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In this work, a varied amount of acetone was employed to dissolve an epoxy resin and then a route was followed to remove the acetone, simulating a frequently used method to disperse nanofillers in thermoset matrices. Analyses were then carried out to address the influence of residual acetone on the curing process and on the epoxy properties. The results showed a detrimental effect on the mechanical properties of the cured epoxy due to the presence of residual acetone and also a less brittle-like fracture of the specimen. Fourier transform infrared spectroscopy and thermogravimetric analyses were additionally used to characterize the cured resins and have also indicated the presence of a small amount of acetone. Nevertheless, rheological measurements indicated that 10.0 wt.% acetone addition on the resin causes a significant decrease in viscosity (around 50%) which may promote a better dispersion of nanofillers.
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76 Polímeros: Ciência e Tecnologia, vol. 18, nº 1, p. 76-80, 2008
Autor para correspondência: Luiz A. F. Coelho, UDESC - Centro de Ciências Tecnológicas, Campus Universitário s/n, CP 631, Bairro Bom Retiro,
CEP: 89223-100, Joinville, SC, Brasil. E-mail:
ity of the neat epoxy which makes the dispersion of these
finely divided materials very challenging.
In this context, the goal of this work is to study the effect
of acetone solvent on the curing process as well as on the
properties of epoxy matrices. Thus, acetone/epoxy solutions
of different acetone concentrations, namely 0.0, 7.0, 10.0 or
13.0 wt.%, were prepared and then subjected to a mild pro-
cessing route to remove acetone. Viscosimetric, thermogra-
vimetric, tensile and morphological tests were performed in
order to evaluate possible changes in the samples. In addi-
tion, Fourier transform infrared spectroscopy (FTIR) analy-
ses were also employed in the search for changes in their
molecular structure.
The epoxy resin and the hardener used were araldite GY
251 (diglycidylether of bisphenol A, DGEBA, Huntsmann)
and aradur HY 956 (Huntsmann), respectively. Acetone
(Quimidrol, 99.5% purity) was the chosen solvent.
A certain amount of acetone (7.0, 10.0, or 13.0% of the
resin weight) was added to the resin and the mixture was
simultaneously sonicated in a Sonics Vibration (500 W) and
magnetically stirred for an hour. The mixture was then sub-
jected to heating at 50 °C for an hour and conditioned under
vacuum for five hours. Finally, hardener was added to the
mixture with a 5:1 (w/w) epoxy resin:hardener ratio and ho-
mogenized. The curing process took place at room tempera-
The addition of solvents to thermoset resins is a possible
route to decrease resin viscosity, allowing a better distribu-
tion of fillers including, more recently, carbon nanotubes
Although the use of a solvent is beneficial to filler dis-
persion, it originates difficulties related to solvent removal
and the effect of residual solvent on resin characteristics.
Thus, the optimal, i.e. minimum, amount of solvent must
be identified and used, since even a small amount of sol-
vent left on the matrix may be responsible for hindering the
cross-linking process, being deleterious to the mechanical
properties of the resin.
Lau et al.[4] studied how traces of solvent may alter the
epoxy cross-linking process. The authors demonstrated that
the boiling point of solvents may be used as an attempt to
establish a trend regarding the effect on thermal and me-
chanical properties of epoxy. The influence of the solvent
was ultimately attributed to the different amount of unre-
acted epoxide groups and the extent of cure reaction. Hong
and Wu[5] studied the influence of different solvents on the
curing process of epoxy and dicyandiamide. According
to these authors, differential scanning calorimetry (DSC)
analyses revealed that the presence of solvent in the epoxy
resin results in lower curing exotherm, initial curing rate,
reaction rate, reaction order and glass transition tempera-
ture. They also found the most significant changes for the
solvents with higher boiling temperature.
