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Study of Fracture Behavior of Hybrid Polypropylene-Based Composites Containing Glass and Basalt Fibers

Sadeghi Nejad Parizi, Mohammad Reza | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57682 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Bagheri, Reza
  7. Abstract:
  8. The use of multi-layer random polypropylene (PPR) pipes of pipe-grade is expanding in the construction industry. The middle layer of these pipes is traditionally reinforced with glass fibers to meet the temperature and internal pressure conditions of the pipe. In recent years, with the aim of improving the lifespan and efficiency of these pipes and considering the perspective of using natural materials instead of synthetic materials, the use of basalt fibers has also been on the agenda of the pioneers of this industry. Basalt fibers are natural mineral fibers obtained from volcanic rocks. Compared to glass fibers, basalt fibers have approximately 5% higher density; however, their tensile, compressive, and elastic modulus are 15-20% higher. Moreover, these fibers provide good thermal and acoustic insulation, and since they are produced from renewable resources, replacing glass fibers with basalt fibers is considered a move toward environmental protection. The use of natural materials in the industry may have negative consequences due to their unstable properties. This research, carried out in three separate phases, involved the production of PP/20GF and PP/20BF composites using a twin-screw extruder, and hybrid composites containing both types of glass and basalt fibers were manufactured using an injection molding machine. In the first phase, an attempt was made to study the properties by manufacturing PP/20GF, PP/20BF composites, and a hybrid composite containing both types of glass and basalt fibers. In the second phase of the research, efforts were focused on manufacturing the optimal PP/20B composite to achieve proper adhesion between the fibers and the substrate, while also ensuring optimal mechanical properties for this composite. In the third phase of the research, hybrid composites containing both glass and basalt fibers were manufactured using the optimal composite from the second phase. In all three research phases, the produced specimens were subjected to tensile and impact tests to evaluate the mechanical properties. Transmission optical microscopy (TOM) and field emission scanning electron microscopy (FESEM) were used to evaluate the fracture behavior of the samples. Differential scanning calorimetry (DSC) was also employed to evaluate the crystal structure of the samples. The results of the research in the first phase demonstrated that in the PP/20GF composite, the use of 1.7% compatibilizer ensured proper adhesion between the fibers and the matrix; however, this amount of compatibilizer was not sufficient for the PP/20B composite. As a result, the second phase of the research was planned and carried out. In the second phase, it was determined that the PP/20B composite with 7.5% compatibilizer had optimal mechanical properties among other samples and proper adhesion between the fibers and its matrix. Consequently, this sample was used in the manufacture of hybrid composites containing both types of glass and basalt fibers in the third phase of the research. In the third phase, it was determined that the PP/10GF/10BF sample had the highest crystallinity percentage among all the produced samples. The results of the tensile test to evaluate tensile strength for the samples in the third phase also indicated that the PP/15GF/5BF and PP/10GF/10BF samples increased this parameter by about 130% and 126%, respectively, compared to the pure polypropylene sample. Additionally, the impact test results in the third phase of the research revealed that the simultaneous addition of both types of glass and basalt fibers to the polypropylene matrix in the PP/10GF/10BF sample increased impact resistance by approximately 30% compared to the pure polypropylene sample. This composite showed the highest impact resistance among all the produced samples, making it highly significant for applications in the pipe industry
  9. Keywords:
  10. Hybrid Composite ; Compatibilizer ; Basalt Reinforcing Fiber ; Pipe Grade Polypropylene ; Glass Reinforcing Fiber

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