1,720,991 research outputs found
GNP DISPERSION BY REACTIVE EXTRUSION FOR THERMALLY CONDUCTIVE POLYMER NANOCOMPOSITES
No full textThermally conductive polymer nanocomposites are of great interest in substituting metal components in all those applications where corrosion resistance, lightweight and processability are required. Nanoparticles with extremely high thermal conductivity (Carbon Nanotubes, Graphene and Graphene Nanoplatelets, hexagonal Boron Nitride) are expected to confer a huge improvement to polymer thermal properties. Recently, Graphene Nanoplatelets (GNP) have become an interesting option due to their geometry, which allows to obtain an higher contact between nanoparticles [1,2,3]. However, it is critical to obtain a good dispersion degree of GNP in polymer matrix, especially during melt mixing. In this work, a GNP with an expanded structure has been melt mixed with cyclic butylene terephthalate (CBT). These mixed oligomers are known to have a very low viscosity that can allow to a complete filling of the expanded structure, which is preliminar to the obtainment of a good exfoliation degree. This can lead to an higher contact between nanoparticles, with a consequent improvement in the thermal conductivity of the nanocomposite. Moreover, in a second step, during melt mixing a tin catalyst was added to the compound; this is known to open the cyclic structure, starting CBT polymerization into poly (butylene terephthalate) (pCBT). During polymerization the molecular weight, and the viscosity, of the molten system increase, and consequently raise the shear stresses that can have a key role in the optimization of the exfoliation degree. This, combined to the higher crystallinity of pCBT respect to CBT, can push to the obtainment of high thermally conductive polymer nanocomposite
Thermally conductive polymer/graphene-related materials nanocomposites prepared by melt reactive processing
Full text linkPolymer nanocomposites containing graphene-related materials attracted a wide research interest thanks to the combination of the processability, lightweight and corrosion resistance typical of polymers, with the outstanding properties of graphene-related materials, including mechanical properties, thermal conductivity and electrical conductivity. Nanocomposites exploiting graphene-related materials are indeed showing interesting properties and several industrial applications for such nanomaterials are currently being developed, including structural materials, as well as functional materials, electrodes and conductors in flexible electronics, waste heat management, gas-barrier materials, etc., also taking into advantage of the large European initiative for graphene research, development and application called Graphene Flagship (http://graphene-flagship.eu/). This thesis aims to the preparation of polymer nanocomposites, exploiting graphene-related materials, by the development of industrially viable preparation methods, for the application as heat management materials. These are currently of interest in several application fields, including low temperature heat recovery, heat exchange in highly corrosive environments as well as heat dissipation in electronics and flexible electronics. Beside the thermal conductivity property, this PhD thesis was aimed at the fundamental understanding of phenomena controlling nanoparticle dispersion into the polymer matrix as well as the correlations between structure and properties of the prepared materials, including electrical conductivity, rheological properties and polymer crystallization phenomena. As the availability of graphene (i.e. a single layer of sp2 carbons) nanoflakes remains extremely limited and insufficient for the exploitation in large scale applications embedding graphene in the polymer bulk, different types of graphene-related materials were selected for exploitation in this PhD thesis, namely graphite nanoplatelets (GNP) and reduced graphene oxide (rGO). In particular, different grades of GNP and rGO were selected aiming at the correlation between their quality, mainly in terms of defectiveness and aspect ratio, and the properties of their corresponding polymer nanocomposite. For these reasons, the initial part of this thesis is focused on thorough characterization of nanoflake quality, i.e. defectiveness and aspect ratio, through electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis. On the other hand, the second part is focused on the preparation and detailed characterization of nanocomposites prepared by ring opening polymerization of polyester oligomers (CBT) during melt mixing in presence of graphene-related materials. In particular, the effects of the exploitation of different graphene-related materials, of the polymerization during reactive mixing and of the processing parameters (processing temperature, time and shear rate) on the electrical and thermal properties of polymer nanocomposites is addressed. Thorough characterization of the effect of the exploitation of pristine and high temperature-annealed reduced graphene oxide on the nanocomposite properties is also reported, in terms of both of conductivities and modification in the crystallization of the polymer matrix. The results reported in this thesis demonstrate the viability of CBT polymerization during melt mixing with graphene-related materials to produce thermally and electrically conductive polymer nanocomposites aiming at possible industrial applications
Aging of EVA/organically modified clay: Effect on dispersion, distribution and combustion behavior
No full textHeating of polymer layered silicates nanocomposites, under air, promotes lamellas migration toward the surface. In this communication we show that aging a poly[ethylene-co-(vinylacetate)] (EVA)-organically modified clay (Cloisite 20A) nanocomposite, at temperature close to the melting point, strongly affects its combustion behavior. The thermal treatment leads to lamella exfoliation which allows an easier migration of the clay toward the surface during the early stage of combustion. This promotes the formation of a thin film, made of lamellas and polymer matrix, that traps the volatile degradation products and enormously delay the time to ignition. At the end of the combustion the film is, however, preserved
Invecchiamento di nanocompositi EVA/C20A: effetti su dispersione, distribuzione e com¬portamento alla combustione
No full textCarbon Nanotubes migration and segregation at the interface in immiscible polymer blends
No full textSelective localization of nanoparticles in immiscible polymer blends, during melt blending, is a well-known phenomenon[1] for different kind of particles, such as lamellar clays [2], carbon black and carbon nanotubes[3], nanographite[4], etc. Particles distribution in polymer blends prepared by melt blending depends both from thermodynamic (interfacial tensions) and kinetic (viscosity, time, temperatures) factors. In this work from has been studied the diffusion of CNT from a PP matrix to another polymer (PVC or PA6
Graphene nanoplatelets for thermally conductive polymer nanocomposites
No full textThermally conductive polymer composites offer new possibilities for replacing metal parts in low temperature heat exchangers, thanks to the polymer advantages such as light weight, corrosion resistance and ease of processing. The search for polymer based materials that conduct heat well has become essential for several applications. Current interest to improve the thermal conductivity of polymers is focused on the selective addition of nanofillers with high thermal conductivity, like carbon nanotubes (CNTs) and graphene nanoplatelets (GNP). However, to exploit the potential of such nanoparticles, both the dispersion of nanoparticles and the properties of thermal interfaces between nanoparticles (the two main limitations) has to be carefully designed and controlle
GRAPHITE NANOPLATELETS DISPERSION BY MELT REACTIVE EXTRUSION FOR THE PREPARATION OF THERMALLY CONDUCTIVE POLYMER NANOCOMPOSITES
No full textGraphene nanoplatelets per la preparazione di nanocompositi polimerici termicamente conduttivi
No full textGRAPHITE NANOPLATELETS DISPERSION BY MELT REACTIVE EXTRUSION FOR THE PREPARATION OF THERMALLY CONDUCTIVE POLYMER NANOCOMPOSITES
No full textThermally conductive polymer nanocomposites are of great interest in substituting metal components in all those applications where corrosion resistance, lightweight and ease of processability are required. Graphene NanoPlatelets (GNP) are promising nanofillers thanks to their geometry, which allows to obtain an higher contact area between particles in composites [1,2,3]. However, it is often critical to obtain a good dispersion degree of GNP. In this work, different types of GNPs have been melt mixed with cyclic butylene terephthalate (CBT), being low viscosity oligomers which polymerize during melt mixing in the presence of an appropriate catalyst. Thermal conductivity of the polymer nanocomposite is measured and correlated to dispersion obtained and GNP propertie
Migrazione e segregazione di nanotubi di carbonio all’interfaccia tra polimeri immiscibili
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