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The effect of acetone addition on the properties of epoxy

March 2008
Polímeros 18(1)

DOI:10.1590/S0104-14282008000100015

License
CC BY 4.0

Authors:

Marcio Loos

Universidade Federal de Santa Catarina

Luiz Antonio Ferreira Coelho

Santa Catarina State University

Sergio Pezzin

Santa Catarina State University

Sandro Campos Amico

Federal University of Rio Grande do Sul

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.

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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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: dma2lafc@joinville.udesc.br

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.

Experimental

Materials

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.

Methodology

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-

Introduction

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

(CNTs)[1-3].

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

DEMAT, PPGEM, UFRGS

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

Viscosity

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)

160

140

120

100

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-

ing.

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].

Thermogravimetry

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.

100

0 200 400 600 800

Temperature (°C)

Weight (%)

0.0 wt. %

7.0 wt. %

10.0 wt. %

13.0 wt. %

(a)

-2

-4

-6

-8

-10

-12

0 200 400 600 800

Temperature (°C)

Deriv weight (%/min)

0.0 wt. %

7.0 wt. %

10.0 wt. %

13.0 wt. %

(b)

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.

Acetone

(wt. %)

Young´s

modulus

(GPa)

Tensile

strength

(MPa)

Elongation

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.

Conclusions

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.

Acknowledgments

The authors would like to thank CAPES-PROCAD (Proj-

ect 0303054) for the ﬁnancial support and for the scholarship

to Mr. M. R. Loos.

References

1. Dong, B.; Yang, Z.; Huang, Y. & Li, H.-L. - Tribol. Lett.,

20, p.251 (2005).

2. Gong, X., Liu, J., Baskaran, S., Voise, R. D. & Young, J.

S. - Chem. Mater., 12, p.1049 (2000).

3. Puglia, D., Valentini, L., Armentano, I. & Kenny, J. M. -

Diam. Relat. Mater., 12, p.827 (2003).

4. Lau, K. T., Lu, M., Lam, C. K., Cheung, H. Y., Sheng,

F. L. & Li, H. L. - Compos. Sci. Technol., 65, p.719

(2005).

This is in qualitative agreement with the work of Dickens[19]

who found that higher amount of residual acetone decreased

strength and modulus (in ﬂexure) of a particular thermoset

resin, which was attributed in their case to the presence of

defects in the specimen, such as porosity originated from ac-

etone evaporation.

Scanning electron microscopy

SEM images of tensile fractured surfaces are presented

in Figure 5. Figure 5a, for the sample which did not use sol-

vent (0.0 wt.% acetone), has shown a typical fragile behavior,

whereas for the 13.0 wt.% acetone sample (Figure 5b,c), a

(a)

(b)

(c)

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).

Loos, M. R. et al. - The effect of acetone addition on the properties of epoxy

80 Polímeros: Ciência e Tecnologia, vol. 18, nº 1, p. 76-80, 2008

14. Evtushenko, Y. M., Ivanov, V. M. & Zaitsev, B. E. - J.

Anal. Chem., 58, p.347 (2003).

15. Mondragon, I. & Bucknall, C. B. - Plast. Rubber Com-

pos., 21, p.275 (1994).

16. Park, S. J., Lee, H. Y., Han, M. & Hong, S. K. - J. Colloid

Interf. Sci., 270, p.288 (2004).

17. Gracia-Fernandez, C. A., Gomez-Barreiro, S., Ruiz-Sal-

vador, S. & Blaine, R. - Prog. Org. Coat., 54, p.332

(2005).

18. Sharmin, E., Imo, L., Ashraf, S. M. & Ahmad, S. - Prog.

Org. Coat., 50, p.47 (2004).

19. Dickens, S. H. & Cho, B. H. - Dent. Mater., 21, p.354

(2005).

20. Lin, Y. C. & Chen, X. - Mater. Lett., 59, p.3831 (2005).

Enviado: 07/06/07

Reenviado: 09/09/07

Aceito: 14/09/07

5. Hong, S. G. & Wu, C. S. - J. Therm. Anal. Calorim., 59,

p.711 (2000).

