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Thermal Decomposition, Thermal Stability, and Flammability Properties of Hybrid Graphene/Clay Polyimide Nanocomposites.

Akinyi, Caroline
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1692272773468514

Abstract Details

2023, PhD, University of Cincinnati, Engineering and Applied Science: Materials Science.
Polyimides have gained more attention in recent years due to their high thermal stability, good interfacial bonding, light weight, and good wear resistance and corrosion, factors that make them find great applications in the field of aerospace and advanced equipment. Many advancements have been made in improving the thermal, mechanical, and wear properties of polyimides. The use of nanofillers such as carbon nanotubes, graphene, graphene oxide, clay, and alumina has been studied. Some challenges with nanofillers are dispersion in the polymer matrix and interfacial adhesion; this has led to surface modification of the fillers. Differential scanning calorimetry and thermogravimetric analysis were used to study the thermal degradation, stability, and the heat of decomposition of polyimide-graphene and polyimide-graphene-clay nanocomposites. Polyimide-graphene nanocomposites containing 10, 20, 30, 40, and 50 wt.% of multilayered graphene sheets were heated at a rate of 10 and 30 °C/min in air and in nitrogen atmosphere, respectively. The rate of mass loss was found to remarkably decrease by up to 198% for nanocomposites containing 50 wt.% of graphene. The enthalpy change resulting from the decomposition of the imide ring was found to decrease by 1166% in nitrogen atmosphere, indicating the outstanding heat-shielding properties of multilayered graphene sheets due to their high thermal conductivity. The enthalpy changes due to combustion, obtained from differential scanning calorimetry, were used to calculate the theoretical heat release rates, a major parameter in the determination of flammability of polymers. The heat release rate decreased by 62% for composites containing 10 wt.% of graphene compared to the neat polyimide matrix. The combined interaction of graphene and polyimide led to an overall decrease in the heat release rate. Thermogravimetric data was used to predict the limiting oxygen index of the neat polyimide and the nanocomposites. The limiting oxygen index of the polyimide nanocomposite was calculated by using the char retention, and it was found to increase by up to 24% at 50 wt.% graphene loading over that of the neat matrix. The interaction between clay and graphene to enhance the thermal and thermo-oxidative stability of the nanocomposites was studied. Polyimide-graphene nanocomposite containing approximately 12.48 vol.% graphene was used as the base nanocomposite, into which varying amounts of clay were added (0.45–9 vol.% clay). Thermogravimetric studies in nitrogen and air atmospheres showed an improvement in thermal decomposition temperature by up to 50 °C. The presence of both fillers leads to increased restriction in the mobility of polymer chains, and thus assists in char formation. It was observed that the presence of clay led to higher decomposition temperatures of the char formed in air atmosphere (up to 80 °C higher). This led to the conclusion that clay interacts with graphene in a synergistic manner, hence improving the overall stability of the polyimide-graphene-clay nanocomposites.
Jude Iroh, Ph.D. (Committee Chair)
Vesselin Shanov, Ph.D. (Committee Member)
Yoonjee Park, Ph.D. (Committee Member)
Peter Disimile, Ph.D. (Committee Member)
131 p.
Materials Science
Polyimide; Imidization; Clay; Nanocomposites; Graphene; Thermogravimetric Analysis

Recommended Citations

Citations

  • Akinyi, C. (2023). Thermal Decomposition, Thermal Stability, and Flammability Properties of Hybrid Graphene/Clay Polyimide Nanocomposites. [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1692272773468514

    APA Style (7th edition)

  • Akinyi, Caroline. Thermal Decomposition, Thermal Stability, and Flammability Properties of Hybrid Graphene/Clay Polyimide Nanocomposites. 2023. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1692272773468514.

    MLA Style (8th edition)

  • Akinyi, Caroline. "Thermal Decomposition, Thermal Stability, and Flammability Properties of Hybrid Graphene/Clay Polyimide Nanocomposites." Doctoral dissertation, University of Cincinnati, 2023. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1692272773468514

    Chicago Manual of Style (17th edition)

ucin1692272773468514
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This open access ETD is published by University of Cincinnati and OhioLINK.
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