- Email: [email protected]
phenol-formaldehyde resin blend fiber
Letters to the Editor / Carbon 38 (2000) 1499 – 1524
Schobert of Penn State for his support, and Dr. T. Edwards of AFRL /APPD for his interest. We wish to express our gratitude to Prof. Akira Tomita of Tohoku University, Japan for his advice and helpful discussions.
[8] [9]
References
[10]
[1] Iijima S. Nature 1991;354:56–8. [2] Terrones M, Grobert N, Olivares J, Zhang JP, Terrones H, Kordatos K, Hsu WK, Hare JP, Townsend PD, Prassides K, Cheetham AK, Kroto HW, Walton DRM. Nature 1997;388:52–5. [3] Andrews R, Jacques D, Rao AM, Derbyshire F, Qian D, Fan X, Dickey EC, Chen J. Chem Phys Lett 1999;303:467–74. [4] Hsu WK, Hare JP, Terrones H, Kroto HW, Walton DRM. Nature 1995;377:687. [5] Kyotani T, Tsai LF, Tomita A. Chem Mater 1995;7:1427–8. [6] Kyotani T, Pradhan BK, Tomita A. Bull Chem Soc Jpn 1999;72:1957–70. [7] Thess A, Lee R, Nikolaev P, Dai HJ, Petit P, Robert J, Xu
[11]
[12] [13] [14] [15] [16] [17] [18]
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CH, Lee YH, Kim SG, Rinzler AG, Colbert DT, Scuseria GE, Tomanek D, Fisher JE, Smalley RE. Science 1996;273:483–7. Smith DJ, McCartney MR, Tracz E, Borowiecki T. Ultramicroscopy 1990;34:54–9. Audier M, Oberlin A, Coulon M. J Crystal Growth 1981;55:549–56. Oberlin A, Endo M, Koyama T. J Crystal Growth 1976;32:335–49. Linne DD, Meyer ML, Edwards T, Eitman DA. Paper AIAA 97-3041. 33rd AIAA /ASME / SAE /ASEE Joint Propulsion Conference, July 6–9, 1997. Altin O, Eser S. Ind Eng Chem Res 2000;39:642–5. Howard JB, Das Chowdhury K, Vander Sande JB. Nature 1994;376:603. Ugarte D. Nature 1992;359:707–9. Harris PJF. J Microsc 1996;186:88–90. Ando Y. Carbon 1995;33:171–5. Iijima S, Ichihashi T, Ando Y. Nature 1992;356:776–8. Ebbesen TW. Acc Chem Res 1988;31:558–66.
A TG-MS study of poly(vinyl butyral) / phenol-formaldehyde resin blend fiber Jun-ichi Ozaki*, Wataru Ohizumi, Asao Oya Faculty of Engineering, Gunma University, 1 -5 -1, Tenjin-cho, Kiryu, Gunma 376 -8515, Japan Received 18 December 1999; accepted 5 May 2000 Keywords: A. Carbon fibers; B. Carbonization; C. Thermal analysis; D. Chemical structure
One of the factors needed for designing carbon materials is the selection of raw materials. Accumulated data on the carbonization of organic polymers enable the manufacturing of various types of carbon products, ranging from carbon fibers to glassy carbons [1]. Polymer alloys such as block copolymers, graft copolymers, physical blends and chemical blends, are essentially multi-component polymer systems, which sometimes show superior properties to the properties of each component polymer [2]. This fact gives us an expectation of widening the spectrum of the available raw materials for carbonization, and hence of manufacturing a variety of carbon materials. We are interested in the preparation of electronically or chemically functional carbons by modifying the carbonization processes [3–5]. Beside this, we also believe some novel polymer or organic materials would be suitable *Corresponding author. Tel.: 181-277-30-1352; fax: 181277-1353. E-mail address: [email protected] (J.-i. Ozaki).
