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Manufacturing and Mechanical Properties and Microstructure Optimization of the Ternary Polypropylene-based Composite Reinforced by Short Flax Fibers and Toughened by Poe Rubber Particles

Bahrami, Reza | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51745 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Bagheri, Reza; Seyed Reyhani, Morteza
  7. Abstract:
  8. Recently, Polypropylene has been extensively used in a variety of applications in the polymer industry, but its quite low stiffness and toughness limit this polyolefin’s application in the engineering functions; thus, the market of polymer blend and composite manufacturing has grown noticeably in the last few years. In the current project, short Flax fibers are used in order to reinforce the PP matrix. Firstly, Flax fibers were washed with the gentle and harsh condition during the alkalization process, then the optimized alkalization condition was determined through comparison of results from X-ray Diffraction (XRD ), Attenuated Total Reflectance FTIR (ATR-FTIR) and microscopic surface observations by Scanning Electron Microscope (SEM) conducted on the raw and treated fibers. The results showeed that the fibers washed through alkalization gentle setting were not undergone any degradation, and become suitable chemically for using in the PP-based composites. Next, binary composites were manufactured through extrusion and injection molding process, and their mechanical properties were studied by tensile and impact tests. Moreover, the fracture surface of the impact specimens was examined by SEM observations, and the four-point bending specimens’ crack tips were studied through Transmission Optical Microscopy (TOM) images. The results show that composites without compatibilizer in their composition did not demonstrate any enhancement in their yield strength due to the weak interface between fibers and the matrix so that the yield strength increased only by 10% in the composite containing 30 wt.% ALK1 fibers without MAPP; but its impact strength increased from 1.5 kJ/m2 in the pure PP to 4 kJ/m2. In contrast, adding compatibilizer promoted the composite’s interface strength so that the yield strength so that the yield strength increased by 75% in the composite containing 30 wt.% ALK1 fibers with 3 wt.% MAPP. Furthermore, the presence of 3 wt.% MAP increased composite’s impact strength to 4 kJ/m2 , and altered the composite’s fracture mechanism. Given the fact that adding short fibers do not promote the PP impact strength significantly, ternary composites were manufactured by adding POE rubber particles in order to increase the composite’s toughness. The mechanical properties of these ternary composites were examined through the tensile and impact tests, and their fracture mechanism was studied by the fracture surface and crack tip observations which resulted in the elevation of the impact strength to 10 kJ/m2 in the composite containing 30 wt.% fibers, 3 wt.% MAPP and 20 wt.% POE particles. Finally, the composite containing 20 wt.% fibers, 3 wt.% MAPP and 10 wt.% rubber was selected as the optimum specimen due to the mechanical properties and the ease of manufacturing since it demonstrated 100%, 16% and 230% increase in the elastic module, yield strength, and impact strength respectively
  9. Keywords:
  10. Natural Fiber ; Fracture Micromechanism ; Ternary Composite ; Carbon Footprint Reduction ; Short Fiber Composite ; Rubber Toughening

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