2018 5th Global Conference on Polymer and Composite Materials (PCM 2018)
Biography: Juana Abenojar studied Chemistry at Universidad Complutense de Madrid (Spain) and received her Ph.D. in Materials Science and Engineering at Universidad Carlos III de Madrid (Spain) in 2003. Currently she is researcher in Material Performance Group of this University and participates in numerous regional, national and European R&D projects. Besides, she is author/co-author of more than 70 research papers in journals included in JCR and she has attended numerous national and international conferences. Her research interests include on powder technology, surface treatments, developing materials for nuclear applications, polymer composites and adhesives.
She is Member of the Coordinating Committee of the Spanish Adhesion and Adhesives Group (GEAA) and the Scientific Committees of "International Congress of Adhesion and Adhesives" and "International Conference on Fracture, Fatigue and Wear"
Speech Title: Kinetics of curing process in carbon based epoxy nano-composite
Aims: Epoxy resins are structural adhesives. Their high crosslinking supposes too much rigidity, resulting in low toughness. Nano-filled additions could modify toughness, but they could modify the curing process of the resin too. Quality requirements of nano-composite (NC) imply a control of their curing process to ensure the mechanical properties of the material. Therefore, the objective of this work is to study the influence of carbon-based nano-additions in the curing and kinetics process of an epoxy resin.
Methods: The first part was mixing Araldite 2020 and different types of nano-carbon materials (graphene -G-, graphene oxide -GO-, chemically exfoliated graphite nano-platelets -GKOH- and multi-walled carbon nano-tubes -CNT-, all in 0.5 wt%). Differential scanning calorimetry was used to determine the kinetics of the curing process of nano-composites. For this purpose, a DSC822 equipment from Mettler Toledo GmbH (Greifensee, Switzerland) was used, within which were carried out non-isothermal cycles from 0 to 200 °C at different heating rates (5, 10 and 20 °C / min). Activation energy (Ea) was calculated by Kissinger, Kamal and Model Free (MFK) methods.
Results: The Kamal method provides information on the n-order constant (k1) and the auto-catalytic (k2). As in all curing processes of an epoxy resin, the slowest reactions are the n-order; therefore the constants, and consequently the reaction rate, increase with the test rate. In this work, all NCs decrease the constants and reaction order, so the reactions are slower and there are fewer species involved in the reaction. Ea calculated from k1 increases for the NC with G and CNT and decreases for GO and GKOH, probably due to the presence of OH groups. The Kissinger method provides similar values and the MFK method gives the variations of Ea with the conversion degree. Ea are similar for 50% curing for all NCs. However it needs less Ea at the beginning of the reaction for the NC with CNT and much more at the end of the reaction for the one that contains GO.
Conclusions: The three methods used are complementary and provide information on the curing process of the nano-composites.