materials for such functional carbon materials. In this sense, polymer alloys are attractive materials and we are studying the carbonization of polymer blends. In this paper, we present a TG-MS observation of a polymer blend consisting of phenol formaldehyde (PF) resin and poly(vinyl butyral) (PVB), which was a candidate to give a porous polymer fiber without physical activation by steam or carbon dioxide [4]. Details of the sample preparation procedure are described elsewhere [5]. Two samples were made, one is the pristine PF fiber and another is the polymer blend fiber of PF and PVB. These samples were subjected to FT-IR and TG-MS measurements with an FT-IR spectrometer (Perkin-Elmer, 1650) and with an experimental apparatus consisting of a TG / DTA analyzer (Rigaku Thermoplus 8160) coupled with a quadrupole mass spectrometer (Hewlett Packard, Mass Selective Detector 5973), respectively. FT-IR spectra were recorded for KBr disks of the samples. For TG-MS measurements, about 4 mg of sample was taken onto a platinum pan, and was pyrolyzed in a
0008-6223 / 00 / $ – see front matter 2000 Elsevier Science Ltd. All rights reserved. PII: S0008-6223( 00 )00113-5
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Letters to the Editor / Carbon 38 (2000) 1499 – 1524
Fig. 1. Comparison of the FT-IR spectra between the virgin and the cured samples. (a) phenol-formaldehyde resin, (b) PVB / phenolformaldehyde blend.
Fig. 2. TG-MS diagrams of the cured phenol-formaldehyde resin. Top: Selected ion chromatogram of formaldehyde, middle: phenols and bottom: weight loss curve.
Letters to the Editor / Carbon 38 (2000) 1499 – 1524
stream of helium (99.9999%) at a heating rate of 308C / min. The scanned mass range was m / z51.6|250, because species with higher m / z value than 250 were found to be minor constituents in the preliminary runs. After determining the target species, the final measurements were performed by setting the mass spectrometer at the selected ion monitoring (SIM) mode. Comparisons of FT-IR spectra are made in Fig. 1 between the virgin and the cured pristine PF samples. Upon curing, a development of 1480 cm 21 peak and a change in the shape of the broad band lying 3200–3550 cm 21 are observed. The former can be taken as the sign of the introduction of methylene bridge [6–9] by curing. The latter broad band was assigned to the hydroxyl group stretching mode, which was modulated by hydrogen bonds [6–9]. This band seems to be constituted of at least two components, one peaked at 3420 cm 21 and another at 3520 cm 21 . Although we do not understand the differences between these two components, the environments of the hydroxyl group would be altered by curing. The FT-IR spectrum of the virgin polymer blend sample (Fig. 1(b)) showed a very broad OH-band which could be interpreted as the formation of hydrogen bonds between
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the OH groups of PVB and of phenol-formaldehyde resin. After curing, the broad OH-band turned into the same shape as the shape of the cured pristine PF sample, which means the OH-group in PVB did not contribute to the OH-bands. Some chemical changes on the OH-groups of PVB upon the curing treatment could be a possible explanation for the disappearance of the contribution. Other differences between the virgin and the cured polymer blend samples were the appearance of three additional peaks appearing at 1020 cm 21 , 1480 cm 21 and 1730 cm 21 , which were assigned to the characteristic vibrations of aryl-O-alkyl bond, CH 2 -deformation [7] and carboxyl group, respectively. The results of TG-MS study are presented in Figs. 2 and 3. The weight loss curves of the polymers were similar to the results presented in the previous paper [4]. In both cases, each weight loss was completely accompanied by corresponding gas evolutions. The pristine PF sample showed an emission of m / z529 species at around 2808C and formations of three main species of m / z594, m / z5 108 and m / z5122 at around 4808C. The former species was assigned to formaldehyde that might be trapped in the three dimensional network of PF resin, and the latter three
Fig. 3. TG-MS diagrams of the cured PVB / phenol-formaldehyde blend. Top: Selected ion chromatogram of formaldehyde, middle: phenols and bottom: weight loss curve.