Nevertheless, it is important to bear in mind that the
use of a solvent is very important as a way to adequately
prepare nanocomposites using CNTs as fillers in epoxy
matrices[4,6,7]. This is a necessary step due to the high viscos-
The Effect of Acetone Addition on the Properties of Epoxy
Marcio R. Loos, Luiz Antonio F. Coelho, Sérgio H. Pezzin
Centro de Ciências Tecnológicas, UDESC
Sandro C. Amico
Abstract: In this work, a varied amount of acetone was employed to dissolve an epoxy resin and then a route was followed
to remove the acetone, simulating a frequently used method to disperse nanofillers in thermoset matrices. Analyses were
then carried out to address the influence of residual acetone on the curing process and on the epoxy properties. The results
showed a detrimental effect on the mechanical properties of the cured epoxy due to the presence of residual acetone and
also a less brittle-like fracture of the specimen. Fourier transform infrared spectroscopy and thermogravimetric analyses
were additionally used to characterize the cured resins and have also indicated the presence of a small amount of acetone.
Nevertheless, rheological measurements indicated that 10.0 wt.% acetone addition on the resin causes a significant decrease
in viscosity (around 50%) which may promote a better dispersion of nanofillers.
Keywords: Acetone, epoxy, curing process, mechanical and physical properties.
Loos, M. R. et al. - The effect of acetone addition on the properties of epoxy
Polímeros: Ciência e Tecnologia, vol. 18, nº 1, p. 76-80, 2008 77
acetone appears to show a slightly lower viscosity than the
other samples for all shear rates tested.
Infrared spectroscopy
The FTIR spectra can provide information regarding
changes in the molecular structure of the samples through
the displacement, widening, appearance or lack of bands. As
can be seen in Figure 2 for the various solutions in uncured
state, the bands are quite similar, indicating that the use of
acetone does not appear to change the chemical structure of
the epoxy, similar to what has been suggested by Lau[4].
The peaks specifically related to acetone[9,10],
1708-1715 cm-1 (stretching of the C=O), 1731-1737 cm-1
(stretching of the gas phase of the C=O) and 3000-3005 cm-1
(stretching of the C=H) could not be separately identified due
to superposition with epoxy related peaks, especially the ab-
sorptions due to the stretching of the C=O and the C=H, at
1725 and 3005-3055 cm-1, respectively[4,11].
The most characteristic absorptions of the uncured epoxy
include a band around 910-920 cm-1[12-14], due to the contrac-
tion of the C-C bond and the stretching of both C-O bonds,
and a shoulder at 858 cm-1, due to the stretching of one C-O
bond and contraction of the other C-O bond of the epoxide
group[4]. After curing, the former band decreases in intensity,
shifts to higher values and may even split, whereas the shoul-
der disappears. Another reported feature of the cured epoxy
may include the appearance of a band around 1650 cm-1 re-
lated to the formation of an imino group. A full list of epoxy
infrared absorptions may be found in the work of Lau[4].
The FTIR may give more insight into the role of acetone
and for that, the band between 910-920 cm-1, was chosen as
the reference band. Comparing the spectra of the cured and
uncured resin, without acetone (Figure 3), it can be seen that
the reference band disappears if the epoxy is fully cured. On
the other hand, this band still remains for the samples with
acetone, although it has been shifted from 910 to 925 cm-1
and decreased in intensity, compared to the uncured curve.
ture for 24 hours under continuous vacuum. Samples without
acetone, called 0.0 wt.% of acetone, were also prepared for
comparison, using the same mixture and curing procedure.
Sample characterization
The viscosity of the epoxy/acetone mixtures was mea-
sured with the aid of a cone/plate apparatus (Brookfield CAP
2000). Thermogravimetric analyses (TGA) were conducted in
a Netzsch (STA 449C) equipment, heating the samples from
15 to 900 °C at a heating rate of 10 °C/min under nitrogen
atmosphere. Fourier transform infrared spectroscopy (FTIR)
analyses were conducted in a Perkin-Elmer Spectrum One B
equipment with a resolution of 4 cm-1, from 4000 to 650 cm-1,
on transmission mode.
Tensile tests, according to ASTM D638, were performed
in a Universal Testing Machine Emic DL 3000, with a 500
kgf load-cell and a 5 mm/min cross-head speed. Morphologi-
cal characterization of the fractured surface of the samples
was carried out via scanning electron microscopy - SEM
(equipment Zeiss DSM 940 A at 15 kV).
