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

Abstract

Abstract. Motivated by the widespread and contradictory results regarding the glass transition temperature of carbon nanotube (CNT)/epoxy composites, we reviewed and analyzed the literature results dealing with the effect of unmodified multiwall carbon nanotubes (MWNT) on the cure behaviour of an epoxy resin (as a possible source of this discrepancy). The aim of this work was to clarify the effective role of unmodified multiwall carbon nanotubes on the cure kinetics and glass transition temperature (Tg) of their epoxy composites. It was found that various authors reported an acceleration effect of CNT. The cure reaction was promoted in its early stage which may be due to the catalyst particles present in the CNT raw material. While SWNT may lead to a decrease of Tg due to their bundling tendency, results reported for MWNT suggested an increased or unchanged Tg of the composites. The present status of the literature does not allow to isolate the effect of MWNT on the Tg due to the lack of a study providing essential information such as CNT purity, glass transition temperature along with the corresponding cure degree. Vol.3, No.9 (2009) [588][589][590][591][592][593][594] Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2009.73 Keywords: nanocomposites, carbon nanotubes, cure kinetics, glass transition temperature eXPRESS Polymer Letters Cure kineticsIn the literature, different works were dedicated to the determination of the effect of CNT on the cure kinetics of an epoxy resin. Puglia et al. [1] claimed an acceleration effect of single wall carbon nanotubes (SWNT) on the cure reaction of the DGEBA/DETA epoxy system studied with dynamic and isothermal DSC. In that work, the decrease of the peak temperature (that is the temperature at the heat flow peak) in dynamic scans and the decrease of the time at heat flow peak in isothermal scans were taken as the proof of the acceleration in the early stage of the cure process. The presence of amine functional groups (-NH 2 ) on the surface of the SWNT that may react with the epoxy ring was the origin of the modification of the cure behaviour as shown in a paper from the same group presenting additional data on the same samples [2]. Xie et al. [3] also reported an acceleration effect in the case of multiwall carbon nanotubes (MWNT) for the TGDDM/DDS epoxy system using isothermal DSC. The higher initial reaction rate of the composites compared to the unfilled resin, the decrease of the time at maximum reaction rate and of the activation energy with increasing MWNT content were the indication of the acceleration effect. Evidence of the presence of hydroxyl groups (-OH) on the surface of the MWNT by FTIR spectroscopy which have a catalytic effect on epoxy ring opening was in that case the source of the modified cure. The last stage of the cure remained unaffected by MWNT. The same group reported [4] on the effect of carbon nanofibres (CNF) on the cure behaviour of the same epoxy system. They found a very small acceleration effect of CNF in the...

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Effects of graphene oxides on the cure behaviors of a tetrafunctional epoxy resin

“…Numerous studies on cure kinetics of epoxy in presence of carbon-based nanofillers have been investigated [16][17][18][19][20][21][22][23][24][25]. Recently, Allaoui and El Bounia [16] had reviewed the influence of CNTs on the cure kinetics of epoxy resin. Our previous studies showed that the addition of CNTs could accelerate the cure reaction of epoxy resin, while CNFs had only a negligible effect on the cure kinetics of the epoxy [17,18].…”

“…Differential scanning calorimetry (DSC) may be considered as one of the most interesting techniques for kinetic analysis of cure reactions of thermosetting systems [13][14][15]. Numerous studies on cure kinetics of epoxy in presence of carbon-based nanofillers have been investigated [16][17][18][19][20][21][22][23][24][25]. Recently, Allaoui and El Bounia [16] had reviewed the influence of CNTs on the cure kinetics of epoxy resin.…”

A detailed study of α-relaxation in epoxy/carbon nanoparticles composites using computational analysis

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