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Graphite Nanoplatelet Filler-Modified Polyurethane Nanocomposites for Thermal Transport Enhancement Open Access


Other title
thermal conductivity
graphite nanoplatelets
Type of item
Degree grantor
University of Alberta
Author or creator
Akram, Usama
Supervisor and department
McDonald, André (Department of Mechanical Engineering)
Mertiny, Pierre (Department of Mechanical Engineering)
Examining committee member and department
McDonald, André (Department of Mechanical Engineering)
Mertiny, Pierre (Department of Mechanical Engineering)
Tsai, Peichun Amy (Department of Mechanical Engineering)
Chung, Hyun-Joong (Department of Chemical and Materials Engineering)
Department of Mechanical Engineering

Date accepted
Graduation date
2017-11:Fall 2017
Master of Science
Degree level
The use of polymers in applications such as electronic packaging, heat exchangers, and thermal pastes is limited by their inability to dissipate accumulated heat effectively. Nano-scale filler modifiers may be used to improve the transport of thermal energy through polymer materials. Studies of thermally-enhanced polymer nanocomposites have shown minimal enhancement by filler addition due to the presence of an interfacial or Kapitza resistance caused by phonon mismatch. In this study, a graphite nanoplatelet (GNP) filler modifier was added to polyurethane (PU) that is typically used in high wear applications. Due to PU’s low thermal conductivity of 0.2 W/m-K, accumulated heat can cause degradation and early failure. A specialized curing chamber, allowing for the application of heat and high vacuum pressure was used to produce high quality nanocomposite specimens with minimal void content. GNP-PU specimens modified with up to 4% GNP filler weight content were produced through solution blending. X-Ray Diffraction (XRD) analysis performed on the specimens to investigate filler dispersion suggested that no intercalation or exfoliation of the nanofillers had occurred. The bulk thermal conductivity of the filler-modified PU specimens was tested using the hot disk method. A linear enhancement trend, reaching a maximum bulk conductivity value of 0.43 W/m-K, with no percolating behavior, was observed for the thermal conductivity of the GNP-PU modified nanocomposite. These experimental values were found upon comparison to be in agreement with results of second-order analytical models based on the series model. Differential scanning calorimetry (DSC) was performed to measure the specific heat capacity of the test specimens for anisotropic hot disk testing. Results of anisotropic hot disk testing showed a higher in-plane thermal conductivity value as compared to thermal conductivity in the through-thickness direction in all modified specimens. Further compression testing and hot disk analysis at various probing depths suggested filler alignment in the in-plane direction as well as GNP settlement at the base of the nanocomposite specimens.
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