Journal of Oil, Gas and Petrochemical Technology

Journal of Oil, Gas and Petrochemical Technology

Tensile behavior of extruded poly (lactic acid) films during stretching at different conditions

Document Type : Research Paper

Authors
1 Faculty of Petroleum, Gas and Petrochemical Engineering, Persian Gulf University, Bushehr 75169, Iran
2 Kunststofftechnik Paderborn (KTP), Paderborn University, Paderborn 33098, Germany
Abstract
As a commercially available biodegradable and bio-based polymer, Poly (lactic acid) is accepted to be a promising potential to replace conventional polymers in packaging applications. Oriented PLA films are obtained through stretching at temperatures above the glass transition temperature. The present study evaluates the effects of both temperature and drawing speed during stretching on the tensile behavior and surface morphology of PLA films. Increasing the drawing speed enhances the strain hardening behavior. Conversely, there is a noticeable reduction in strain hardening as stretching temperature increases from 70 to 80 °C. Besides, stretching at 90 °C eliminates, thoroughly, the strain hardening behavior at lower drawing speeds. However, stretching the PLA film at 90 °C and at a high drawing speed (30 mm/sec) stimulates the strain hardening behavior demonstrating chain extension exceeds the chain relaxation at such a high drawing speed. The surface morphology of PLA films observed by scanning electron microscopy (SEM) reveals no crystalline structures on the film surface of PLA films stretched at 70 and 80 °C. The SEM image of PLA film stretched at 90 °C indicates formation of crystalline lamellae which is attributed to cold crystallization during stretching.
Keywords

  1. Ou, M. Cakmak. "Influence of biaxial stretching mode on the crystalline texture in polylactic acid films". Polymer, vol. 49, pp. 5344-5322, 2008.
  2. -C. Tsai, R.-J. Wu, H.-Y. Cheng, S.-C. Li, Y.-Y. Siao, D.-C. Kong, G.-W. Jang. "Crystallinity and dimensional stability of biaxial oriented poly (lactic acid) films". Polymer Degradation and Stability, vol. 95, pp. 1292-1298, 2010.
  3. Jariyasakoolroj, K. Tashiro, H. Wang, H. Yamamoto, W. Chinsirikul, N. Kerddonfag, S. Chirachanchai. "Isotropically small crystalline lamellae induced by high biaxial-stretching rate as a key microstructure for super-tough polylactide film". Polymer, vol. 68, pp. 234-245, 2015.
  4. -R. Gao, Y. Li, H.-D. Huang, J.-Z. Xu, L. Xu, X. Ji, G.-J. Zhong, Z.-M. Li. "Extensional stress-induced orientation and crystallization can regulate the balance of toughness and stiffness of polylactide films: interplay of oriented amorphous chains and crystallites". Macromolecules, vol. 52, pp. 5278-5288, 2019.
  5. Li, L. Liu, Y. Rao, L. Ran, T. Wu, R. Nie, D. S. Anna, Y. Li, Z. Che. "Mechanical and antibacterial properties of oriented poly (lactic acid)". Polymer Engineering and Science, vol. 59, pp. 2121-2127, 2019.
  6. Jariyasakoolroj, K. Tashiro, W. Chinsirikul, N. Kerddonfag, S. Chirachanchai. "Microstructural analyses of biaxially oriented polylactide/modified thermoplastic starch film with drastic improvement in toughness". Macromolecular Materials and Engineering, vol. 304, pp. 1900340, 2019.
  7. Palai, S. Mohanty, S. K. Nayak. "Synergistic effect of polylactic acid (PLA) and Poly (butylene succinate-co-adipate) (PBSA) based sustainable, reactive, super toughened eco-composite blown films for flexible packaging applications". Polymer Testing, vol. 83, pp. 106130, 2020.
  8. Xu, J.-F. Tahon, I. De-Waele, G. Stoclet, V. Gauc. "Brittle-to-ductile transition of PLA induced by macromolecular orientation". eXPRESS Polymer Letters, vol. 14, pp. 1034-1047, 2020.
  9. Mulligan, M. Cakmak. "Nonlinear mechanooptical behavior of uniaxially stretched poly(lactic acid): dynamic phase behavior". Macromolecules, vol. 38, pp. 2333-2344, 2005.
  10. Stoclet, R. Seguela, J. M. Lefebvre, S. Elkoun, C. Vanmansart. "Strain-induced molecular ordering in polylactide upon uniaxial stretching". Macromolecules, vol. 43, pp. 1488-1498, 2010.
  11. C. Velazquez-Infante, J. Gamez-Perez, E. A. Franco-Urquiza, O. O. Santana, F. Carrasco, M. Ll Maspoch. "Effect of the unidirectional drawing on the thermal and mechanical properties of PLA films with different L-isomer content". Journal of Applied Polymer Science, vol. 127, pp. 2661-2669, 2013.
  12. J. Xu, Z. Q. Tian, J. Y. Xie, C. H. Lei. "The structure transformation of pre-oriented polylactic acid film during uniaxial stretching at room temperature". Polymer Crystallization, vol. 2, pp. e10072, 2019.
  13. J. Flory. "Thermodynamics of crystallization in high polymers. I. crystallization induced by stretching". The Journal of Chemical Physics, vol. 15, pp. 397-408, 1947.
  1. Drieskens, R. Peeters, J. Mullens, D. Franco, P. J. Lemstra, D. G. Hristova-Bogaerds. "Structure versus properties relationship of poly(lactic acid). I. effect of crystallinity on barrier properties". Journal of Polymer Science: Part B: Polymer Physics, vol. 47, pp. 2247-2258, 2009.