Results and Discussion
The viscosity of the various epoxy/acetone solutions at
50 °C is shown in Figure 1. The 0.0 wt.% acetone (neat resin)
curve shows a slight tendency to pseudoplastic behavior, that
is the viscosity decreases with shear rate, whereas no clear
trend was observed for the epoxy/acetone solutions in the
studied range of shear rates and the small variation in viscos-
ity appears to be within the experimental error and/or related
to some volatilization of acetone during the experiment.
Nevertheless, comparing the neat epoxy with the other
samples, it can be seen that the addition of acetone decreas-
es, in up to 50%, the viscosity of the resin, what is expected
considering that the solvating effect of the solvent weaken
inter-chain interactions[8]. Besides, the solution with 10% of
0.0 wt.%
7.0 wt.%
10.0 wt.%
13.0 wt.%
1000 2000 3000 4000 5000 6000 7000
Shear rate (s-1)
Viscosity (mPa.s)
Figure 1. Viscosity of the samples with 0.0, 7.0, 10.0 and 13.0 wt.% of
acetone under different shear rates.
Wave number (cm-1)
4000 3500 3000 2500 2000 1500 1000
0.0 wt. %
7.0 wt. %
10.0 wt. %
13.0 wt. %
Figure 2. FTIR spectra obtained for the samples with 0.0, 7.0, 10.0, and
13.0 wt.% of acetone - uncured resin.
Loos, M. R. et al. - The effect of acetone addition on the properties of epoxy
78 Polímeros: Ciência e Tecnologia, vol. 18, nº 1, p. 76-80, 2008
possibly due to the decomposition of lower molecular weight
material, and the other one, between 290-490 °C (peak at
368 °C in Figure 4b), referring to the degradation of the resin
material[17] of higher molecular weight formed during cur-
However, the TG curves obtained for the epoxy with ac-
etone (Figure 4a) have shown a different profile. There is an
initial small weight loss, between 40-140 °C (peak at 89 °C
in Figure 4b), corresponding to the evaporation of trapped
solvent, a similar behavior to that reported by Sharmim[18] for
epoxy/dimethylsulphoxide solution. The derivative TG plot
clearly shows the presence of this extra peak for the acetone
cured epoxy resins.
Figures 4a,b also indicate that the presence of acetone
causes a increase in the intensity of the peak at 240 °C.
Besides, the weight loss in the range 160-290 °C increases
from 5.2%, for the neat resin, to around 9.7% for the other
samples, which suggests that there is comparatively more
material on lower molecular weight chains, which may un-
dergo thermal degradation sooner. This can be attributed to
the incomplete cure of the resin due to the presence of residu-
al acetone, that affects the curing kinetics and, consequently,
the structure of the epoxy resin[12]. The presence of acetone
is likely to decrease the degree of cross-linking, increasing
the chain molecular mobility, ultimately lowering the glass
transition temperature[5].
Tensile properties
Table 1 presents the tensile testing results of the differ-
ent samples. It can be seen that the presence of acetone re-
sulted in a decrease in Young’s modulus, tensile strength and
elongation at break of the epoxy resin. This effect was more
pronounced for resins prepared with a higher acetone con-
tent, reaching a 16-21% decrease in these properties for the
13.0 wt.% acetone sample. The decrease in Young’s modulus
is particularly interesting in ratifying the findings regarding
the mentioned lower degree of crosslinking of the resins in
which acetone had been added. Mondragon[15] also found for
a DGEBA epoxy resin that the presence of a small amount of
solvent (in their case CH2Cl2) at the beginning of the curing
reaction, even if they are later lost by evaporation, have a
measurable effect on curing kinetics and Tg of the resin due
to a modification of the network structure.
The decrease in tensile strength and elongation at break
may be related to the presence of weakly bonded acetone rich
areas of the resin which may act as stress concentration points.
This is an indication that there is acetone left on the epoxy
resin which has affected the cross-linking process, decreas-
ing the conversion degree of reactive groups[4,15].
