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Structural and Physical Effects of Carbon Nanofillers in Thermoplastic and Thermosetting Polymer Systems
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Ever since the discovery of carbon nano materials like carbon nanotube (CNT) and graphene, this class of materials has gained significant attention due to their exotic properties. The principle idea of my present research project is to understand the novel improvements induced in polymer matrices with inclusion of the nanofillers. This thesis is thematically divided into three parts.

In the first part we introduce principle materials that we use for preparation of composites. Methods of nanofiller preparation and different nanocomposites as previously reported in literature are discussed to formulate the basis of our study. Different dispersion techniques are discussed which facilitate uniform nanofiller distribution. A variety of experimental methods are described which were employed to investigate the structure and properties of the composites.

In the second part we discuss in details polyamide-12 (PA12) composites using CNT and graphene as fillers. A marked improvement is recorded in the toughness of the films with incorporation of CNT, dispersed in PA12 using a surfactant. Electrical percolation is also achieved in the otherwise insulating matrix. With PA-12 fibers we explored the effect of fiber processing and CNT incorporation in the mechanical properties. Extensive wide angle x-ray diffraction was carried out to interpret the structural modifications brought about by CNT in the matrix.

The final part of the thesis deals with a thermosetting polymer, epoxy composites. CNT, Graphene and also a mixture of the two nanofillers were used as reinforcing agents. Appreciable improvement was recorded in the mechanical properties, electrical and thermal conductivity of the composites. Detailed optical and electron microscopy was carried out to get a vivid idea of the micro-structure and dispersion.

The presented work demonstrates the significant ability of carbon nanofillers to reinforce polymer matrices enhancing their mechanical, electrical and thermal properties and opening a wide horizon for a variety of applications.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. , p. xiv+96
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 913
Keywords [en]
Polymer, Composite, Carbon nanotube, Graphene
National Category
Composite Science and Engineering
Identifiers
URN: urn:nbn:se:uu:diva-171449ISBN: 978-91-554-8315-9 (print)OAI: oai:DiVA.org:uu-171449DiVA, id: diva2:510866
Public defence
2012-05-04, Polhelmssalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2012-04-11 Created: 2012-03-19 Last updated: 2012-04-19
List of papers
1. Improvement of toughness and electrical properties of epoxy composites with carbon nanotubes prepared by industrially relevant processes
Open this publication in new window or tab >>Improvement of toughness and electrical properties of epoxy composites with carbon nanotubes prepared by industrially relevant processes
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2011 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 22, no 12, p. 125702-Article in journal (Refereed) Published
Abstract [en]

The addition of carbon nanotubes (CNTs) to polymeric matrices or master batches has thepotential to provide composites with novel properties. However, composites with a uniformdispersion of CNTs have proved to be difficult to manufacture, especially at an industrial scale.This paper reports on processing methods that overcome problems related to the control andreproducibility of dispersions. By using a high pressure homogenizer and a three-rollcalendaring mill in combination, CNT reinforced epoxies were fabricated by mould castingwith a well dispersed nanofiller content from 0.1 to 2 wt%. The influence of the nano-carbonreinforcements on toughness and electrical properties of the CNT/epoxies was studied. Asubstantial increase of all mechanical properties already appeared at the lowest CNT content of0.1 wt%, but further raising the nanofiller concentration only led to moderate further changes.The most significant enhancement was obtained for fracture toughness, reaching up to 82%.The low percolation thresholds were confirmed by electrical conductivity measurements on thesame composites yielding a threshold value of only about 0.01 wt%. As corroborated by athorough microscopic analysis of the composites, mechanical and electrical enhancement pointsto the formation of an interconnected network of agglomerated CNTs.

Keywords
CNT, Epoxy
National Category
Composite Science and Engineering
Research subject
Materials Science
Identifiers
urn:nbn:se:uu:diva-169989 (URN)10.1088/0957-4484/22/12/125702 (DOI)
Available from: 2012-03-13 Created: 2012-03-07 Last updated: 2017-12-07Bibliographically approved
2. Comparing carbon nanotubes and graphene nanoplatelets as reinforcements in polyamide 12 composites
Open this publication in new window or tab >>Comparing carbon nanotubes and graphene nanoplatelets as reinforcements in polyamide 12 composites
2011 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 22, no 27, p. 275714-Article in journal (Refereed) Published
Abstract [en]

We investigate the influence of nanofillers including carbon nanotubes (CNTs) and graphene nanoplatelets on a thermoplastic engineering polymer, polyamide 12 (PA12). The comparison between these two important nanofillers as to how they influence the structure and properties of the polymer is systematically studied. The polymer–nanofiller composites were prepared using a twin-screw micro-extruder and the composite was thereafter hot pressed into thin films. The structure (using wide angle x-ray diffraction and differential scanning calorimetry) and properties (through tensile testing and conductivity measurement) of the thin films have been investigated. The composites incorporating surfactant showed the best CNT distribution and dispersion, causing an improvement of up to 80% in the toughness modulus over pure PA12. Electrical percolation could also be achieved at nanofiller concentrations of 1 to 2 wt%. In this study we observed that CNT fillers bring about more pronounced improvements in PA12 compared to graphene nanoplatelets, as far as mechanical and electrical properties are concerned.

