Efficiency of Microwave Heating of Weakly Loaded Polymeric Nanocomposites (original) (raw)
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Thermal conductivity of polymer nanocomposites made with carbon nanofibers
Polymer Engineering and Science, 2008
An internal mixer was used to prepare polycarbonate (PC)-based nanocomposites containing carbon fibers, carbon nanofibers (CNF), and mixtures of the two fillers. The influence of the filler volume fraction, the relative amounts of the two fillers, and the filler orientation relative to the direction of heat flow on the thermal conductivity was examined. Filler orientation was obtained by the extrusion of strands of the nanocomposite. The thermal conductivity was measured using a steady-state heat conduction technique. The CNF were fragile, and their aspect ratio could be decreased during processing. In general, the composite thermal conductivity increased with increasing filler content. Fiber alignment in the heat flux direction resulted in a significant increase in thermal conductivity. Mixing of nanofibers with microfibers resulted contacts between the microfibers. This, together with fiber alignment provided large increases in the thermal conductivity. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Polymer Engineering & Science, 2016
Carbon nanotubes dispersion within the polymer matrix is a very important factor to take into account when developing new nanocomposites with optimized properties. In this article, dispersion studies have been carried out with polypropylene filled with 1% of multiwall carbon nanotubes. The nanocomposites were obtained by melt compounding in a corotative twin screw extruder. Processing parameters as screw speed, screw configuration and feeding technology were modified to analyse their effect onto carbon nanotubes dispersion. Developed nanocomposites were exposed to microwave heating (5.8 GHz, 700 W, 60 min) and heating temperature was monitored. The relation between dispersion level of carbon nanotubes and heating effectiveness was studied. Microwave heating efficiency of carbon nanotubes was increased as dispersion was improved. Electrical conductivity of nanocomposites was measured and used as indirect variable of microwave heating susceptor of carbon nanotubes nanocomposites. Higher electrical conductivity indicates a better microwave susceptor propertiy of the nanocomposite.
Composites Part B: Engineering, 2016
Multiwall carbon nanotubes (MWCNT) and multilayer graphene (MLG) were studied as microwave susceptor additives for polymers. Different percentages of both nanoparticles were added to polypropylene by melt compounding in order to study the microwave absorption and the polymer heating. Polypropylene was selected as polymer matrix due to its unpolar nature to avoid the influence of polymer polarity and evaluate the influence of the nanoparticles. Electrochemical spectroscopy impedance measurements were carried out to evaluate the conductive and dielectric properties of nanocomposites. Results showed that nanocomposites with higher electrical conductivity have better capacity of absorbing microwave radiation. High values of permittivity and loss tangent also increases the microwave radiation absorption and the ability of the material to convert this electromagnetic radiation into heat. Carbon nanotubes showed better microwave susceptor behavior than graphene multilayer. Nanocomposites with 1% w/w of carbon nanotubes can be compared with the heating efficiency of a polypropylene filled with 10% w/w of multilayer graphene. The higher efficiency of carbon nanotubes it is explained by their higher electrical conductivity and optimal dielectric properties of the nanocomposites compared to multilayer graphene polymer systems.
Electrical and Thermal Properties of Conductive Polymer Nanocomposites
Academia Letters, 2021
Exfoliated graphene nanoplatelets (GNP)-3 phr was incorporated into PP with increasing concentration of treated and untreated kenaf flour 0, 10, 20, 30, 40 weight percent respectively and prepared via melt-extrusion using co-rotating twin screw extruder. The resulting polymer nanocomposites (PNCs) were characterized in terms of electrical, thermomechanical, and morphological properties. The coefficients of thermal expansion (CTE) significantly decreased. The electrical properties decreased with increasing fiber content. However, despite the decline in electrical conductivity, the composites were still relatively conductive for applications such as sensors and electromagnetic shielding with fiber inclusion.
