Graphene Nanoplatelets Produced by Thermomechanical Exfoliation of Graphite, and their use in Polyamide Composites
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Authors
Mardlin, Kent
Date
Type
thesis
Language
eng
Keyword
Graphite , Graphene Nanoplatelet , Exfoliation , Thermomechanical , Characterization , Nanocomposites , Mechanical Properties , Multifunctional properties
Alternative Title
Abstract
This thesis presents a new thermomechanical exfoliation (TME) method to produce graphene nanoplatelets (GNPs) from flake graphite. GNPs having specific surface area up to ~430 m2/g are produced under the action of shear forces, which serve to delaminate graphite, using a lab-scale polymer batch mixer equipped with roller rotors at a set temperature of 250 oC and 150 rpm. The corresponding energy requirement is 35-60 kJ/g for an operation that lasts 90-100 minutes. Bulk characterization showed the resulting product comprises a mixture of up to 68 wt% GNPs, the rest of it being residual micrographite. Electron microscopy images and atomic force microscopy (AFM) revealed that the lateral dimensions of the GNP flakes are 0.1 – 1.5 µm, with thickness as low as 0.9 nm, which suggests the presence of few-layered graphene with aspect ratios up to 250.
Graphite and GNPs were used as fillers in a polyamide 6,12 (PA) matrix. Graphite increased the thermal conductivity more than GNP, up to 3-fold higher than neat PA, due to its larger particle size and therefore lower interfacial thermal resistance. GNP composites had an electrical percolation threshold of ~30 wt%, and maximum electrical conductivity of 10-1 S/m, whereas graphite did not percolate. Both fillers increased the flexural modulus up to 240% and decreased the flexural strain to 20% of the neat PA, at 40 wt% filler loading. Both fillers also increased the impact strength, but 20 wt% GNP saw the largest increase of 300%, compared to neat PA. To further improve the impact strength and the flexural strain, a maleated ethylene-octene copolymer (EOC) was added to 30 wt% GNP/PA composites. The resultant blend was still electrically conductive and up to 700% tougher than neat PA.
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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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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.