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Letters to the Editor / Carbon 38 (2000) 1499 – 1524
Fig. 4. (1) Formation of phenols in the major weight loss region (based on ref. [12]).
were assigned to phenol, cresols and xylenols, respectively. Trick and Saliba [11] studied thermal degradation of phenol formaldehyde resin. They explained the formation of phenol and cresols due to the scission of a terminal benzene ring depending on the position of scission as shown in Eq. (1) (Fig. 4). Allen et al. pointed out the possibility of formation of xylenol or trimethylphenol during the pyrolysis of the highly condensed phenol formaldehyde resin [12]. The main products in the pyrolysis of the pristine fiber were phenol and cresols, and a less amount of xylenols. Our observation indicated that the reaction responsible for the major weight loss was not only due to the elimination of the unstable terminal groups but also due to the elimination of the inner unit of the networking structure as indicated in Eq. (1). No formation of water in the lower temperature region that could be assigned to as the occurrences of dehydration-condensation involving phenolic OH groups pointed out in ref. [9,10]. The products
Fig. 5. Reactions expected for the blend. (2) hydrolysis of PVB takes place followed by the formation of formal (3). The hydroxyl group reacts with the phenyl ring to form an aryl-O-alkyl bond (4).
Letters to the Editor / Carbon 38 (2000) 1499 – 1524
evolution patterns of the polymer blend sample deviated from the pristine PF sample in the following respects: i.e. the appearance of an additional formation of m / z529 species at around 4008C, the onset temperature of the formation of phenols down to 4508C and the alteration of the main product from phenol to xylenols. In the following paragraphs, discussions on the deviations mentioned above are made. When PVB alone was subjected to TG-MS measurement, the polymer showed a rapid decrease in weight which was accompanied by the production of butanal at 350–4508C. No formation of butanal was detected in the pyrolysis of the polymer blend, instead of this the additional formation of formaldehyde was observed around this temperature range. This indicated a possibility of alteration of butanal moiety in PVB during the curing with HCHO / HCl solution. Acetals like PVB are hydrolyzed in the presence of acid to give poly(vinyl alcohol) (Eq. (2) (Fig. 5). At the same time, formaldehyde included in the curing solution reacts with the OH-groups in PVA (Eq. (3)), as in the manner of manufacturing Vinylon 1 [13]. Thermal degradation of Vinylon could be responsible for the additional formation of formaldehyde. It is also possible to take place a further reaction between the phenyl ring of PF resin and the hydroxyl group of PVB to give the ether structure 2 as shown in Eq. (4). This structure explains why we obtained the similarity in the IR spectra between OH-bands of the cured pristine sample and the cured polymer blend sample to each other, and why we observed the appearance of the aryl-O-alkyl band after curing of the polymer blend sample. The structure shown by 2 can be taken as a kind of graft copolymers, and hence the two polymers are microscopically mixed in the material. However, this structure would restrict the development of the three dimensional network in the material because of steric hindrance. Consequently, the three-dimensional networks of the PF moieties were not extended throughout the material, which resulted in two effects on the pyrolysis of the polymer blend fiber. One is to decrease the main pyrolysis temperature because of the less stability of the small clusters of PF moieties. Another is to increase the formation of xylenols, because the inner unit of the networking structure are easily eliminated during pyrolysis. In the present case, the pyrolysis of the polymer blend was different from the superimposition of the pyrolyses of the constituent polymers. This introduces difficulties in designing carbon materials by using polymer blends, however, we still have the possibility of obtaining carbon materials with the unexpected properties. In conclusion, polymer blends should be recognized as raw materials that expand the spectrum of the properties of carbon materials.
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Acknowledgements This work was financially supported by a Grant-in-Aid for Scientific Research on Priority Areas (Profect No. 09243101) from the Ministry of Education, Science, Sports and Culture of Japan.
