PROCESSING AND PROPERTIES OF THERMOPLASTIC COMPOSITES CONTAINING GRAPHENE NANOPLATELETS
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Authors
Ho, Quang Binh
Date
Type
thesis
Language
eng
Keyword
Graphene nanoplatelets , Graphene , Thermoplastic composites , Nanocomposites , Graphite , Graphene polyamide composites , Graphene polypropylene composites , Polypropylene foams , Composite foams , GNP , Exfoliation , Compatibilized composites , Graphene nanocomposites , Thermoplastic foams , Fused deposition modeling , Material extrusion , Interfacial adhesion , Interfacial diffusion
Alternative Title
Abstract
The objective of this thesis is to develop thermoplastic composites containing expanded graphite (EG) and graphene nanoplatelets (GNPs) using an industrially-relevant melt compounding method. Improvements in the mechanical, electrical, thermal, rheological properties were examined and interpreted based on filler dispersion and composite morphology.
Polyamide (PA) composites containing well-dispersed, in-situ delaminated GNPs were prepared by melt compounding. Results from scanning electron microscopy, transmission electron microscopy and 3D tomography showed good dispersion of GNPs, which is attributed to the similar surface energies of PA and GNPs. The electrical, thermal, and mechanical properties of the composites were investigated: the electrical percolation threshold was attained at 1.9 vol.% GNPs; the thermal conductivity of 2.5 W‧m-1‧K-1 was obtained at 8 vol.% GNPs; the flexural modulus was 5057 MPa at 15 vol.% GNPs. The impact strength of 64 J/m was achieved by adding an elastomeric impact modifier at 40 wt.%.
GNPs with a specific surface area of 400 m2/g were prepared from EG by thermomechanical exfoliation. A compatibilization approach involving the functionalization of polypropylene (PP) with pyridine moieties was implemented to disperse the fillers in PP. The electrical percolation thresholds were 6 vol.% and 10 vol.% in the compatibilized PP-EG and PP-GNP composites respectively; the maximum electrical conductivity was 10-1 S/m. The GNPs increased the flexural modulus by as much as 95% compared to the unfilled PP, whereas the impact strength remained unaffected up to 10 wt.% GNPs. The EG and GNPs promoted heterogeneous nucleation in the foaming of PP using nitrogen as a blowing agent. The foams had cell densities in the order of 107 cells/cm3, fine cellular structure in the range of 20 μm – 60 μm in diameter, and a five-fold increase in the compressive modulus compared to the neat PP foam.
Finally, this thesis examines the effects of the thermorheological properties of PP blends and composites containing GNPs on the material extrusion characteristics, the interfacial adhesion, and the mechanical properties of the built structures. An elastomeric ethylene-octene copolymer was added at 20 – 40 wt.% to the formulations to improve the interfacial adhesion. The alignment of GNPs during processing resulted in anisotropy in thermal and flexural properties.
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Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada
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Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
CC0 1.0 Universal
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
CC0 1.0 Universal