Effects of cast extrusion line speed on the crystallinity of LLDPE stretch films

Document Type : Research Paper


1 Faculty of Petroleum, Gas and Petrochemical Engineering, Persian Gulf University, Bushehr 75169, Iran

2 Kunststofftechnik Paderborn (KTP), Paderborn University, Paderborn 33098, Germany


In this study, the influence of line speed on the crystallinity of linear low-density polyethylene (LLDPE) stretch films manufactured in a cast extrusion line was examined using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The multilayer LLDPE films were prepared at a wide range of line speeds. The DSC results showed that there was an increase in the crystallinity of films at higher line speeds. The crystallinity increased from 24.5 to 39.8 % while the line speed changed from 200 to 1000 m/min. Evaluating melting endotherms showed that the size of crystals was more uniform as the line speed increased. The crystallinity of films obtained from WAXD analysis exhibited the similar trend of DSC results, though their values were different. Additionally, there was a reduction in the crystal size calculated from WAXD data upon increasing the line speed. The observed increase in crystallinity and decrease in 
crystal size were due to the enhanced flow induced crystallization (FIC) as a result of greater shear stresses the polymer melt encountered at higher line speeds.


[1] S. Auksornkul, S. Soontaranon, C. Kaewhan, P. Prasassarakich. “Effect of the blow-up ratio on morphology and engineering properties of three-layered linear low-density polyethylene blown films”. J. Plast. Film Sheeting, vol. 34, pp. 27–42, 2018.
[2]       C.M. Small, G.M. Mcnally, G. Garrett, W.R. Murphy. “The Characteristics of Polyethylene Film for Stretch and Cling Film Applications”. Dev. Chem. Eng. Miner. Process, vol. 12, pp. 5–20, 2008.
[3]       J. Singh, E. Cernokus, K. Saha, S. Roy. “The Effect of Stretch Wrap Prestretch on Unitized Load Containment”. Packag. Technol. Sci., vol. 27, pp. 944–961, 2014.
[4]       P.M. German, C.B. Johnson, M.G. Williams. “Polyethylene Stretch Film”. US 9,388,306 B2, 2016. https://patents.google.com/patent/US9388306B2/en, 2016.
[5]       L. Castellani, A. Castiglioni, D. Ferri, A. Baraldi, L. Martinelli, S. Rotunno. “Rate effects on adhesion energy between polyethylene films and different substrates”. Eng. Fract. Mech., vol. 149, pp. 387–401, 2015.
[6]       S. Feng, Y. Lin, W. Yu, O. Iqbal, J.C. Habumugisha, W. Chen, L. Meng, A. Lu, L. Li. “Stretch-induced structural transition of linear low-density polyethylene during uniaxial stretching under different strain rates”. Polymer (Guildf), vol. 226, pp. 123795, 2021.
[7]       M. Rennert, S. Fiedler, M. Nase, M. Menzel, S. Günther, J. Kressler, W. Grellmann. “Investigation of the migration behavior of polyisobutylene with various molecular weights in ethylene/α-olefin copolymer blown stretch films for improved cling properties”. J. Appl. Polym. Sci., vol. 131, pp. 40239, 2014.
[8]       H. Zhao, Q. Zhang, S. Ali, L. Li, F. Lv, Y. Ji, F. Su, L. Meng, L. Li. “A real-time WAXS and SAXS study of the structural evolution of LLDPE bubble”. J. Polym. Sci. Part B Polym. Phys., vol. 56, pp. 1404–1412, 2018.
[9]       M. Niaounakis, E. Kontou. “Effect of LDPE on the thermomechanical properties of LLDPE-based films”. J. Polym. Sci. Part B Polym. Phys., vol. 43, pp. 1712–1727, 2005.
[10]    H. Bayazian, A. Yadegari, V. Schöppner. “Probing tensile properties of LLDPE stretch films prepared in cast extrusion process”. Polym. Bull., pp. 1–14, 2021. https://doi.org/10.1007/s00289-021-03599-9
[11]    J.A. Degroot, A.T. Doughty, K.B. Stewart, R.M. Patel. “Effects of cast film fabrication variables on structure development and key stretch film properties”. J. Appl. Polym. Sci., vol. 52, pp. 365–376, 1994.
