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Fabrication and Study of Mechanical Behavior of in Situ Microfibrillar- Reinforced Composites of Polypropylene/Recycled Poly (Ethylene Terephthalate)Toughened with Rubber Particles

Motahari, Tayebeh | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53760 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Bagheri, Reza; Alizadeh, Reza
  7. Abstract:
  8. The use of polymers is increasing day by day due to low density, reasonable price and ability to produce different products. On the other hand, the accumulation of polymer wastes in nature is one of the environmental concerns in today's world, which is mainly due to the widespread use of polymers in the packaging industry and disposable applications. In order to solve this problem, recycling is recommended as the most appropriate and economical solution. Because in addition to consuming polymer waste, it also saves energy and reduces carbon footprint.Polyethylene terephthalate (PET) is one of the polymeric materials which; It has a special place in the packaging industry and is widely used in the manufacture of bottles of beverages. This has made the effort to recycle PET one of the most attractive topics for researchers and industry owners. One of the proposed solutions for recycling PET bottles is its use in the manufacture of polypropylene (PP) based mixtures.In the present project, PET resulting from bottle milling was added to an injection grade polypropylene as a second phase. Blending was performed using a two-screw extruder under the condition that PET particles were distributed in the form of micron-sized fibers in the field. Also, to modify the toughness of microfiber composite, two types of polyolefin elastomers were used in the composition of the mixtures. The rheological behavior of the materials was studied with the aim of modifying the blending process and achieving a microfiber structure. The microstructure of the mixtures was examined by scanning differential calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Tensile and impact tests were used to study the mechanical behavior and light transmission microscopy (TOM) was used to study the mechanism of toughness of the compounds. The results of this study showed that recycled polyethylene terephthalate can act as a germination agent for polypropylene and increase the crystallization temperature of the field by 10 .C. The size of polypropylene spherolites decreased sharply in the presence of PET. A limited amount of β crystals was also observed in the composite samples, which was not seen in the base polymer. The best results were observed in the formation of microfibrillar structure in the sample containing 15% wt of recycled polyethylene terephthalate, the diameter of the fibrils in this sample reached the range of 1-10 micrometers.Mechanical tests showed the highest increase in elastic modulus in a sample containing 20% wt recycled polyethylene terephthalate. Although the impact strength of polypropylene was reduced by about 15% with the addition of PET, the addition of elastomer increased the impact strength values by about 2 times. Microscopic examination of the top of the crack confirmed that the presence of the rubber phase encouraged the underlying polymer to deform the plastic and spread the microcracks in the top of the crack.
  9. Keywords:
  10. Injection Molding ; Polyethylene Terephthalate ; Rubber Toughening ; Recycled Ploypropylene ; Microfibrillar Reinforced Composites ; Microstructure Control ; Recycled Polyethylene Terephthalate (PET)

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