Journal of the Korea Academia-Industrial cooperation Society (한국산학기술학회논문지)

The Korea Academia-Industrial cooperation Society (한국산학기술학회)
권호 표지
DOI QR코드

DOI QR Code

Study on the rheological, thermal and mechanical properties of thermoplastic starch plasticized by glycerol

열가소성 녹말의 유변학 성질, 열적 성질 및 기계적 성질에 관한 연구

  • Bui, Duc Nhat (Division of Advanced Materials Science and Engineering, College of Engineering, Kongju National University) ;
  • Son, Younggon (Division of Advanced Materials Science and Engineering, College of Engineering, Kongju National University)
  • Received : 2018.04.09
  • Accepted : 2018.06.01
  • Published : 2018.06.30
Download PDF
⟨ Previous Next ⟩

Abstract

Thermoplastic starch (TPS) was prepared by mixing starch with glycerol as a plasticizer. The glycerol content ranged from 20 to 35 wt. % and TPS was prepared in a twin screw extruder. The shear viscosity, thermal and mechanical properties of the TPS were investigated. The viscosity of TPS exhibited typical shear thinning behavior: decreasing viscosity with increasing shear rate. The power index, n, increased with increasing glycerol content. This is because as the content of glycerol, a Newtonian fluid, increases, the viscosity behavior of the TPS becomes closer to that of a Newtonian fluid. The thermal behavior of TPS showed that starch and glycerol are miscible. In addition, when TPS was aged for more than one day at room temperature, TPS showed a partially miscible phase structure. The moisture absorbed into the TPS was assumed to change the phase behavior. The mechanical properties of TPS were found to be strongly dependent on the content of the plasticizer. Both the toughness and stiffness increased with increasing plasticizer content. DSC showed that this unusual result was due to the combined effect of humidity and the high amylose content in starch.

녹말에 가소제인 글리세롤을 혼합하여 열가소성 녹말 (thermoplastic starch, TPS)을 제조하였다. 혼합된 글리세롤은 20-35 wt.%의 비율이었고 TPS는 이축 압출기에서 제조하였다. 제조된 TPS의 전단 점도, 열적 성질 및 기계적 강도를 시험하였다. 제조된 TPS는 전단 속도가 증가할수록 점도가 감소하는 전형적인 고분자의 점도 거동을 보였다. 가소제인 글리세롤의 함량이 증가할수록 power index, n은 증가하여 1에 가까운 값을 보였다. 이는 뉴톤성 유체인 글리세롤의 함량이 증가할수록 제조된 TPS의 점도 거동이 뉴톤성 유체에 가까워지기 때문이다. TPS의 열적 거동을 관찰한 결과 녹말과 글리세롤이 한 상(single phase)을 보임을 확인 할 수 있었다. 또한 TPS를 상온에 하루 이상 방치하면 부분적 상용성을 보이는 것으로 관찰되었는데 이는 공기 중의 습기의 작용인 것으로 추정된다. TPS의 기계적인 성질은 가소제의 함량에 크게 의존하는 것을 볼 수 있었는데 가소제의 함량이 증가할수록 인성과 강성 모두 증가하는 것을 관찰하였다. 가소제의 함량이 증가할수록 강성이 증가하는 특이한 현상은 습도와 높은 아밀로즈 함량이 복합적으로 작용하여 생긴 결과임을 DSC 분석을 통해 알 수 있었다.

