made Polyolefins Elsevier.
  14. Deslauriers PJ, McDaniel MP (2007) Short chain branching profiles in polyethylene from the Phillips Cr/silica catalyst. J Polym Sci Part A: Polym Chem 45: 3135-3149
  15. McDaniel MP (2010) A review of the Phillips supported chromium catalyst and its commercial use for ethylene polymerization. Adv Cat 53: 123-606
  16. McDaniel M, Rohlfing D, Benham E (2003) Long chain branching in polyethylene from the Phillips chromium catalyst. Polym Reac Eng 11: 101-132
  17. Tso CC, DesLauriers PJ (2004) Comparison of methods for characterizing comonomer composition in ethylene 1-olefin copolymers: 3D-TREF vs. SEC-FTIR. Polymer 45: 2657-2663
  18. Shen G, Shen H, Xie B, Yang W, Yang M (2013) Crystallization and fracture behaviors of high-density polyethylene/linear low-density polyethylene blends: The influence of short-chain branching. J Appl Polym Sci 129: 2103-2111
  19. Shan CLP, degroot WA, Hazlitt LG, Gillespie D (2005) A new turbidimetric approach to measuring polyethylene short chain branching distributions. Polymer 46: 11755-11767
  20. Torabi S, Fazeli N (2009) A rapid quantitative method for determination of short chain branching content and branching distribution index in LLDPEs by DSC. Polym Test 28: 866-870
  21. Ramachandran R, Beaucage G, McFaddin D, Merrick-Mack J, Galiatsatos V, Mirabella F (2011) Branch length distribution in TREF fractionated polyethylene. Polymer 52: 2661-2666
  22. Pérez C, Alvarez V, Valles E, Failla M (2012) Crystallization behavior of random ethylene– butene copolymers modified with organic4) peroxide. Thermochim Act 528: 15-22
  23. He F-A,Zhang L-M (2014) Study on branching structure, melting, and crystallization of polyethylene prepared by Nickela-Diimine catalyst covalently intercalated inside oapPOSS-modified laponite clay gallery. Polym Test 35: 80-86
  24. Fazeli N, Arabi H, Bolandi S (2006) Effect of branching characteristics of ethylene/1-butene copolymers on melt flow index. Polym Test 25: 28-33
  25. Gupta P, Wilkes GL, Sukhadia AM, Krishnas-wamy RK, Lamborn MJ, Wharry SM, Tso CC, DesLauriers PJ, Mansfield T, Beyer FL (2005) Does the length of the short chain branch affect the mechanical properties of linear low density polyethylenes? An investigation based on films of copolymers of ethylene/1-butene, ethylene/1- hexene and ethylene/1-octene synthesized by a single site metallocene catalyst. Polymer 46: 8819-8837
  26. Hussein IA (2003) Influence of composition distribution and branch content on the miscibility of m-LLDPE and HDPE blends: Rheological investigation. Macromolecules 36: 2024-2031
  27. Kessner U, Kaschta J, Stadler FJ, Le Duff CS, Drooghaag X, Münstedt H (2010) Thermorheological behavior of various short-and long-chain branched polyethylenes and their correlations with the molecular structure. Macromolecules 43: 7341-7350
  28. Hosoda S, Nozue Y, Kawashima Y, Suita K, Seno S, Nagamatsu T, Wagener KB, Inci B, Zuluaga F, Rojas G (2010) Effect of the sequence length distribution on the lamellar crystal thickness and thickness distribution of polyethylene: perfectly equisequential ADMET polyethylene vs ethylene/ α-olefin copolymer. Macromolecules 44: 313-319
  29. Nitta Kh,Tanaka A (2001) Dynamic mechanical properties of metallocene catalyzed linear polyethylenes. Polymer 42: 1219-1226
  30. Stadler FJ, Kaschta J, Münstedt H (2008) Thermorheological behavior of various long-chain branched polyethylenes. Macromolecules 41: 1328-1333
  31. Stadler FJ, Gabriel C, Münstedt H (2007) Influence of short-chain branching of polyethylenes on the temperature dependence of rheological properties in shear. Macromol Chem Phys 208: 2449-2454
  32. Carella J, Gotro J, Graessley W (1986) Thermorheological effects of long-chain branching in entangled polymer melts. Macromolecules 19: 659-667
  33. Mavridis H, Shroff R (1992) Temperature dependence of polyolefin melt rheology. Polym Eng & Sci 32: 1778-1791
  34. Starck P,Löfgren B (2002) Thermal properties of ethylene/long chain α-olefin copolymers produced by metallocenes. Eur Polym J 38: 97- 107
  35. Vanden Eynde S, Mathot V, Koch M, Reynaers H (2000) Thermal behaviour and morphology of homogeneous ethylene–propylene and ethylene– 1-butene copolymers with high comonomer contents. Polymer 41: 3437-3453
