Effect of Carboxyl Functionalized MWCNTs on the Cure Behavior of Epoxy Resin (original) (raw)
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Cure behavior of epoxy/MWCNT nanocomposites: The effect of nanotube surface modification
Polymer, 2008
The effect of carboxyl and fluorine modified multi-wall carbon nanotubes (MWCNTs) on the curing behavior of diglycidyl ether of bisphenol A (DGEBA) epoxy resin was studied using differential scanning calorimetry (DSC), rheology and infrared spectroscopy (IR). Activation energy (Ea) and rate constants (k) obtained from isothermal DSC were the same for the neat resin and fluorinated MWCNT system (47.7 and 47.5 kJ/mol, respectively) whereas samples containing carboxylated MWCNTs exhibited a higher activation energy (61.7 kJ/mol) and lower rate constant. Comparison of the activation energies, rate constants, gelation behavior and vitrification times for all of the samples suggests that the cure mechanisms of the neat resin and fluorinated sample are similar but different from the carboxylated sample. This can be explained by the difference in how the fluorinated nanotubes react with the epoxy resin compared to the carboxylated nanotubes. Although the two systems have different reaction mechanisms, both systems have similar degrees of conversion as calculated from the infrared spectroscopic data, glass transition temperature (Tg), and predictions based on DSC data. This difference in reaction mechanism may be attributed to differences in nanotube dispersion; the fluorinated MWCNT system is more uniformly dispersed in the matrix whereas the more heterogeneously dispersed carboxylated MWCNTs can hinder mobility of the reactive species and disrupt the reaction stoichiometry on the local scale.
Cure kinetics of epoxy nanocomposites affected by MWCNTs functionalization: a review
TheScientificWorldJournal, 2013
The current paper provides an overview to emphasize the role of functionalization of multiwalled carbon nanotubes (MWCNTs) in manipulating cure kinetics of epoxy nanocomposites, which itself determines ultimate properties of the resulting compound. In this regard, the most commonly used functionalization schemes, that is, carboxylation and amidation, are thoroughly surveyed to highlight the role of functionalized nanotubes in controlling the rate of autocatalytic and vitrification kinetics. The current literature elucidates that the mechanism of curing in epoxy/MWCNTs nanocomposites remains almost unaffected by the functionalization of carbon nanotubes. On the other hand, early stage facilitation of autocatalytic reactions in the presence of MWCNTs bearing amine groups has been addressed by several researchers. When carboxylated nanotubes were used to modify MWCNTs, the rate of such reactions diminished as a consequence of heterogeneous dispersion within the epoxy matrix. At later s...
Effects of carbon nanotube fillers on the curing processes of epoxy resin-based composites
Journal of Applied Polymer Science, 2006
The effects of different grades of carbon nanotubes on the curing of a typical epoxy resin (EPIKOTE™ resin 862 and EPIKURE™ curing agent W) were examined via differential scanning calorimetry (DSC). It was found that nanotubes could initiate cure at lower temperatures, while the overall curing process was slowed as evidenced by lower total heat of reaction and lower glass transition temperatures of the cured nanocomposites compared to neat epoxy. This finding is practically important as it is essential to have a consistent degree of cure when the properties of thermosets with nanoinclusions are •2• compared to neat resins. It was also found that the inclusion of carbon nanotubes might induce the thermal degradation of epoxy composites at lower temperatures.
Investigation of cure kinetics in epoxy/multiwalled carbon nanotube nanocomposites
Journal of Applied Polymer Science, 2013
With the increased interest in thermoset resin nanocomposites, it is important to understand the effects of the material on nanoscale characteristics. In this study, a curing reaction of an epoxy resin, which contained 0.25, 0.50, or 1.00 wt % of multiwalled carbon nanotubes (MWCNTs), at different heating rates was monitored by differential scanning calorimetry; cure kinetics were also evaluated to establish a relationship between crosslinking (network formation) and mechanical properties. MWCNT concentrations above 0.25 wt % favored crosslinking formation and decreased the activation energy (E a) in the curing reaction. Examination of the kinetic mechanism suggests that the MWCNT locally restricted the spatial volume and favored the formation of nodular morphology in the resin, especially for high MWCNT concentrations. The MWCNT exhibited some entanglement in the matrix, which hindered a more pronounced effect on the mechanical properties.
