Effects of microwave assisted heating of carbon nanofiber reinforced high density polyethylene (original) (raw)
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One of the problems with the use of carbon fiber-reinforced plastics (CFRP) is the difficulty of recycling or disposing of them. Hence, it is necessary to find processes to treat CFRP wastes faster and more effectively. Because carbon fibers are good microwave absorbers, there is significant potential for the use of microwave irradiation for the processing of CFRP wastes. In this study, the relationship of mechanical properties and radiation temperature during microwave irradiation of unidirectional and clothtype CFRP were studied. Experimental results indicate that microwave irradiation degrades CFRP's mechanical properties by breaking down the bond between the polymer matrix and the carbon fibers.
One important thing to be studied in the bonding of thermoplastic composite material using microwave irradiation is the effects of microwave energy on the matrix and fibre reinforcement of the composite. In this research, thirty three percent by weight random glass fibre reinforced polystyrene [PS/GF (33%)] is chosen for the study. Microscopy study is used to find out the microstructural characteristics along and around the interface of the welds. The separation distance of the reinforcing carbon filaments was varied and heat transfer in the material during joining was studied. The reasons why the thermoplastic matrix composite materials were weakened by prolonged microwave irradiation were also studied and analysed.
Efficiency of Microwave Heating of Weakly Loaded Polymeric Nanocomposites
Journal of Engineered Fibers and Fabrics
Electrical and thermal conductivity of materials are typically correlated, while some applications, including thermoelectrics, require these parameters to be controlled independently. Such independent control of thermal and electromagnetic properties can be achieved by using nanocomposites. In this study, nanocomposites were produced by mixing a small amount of carbon nanofibers (CNF), carbon coated cobalt (Co), and nickel nanowires (NiNW) with paraffin, which has low thermal and almost zero electrical conductivity. The fraction of nanoinclusions in the paraffin matrix was very low (below 1%). We showed that the thermal properties of nanocomposites are essentially the same as those of pure paraffin, while electromagnetic properties are significantly different. To determine the dependence of the heating rate on filler concentration, paraffin-based samples were heated in a microwave oven. We found that the heating rate of nanocomposites made of carbon nanofibers is much greater than t...
Microwave Heating for Manufacturing Carbon-Fiber Thermoplastics
MRS Proceedings, 1990
ABSTRACTTraditionally, polymeric composite parts are heated and consolidated in an autoclave. For large parts, such as transport aircraft fuselages or submarine hulls, size becomes a limiting factor. To overcome this limitation and to reduce labor costs we are developing an automated tape placement process. In this process we build composite parts one layer at a time with tape containing carbon fibers impregnated with a thermoplastic. As the tape comes into contact with the part, we apply heat to melt the thermoplastic and apply pressure to consolidate the tape to the part. To support this effort we have developed a proprietary microwave applicator that is suitable for rapidly heating carbon-fiber composites in an automated tape placement process. Small carbon-fiber/poly(aryl-ether-ether-ketone) parts made using the microwave applicator have interlaminar shear strengths of 100 MPa (14.5 ksi), which is almost equal to the 103 MPa (15.0 ksi) obtained using an autoclave.
Carbon nanofibers-reinforced polymer nanocomposites as efficient microwave absorber
2020
Microwave absorbing polymer composites are important for strategic applications in several defense systems for detection and/or deception purposes as well as for other industrial applications, where the enclosed electronic gadgets or human beings need shielding from electromagnetic radiations from the environment. The extent of absorption or reflection of the microwave by these composites, however, can be controlled by proper selection of type of constituting base polymers and reinforcement types, nature of different additives, crosslinking agents used in the polymer formulation, and also on the nature of fabrication of suitable structures, that is, by combination or layering of different constitutive components of the functionally gradient composites. Carbon, besides being an excellent dielectric and lightweight material, exists in various forms like carbon nanotubes, nanospheres, graphene, carbon black, nanofibers, hollow carbon nanostructures, etc. and many of these, especially t...
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 A: Applied Science and Manufacturing
Accelerated curing of high performance fibre-reinforced polymer (FRP) composites via microwave heating or radiation, which can significantly reduce cure time and increase energy efficiency, has several major challenges (e.g. uneven depth of radiation penetration, reinforcing fibre shielding, uneven curing, introduction of hot spots etc). This article reviews the current scientific challenges with microwave curing of FRP composites considering the underlying physics of microwave radiation absorption in thermoset-matrix composites. The fundamental principles behind efficient accelerated curing of composites using microwave radiation heating are reviewed and presented, especially focusing on the relation between penetration depth, microwave frequency, dielectric properties and cure degree. Based on this review, major factors influencing microwave curing of thermoset-matrix composites are identified, and recommendations for efficient cure cycle design are provided.
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.
Fiber Reinforced Polyester Resins Polymerized by Microwave Source
Journal of Materials Engineering and Performance, 2007
Polyester resin based composite materials are widely used in the manufacture of fiberglass boats. Production time of fiberglass laminate components could be strongly reduced by using an intense energy source as well as microwaves. In this work a polyester resin was used with 2% by weight of catalyst and reinforced with chopped or woven glass fabric. Pure resin and composite samples were cured by microwaves exposition for different radiation times. A three point bending test was performed on all the cured samples by using an universal testing machine and the resulting fracture surfaces were observed by means of scanning electron microscopy (SEM). The results of mechanical and microscopy analyses evidenced that microwave activation lowers curing time of the composite while good mechanical properties were retained. Microwaves exposition time is crucial for mechanical performance of the composite. It was evidenced that short exposition times suffice for resin activation while long exposure times cause fast cross linking and premature matrix fracture. Furthermore high-radiation times induce bubbles growth or defects nucleation within the sample, decreasing composite performance. On the basis of such results microwave curing activation of polyester resin based composites could be proposed as a valid alternative method for faster processing of laminated materials employed for large-scale applications.