  36. Zhang M, Lynch D, Wanke S (2001) Effect of molecular structure distribution on melting and crystallization behavior of 1-butene/ethylene copolymers. Polymer 42: 3067-3075
  37.  Naddeo C, Guadagno L, De Luca S, Vittoria V, Camino G (2001) Mechanical and transport properties of irradiated linear low density polyethylene (LLDPE). Polym Degrad Stabil 72: 239-247
  38. Krupa I, Luyt AS (2001) Thermal and mechanical properties of extruded LLDPE/wax blends. Polym Degrad Stabil 73: 157-161
  39. Goldberg VM, Kolesnikova NN, Paverman NG, Kavun SM, Stott PE, Gelbin ME (2001) Thermo-oxidative degradation of linear low density poly(ethylene) in the presence of carbon black: a kinetic approach. Polym Degrad Stabil 74: 371- 385
  40. Xie R, Qu B, Hu K (2001) Dynamic FTIR studies of thermo-oxidation of expandable graphite-based halogen-free flame retardant LLDPE blends. Polym Degrad Stabil 72: 313-321
  41. Wang Z, Wu G, Hu Y, Ding Y, Hu K, Fan W (2002) Thermal degradation of magnesium hydroxide and red phosphorus flame retarded polyethylene composites. Polym Degrad Stabil 77: 427-434
  42. Gulmine JV, Janissek PR, Heise HM, Akcelrud L (2003) Degradation profile of polyethylene after artificial accelerated weathering. Polym Degrad Stabil 79: 385-397
  43. Naddeo C, Guadagno L, Vittoria V (2004) Photooxidation of spherilene linear low-density polyethylene films subjected to environmental weathering. 1. Changes in mechanical properties. Polym Degrad Stabil 85: 1009-1013
  44. Abbas-Abadi MS, Haghighi MN, Yeganeh H (2012) The effect of temperature, catalyst, different carrier gases and stirrer on the produced transportation hydrocarbons of LLDPE degradation in a stirred reactor. J Anal Appl Pyro 95: 198-204
  45. Gascoin N, Fau G, Gillard P, Mangeot A (2013) Experimental flash pyrolysis of high density polyethylene under hybrid propulsion conditions. J Anal Appl Pyro 101: 45-52
  46. Arabiourrutia M, Elordi G, Lopez G, Borsella E, Bilbao J, Olazar M (2012) Characterization of the waxes obtained by the pyrolysis of polyolefin plastics in a conical spouted bed reactor. J Anal Appl Pyro 94: 230-237
  47. Murata K, Brebu M, Sakata Y (2010) The effect of silica–alumina catalysts on degradation of polyolefins by a continuous flow reactor. J Anal Appl Pyro 89: 30-38
  48. De Stefanis A, Cafarelli P, Gallese F, Borsella E, Nana A, Perez G (2013) Catalytic pyrolysis of polyethylene: A comparison between pillared and restructured clays. J Anal Appl Pyro 104: 479-484
  49. Singhal R, Singhal C, Upadhyayula S (2010) Thermal-catalytic degradation of polyethylene over silicoaluminophosphate molecular sieves-A thermogravimetric study. J Anal Appl Pyro 89: 313-317
  50. Renzini MS, Lerici LC, Sedran U, Pierella LB (2011) Stability of ZSM-11 and BETA zeolites during the catalytic cracking of low-density polyethylene. J Anal Appl Pyro 92: 450-455
  51. He P, Xiao Y, Zhang P, Xing C, Zhu N, Zhu X, Yan D (2005) Thermal degradation of syndiotactic polypropylene and the influence of stereoregularity on the thermal degradation behaviour by in situ FTIR spectroscopy. Polymer Degrad Stabil 88: 473-479
  52. Westerhout R, Waanders J, Kuipers J, Van Swaaij W (1997) Kinetics of the low-temperature pyrolysis of polyethene, polypropene, and polystyrene modeling, experimental determination, and comparison with literature models and data. Ind Eng Chem Res 36: 1955-1964
  53. Abbas-Abadi MS, Haghighi MN, Yeganeh H (2013) Evaluation of pyrolysis product of virgin high density polyethylene degradation using different process parameters in a stirred reactor. Fuel Process Technol 109: 90-95
  54. Abbas-Abadi MS, Haghighi MN, Yeganeh H, Bozorgi B (2013) The effect of melt flow index, melt flow rate, and particle size on the thermal degradation of commercial high density polyethylene powder. J Therm Anal ad Calor 114: 1333-1339
  55. Kebritchi A, Nekoomanesh H. M, Mohammadi F, Khonakdar HA (submitted) The interrelationship of microstructure and low/high temperature thermal behavior of fractionated ethylene/1- butene copolymer. Iran. Polym. J
  56. Fu Y,Lim L-T (2012) Investigation of multiple-component diffusion through LLDPE film using an FTIR-ATR technique. Polym Test 31: 56-67