Keywords
CNT, Polymer composite, Graphene
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-168031 (URN)10.1088/0957-4484/22/27/275714 (DOI)
Available from: 2012-02-06 Created: 2012-02-03 Last updated: 2017-12-08Bibliographically approved
3. Investigation of crystalline and tensile properties of carbon nanotube-filled polyamide-12 fibers melt-spun by industry-related processes
Open this publication in new window or tab >>Investigation of crystalline and tensile properties of carbon nanotube-filled polyamide-12 fibers melt-spun by industry-related processes
2012 (English)In: Journal of Engineered Fibers and Fabrics, ISSN 1558-9250, E-ISSN 1558-9250, Vol. 7, no 3Article in journal (Refereed) Published
Abstract [en]

The paper addresses the influence of carbon nanotubes (CNT) on the structure and mechanical properties of high tensile strength thermoplasticpolymer fibers. Polyamide (PA) fibers with different draw ratios, with and without CNTs as fillers, and having mechanical properties close to industrial standards were spun in a pilot melt spinning plant. The morphology of the fibers was investigated using optical microscopy, nuclear magnetic resonance (NMR) and 2-D wide angle x-ray diffraction (WAXD). Differential scanning calorimetry (DSC) was carried out to get an estimation of the crystallinity. For a concise interpretation of the results of tensile measurements performed on the fibers, a parameter was developed to account for the detrimental influence of polymer extrusion on their mechanical properties. CNTs seem to act as sites for the growth of un-oriented crystalline domains converted from oriented regions, without yielding a mechanical reinforcing effect.

National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:uu:diva-169990 (URN)
Available from: 2012-03-13 Created: 2012-03-07 Last updated: 2017-12-07Bibliographically approved
4. Mechanical reinforcement and thermal conductivity in expanded graphene nanoplatelets reinforced epoxy composites
Open this publication in new window or tab >>Mechanical reinforcement and thermal conductivity in expanded graphene nanoplatelets reinforced epoxy composites
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2012 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 531, p. 6-10Article in journal (Refereed) Published
Abstract [en]

Influence of reinforcements on mechanical and thermal properties of graphene nanoplatelets/epoxy com-posites is investigated. Amine functionalized expanded graphene nanoplatelets (EGNPs) were dispersed within epoxy resins using high-pressure processor followed by three roll milling. Functionality on the EGNPs was confirmed with FTIR and micro-Raman spectroscopy. Bending and nano-mechanical testingwas performed on the composites. Incorporation of EGNPs improved the flexural modulus and hardness of the composite and increased fracture toughness by up to 60%. Marked improvement was observed inthermal conductivity of the composites reaching 36% at 2 wt.% loading. Functionalized EGNPs exhibited significant improvements indicating favorable interaction at EGNPs/polymer interface.

National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:uu:diva-169994 (URN)10.1016/j.cplett.2012.02.006 (DOI)
Available from: 2012-03-13 Created: 2012-03-07 Last updated: 2017-12-07Bibliographically approved
5. The size and synergy effects of graphene nanoplatelets andcarbon nanotubes in mechanical properties of epoxy composites.
Open this publication in new window or tab >>The size and synergy effects of graphene nanoplatelets andcarbon nanotubes in mechanical properties of epoxy composites.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

We study mechanical reinforcement in a widely used epoxy matrix with the addition of graphenenanoplatelets (GnPs) and various mixture ratios of carbon nanotubes (CNTs) withGnPs. Two different dimensions of GnPs were used with flake sizes of 5 mm and 25 mm toinvestigate the influence of nanofiller size on the composite properties. In the GnP reinforcedcomposites, the bigger flakes showed greater reinforcement at all GnP concentrations. The influenceof size on properties is significant as bigger flakes actively control the failure mechanismsin the composite. In the mixture samples, highest CNT content (9:1) showed significantimprovement in fracture toughness of 76 %. For composites with mixtures of CNTs andGnPs, the CNT:GnP ratio is an interesting factor significantly influencing the properties ofthe epoxy matrix. The combination of high aspect ratio of CNTs and larger surface area ofGnPs contribute to the synergistic effect of the CNT-GnP hybrid samples. Thermal conductivityconsistently increases with the incorporation of GnPs in the matrix. Transmission electronmicroscopy (TEM) images confirm the uniform nanofiller dispersion achieved in thecomposites with GnP. For the hybrid samples the CNTs are seen to align themselves on theGnP flakes creating an inter-connected strong nanofiller network in the matrix. The homogenousnanofiller dispersions have been achieved by high shear calendaring which is a methodcapable of being industrially scaled up.

National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:uu:diva-171572 (URN)
Available from: 2012-03-22 Created: 2012-03-21 Last updated: 2012-04-13Bibliographically approved

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