References [1] See, for example, Marsh H, Heintz EA, Rodriguez-Reinoso F, editor. Introduction to Carbon Technology, University of Alicante, Secretariado de Publicaciones, 1997. [2] Kienzle SY. Polymer blends and alloys: Expanding opportunities for plastics. In: Kohudic MA, editor. Advances in Polymer Blends and Alloys Technology, vol. 1, Lancaster: Technomic, 1988: p. 1–11. [3] Ozaki J, Mitsui M, Nishiyama Y. Carbonization of ferrocene containing polymers and their electrochemical properties. Carbon 1998;36:131–5. [4] Ozaki J, Endo N, Ohizumi W, Igarashi K, Nakahara M, Oya A, Yoshida S, Iizuka T. Novel preparation method for production of mesoporous carbon fiber from polymer blend. Carbon 1997;35:1031–3. [5] Ozaki J, Ohizumi W, Endo N, Igarashi K, Oya A, Yoshida S, Iizuka T, Roman-Martinez MC, Linares-Solano A. Preparation of platinum loaded carbon fiber by using polymer blend. Carbon 1997;35:1676–7. [6] Ouchi K. Infra-red study of structural changes during the pyrolysis of a phenol-formaldehyde resin. Carbon 1966;4:59–66. [7] Morterra C, Low MJD. IR studies of carbons-VII. The pyrolysis of a phenol-formaldehyde resin Carbon 1985;23:525–30. [8] Jenkins GM, Kawamura K, Ban LL. Formation and structure of polymeric carbons. Proc R Soc Lond A 1972;327:501–17. [9] Costa L, Rossi di Montelera L, Camino G, Weil ED, Pearce EM. Structure-charring relationship in phenol-formaldehyde type resins. Polymer Degradation and Stability 1997;56:23– 35. ¨ [10] Fitzer E, Shafer W. The effect of crosslinking on the formation of glasslike carbons from thermosetting resins. Carbon 1970;8:353–64. [11] Trick KA, Saliba TE. Mechanisms of the pyrolysis of phenolic resin in a carbon / phenolic composite. Carbon 1995;33:1509–15. [12] Allen Jr. Chemistry of synthetic varnish resins. I., Meharg VE, Shamidt JH, Ind. Eng. Chem. 1934;26:663–9. [13] Peters R.H., Textile Chemistry, Vol. 1. Amsterdam, Elsevier, 1963: 404–60.
Schobert of Penn State for his support, and Dr. T. Edwards of AFRL /APPD for his interest. We wish to express our gratitude to Prof. Akira Tomita of Tohoku University, Japan for his advice and helpful discussions.
[8] [9]
References
[10]
[1] Iijima S. Nature 1991;354:56–8. [2] Terrones M, Grobert N, Olivares J, Zhang JP, Terrones H, Kordatos K, Hsu WK, Hare JP, Townsend PD, Prassides K, Cheetham AK, Kroto HW, Walton DRM. Nature 1997;388:52–5. [3] Andrews R, Jacques D, Rao AM, Derbyshire F, Qian D, Fan X, Dickey EC, Chen J. Chem Phys Lett 1999;303:467–74. [4] Hsu WK, Hare JP, Terrones H, Kroto HW, Walton DRM. Nature 1995;377:687. [5] Kyotani T, Tsai LF, Tomita A. Chem Mater 1995;7:1427–8. [6] Kyotani T, Pradhan BK, Tomita A. Bull Chem Soc Jpn 1999;72:1957–70. [7] Thess A, Lee R, Nikolaev P, Dai HJ, Petit P, Robert J, Xu
[11]
[12] [13] [14] [15] [16] [17] [18]
1515
CH, Lee YH, Kim SG, Rinzler AG, Colbert DT, Scuseria GE, Tomanek D, Fisher JE, Smalley RE. Science 1996;273:483–7. Smith DJ, McCartney MR, Tracz E, Borowiecki T. Ultramicroscopy 1990;34:54–9. Audier M, Oberlin A, Coulon M. J Crystal Growth 1981;55:549–56. Oberlin A, Endo M, Koyama T. J Crystal Growth 1976;32:335–49. Linne DD, Meyer ML, Edwards T, Eitman DA. Paper AIAA 97-3041. 33rd AIAA /ASME / SAE /ASEE Joint Propulsion Conference, July 6–9, 1997. Altin O, Eser S. Ind Eng Chem Res 2000;39:642–5. Howard JB, Das Chowdhury K, Vander Sande JB. Nature 1994;376:603. Ugarte D. Nature 1992;359:707–9. Harris PJF. J Microsc 1996;186:88–90. Ando Y. Carbon 1995;33:171–5. Iijima S, Ichihashi T, Ando Y. Nature 1992;356:776–8. Ebbesen TW. Acc Chem Res 1988;31:558–66.
