Effect of Carbon Nanofiber Heat Treatment on Physical Properties of Polymeric Nanocomposites—Part I

Abstract

The definition of a nanocomposite material has broadened significantly to encompass a large variety of systems made of dissimilar components and mixed at the nanometer scale. The properties of nanocomposite materials also depend on the morphology, crystallinity, and interfacial characteristics of the individual constituents. In the current work, vapor-grown carbon nanofibers were subjected to varying heat-treatment temperatures. The strength of adhesion between the nanofiber and an epoxy (thermoset) matrix was characterized by the flexural strength and modulus. Heat treatment to 1800 • C demonstrated maximum improvement in mechanical properties over that of the neat resin, while heat-treatment to higher temperatures demonstrated a slight decrease in mechanical properties likely due to the elimination of potential bonding sites caused by the elimination of the truncated edges of the graphene layers. Both the electrical and thermal properties of the resulting nanocomposites increased in conjunction with the increasing heat-treatment temperature.

Preparation, Characterization, and Modeling of Carbon Nanofiber/Epoxy Nanocomposites

“…The relatively low efficiency of catalyst results in microstructural defects in CNFs, which require special treatments in order for CNFs to achieve desired properties. A number of treatment methods have been used, which include acid treatment [3,4], heat treatment (to eliminate defects) [5], plasma treatment (to purify) [6], and surface functionalization (to improve interface adhesion) [7,8]. Because of their high aspect ratio and high surface energy (due to nanoscale diameters), CNFs tend to agglomerate, leading to inhomogeneous dispersion.…”

“…Far from the transition, the conductivity increased by two orders of magnitude. Other studies on electrical properties of CNF/epoxy nanocomposites did not focus on the percolation behavior, but rather on the effect of CNFs' heat treatment [5] or on the effect of the viscosity of epoxy matrix [9] on the electrical conductivity of CNF/epoxy nanocomposites. Moreover, none of these papers discussed the dielectric properties of CNF/epoxy nanocomposites.…”

The dominant role of tunneling in the conductivity of carbon nanofiber‐epoxy composites

“…With the goal of obtaining high mechanical and electrical performance in VGCNF/epoxy composites, the focus has been in the development of processing methods to achieve homogeneous dispersion of the fillers in the epoxy matrix. In particular, acetone solvent/epoxy infusion and mixing 5; mixing carried out through high‐intensity ultrasonic irradiation 6; combination of ultrasonication and mechanical mixing 7; sonication and conventional stirring 8; and preparation methods involving heat treatment of the fibers 9 have been successfully tested and the effect of VGCNF loading on the electrical and mechanical macroscopic response has been evaluated. In particular, the effect of different dispersion states on the rheological and AC conductivity properties of VGCNF epoxy suspensions prepared by simple hand mixing 10 has been reported, and an electrical threshold at 0.5 wt.% loading has been achieved.…”

Relationships between nanofiller morphology and viscoelastic properties in CNF/epoxy resins

“…Prior to the epoxy cure, the quality of dispersion is a critical step. Conversely, CNFs can be manufactured with some morphological and structural properties suitable to reduce the interactions among their walls [9][10][11]. In fact, unlike CNTs for which van der Waals forces cause the nanotubes to form ropes or reassemble after being dispersed, CNFs are less affected by van der Waals forces and tend to stay dispersed for longer periods of time.…”