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Fabrication and Assessment of Physical and Mechanical Properties of Thermoplastic Starch/ Cellulose Nanofibers Biocomposites

Ghasemi, Amir | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46540 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Bagheri, Reza
  7. Abstract:
  8. Due to the negative effects of conventional plastics on the environment, especially in the packaging sector, extensive efforts have been put to replace these polymers with biodegradable polymers. Starch is one of the biodegradable polymers which has attracted a lot of attentions because of low cost and good process ability. Native starch has the form of granule and can be processed to a continuous phase after gelatinization in the presence of a plasticizer. The resulting material is a biodegradable plastic-like material called thermoplastic starch (TPS) which is processed using conventional technologies, but suffers from low mechanical properties and high hydrophilicity. Addition of natural fibers to TPS matrix is a promising approach to improve mechanical properties and lower water uptake of TPS. Natural fibers are biodegradable and less hydrophilic than starch and because of chemical similarities between the two, a strong bonding can be formed between fibers and TPS matrix which results in good mechanical properties. In this project, 28 wt% glycerol, and 20 wt% distilled water are used to plasticize starch and cellulose nano fibers are incorporated as reinforcement. X-ray diffraction patterns show that crystalline structure of native starch is completely destroyed in the presence of glycerol during extrusion. Tensile test indicates that by incorporating 1.5 phr cellulose nano fibers, elastic modulus and tensile strength of TPS increase from 350 MPa and 5.3 MPa to 875 MPa and 10.3 MPa, respectively. Results also show that nanofibers are able to decrease water uptake and increase thermal stability of TPS. Moreover, increasing the content of cellulose nano fibers improves impact strength of nanocomposites in an efficient manner, because of strong adhesion between TPS matrix and nanofibers which is confirmed by SEM images. Furthermore, biodegradation tests, carried out for TPS alone and for TPS/Cellulose nanofibers, and followed by released CO2 measurements, revealed that biodegradation was enhanced for the nanocomposites in comparison with TPS
  9. Keywords:
  10. Thermoplastic Starch ; Mechanical Properties ; Biodegradability ; Cellulose Nanofiber ; Biodegradable Nanocomposites

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