A TG-MS study of poly(vinyl butyral) / phenol-formaldehyde resin blend fiber Jun-ichi Ozaki*, Wataru Ohizumi, Asao Oya Faculty of Engineering, Gunma University, 1 -5 -1, Tenjin-cho, Kiryu, Gunma 376 -8515, Japan Received 18 December 1999; accepted 5 May 2000 Keywords: A. Carbon fibers; B. Carbonization; C. Thermal analysis; D. Chemical structure
One of the factors needed for designing carbon materials is the selection of raw materials. Accumulated data on the carbonization of organic polymers enable the manufacturing of various types of carbon products, ranging from carbon fibers to glassy carbons [1]. Polymer alloys such as block copolymers, graft copolymers, physical blends and chemical blends, are essentially multi-component polymer systems, which sometimes show superior properties to the properties of each component polymer [2]. This fact gives us an expectation of widening the spectrum of the available raw materials for carbonization, and hence of manufacturing a variety of carbon materials. We are interested in the preparation of electronically or chemically functional carbons by modifying the carbonization processes [3–5]. Beside this, we also believe some novel polymer or organic materials would be suitable *Corresponding author. Tel.: 181-277-30-1352; fax: 181277-1353. E-mail address: [email protected] (J.-i. Ozaki).
materials for such functional carbon materials. In this sense, polymer alloys are attractive materials and we are studying the carbonization of polymer blends. In this paper, we present a TG-MS observation of a polymer blend consisting of phenol formaldehyde (PF) resin and poly(vinyl butyral) (PVB), which was a candidate to give a porous polymer fiber without physical activation by steam or carbon dioxide [4]. Details of the sample preparation procedure are described elsewhere [5]. Two samples were made, one is the pristine PF fiber and another is the polymer blend fiber of PF and PVB. These samples were subjected to FT-IR and TG-MS measurements with an FT-IR spectrometer (Perkin-Elmer, 1650) and with an experimental apparatus consisting of a TG / DTA analyzer (Rigaku Thermoplus 8160) coupled with a quadrupole mass spectrometer (Hewlett Packard, Mass Selective Detector 5973), respectively. FT-IR spectra were recorded for KBr disks of the samples. For TG-MS measurements, about 4 mg of sample was taken onto a platinum pan, and was pyrolyzed in a
0008-6223 / 00 / $ – see front matter 2000 Elsevier Science Ltd. All rights reserved. PII: S0008-6223( 00 )00113-5
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Letters to the Editor / Carbon 38 (2000) 1499 – 1524
Fig. 1. Comparison of the FT-IR spectra between the virgin and the cured samples. (a) phenol-formaldehyde resin, (b) PVB / phenolformaldehyde blend.
Fig. 2. TG-MS diagrams of the cured phenol-formaldehyde resin. Top: Selected ion chromatogram of formaldehyde, middle: phenols and bottom: weight loss curve.