Thermogravimetric analysis (Figure 4) of the neat cured
epoxy[16] has shown two major weight loss events in Figure 4a,
the first, between 160-290 °C (peak at 240 °C in Figure 4b),
1900 1700 1500 1300 1100 900 700
Wave number (cm-1)
13.0 wt. %
10.0 wt. %
7.0 wt. %
0.0 wt. %
0.0 wt. % - uncured
Figure 3. FTIR spectra obtained for the samples with 0.0, 7.0, 10.0, and
13.0 wt.% of acetone after the curing process.
0 200 400 600 800
Temperature (°C)
Weight (%)
0.0 wt. %
7.0 wt. %
10.0 wt. %
13.0 wt. %
0 200 400 600 800
Temperature (°C)
Deriv weight (%/min)
0.0 wt. %
7.0 wt. %
10.0 wt. %
13.0 wt. %
Figure 4. a) TG; and b) DTG curves for the samples with 0.0, 7.0, 10.0 and
13.0 wt.% of acetone.
Table 1. Tensile properties of the samples.
(wt. %)
at break
0.0 2.5 + 0.3 42.8 + 2.0 2.8 + 0.4
7.0 2.3 ± 0.1 40.8 ± 1.0 2.5 ± 0.4
10.0 2.2 ± 0.4 38.7 ± 0.8 2.5 ± 0.4
13.0 2.1 ± 0.2 34.4 ± 3.0 2.2 ± 0.4
Loos, M. R. et al. - The effect of acetone addition on the properties of epoxy
Polímeros: Ciência e Tecnologia, vol. 18, nº 1, p. 76-80, 2008 79
less brittle-like fracture is observed. This may be compared
to a less extent to the effect of moisture on saturated epoxy
specimens, which show a transition to ductile behavior due
to moisture-induced plasticization, i.e. from a brittle fracture
mechanism such as crazing to a ductile mechanism such as
bulk shear yielding[20]. This could explain some near circu-
lar or ellipsoid patterns left on the fractured surface of the
13.0 wt.% acetone sample.
Furthermore, no apparent porosity was found in any of
the micrographs taken, indicating that the difference in me-
chanical properties is indeed a consequence of alterations in
the characteristics of the resin material.
The influence of the presence of residual solvent, namely
acetone, on the characteristics of an epoxy resin was studied.
It may be concluded that care must be exercised in order to
ensure that all solvent is removed before curing, otherwise
the cross-linking process is altered, leading to significant
changes in physical and mechanical properties, for instance
the Young´s modulus, even if only a small amount of solvent
is left on the matrix. The molecular strucuture of the cured
resin has also been affected, as detected by FTIR analyses,
and SEM micrographs showed a less brittle-like fracture for
the material to which acetone had been added. Thermal deg-
radation has also been affected by the acetone.
Nevertheless, a 50% reduction in viscosity due to solvent
solvating of the DGEBA molecules was found when 10 wt.%
of acetone was added to the epoxy resin, which is very bene-
ficial to processes where finely divided fillers are to be incor-
porated and dispersed into highly viscous polymer resins as a
consequence of a stirring process, helping defining more suit-
able conditions for the preparation of epoxy nanocomposites
with carbon nanotubes when following this solvent route.
The authors would like to thank CAPES-PROCAD (Proj-
ect 0303054) for the financial support and for the scholarship
to Mr. M. R. Loos.
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etone evaporation.
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Figure 5. Micrograph of fractured samples with 0.0 (a) and 13.0 wt. % of
acetone at different magnifications, 200 and 500x (b and c respectively).
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Enviado: 07/06/07
Reenviado: 09/09/07
Aceito: 14/09/07
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... On the other hand, this peak is not visible in the adhesive sample that contained no IPA. Having solvent within the structure of the adhesive may have altered the crosslinking process and caused a reduction in the molecular weight of some of the polymer chains [53]. ...
... In samples designed to observe this phenomenon, TGA confirmed that the presence of varying weight percentages of IPA in the adhesive affected its decomposition. Figure 2 shows how a higher wt.% of IPA caused higher weight loss from 100-320 °C, which is due to the IPA likely influencing the curing process of the adhesive [6,53]. This affected its chemical structure by possibly increasing the presence of lower molecular weight chains, which underwent thermal degradation earlier. ...
