nueva página del texto (beta)
Inglés (pdf)
Artículo en XML
Referencias del artículo
Traducción automática
Enviar artículo por email
Permalink
Texto completo disponible sólo en PDF.
Servicios Personalizados
Revista
Articulo
Indicadores
-
Citado por SciELO -
Accesos
Links relacionados
-
Similares en
SciELO
Compartir
TIP. Revista especializada en ciencias químico-biológicas
versión impresa ISSN 1405-888X
TIP vol.9 no.1 Ciudad de México jun. 2006
Artículos originales
Mechanism of radiation-chemical and pyrolytic transformations in lexan ®
Mecanismo químico de transformaciones radiolíticas y pirolíticas en lexan ®
1Instituto de Ciencias Nucleares, UNAM. E-mail: aliev@nucleares.unam.mx.
2Laboratory of Plasma Chemistry and Planetary Studies. Ciudad Universitaria, Apdo. Postal 70-543, СР. 04510, México, D.F. Instituto de Ciencias Nucleares, UNAM.
We report here a new approach to study the mechanism of radiation-chemical transformations in polymeric materials based on the combined analysis of radiolytic gases, and pyrolytic products from preirradiated polymers by flash pyrolysis coupled to gas chromatography -Fourier transformed infrared spectroscopy- mass spectrometry with electron impact mode (GC-FTIR-MS). Lexan® (bisphenol-A polycarbonate) was studied in the dose range from 0.125 to 1.0 MGy. Lexan irradiation was accompanied by the preferential release of carbon monoxide followed by minor production of hydrogen, carbon dioxide and methane. Pyrolyzed Lexan releases mainly carbon dioxide, methane, benzene, toluene, phenol and 4-methyl-phenol. On the basis of these results we suggest two main pathways of Lexan radiation-induced scission with equal probabilities: (a) carbonate bond and (b) aliphatic-aromatic bond ruptures.
Key Words: Lexan; radiolysis; flash pyrolysis; GC-FTIR-MS; mechanism of degradation
Reportamos una nueva metodología para estudiar el mecanismo de transformaciones por radiación en materiales poliméricos basada en el análisis combinado de los gases de origen radiolítico, y los productos pirolíticos, generados mediante la pirólisis rápida de polímeros pre-irradiados, acoplado a la cromatografía de gases -espectroscopia de infrarrojo con transformada de Fourier- espectrometría de masas por impacto electrónico. El Lexan® (policarbonato de bisfenol-A) fue estudiado en el rango de dosis de 0.125 a 1.0 MGy. La irradiación del Lexan estuvo acompañada por la liberación preferencial del monóxido de carbono seguida de una producción menor de hidrógeno, dióxido de carbono y metano. El Lexan pirolizado liberó principalmente dióxido de carbono, metano, benceno, tolueno y 4-metilfenol. Con base en los resultados obtenidos sugerimos dos vías principales para la incisión del Lexan por radiación con igual probabilidad: (a) ruptura del enlace carbonato y (b) ruptura del enlace alifático-aromático.
Palabras Clave: Lexan; radiólisis; pirólisis instantánea; CG-IRTF-EM; mecanismo de degradación
Acknowledgements
The authors thank Francisco Garcia from ICN-UNAM for sample irradiation. We are indebted to Dr. Jay LaVerne from the Radiation Laboratory of the University of Notre Dame in Indiana for useful discussion of this work. Financial support from the UNAM project INI 01903 and the CONACyT project 46137 are gratefully acknowledged.
