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Controlling the Crystal Structure and Mechanical Properties of Random Polypropylene: the Role of Beta Nucleating Agent, Isotactic Polypropylene and Glass Fibers

Ghorbani, Hamed | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57510 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Bagheri, Reza
  7. Abstract:
  8. Compared to block copolymer, random copolymer polypropylene (PPR) has lower toughness and impact resistance, and this defect creates limitations in the use of this polymer in some applications, including in the pipe industry. Creating a beta crystal structure in random polypropylene with the help of nucleating agent is a well-known method to solve this weakness. Following the previous activities in this group, the current research was defined based on the construction of beta nucleator based on calcium pimalat and its use in pipe-grade random polypropylene. Four methods were used to add germinating agent to polymer in this research. Synthesis of germinating agent and then adding it to the polymer directly (1) or with the help of a masterbatch (2) and in addition to making the germinating agent by adding its precursors to the polymer directly (3) and or in the masterbatch construction phase (4), the methods used in this research were It is worth mentioning that the masterbatch was made in two different ways, in the first case, random copolymer was used as the base of the masterbatch, and in the second case, isotectic propylene (iPP) was used as the base of the masterbatch. The samples needed for the tests were produced by compression molding method. Crystal structure evaluation was done by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) methods. Tensile and impact tests were used to investigate mechanical behavior, and transmission light microscope (TOM) and scanning electron microscope (SEM) tests were used for microstructural studies. The results of crystal structure evaluation showed that the most effective method of adding germinating agent is the use of masterbatch containing pre-synthesized germinating agent. Also, these tests showed the concentration of 0.2% as the optimal amount of germinating agent in the polymer. In addition, the highest germinating effectiveness was observed in the combination that used iPP as the base of the masterbatch. The results showed that the addition of 0.2% nucleating agent with iPP base masterbatch can increase the total amount of crystallinity in random copolymer from 23% to 51%, while 76% of the resulting crystals are beta type. The creation of this amount of beta crystal in the random copolymer increased the impact strength by 100%. Microscopic tests also showed a significant decrease in the size of spherulites with the addition of germinating agent. In the final part of this research and according to the need of the pipe industry for the combination of random copolymer reinforced with glass fibers, three samples containing 20% by weight of glass fibers were also made and identified. The results of this part of the research showed that the presence of glass fibers in the composition will not have a negative effect on the germinating performance. In addition, it was shown that the use of beta nucleator in the random copolymer composite containing glass fibers increases the impact strength by more than 40%, despite reducing the elastic modulus by a maximum of 15%
  9. Keywords:
  10. Glass Fibers ; Nucleating Agent ; Isotactic Polypropylene ; Random Polypropylene ; Beta Nucleating Agent ; Copolymer Polypropylene

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