  57. Kim YM,Park JK (1996) Effect of short chain branching on the blown film properties of linear low density polyethylene. J Appl Polym Sci 61: 2315-2324
  58.  Defoor F, Groeninckx G, Schouterden P, Van der Heijden B (1992) Molecular, thermal and morphological characterization of narrowly branched fractions of 1-octene linear low-density polyethylene: 1. molecular and thermal characterization. Polymer 33: 3878-3883
  59. Zhang M, Wanke SE (2003) Quantitative determination of short-chain branching content and distribution in commercial polyethylenes by thermally fractionated differential scanning calorimetry. Polym Eng Sci 43: 1878-1888
  60. Kakugo M, Miyatake T, Mizunuma K (1991) Chemical composition distribution of ethylene- 1-hexene copolymer prepared with titanium trichloride-diethylaluminum chloride catalyst. Macromolecules 24: 1469-1472
  61. Adisson E, Ribeiro M, Deffieux A, Fontanille M (1992) Evaluation of the heterogeneity in linear low-density polyethylene comonomer unit distribution by differential scanning calorimetry characterization of thermally treated samples. Polymer 33: 4337-4342
  62. Hosoda S (1988) Structural distribution of linear low-density polyethylenes. Polymer J. 20: 383- 397
  63. Shanks R, Amarasinghe G (2000) Comonomer distribution in polyethylenes analysed by DSC after thermal fractionation. J Thermal Anal Calorimetry 59: 471-482
  64. Yoon J-S, Lee D-H, Park E-S, Lee I-M, Park D-K, Jung S-O (2000) Thermal and mechanical properties of ethylene/α-olefin copolymers produced over (2-MeInd)2ZrCl2/MAO system. Polymer 41: 4523-4530
  65. Teng H, Shi Y, Jin X (2002) Novel characterization of the crystalline segment distribution and its effect on the crystallization of branched polyethylene by differential scanning calorimetry. J Polym Sci Part B: Polym Phys 40: 2107-2118
  66. Fan Z, Wang Y, Bu H (2003) Influence of intermolecular entanglements on crystallization behavior of ultra-high molar mass polyethylene. Polym Eng Sci 43: 607-614
  67. Mortazavi SMM, Arabi H, Zohuri G, Ahmadjo S, Nekoomanesh M, Ahmadi M (2010) Copolymerization of ethylene/α- olefins using bis(2-phenylindenyl)zirconium dichloride metallocene catalyst: structural study of comonomer distribution. Polym Int 59: 1258-1265
  68. E. Gauthier BL, F.J.J.M. Cuoq, P.J. Halley, K.A. George (2012) Correlation between chain microstructural changes and embrittlement of LLDPE-based films during photo- and thermo-oxidative degradation. Polym Degrad Stabil: 1-12
  69. Pérez CJ, Failla M, Carella J (2013) SSA study of early polyethylenes degradation stages. Effects of attack rate, of average branch length, and of backbone polymethylene sequences length distributions. Polym Degrad Stabil 98: 177-183
  70. Paredes B, Soares JB, van Grieken R, Carrero A, Suarez I (2007) Characterization of ethylene- 1-Hexene copolymers made with supported metallocene catalysts: influence of support type. Macromol Symp 257: 103-111
  71. Assumption H, Vermeulen J, Jarrett WL, Mathias LJ, Van Reenen A (2006) High resolution solution and solid state NMR characterization of ethylene/1-butene and ethylene/1-hexene copolymers fractionated by preparative temperature rising elution fractionation. Polymer 47: 67-74
  72. Simanke A, Galland G, Baumhardt Neto R, Quijada R, Mauler R (1999) Influence of the type and the comonomer contents on the mechanical behavior of ethylene/α-olefin copolymers. J Appl Polym Sci 74: 1194-1200
  73. Kale L, Plumley T, Patel R, Redwine O, Jain P (1996) Structure-property relationships of ethylene/1-octene and ethylene/1-butene copolymers made using INSITE technology. J Plast film Sheet 12: 27-40
  74. Bonner J, Frye C, Capaccio G (1993) A novel calibration for the characterization of polyethylene copolymers by temperature rising elution fractionation. Polymer 34: 3532-3534
  75. Ungar G, Keller A (1987) Inversion of the temperature dependence of crystallization rates due to onset of chain folding. Polymer 28: 1899- 1907
  76. Stack GM, Mandelkern L (1988) On the crystallization of high molecular weight normal hydrocarbons. Macromolecules 21: 510-514

Volume 1, Issue 2
Summer and Autumn 2014
Pages 117-129
  • Receive Date: 09 July 2014
  • Revise Date: 17 September 2014
  • Accept Date: 01 November 2014