References
1. Clough, R.L. & Shalaby, S.W. Radiation Effects on Polymers. ACS Symposium Series 475 (American Chemical Society, Washington, 1991). [ Links ]
2. Ivanov, V.S. Radiation Chemistry of Polymers, 123-196 (VSP, Utrecht, 1992). [ Links ]
3. Tabata,Y. CRC Handbook of Radiation Chemistry, 721-750 (CRC Press, Boca Raton, 1991) . [ Links ]
4. Woods, R.J. & Pikaev, A.K. Applied Radiation Chemistry: Radiation Processing, 341-391 (John Wiley & Sons, New York, 1994). [ Links ]
5. Bhattacharya, A. Radiation and industrial polymers. Prog. Polym. Sci. 25 (3), 371-401 (2000). [ Links ]
6. Golden, J.H. & Hazell, E.A. Degradation of polycarbonate by ionizing radiation. J. Polym. Sci. A 1 (8), 1671-1686 (1963). [ Links ]
7. Hama, Y. & Shinohara, K. J. Electron spin resonance studies of polycarbonate irradiated by γ-rays and ultraviolet light. J. Polym. Sci. A-l 8 (3), 651-663 (1970). [ Links ]
8. Ouano, A.C., Johnson, D.E., Dawson, B. & Pederson, L.A. Chain scission efficiency of some polymers in γ-radiation. J.Polym. Sci., Polym. Chem. Ed. 14 (4), 701-711 (1976). [ Links ]
9. Acierno, D., La Mantia, F.P., Spadaro, G., Titomanlio, G. & Calderaro, E. Effect of radiation conditions on some properties of a polycarbonate. Radiat. Phys. Chem. 17 (1), 31-34 (1981). [ Links ]
10. Kalkar, A.K., Kundagol, S., Chand, S. & Chandra, S. Effect of gamma-irradiation on structural and electrical properties of poly (bisphenol-A carbonate) films. Radiat. Phys. Chem. 39 (5),435-442 (1992). [ Links ]
11. Shamshad, Α., Rashid, M. & Husain, A. High gamma dose dosimetry by polycarbonates. Radiat. Phys. Chem. 50 (3), 307-311 (1997). [ Links ]
12. Araujo, E.S., Khoury, HJ. & Silveira, S.V. Effects of gamma-irradiation on some properties of durolon polycarbonate. Radiat. Phys. Chem. 53 (1) , 79-84 (1998) . [ Links ]
13. Navarro-González, R. & Aliev, R. Gaseous products formed by gamma-irradiation of bisphenol-A polycarbonate. Polym. Bull. 45 (4-5),419-424 (2000). [ Links ]
14. Pu, H., Tang, X. & Хu, X. Studies on polycarbonate/polystyrene/polycarbonate-g-polystyrene blends. Polym. Intern. 43 (1), 33-38 (1997). [ Links ]
15. Aliev, R., Garcia, P. & Burlilo, G. Graft polymerization of acrylic acid onto polycarbonate by the preirradiation method. Radiat. Phys. Chem. 58 (3), 299-304 (2000). [ Links ]
16. Aliev, R., Cedillo, G. & Burlilo, G. Radiation crosslinking of bisphenol-A polycarbonate in the presence of bisphenol-a dimethacrylate and triallyl cyanurate. Polym. Bull. 45 (2), 167-174 (2000). [ Links ]
17. Ohtani, H. & Tsuge, S. in: Applied Polymer Analysis and Characterization (ed. Mitchell, J.Jr.) 217-232 (Hanser Publishers, Munich, 1987). [ Links ]
18. Hammond, T. & Lehrle, R.S. in: Comprehensive Polymer Science, v.1 (ed. Booth, C. & Price, C.) 589-612 (Pergamon Press, Oxford, 1989). [ Links ]
19. Crompton, T.R. Practical Polymer Analysis, 655 (Plenum Press, New York, 1993). [ Links ]
20. Applied Pyrolysis Handbook (ed.Wampler T.P.) (Marcel Dekker, New York, 1995) . [ Links ]
21. Blazsó, M. Recent trends in analytical and applied pyrolysis of polymers. J. Anal. Appi. Pyrolysis 39 (1), 1-25 (1997). [ Links ]
22. Tsuge, S., Okumoto, T., Sugimura, Y. & Takeuchi, T. J. Pyrolys-gas chromatographic investigation of fractioned polycarbonates. Chromatogr. Sci. 7 (2), 253-256 (1969). [ Links ]
23. Ito, Y., Ogasawara, H., Ishida, Y., Ohtani, H. & Tsuge, S. Characterization of end groups in polycarbonates by reactive pyrolysis-gas chromatography. Polym. J. 28 (12), 1090-1095 (1996). [ Links ]
24. Wiley, R.H. Mass spectral characteristics of poly(4,4'- isopropylidenediphenyl carbonate). Macromolecules 4 (2), 254-259 (1971). [ Links ]
25. Foti, S., Giuffrida, M., Maravigna, P. & Montaudo, G. Direct mass spectrometry of polymers. VII. Primary thermal fragmentation processes in polycarbonates. J. Polym. Sci., Polym. Chem. Ed. 21 (6), 1567-1581 (1983). [ Links ]
26. Puglisi, C. & Sfuriale, L. Thermal decomposition processes in aromatic polycarbonates investigated by mass spectrometry. Macromolecules 32 (7), 2194-2203 (1999). [ Links ]
Received: February 13, 2006; Accepted: June 19, 2006
This is an open-access article distributed under the terms of the Creative Commons Attribution License