Keywords

References

  1. H. Liu, F. Xie, L. Yu, L. Chen, L. Li, "Thermal processing of starch-based polymers", Prog. Polym. Sci., vol. 34, pp. 1348-1368, 2009. DOI: https://doi.org/10.1016/j.progpolymsci.2009.07.001
  2. A. Carvalho, A. Job, N. Alves, A. Curvelo, A. Gandini, "Thermoplastic starch/ natural rubber blends", Carbohydr. Polym, vol. 53, pp. 95-99, 2003. DOI: https://doi.org/10.1016/S0144-8617(03)00005-5
  3. F. Gonzalez, B. Ramasy, B. Favis, "Rheological and thermal properties of thermoplastic starch with high glycerol content", Carbohydr. Polym, vol. 58, pp. 139-147, 2004. DOI: https://doi.org/10.1016/j.carbpol.2004.06.002
  4. D. Rosa, C. Guedes, C. Carvalho, "Processing and thermal, mechanical and morphological characterization of post-consumer polyolefins/thermoplastic starch blends", J. Mater. Sci, vol. 42, pp. 551-557, 2007. DOI: https://doi.org/10.1007/s10853-006-1049-9
  5. T. Bourtoom, "Plasticizer effect on the properties of biodegradable blend film from rice starchchitosan", Songklankarain J. Sci. Technol, vol. 30, no. 1, pp. 149-165, 2008.
  6. J. Yang, Y. Jiugao, X. Ma, "A novel plasticizer for the preparation of thermoplastic starch", Chine. Chem. Lett, vol. 17, pp. 133-136, 2006.
  7. N. Wang, Y. Jiugao, P. Chang, X. Ma, "Influence of formamide and water on the properties of thermoplastic starch/poly(lactic acid) blends", Carbohydr. Polym, vol. 71, no. 1, pp. 109-118, 2008. DOI: https://doi.org/10.1016/j.carbpol.2007.05.025
  8. X. Ma, Y. Jiugao, J. Wan, "Urea and ethanolamine as a mixed plasticizer for thermoplastic starch", Carbohydr. Polym, vol. 64, pp. 267-273, 2006. DOI: https://doi.org/10.1016/j.carbpol.2005.11.042
  9. X. Ma, Y. Jiugao, "The plasticizers containing amide groups for thermoplastic starch", Carbohydr. Polym, vol. 57, pp. 197-203, 2004. DOI: https://doi.org/10.1016/j.carbpol.2004.04.012
  10. N. Wang, Y. Jiugao, X. Ma, W. Ying. "The influence of citric acid on the properties of thermoplastic starch/linear low- density polyethylene blends". Carbohydr. Polym, vol. 67, pp. 446-453, 2007. DOI: https://doi.org/10.1016/j.carbpol.2006.06.014
  11. S. Tajuddin, F. Xie, T. Nicholson, P. Liu, P. Halley, "Rheological properties of thermoplastic starch studied by multipass rheometer", Carbohydr. Polym, vol. 83,pp. 914-919, 2011. DOI: https://doi.org/10.1016/j.carbpol.2010.08.073
  12. J. Willett, B. Jasberg, C. Swanson, "Rheology of thermoplastic starch: Effects of temperature, moisture content, and additives on melt viscosity", Polym. Eng. Sci, vol. 35, pp. 202-210, 1995. DOI: https://doi.org/10.1002/pen.760350214
  13. Y. Jiugao, N. Wang, X. Ma, "The effects of citric acid on the properties of thermoplastic starch plasticized by glycerol." Starch, vol. 57, pp. 494-504, 2005. DOI: https://doi.org/10.1002/star.200500423
  14. Y. Son, "Determination of shear viscosity and shear rate from pressure drop and flow rate relationship in a rectangular channel", Polymer, vol. 48, no. 2, pp. 632-637, 2007. DOI: https://doi.org/10.1016/j.polymer.2006.11.048
  15. N. Wang, J. Yu, P. R. Chang, X. Ma, "Influence of Citric Acid on the Properties of Glycerol-plasticized dry Starch (DTPS) and DTPS/Poly(lactic acid) Blends." Starch, vol. 59, pp. 409-417, 2007. DOI: https://doi.org/10.1002/star.200700617
  16. A.L. Da Roz, A.J.F. Carvalho, A. Gandini, A. A. S. Curvelo, "The effect of plasticizers on thermoplastic starch compositions obtained by melt processing", Carbohydrate Polymers, vol. 63, pp. 417-424, 2006. DOI: https://doi.org/10.1016/j.carbpol.2005.09.017
  17. R. L. Shogren, C. L. Swanson, A. R. Thomson, "Extrudates of cornstarch with urea and glycols-structure mechanical property relations", Starch, vol. 44, pp. 335-338, 1992. DOI: https://doi.org/10.1002/star.19920440905
  18. J. J. G. Van Soest, D. B. Borger, "Structure and properties of compression-molded thermoplastic starch materials from normal and high-amylose maize starches", J. Appl. Polym. Sci., vol. 64, no. 4, pp. 631-644, 1997. https://doi.org/10.1002/(SICI)1097-4628(19970425)64:4<631::AID-APP2>3.0.CO;2-O
  19. J. Yu, J. Wang, X. Wu, P. Zhu, "Effect of Glycerol on Water Vapor Sorption and Mechanical Properties of Starch/Clay Composite Films", Starch, vol. 60, pp. 257-262, 2008. DOI: https://doi.org/10.1002/star.200700695