Letters to the Editor / Carbon 38 (2000) 1499 – 1524
stream of helium (99.9999%) at a heating rate of 308C / min. The scanned mass range was m / z51.6|250, because species with higher m / z value than 250 were found to be minor constituents in the preliminary runs. After determining the target species, the final measurements were performed by setting the mass spectrometer at the selected ion monitoring (SIM) mode. Comparisons of FT-IR spectra are made in Fig. 1 between the virgin and the cured pristine PF samples. Upon curing, a development of 1480 cm 21 peak and a change in the shape of the broad band lying 3200–3550 cm 21 are observed. The former can be taken as the sign of the introduction of methylene bridge [6–9] by curing. The latter broad band was assigned to the hydroxyl group stretching mode, which was modulated by hydrogen bonds [6–9]. This band seems to be constituted of at least two components, one peaked at 3420 cm 21 and another at 3520 cm 21 . Although we do not understand the differences between these two components, the environments of the hydroxyl group would be altered by curing. The FT-IR spectrum of the virgin polymer blend sample (Fig. 1(b)) showed a very broad OH-band which could be interpreted as the formation of hydrogen bonds between
1517
the OH groups of PVB and of phenol-formaldehyde resin. After curing, the broad OH-band turned into the same shape as the shape of the cured pristine PF sample, which means the OH-group in PVB did not contribute to the OH-bands. Some chemical changes on the OH-groups of PVB upon the curing treatment could be a possible explanation for the disappearance of the contribution. Other differences between the virgin and the cured polymer blend samples were the appearance of three additional peaks appearing at 1020 cm 21 , 1480 cm 21 and 1730 cm 21 , which were assigned to the characteristic vibrations of aryl-O-alkyl bond, CH 2 -deformation [7] and carboxyl group, respectively. The results of TG-MS study are presented in Figs. 2 and 3. The weight loss curves of the polymers were similar to the results presented in the previous paper [4]. In both cases, each weight loss was completely accompanied by corresponding gas evolutions. The pristine PF sample showed an emission of m / z529 species at around 2808C and formations of three main species of m / z594, m / z5 108 and m / z5122 at around 4808C. The former species was assigned to formaldehyde that might be trapped in the three dimensional network of PF resin, and the latter three
Fig. 3. TG-MS diagrams of the cured PVB / phenol-formaldehyde blend. Top: Selected ion chromatogram of formaldehyde, middle: phenols and bottom: weight loss curve.
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Letters to the Editor / Carbon 38 (2000) 1499 – 1524
Fig. 4. (1) Formation of phenols in the major weight loss region (based on ref. [12]).
were assigned to phenol, cresols and xylenols, respectively. Trick and Saliba [11] studied thermal degradation of phenol formaldehyde resin. They explained the formation of phenol and cresols due to the scission of a terminal benzene ring depending on the position of scission as shown in Eq. (1) (Fig. 4). Allen et al. pointed out the possibility of formation of xylenol or trimethylphenol during the pyrolysis of the highly condensed phenol formaldehyde resin [12]. The main products in the pyrolysis of the pristine fiber were phenol and cresols, and a less amount of xylenols. Our observation indicated that the reaction responsible for the major weight loss was not only due to the elimination of the unstable terminal groups but also due to the elimination of the inner unit of the networking structure as indicated in Eq. (1). No formation of water in the lower temperature region that could be assigned to as the occurrences of dehydration-condensation involving phenolic OH groups pointed out in ref. [9,10]. The products
Fig. 5. Reactions expected for the blend. (2) hydrolysis of PVB takes place followed by the formation of formal (3). The hydroxyl group reacts with the phenyl ring to form an aryl-O-alkyl bond (4).
