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    Kinetics of carbon nanotube-loaded epoxy curing: rheometry, differential scanning calorimetry, and radio frequency heating
    (Elsevier, 2021) Tezel, Güler Bengüsu; Sarmah, Anubhav; Desai, Suchi; Vashisth, Aniruddh; Green, Micah J.
    The isothermal curing kinetics of carbon nanotube loaded epoxy was investigated using rheometry and differential scanning calorimetry (DSC) at a range of temperatures. Rheo-kinetics was used to observe time-dependent rheological changes in elastic (G?) and viscous (G?) moduli, and complex viscosities of epoxy-CNT samples during isothermal curing. DSC measurements were also performed to monitor the curing reaction, in order to compare against the rheo-kinetic parameters. The Kamal-Sourour kinetic model describes the curing of the epoxy-CNT system for rheo-kinetics and DSC well. The activation energies of the curing reaction were found to be ?36 kJ/mol and ?33 kJ/mol using rheo-kinetics analysis and DSC, respectively. In addition, radio-frequency (RF) electromagnetic fields were used to heat and cure the epoxy-CNT sample; such heating techniques are valuable in a number of epoxy processing technologies. G?, G?, and complex viscosities of RF heated samples were measured to monitor RF-aided curing. This allows us to monitor the curing kinetics inside samples being heated by RF fields; the data indicate that RF-aiding curing is faster than curing rates for samples undergoing curing inside a measurement device such as a rheometer or DSC, because the heat generated is immediate and volumetric.
  • Küçük Resim
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    Rapid manufacturing via selective radio-frequencyheating and curing of thermosetting resins
    (Wiley-V C H Verlag GMBH, 2022) Sarmah, Anubhav; Desai, Suchi K.; Tezel, Güler Bengüsu; Vashisth, Aniruddh; Mustafa, Mazin M.; Arole, Kailash
    A new method for additive manufacturing of thermosetting resins using selective, localized radio-frequency (RF) heating and curing in a thermoset reservoir is demonstrated. The use of a local RF applicator addresses the challenge of selective curing and printing of heat-curable thermosets from a reservoir of resin, without the addition of photocurable acrylates. The filler of interest is multi-walled carbon nanotubes, which heat up rapidly in response to an RF field. A target temperature can be maintained by modulating the RF power. Multilayered structures were 3D printed by moving the RF applicator relative to the resin reservoir, selectively curing the resin exposed to the field; this process was repeated for each layer. Thermal and mechanical properties of RF-printed samples were compared against conventional samples, with both methods showing similar glass transition temperatures and storage moduli; the RF-heated samples showed a more uniform morphology with lesser voids. The 3D printing process (temperature and conversion varying in space and time) is modeled to demonstrate the scope of this method in printing complex structures. This method of multilayered additive manufacturing of thermosetting resins allows for rapid, free-form processing.