Curing and percolation for carbon black-epoxy-amine nanocomposites

T.H. Wu, A. Foyet, A. Kodentsov, L.G.J. van der Ven, R.A.T.M. van Benthem, G. de With (Corresponding author)

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Abstract

Particle agglomeration in carbon black (CB) filled epoxy (CB-E) and carbon black filled epoxy-amine (CB-EA) nanocomposites with CB concentrations ranging from 0.25 to 1.25 vol% was investigated by performing conductivity measurements as a function of time at 20 °C. For the thermoplastic CB-E samples the change in conductivity was not pronounced, while for the thermosetting CB-EA samples a percolation transition was observed appearing at ≅ 0.2 vol%. The concentration 1.25 vol% was selected for both CB-E and CB-EA samples to perform in situ isothermal electrical conductivity measurements at 20, 50, 70, and 100 °C, respectively. At higher temperature, the agglomeration process was faster, resulting in an initially sharp increase of conductivity. Despite the conductivity development of CB-EA samples being faster than that of CB-E samples, they are reaching lower final conductivity values, indicating that cluster aggregation for the CB-EA samples is restricted by polymer gelation, as confirmed by scanning and isothermal differential scanning calorimetry (DSC). Furthermore, thermodynamic DSC studies showed that no particle-particle and particle-polymer chemical reactions occurred during the epoxy-amine curing. However, physical adsorption of the epoxy and amine components on the CB particles is the likely cause for the observed slightly higher amine-epoxy reaction rates in the presence of CB. Particle agglomeration is thereby attributed to be controlled by diffusion-limited cluster aggregation (DLCA). Finally, the microstructures of CB-EA samples after curing were investigated by using TEM. The fractal dimension df was determined and showed a smaller value as compared to the universal DLCA value, illustrating the influence of gelation on fractal formation in this system.

Original languageEnglish
Article number107672
Number of pages8
JournalComposites Science and Technology
Volume181
DOIs
Publication statusPublished - 8 Sep 2019

Keywords

  • Curing
  • Differential scanning calorimetry (DSC)
  • Electrical properties
  • Polymer-matrix composites (PMCs)

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