Letters to the Editor / Carbon 38 (2000) 1499 – 1524
evolution patterns of the polymer blend sample deviated from the pristine PF sample in the following respects: i.e. the appearance of an additional formation of m / z529 species at around 4008C, the onset temperature of the formation of phenols down to 4508C and the alteration of the main product from phenol to xylenols. In the following paragraphs, discussions on the deviations mentioned above are made. When PVB alone was subjected to TG-MS measurement, the polymer showed a rapid decrease in weight which was accompanied by the production of butanal at 350–4508C. No formation of butanal was detected in the pyrolysis of the polymer blend, instead of this the additional formation of formaldehyde was observed around this temperature range. This indicated a possibility of alteration of butanal moiety in PVB during the curing with HCHO / HCl solution. Acetals like PVB are hydrolyzed in the presence of acid to give poly(vinyl alcohol) (Eq. (2) (Fig. 5). At the same time, formaldehyde included in the curing solution reacts with the OH-groups in PVA (Eq. (3)), as in the manner of manufacturing Vinylon 1 [13]. Thermal degradation of Vinylon could be responsible for the additional formation of formaldehyde. It is also possible to take place a further reaction between the phenyl ring of PF resin and the hydroxyl group of PVB to give the ether structure 2 as shown in Eq. (4). This structure explains why we obtained the similarity in the IR spectra between OH-bands of the cured pristine sample and the cured polymer blend sample to each other, and why we observed the appearance of the aryl-O-alkyl band after curing of the polymer blend sample. The structure shown by 2 can be taken as a kind of graft copolymers, and hence the two polymers are microscopically mixed in the material. However, this structure would restrict the development of the three dimensional network in the material because of steric hindrance. Consequently, the three-dimensional networks of the PF moieties were not extended throughout the material, which resulted in two effects on the pyrolysis of the polymer blend fiber. One is to decrease the main pyrolysis temperature because of the less stability of the small clusters of PF moieties. Another is to increase the formation of xylenols, because the inner unit of the networking structure are easily eliminated during pyrolysis. In the present case, the pyrolysis of the polymer blend was different from the superimposition of the pyrolyses of the constituent polymers. This introduces difficulties in designing carbon materials by using polymer blends, however, we still have the possibility of obtaining carbon materials with the unexpected properties. In conclusion, polymer blends should be recognized as raw materials that expand the spectrum of the properties of carbon materials.
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Acknowledgements This work was financially supported by a Grant-in-Aid for Scientific Research on Priority Areas (Profect No. 09243101) from the Ministry of Education, Science, Sports and Culture of Japan.
References [1] See, for example, Marsh H, Heintz EA, Rodriguez-Reinoso F, editor. Introduction to Carbon Technology, University of Alicante, Secretariado de Publicaciones, 1997. [2] Kienzle SY. Polymer blends and alloys: Expanding opportunities for plastics. In: Kohudic MA, editor. Advances in Polymer Blends and Alloys Technology, vol. 1, Lancaster: Technomic, 1988: p. 1–11. [3] Ozaki J, Mitsui M, Nishiyama Y. Carbonization of ferrocene containing polymers and their electrochemical properties. Carbon 1998;36:131–5. [4] Ozaki J, Endo N, Ohizumi W, Igarashi K, Nakahara M, Oya A, Yoshida S, Iizuka T. Novel preparation method for production of mesoporous carbon fiber from polymer blend. Carbon 1997;35:1031–3. [5] Ozaki J, Ohizumi W, Endo N, Igarashi K, Oya A, Yoshida S, Iizuka T, Roman-Martinez MC, Linares-Solano A. Preparation of platinum loaded carbon fiber by using polymer blend. Carbon 1997;35:1676–7. [6] Ouchi K. Infra-red study of structural changes during the pyrolysis of a phenol-formaldehyde resin. Carbon 1966;4:59–66. [7] Morterra C, Low MJD. IR studies of carbons-VII. The pyrolysis of a phenol-formaldehyde resin Carbon 1985;23:525–30. [8] Jenkins GM, Kawamura K, Ban LL. Formation and structure of polymeric carbons. Proc R Soc Lond A 1972;327:501–17. [9] Costa L, Rossi di Montelera L, Camino G, Weil ED, Pearce EM. Structure-charring relationship in phenol-formaldehyde type resins. Polymer Degradation and Stability 1997;56:23– 35. ¨ [10] Fitzer E, Shafer W. The effect of crosslinking on the formation of glasslike carbons from thermosetting resins. Carbon 1970;8:353–64. [11] Trick KA, Saliba TE. Mechanisms of the pyrolysis of phenolic resin in a carbon / phenolic composite. Carbon 1995;33:1509–15. [12] Allen Jr. Chemistry of synthetic varnish resins. I., Meharg VE, Shamidt JH, Ind. Eng. Chem. 1934;26:663–9. [13] Peters R.H., Textile Chemistry, Vol. 1. Amsterdam, Elsevier, 1963: 404–60.