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Study the Effects of Components Ratio on Microstructure and Mechanical Properties of Polyethylene Ternary Blend (HDPE/LLDPE/LDPE)

Eslamian, Mohammad Javad | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46610 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Bagheri, Reza
  7. Abstract:
  8. Melt blending of polymers is a rather cheap and easy approach for obtaining new set of properties compared to synthesizing new polymeric materials. For the same reason, binary and ternary polyethylene blends are made to provide added value for different applications. Polyethylene blends are commonly composed of high density polyethylene (HDPE), low density polyethylene (LDPE) and linear low density polyethylene (LLDPE). Although the Mechanical and physical properties of polyethylene binary blends have been studied extensively, microstructure and mechanical properties of polyethylene ternary blends have been the subject of very few studies. In this work, samples with 40-60 Wt. % HDPE and different amount of LDPE and LLDPE were melt blended. Then the molecular and crystalline structures of the blends were examined by physical evaluations, including FTIR, DSC, WAXS and SAXS measurements, and microscopic observations, i.e. TOM and FE-SEM techniques. To determine the relation of microstructure and mechanical properties, low strain tensile properties such as elastic modulus, yield strength and elongation to yield percent were measured. According to physical results, the microstructure depends on the ratio of the components. Generally, crystalline structure of the blends includes two types of crystals: 1- HDPE-rich Crystals contain LLDPE and partial amount of LDPE and 2- LDPE-rich crystals contain LLDPE. In blends with 40 wt. % HDPE, phase separation of the components overcomes to their co-crystallization and the tensile properties of these blends strongly depend on the LDPE-rich tiny crystals. Likely, the LDPE-rich crystals reinforce the amorphous phase and tie molecules. In blends with 60 wt. % HDPE, the co-crystallization of the components precedes the phase separation and tensile properties are a function of the HDPE-rich lamellae thickness and crystallinity of the blend. Finally, in blends with 50 wt. % HDPE, the competition between phase separation and co-crystallization phenomena determines the microstructure and mechanical properties. In other words, microstructure and mechanical properties are composition dependent
  9. Keywords:
  10. High Density Polyethylene ; Low Density Poly Ethylene(LDPE) ; Mechanical Properties ; Microstructure ; Linear Low Density Poly Ethylene ; Ternary Blends ; Components Ratio

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