... In samples designed to observe this phenomenon, TGA confirmed that the presence of varying weight percentages of IPA in the adhesive affected its decomposition. Figure 2 shows how a higher wt.% of IPA caused higher weight loss from 100-320 • C, which is due to the IPA likely influencing the curing process of the adhesive [6,53]. This affected its chemical structure by possibly increasing the presence of lower molecular weight chains, which underwent thermal degradation earlier. ...
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Solutions of DGEBA (a diglycidylether of bisphenol-A) epoxy resin in CH2Cl2 were heated under vacuum to remove most of the solvent, before being mixed with diaminodiphenylmethane hardener and cured. Resin compositions prepared in this way, with stoichiometric ratios between 0·5 and 2·0, were subjected to dynamic mechanical and Fourier-transform-IR analysis. Measurements were also made of residual solvent content. Parallel experiments were carried out on control samples prepared without using solvent. The results show that small amounts of CH2Cl2, which are present at the beginning of the curing reaction, but lost by evaporation later, have a measurable effect on the kinetics of cure and the Tg of the resin. These observations are relevant to thermoplastic-toughened epoxy resins, which are usually blended with the aid of a solvent. It is concluded that the effects of introducing solvent into the process on the Tg of the cured resin are due to a modification of the network structure.
The degradation of the epoxy system diglycidyl ether of bisphenol A (this epoxy is also named DGEBA (n=0), where n indicates the number of structural units inside the molecule) cured with hardener metaxylilene diamine (m-XDA) was studied on a dynamic basis using TGA and modulated TGA techniques under a nitrogen atmosphere with 5% O2. We observed that under such atmosphere the degradation process becomes more complex. The experimental results showed that modulated thermogravimetric analysis provides key information on the activation energy values, which are consistent with values found in the literature and others obtained by methods derived from TGA measurements.
The principal objectives of this paper are: (1) to present one application of the FT-NIR spectroscopy and (2) to give trends of the NIR analysis. An investigation of the kinetic of an epoxy (DGEBA)/triamine (liquid hardener T403) system was carried out by near infrared (NIR) spectroscopy, DSC and SEC. This homogeneous model system involves a simple addition reaction mechanism leading to an exothermic reaction between epoxide and amine hydrogen functional groups. The extent of reaction was calculated from NIR absorption band at 4528 cm−1 which depends on epoxide concentration. The comparison of the extent of reaction evaluated from DSC and SEC results shows an excellent agreemnt with NIR results for this epoxy formulation. The wide field of application and the increasing number of manufacturers presenting low cost FT-NIR spectrometers can help the increase of the number of laboratories using NIR spectroscopy. On the other hand, one of the main advantage of NIR analysis technique versus DSC or SEC is the possibility of real time analysis, at-line and on-line monitoring. Thus the recent developments and trends of this technique (NIR) are also presented in a short overview.
Multi-walled carbon nanotubes/epoxy resin (MWNTs/EP) nanocomposites with different MWNTs contents have been prepared successfully. The influence of MWNTs on the friction and wear behaviors of the nanocomposites was investigated by a friction and wear tester under dry-sliding contact conditions. The relative humidity of the air was about 50±10%. Contrast to pure EP, MWNTs/EP nanocomposites showed not only higher wear resistance but also smaller friction coefficient. MWNTs could dramatically reduce the friction and improve the wear resistance behaviors of the nanocomposites. The mechanisms of the significant improvements on the tribological properties of the MWNTs/EP nanocomposites were also discussed.
The effects of solvents on the curing behaviors of an epoxy (diglycidyl ether of bisphenol-A) and dicyandiamide/2-methyl imidazole system have been studied with differential thermal calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). From DSC analyses of the specimens prepared with unsealed aluminum pans, the reaction exotherm, the time to maximal curing rate, the glass-transition temperature, the rate constant, and the reaction order of the epoxy system decrease in the presence of solvents were obtained. The changes were in the order of toluene>tetra-hydrofuran>acetone and which are consistent with the order of their boiling points. The heat absorbed during the solvent evaporation consumed the curing exotherm and resulted in a change in temperature dependent curing mechanisms. The results from FTIR spectra confirmed that the composition of the cured resin was influenced by the curing temperature and the type of the solvent used.
