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An Investigation on Mechanical Behavior of Polypropylene/Polyethylene Blend - Calcium Carbonate Nano Composite

Shayesteh Zeraati, Ali | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41119 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Bagheri, Reza
  7. Abstract:
  8. Polymer blending has an important role in preparation of materials with suitable properties without synthesizing new polymers. One of these blends is polypropylene (PP)/ polyethylene (PE). PE is added for improving the impact strength and toughness of PP. For improvementof the properties, a compatibilizer is used due to incompatibility of the PP/PE blend. Improving the impact properties is usually related to the reduction in stiffness. Considering the importance of stiffness in many industrial applications, mineral fillers are employed for increasing the stiffness. In this research, the goal has been to manufacture polypropylene-based ternary composite(Polypropylene/ Polyethylene/Nanometric calcium carbonate) in order to obtain mixtures with high toughness and stiffness. First, by making binary and ternary blend of PP/PE with and without compatibilizer, the effect of high density polyethylene (HDPE) on physical, mechanical, and deformation micromechanisms of PP were investigated. Then, by tailoring of these blends, nanocomposites in the presence of Nanometric calcium carbonate were prepared. Physical properties and deformation micromechanisms were studied by XRD, DSC, TOM, and SEM techniques and mechanical properties were evaluated via tensile and impact tests. Results show that adding HDPE to PP makes significant changes in crystallization behavior. Synergism was observed in modulus, yield, and impact strength. Adding of up to 10 percent HDPE caused the modulus, yield, and impact strength to improve 5%, 4%, and 59%, respectively. In the presence of compatibilizer, impact strength shows higher enhancement (80% for a 10-percent HDPE) while synergism in modulus and yield strength was still observed. Fracture micromechanism for PP, being firstly single crazing, changes to multiple crazing in the presence of HDPE. Ten-percent-HDPE blends with/without compatibilizer were selected to make the nanocomposites. By adding nanometric calcium carbonate to the blends, modulus was improved but yield and impact strengths were deteriorated. Increase in the elastic modulus reaches 20% for up to 15 percent calcium carbonate. Crazing and shear yielding are fracture micromechanisms in the presence of nano particles
  9. Keywords:
  10. Polypropylene ; Polyethylene ; Nanometric Calcium Carbonate ; Toughness ; Rigidity ; Impact Strength

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