Effect of Nanotube Functionalization on the Coefficient of Thermal Expansion of Nanocomposites

Abstract

Single‐walled carbon nanotubes (SWNTs) are functionalized through both covalent and noncovalent bonding approaches to enhance dispersion and interfacial bonding. The coefficient of thermal expansion (CTE) of the functionalized‐SWNT‐reinforced epoxy composites are measured with a thermal mechanical analyzer (TMA). Experimental results indicate that changes of the glass‐transition temperature (Tg) in functionalized SWNT–polymer composites are dependent upon the functionalization methods. The CTE below the glass‐transition temperature of nanocomposites with a 1 wt % loading of nanotubes is substantially diminished compared to a neat polymer. A reduction in the CTE of up to 52 % is observed for nanocomposites using functionalized nanotubes. However, the CTE above the Tg significantly increases because of the contribution from phonon mode and Brownian motions of a large number of SWNTs in resin‐crosslinked networks, but the increments are compromised by possible interfacial confinement. A tunable CTE induced through nanotube functionalization has application potentials for high‐performance composites, intelligent materials, and circuit protections.

Morphology, thermal expansion, and electrical conductivity of multiwalled carbon nanotube/epoxy composites

“…Wang et al 23 also observed a thermal expansion coefficient close to 6.5 3 10 25 8C 21 before T g for an epoxy system and values in the range of 6 to 3 3 10 25 8C 21 for nanocomposites based on pristine and modified SWNTs.…”

“…However, the processing variables are as important as the formulation, and the use of a surfactant and a solvent in a dispersion stage led to a decrease in T g in SWNT/epoxy materials in the work of Liao et al, 9 for instance. Moreover, the 23 also shows a decrease in the epoxy/SWNT glass transition for both pristine and functionalized CNTs. In this work, the differences related to the main transition are in the range of T g accuracy both for series 1 and 2.…”

How carbon nanotubes affect the cure kinetics and glass transition temperature of their epoxy composites? – A review

“…We thus compiled and analyzed data values of glass transition temperature of CNT/epoxy composites from different articles. The CNT used in these works were unmodified MWNT [8][9][10][11][12][13][14][15][16] or unmodified SWNT [5,[17][18][19][20][21][22]. The data relative to preparation method of the composites, glass transition temperature and its measurement method are summarized in Table 1.…”

Enhanced Thermal Actuation in Thin Polymer Films Through Particle Nano‐Squeezing by Carbon Nanotube Belts

“…The number of publications specifically investigating the thermal expansion of nanocomposites, rather than bulk materials, is relatively limited. [8][9][10][11][12] Through the use of molecular dynamics (MD) simulations, Wei et al observed a signifi cant increase of the α for SWNT-polyethylene composites above T g and attributed this to an equivalent increase in the excluded volume of the embedded CNTs as a function of temperature. [ 9 , 10 ] Other studies have shown that the α of the composite above its T g can be tuned by nanotube functionalization.…”