Journal of Polymer Science Part B: Polymer Physics, 2010
A new class of nanocomposite has been fabricated from liquid crystalline (LC) epoxy resin of 4,4 0-bis(2,3-epoxypropoxy) biphenyl (BP), 4,4 0-diamino-diphenyl sulfone (DDS), and multiwalled carbon nanotubes (CNTs). The surface of the CNTs was functionalized by LC epoxy resin (ef-CNT). The ef-CNT can be blended well with the BP that is further cured with an equivalent of DDS to form nanocomposite. We have studied the curing kinetics of this nanocomposite using isothermal and nonisothermal differential scanning calorimetry (DSC). The dependence of the conversion on time can fit into the autocatalytic model before the vitrification, and then it becomes diffusion control process. The reaction rate increases and the activation energy decreases with increasing concentration of the ef-CNT. At 10 wt % of ef-CNT, the activation energy of nanocomposite curing is lowered by about 20% when compared with the neat BP/DDS resin. If the ef-CNT was replaced by thermal-insulating TiO 2 nanorods on the same weight basis, the decrease of activation energy was not observed. The result indicates the accelerating effect on the nanocomposite was raised from the high-thermal conductivity of CNT and aligned LC epoxy resin. However, at ef-CNT concentration higher than 2 wt %, the accelerating effect of ef-CNTs also antedates the vitrification and turns the reaction to diffusion control driven. As the molecular motions are limited, the degree of cure is lowered. V
Journal of Applied Polymer Science, 2012
In this article, the effect of combined temperature‐concentration and shear rate conditions on the rheology of double‐walled carbon nanotubes (DWCNTs)/RTM6‐Epoxy suspension was investigated to determine the optimum processing conditions. The rheological behavior and cure kinetics of this nanocomposite are presented. Cure kinetics analysis of the epoxy resin and the epoxy resin filled with DWCNTs was performed using Differential Scanning Calorimeter (DSC) and parameters of the kinetics model were compared. The DWCNTs have an acceleration effect on the reaction rate of the epoxy resin but no significant effect is noted on the glass transition temperature of the epoxy resin. This study reveals that the effect of shear‐thinning is more pronounced at high temperatures when DWCNTs content is increased. In addition, the steady shear flow exhibits a thermally activated property above 60°C whereas the polymer fluid viscosity is influenced by the free volume and cooperative effects when the t...
Cure Behavior and Physical Properties of Epoxy Resin—Filled with Multiwalled Carbon Nanotubes
Journal of Nanoscience and Nanotechnology, 2010
Carbon nanotubes (MWCNT) into epoxy diglycidil-ether bisphenol-A (DGEBA), cured with 4,4' diamine-dibenzyl-sulfone (DDS): i) mechanical mixing for either 60 or 120 minutes; ii) high energy ball milling for 30 minutes; iii) ultrasonication for 20 minutes. The mechanical properties of the obtained samples were monitored and used in order to guide the selection of the most promising composite system. The best results were obtained by using, as method of incorporation of carbon nanotubes in the resin, sonication for 20 minutes. Moreover it was found that the presence of an accelerating agent, BF 3 , commonly used for the cure reaction, is ineffective in the presence of carbon nanotubes, besides leading to composites with a lower glass transition. Afterwards resins with increasing MWCNT concentration were prepared and the thermal properties analyzed, showing a slight improvement in either the glass transition or the degradation temperature.
The effect of a doubly modified carbon nanotube derivative on the microstructure of epoxy resin
Polymer, 2014
The surface of multi wall carbon nanotubes (MWCNTs) was first covalently functionalized with oleyl amine and then non-covalently wrapped with polycarbosilane (PCS). The hybrid functional groups were chosen to introduce different features in the MWCNTs properties. For covalent functionalization a long chain unsaturated aliphatic amine was used to simultaneously achieve the dissociation of MWCNT bundles along with the dispersion and interaction with the host matrix using the amide functionality and double bond. On the other hand, a thermally stable polymer was selected which can interact with both resin and glass fabric to promote interfacial adhesion. This hybrid doubly modified MWCNT is thus possesses duel advantages in glass fiber based epoxy composite. The pristine, covalent, noncovalent and covalent-noncovalent doubly modified MWCNT systems were used to study the viscoelastic behavior and interactions of functionalized MWCNTs in the matrix above and below the glass transition temperature of the matrix. The PCS coating on the MWCNTs is amorphous and thermally insulating whereas the nanotube is highly graphitized and thermally conducting. This contrasting behavior provides us to insight into the temperature dependant resin microstructure and curing thermodynamics of epoxy resin in the presence of MWCNTs.