[12]    M.I. Babaghayou, A.H.I. Mourad, N. Cherunurakal. “Anisotropy evaluation of LDPE/LLDPE/PIB trilayer films”. 2020 Advances in Science and Engineering Technology International Conferences, ASET 2020. Institute of Electrical and Electronics Engineers Inc. (2020). https://doi.org/10.1109/ASET48392.2020.9118263
[13]    W. Du, Y. Ren, Y. Tang, Y. Shi, X. Yao, C. Zheng, X. Zhang, M. Guo, S. Zhang, L.Z. Liu. “Different structure transitions and tensile property of LLDPE film deformed at slow and very fast speeds”. Eur. Polym. J. vol., 103, pp. 170–178, 2018.
[14]    D. Nagy, K. Belina, E. Kókai. “Research and Manufacture of Stretch Films using LLDPE blends”. IOP Conference Series: Materials Science and Engineering. pp. 012064. Institute of Physics Publishing (2018).
[15]    V. Compañ, L.F. Del Castillo, S.I. Hernández, M.M. López-González, E. Riande. “On the crystallinity effect on the gas sorption in semicrystalline linear low density polyethylene (LLDPE)”. J. Polym. Sci. Part B Polym. Phys., vol. 45, pp. 1798–1807, 2007.
[16]    G.M. McNally, C.M. Small, W.R. Murphy, G. Garrett. “The Effect of Polymer Properties on the Mechanical Behavior and Morphological Characteristics of Cast Polyethylene Film for Stretch and Cling Film Applications”. J. Plast. Film Sheeting., vol. 21, pp. 39–54, 2005.
[17]    M. Andreev, D.A. Nicholson, A. Kotula, J.D. Moore, J. den Doelder, G.C. Rutledge. “Rheology of crystallizing LLDPE.” J. Rheol., vol. 64, pp. 1379–1389, 2020.
[18]    S.H. Tabatabaei, P.J. Carreau, A. Ajji. “Effect of processing on the crystalline orientation, morphology, and mechanical properties of polypropylene cast films and microporous membrane formation”. Polymer (Guildf), vol. 50, pp. 4228–4240, 2009.
[19]    S. Yakovlev, D. Fiscus, P. Brant, J. Butler, D.G. Bucknall, K.H. Downing. “Mechanism of stress induced crystallization of polyethylene”. Polymer (Guildf), vol. 175, pp. 25–31, 2019.
[20]    H. Zhao, Q. Zhang, L. Li, W. Chen, D. Wang, L. Meng, L. Li. “Synergistic and Competitive Effects of Temperature and Flow on Crystallization of Polyethylene during Film Blowing”. ACS Appl. Polym. Mater., vol. 1, pp. 1590–1603, 2019.
[21]    V. Schöppner, H. Bayazian, A. Yadegari, H. Haddad. “Orientation in LLDPE cast films manufactured under different processing parameters”. AIP Conference Proceedings. pp. 020022. American Institute of Physics Inc. (2020).
[22]    K.G. Schurzky. “Design Parameters for LLDPE Film Resin Selection”. J. Plast. Film Sheeting., vol. 1, pp. 142–151, 1985.
[23]    A. Yadegari, J. Morshedian, H.A. Khonakdar, U. Wagenknecht, G. Heinrich, M. Malanin, K.J. Eichhorn, D. Fischer. “Correlation of crystal alignment with interphase content in oriented high density polyethylene cast films”. CrystEngComm., vol. 18, pp. 2337–2346, 2016.
[24]    P.H. Hermans, A. Weidinger. “On the determination of the crystalline fraction of polyethylenes from X-ray diffraction”. Die Makromol. Chemie., vol. 44, pp. 24–36, 1961.
[25]    P.P. Kundu, J. Biswas, H. Kim, S. Choe. “Influence of film preparation procedures on the crystallinity, morphology and mechanical properties of LLDPE films”. Eur. Polym. J., vol. 39, pp. 1585–1593, 2003.
[26]    Y. Takahashi, T. Ishida, M. Furusaka. “Monoclinic-to-orthorhombic transformation in polyethylene”. J. Polym. Sci. Part B Polym. Phys., vol. 26, pp. 2267–2277, 1988.
[27]    H. Uehara, M. Kakiage, T. Yamanobe, T. Komoto, S. Murakami. “Phase Development Mechanism during Drawing from Highly Entangled Polyethylene Melts”. Macromol. Rapid Commun., vol. 27, pp. 966–970, 2006.
[28]    S.J.S. Qazi, A.R. Rennie, J.K. Cockcroft, M. Vickers. “Use of wide-angle X-ray diffraction to measure shape and size of dispersed colloidal particles”. J. Colloid Interface Sci. vol. 338, pp. 105–110, 2009.