Effects of microwave assisted heating of carbon nanofiber reinforced high density polyethylene
Journal of Materials Processing Technology, 2007
Carbon nanofiber and carbon nanotube reinforced polymer composites have shown promise due to their enhanced mechanical, electrical, thermal, and dielectric properties. In this study, vapor grown carbon nanofiber reinforced polyethylene composites were exposed to microwave radiation in a conventional resonance cavity microwave oven to explore the possibility of using microwave energy to assist the processing of carbon nanofiber reinforced thermoplastic composites and determine the effect of microwave radiation exposure on material properties. Average temperatures of up to 40 °C above ambient were measured after 5 min of microwave exposure. The effect of high power microwave radiation on the physical integrity of the composites via dynamic mechanical analysis, tensile tests, and dielectric analysis is presented. A drop of 50% in failure strain has been observed for composites with 15 and 20 wt% nanofiber concentrations after exposure to microwave radiation.
We have investigated different strategies to control conductive network structuring in conductive polymer nanocomposites (CPC). Exclusion volumes, specific adsorption, and solvent evaporation were used to confine conducting nanofillers. This was found to be necessary to obtain samples with reproducible and stable characteristics for the development of vapor and temperature sensors or self regulated heating elements. Promising results are obtained combining nano and micro fillers by double filler percolation. The addition of 10% of rubber micro particles into polycarbonate-carbon black CPC allows decreasing the percolation threshold from 15 to 5%v/v whereas adding 30%v/v of BN into syndiotactic polystyrene/polyethylene-carbon black CPC decreases the thermal gradient under a heat flow of 1200W.m-2 by a factor 3.
Effect of carbon nanofibers content on thermal properties of ceramic nanocomposites
Journal of Composite Materials, 2011
The thermal properties of carbon nanofibers (CNFs)-alumina and CNFs-zirconia nanocomposites densified by spark plasma sintering technique were evaluated. The influence of CNFs content and type of ceramic matrix on thermal conductivity of ceramic-CNFs materials, measured by the laser-flash method, was studied. The effect of CNFs depends noticeably on the ceramic component and thus, an increase of 83% and a decrease of 97% in thermal conductivity at room temperature is observed when 80 vol% of CNFs is added to ZrO2 and Al2O3, respectively. However, even if the thermal conductivity is lower, the efficiency of heat transfer to the environment in CNFs/Al2O3 nanocomposites is better than that corresponding to monolithic alumina. This behavior is due to CNFs arrangement in dense materials. Considering the low electrical resistivity for CNFs/ Al2O3 and CNFs/ ZrO2 materials (10−1–10−2 Ω·cm), these nanocomposites are promising candidates as thermoelectric materials that require low thermal co...
Electrically and Thermally Conducting Nanocomposites for Electronic Applications
2010
Nanocomposites made up of polymer matrices and carbon nanotubes are a class of advanced materials with great application potential in electronics packaging. Nanocomposites with carbon nanotubes as fillers have been designed with the aim of exploiting the high thermal, electrical and mechanical properties characteristic of carbon nanotubes. Heat dissipation in electronic devices requires interface materials with high thermal conductivity. Here, current developments and challenges in the application of nanotubes as fillers in polymer matrices are explored. The blending together of nanotubes and polymers result in what are known as nanocomposites. Among the most pressing current issues related to nanocomposite fabrication are (i) dispersion of carbon nanotubes in the polymer host, (ii) carbon nanotube-polymer interaction and the nature of the interface, and (iii) alignment of carbon nanotubes in a polymer matrix. These issues are believed to be directly related to the electrical and thermal performance of nanocomposites. The recent progress in the fabrication of nanocomposites with carbon nanotubes as fillers and their potential application in electronics packaging as thermal interface materials is also reported.
Physics Letters A, 2013
Molecular dynamics simulations have been utilized to study thermal conductivity of liquid and solid mixtures of paraffin and carbon-based high aspect-ratio nano-additives, i.e. carbon nanotubes and graphene. In agreement with existing experimental data, we observe high enhancement in thermal conductivity through adding these graphitic nano-additives into paraffin, particularly in the solid phase. We demonstrate that this significant improvement is mainly achieved by the enhancement in thermal conductivity of the matrix itself. This is caused by carbon nanotubes and graphene promoting ordering of the matrix molecules which consequently leads to improvement of its thermal conductivity.