Interfacial interaction is one of the most critical issues in carbon nanotube/polymer composites. In this paper the role of nonionic surfactant is investigated. With the surfactant as the processing aid, the addition of only 1 wt % carbon nanotubes in the composite increases the glass transition temperature from 63 °C to 88 °C. The elastic modulus is also increased by more than 30%. In contrast, the addition of carbon nanotubes without the surfactant only has moderate effects on the glass transition temperature and on the mechanical properties. This work points to the pathways to improve dispersion and to modify interfacial bonding in carbon nanotube/polymer composites.
The effects of the incorporation of single-walled carbon nanotubes (SWNTs) on the cure reaction of a diglycidyl ether of bisphenol A-based (DGEBA) epoxy resin is investigated by thermal analysis and Raman spectroscopy. The results of the investigation show that SWNTs act as a strong catalyst. A shift of the exothermic reaction peak to lower temperatures is in fact observed in the presence of SWNTs. Moreover, these effects are already noticeable at the lowest SWNT content investigated (5%) with slightly further effects at higher concentrations, suggesting a saturation of the catalysing action at the higher concentrations studied (10%). The thermal stability of cured DGEBA and DGEBA/SWNT composites was examined by thermogravimetry, showing a faster thermal degradation for DGEBA-SWNT composites. Raman spectroscopy was successfully applied to demonstrate that the changes observed in the cure reaction of the composites lead to a different residual strain on the SWNT bundles, following a different intercalation of the epoxy matrix.
Epoxy resins are attractive materials for many engineering applications, as they are low in density, have excellent mechanical properties and are easily fabricated by processes such as injection molding, extrusion and vacuum forming. However, the hostile humid environment can degrade the epoxy system because most epoxies absorb moisture. In this paper, the tensile fracture surfaces have been analyzed by a scanning electron microscopy (SEM) for the initial dry, moisture-saturated (preconditioned under hygrothermal conditions, 85 °C/85%RH) and completely desorbed (dry under thermal conditions, 85 °C) specimens, respectively. Furthermore, fracture surface patterns are simulated by computer, based on the theory that the conic-shaped pattern is due to the intersection between a moving planar crack front and a radically growing circular craze or secondary crack front. From the fractographic analysis and computer simulation results, it can be concluded that there is a close relationship between the velocity ratios u / v and the effect of hygrothermal conditions. Additionally, the transition of brittle/ductile appeared because of the effect of hygrothermal conditions.
A series of microcapsules filled with epoxy resins with poly(urea–formaldehyde) (PUF) shell were synthesized by in situ polymerization, and they were heat-treated for 2 h at 100 °C, 120 °C, 140 °C, 160 °C, 180 °C and 200 °C. The effects of surface morphology, wall shell thickness and diameter on the thermal stability of microcapsules were investigated. The chemical structure and surface morphology of microcapsules were investigated using Fourier-transform infrared spectroscope (FTIR) and scanning electron microscope (SEM), respectively. The thermal properties of microcapsules were investigated by thermogravimetric analysis (TGA and DTA) and by differential scanning calorimetry (DSC). The thermal damage mechanisms of microcapsules at lower temperature (<251 °C) are the diffusion of the core material out of the wall shell or the breakage of the wall shell owing to the mismatch of the thermal expansion of core and shell materials of microcapsules. The thermal damage mechanisms of microcapsules at higher temperature (>251 °C) are the decomposition of shell material and core materials. Increasing the wall shell thickness and surface compactness can enhance significantly the weight loss temperatures (Td) of microcapsules. The microcapsules with mean wall shell thickness of 30 ± 5 μm and smoother surface exhibit higher thermal stability and can maintain quite intact up to approximately 180 °C.
The IR spectra of 40% acetone solutions of epoxy resins with different molecular mass were studied. A correlation was found between the intensities of some absorption bands for the determination of epoxide (920 cm–1) and hydroxyl (3450 cm–1) groups and for the estimations of the average molecular mass of the resin (1108 cm–1).