6. Liao, Y. H., Marietta-Tondin, O., Liang, Z. Y., Zhang,

C. & Wang, B. - Mat. Sci. Eng. A-Struct, 385, p.175

(2004).

7. Song, Y. S. & Youn, J. R. - Carbon, 43, p.1378 (2005).

8. Qian, J. W., Miao, Y. M., Zhang, L. & Chen, H. L. - J.

Membrane Sci., 203, p.167 (2002).

9. Max, J. J. & Chapados, C. - J. Chm. Phys., 126, Art.

(2007).

10. Torii, H., Musso, M. & Giorgini, M. G. - J Phys Chem A,

109, p.7797 (2005).

11. Lachenal, G., Pierre, A. & Poisson, N. - Micron, 27,

p.329 (1996).

12. Hong, S. G. & Wu, C. S. - Thermochim. Acta, 316, p.167

(1998).

13. Yuan, L., Liang, G. Z., Xie, J. Q., Guo, J. & Li, L. -

Polym. Degrad. Stabil., 91, p.2300 (2006).

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CO 2 laser ablation is a rapid and precise technique for machining microfluidic devices. And also, low-cost epoxy resin (ER) proved the great feasibility of fabricating these devices using the CO 2 laser ablation technique in our previous studies. However, such a technique has shown negative impacts on such ER-based microfluidics as rough surface microchannels, and thermal defects. Therefore, incorporating different proportions of boric acid (BA) into epoxy resin formulation was proposed to obviate the genesis of these drawbacks in ER-based microfluidics. The structural and optical properties of plain ER- and B-doped ER-based chips were characterized by Fourier transform infrared (FT-IR) and UV/Vis spectral analyses. Furthermore, their thermal properties were studied by thermo-gravimetric (TGA) and differential scanning calorimetric (DSC) analysis. A CO 2 laser ablation machine was used in vector mode to draw the designed micro-channel pattern onto plain ER- and B-doped ER-based chips. The quality of microchannels engraved onto these chips was assessed using 3D laser microscopy. This microscopic examination showed a noticeable reduction in the surface roughness and negligible bulge heights in the laser-ablated micro-channels. On the other hand, overall and specific migration using gravimetric methods and gas chromatography-mass spectrometry (GC–MS), respectively, and PCR compatibility test were performed to explore the convenience of these micro-plates for the biological reactions. These findings validated the applicability of B-doped ER-based microfluidics in bio-analytical applications as a result of the effective role of boric acid in enhancing the thermal properties of these chips leading to get micro-channels with higher quality with no effect on the biological reactions.

Effects of residual dichloromethane solvent on the cure of epoxy resin

Article

Jan 1994

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.

Study of the degradation of a thermoset system using TGA and modulated TGA

Article

Dec 2005
PROG ORG COAT

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.

FT-NIR spectroscopy: Trends and application to the kinetic study of epoxy/triamine system (Comparison with DSC and SEC results)

Article

Oct 1996
MICRON

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.

Study on Tribological Properties of Multi-walled CarbonNanotubes/Epoxy Resin Nanocomposites

Article

Dec 2005

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.

DSC and FTIR analysis of the curing behaviors of epoxy/DICY/solvent open systems

Article

Jun 1998
THERMOCHIM ACTA

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.

Surfactant-Assisted Processing of Carbon Nanotube/Polymer Composites

Article

Mar 2000

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.

D. Puglia, L. Valentini, I. Armentano, J.M. Kenny (2003) Effects of single-walled carbon nanotube incorporation on the cure reaction of epoxy resin and its detection by Raman spectroscopy, Diamond and Related Materials 12 (3-7) 827-832. DOI: 10.1016/S0925-9635(02)00358-8

Article

Mar 2003
DIAM RELAT MATER

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.

Investigation of the effect of hygrothermal conditions on epoxy system by fractography and computer simulation

Article

Dec 2005
MATER LETT

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.

Thermal stability of microencapsulated epoxy resins with poly(urea–formaldehyde)

Article

Oct 2006

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.

Determination of Epoxide and Hydroxyl Groups in Epoxide Resins by IR Spectrometry

Article

Apr 2003

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).