Study on Effects of Short Wood Fibers on Physical and Mechanical Properties of Biodegradable Composite Based on Thermoplastic Starch

Pesaran Haji Abbas, Ehsan | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42407 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Bagheri, Reza; Sayyed Reihani, Morteza
  7. Abstract:
  8. Due to the negative effects of conventional plastics on the enviroment, 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 processability. 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, 30 wt% glycerol is used to plasticize starch and short wood 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 25 wt% wood fibers, elastic modulus and tensile strength of TPS increase from 96 MPa and 2.8 MPa to 1422 MPa and 8.7 MPa, respectively. Results also show that fibers are able to decrease water uptake and increase thermal stability of TPS. Moreover, surface treatment of wood fibers by NaOH solution slightly improves tensile strength of composites because of better interaction between TPS matrix and fibers which is confirmed by SEM images
  9. Keywords:
  10. Thermoplastic Starch ; Natural Fiber ; Surface Treatment ; Biodegradable Composite

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