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Investigation of the Effect of Nanosilica Surface Modification on Crystalline Microstructure and Rheological and Mechanical Properties of High Density Polyethylene (HDPE)

Pourjabbari Khameneh, Reyhaneh | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58318 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Pircheraghi, Gholamreza
  7. Abstract:
  8. A high flexural modulus and high elasticity are essential for corrugated pipes used for underground wastewater transportation. High density polyethylene (HDPE), a semi-crystalline polymer, is commonly used for the production of these pipes. In this study, a nanocomposite approach was used in which recycled nano-silica from lead-acid battery separators was incorporated in weight fractions of 1%, 3% and 5% to increase the modulus. To improve the dispersion of the nano-silica particles in the polymer matrix and thus the mechanical properties, the nano-silica particles were surface modified with 3-aminopropyltriethoxysilane as coupling agent together with a maleic anhydride grafted HDPE compatibilizer. First, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller analysis (BET) were performed to evaluate the success of the surface modification process, and the results confirmed the successful modification. Subsequently, the effects of the surface modification on the microstructure, thermal properties, mechanical properties and rheological behavior were investigated. Based on the results, a weight fraction of 3% was chosen as the optimum dosage of nano-silica in this study. The addition of 3% by weight of modified nano-silica increased the relative crystallinity by about 27% compared to HDPE. The modulus of elasticity (23%), elongation at break (19%) and yield strength (2%) of the composite sample with 3 wt% modified nano-silica improved compared to HDPE. The increase in flexural strength and flexural modulus for this sample was 12% and 20%, respectively, compared to HDPE. The reduction in impact strength for this sample was less than for the sample with unmodified nano-silica (47%) and amounted to approximately 39%. The results of the rheological frequency sweep tests also showed that the values of terminal viscosity and dynamic moduli in the samples with 3 wt% modified and unmodified nano-silica were higher than the corresponding values for the matrix. Microstructural studies using field emission scanning electron microscopy (FE-SEM) showed a better dispersion of the modified nano-silica particles in the matrix and a better interaction with the polymer matrix compared to the unmodified nano-silica particles
  9. Keywords:
  10. High Density Polyethylene ; Recycled Nanosilica ; Surface Modification ; Microstructure ; Thermal Properties ; Mechanical Properties ; Rheological Properties

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