Chapter 2: Scope and Objectives

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1 Chapter 2: Scope and Objectives 2.1 Introduction Now-a-days the production of polymers and plastics is increasing. Nylon 66 is a widely used yarn as well as engineering resin. Moreover, it is used in outdoor applications and sometimes in the hostile conditions of temperature and mechanical stress. All this can cause various degree of degradation depending on hostility of environment and presence of oxygen. Knowledge of the degradation chemistry of polymers has led to the development of more efficient stabilizers 1 for improving performance in one hand and on other hand the development of sensitizers 2, 3 to produce degradable plastics which may be environmental friendly on the other hand 4. The prime factors causing degradation of polymers are UV radiation or heating effects of solar radiation. Additional relevant factors include ozone, atmospheric contaminants, and high-energy radiations. The impurities present in the commercial polymers are known to initiate photochemical reactions. The main light absorbing species may be carbonyls 5, metallic impurities 6, dienes 7, trienes 8, hydroperoxides 9 and oxygen-polymer charge transfer complexes 10, 11. Photochemistry of aliphatic polyamides has been a matter of great interest for researchers during last three dacades Unlike other polymers, nylon 66 has very complicated photodegradation behavior. Certain impurities (mainly α, β- unsaturated 16, 17, 20, carbonyls) formed during melt processing or thermal degradation are reported 21, 24 to sensitize the photo-oxidation of nylon 66. Ultimately, in the melt processed nylon 66, the presence of these impurities become the major factor, which determines the rate of photo oxidative degradation in nylon 66. Photosensitized oxidation of nylon 66 in the presence of dyes is also an important area of research 19, Photochemical behavior of anthraquinone acid blue dyes in polyamides as well as in model amides has been studied 19, 28. However, there is a lack of basic understanding of dual behavior of this class of dyes. Photostabilization of nylon 66 is also widely studied 29-39, which includes hindered amine light stabilizers 29, UV absorbers 30-32, transition metal salts 33-35, alkali metal salts 36 and inorganic pigments etc. 2.2 Objectives of the present investigation 34

2 The objective of the present investigation is to study the degradation mechanism of nylon 66 upon thermal and photoirradiation. This would provide a basic understanding to the phenomenon of stabilization of this polymer against degradation. The following aspects of degradation and stabilization have been studied: 1. To examine the photo-oxidative degradation in nylon 66. Chemical and physical changes associated with degradation to be studied in details. 2. To study thermal oxidative degradation in nylon 66 at various temperatures and the formation of oxidative products at all these temperatures are to be compared. 3. To examine the photostability of nylon 66 in the presence of anthraquinone acid blue dyes and also to examine the factors affecting the photochemical behavior of this class of dyes. 4. To study the effect of conventional photostabilizers on the photostability of nylon 66 in the presence of anthraquinone acid blue dyes. 5. To design, synthesize and property evolution of specific water soluble UV absorbers in nylon Approaches Degradation studies of nylon Detailed photoproducts formation during photo-irradiation of nylon 66 will be studied by IR and UV spectroscopy Changes in the surface and bulk morphology upon photo-irradiation will be studied and compared with their respective unirradiated samples. Surface morphology will be studied by SEM and bulk morphology will be studied with the help of DSC and XRD techniques Chemical processes associated with thermal oxidative degradation will be studied and compared with their respective neat samples. IR and UV spectroscopy will be used for the characterization of thermal oxidative products being formed during the thermal oxidative degradation of nylon Effect of dyebath ph on the photochemical behavior of dyed nylon 66 will be studied with the help of FTIR spectroscopy. Nylon 66 samples will be dyed at a range of ph and the rate of photo-oxidation will be studied Stabilization studies of nylon Photostabiliztion of nylon 66, in presence of various combinations of a dye, UV absorber and HALS will be studied in details. This is an empirical approach, which enables us to judge the efficiency and optimum quantity of a stabilizer required for the stabilization of a particular substrate Water-soluble UV absorbers with carboxylic acid and sulfonic acid functional groups will be designed and synthesized. Photo-oxidation of nylon 66, dyed and treated with the aqueous solution of these UV absorbers will be studied in details. 35

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4 2.4 References 1. F. Gugumus, Polym. Degrad. Stab. 24, 289 (1989). 2. F. S. Quresh, H. S. Hamid, A. G. Maadhah, M. B. Amin, Prog. Rubb. Plast. Technol., 5 (1) (1989). 3. P. P. Klemchuk, Modern Plastics Int., pp Sept R. V. Wilder, Modern Plastics Int., pp Sept A. Charlesby and R. H. Partridge, Prc. Royal Soc., A283, 312 (1965) 6. N. Uri, Israel J. Chem., 18, 125 (1975). 7. M. V. Amin, G. Scott and L. M. K. Tilakratne, Eur. Polym. J., 11, 85 (1975). 8. J. F. Heacock, F. B. Mallory and F. P. Gay, J. Polym. Sci., A-1; Polym. Chem. Ed., 6, 2921 (1968). 9. D. G. M. Wood and T. M. Kollman, Chem. Ind., 423 (1972). 10. V. K. Milincshuk, Vysokomol. Soed., 7, 1293 (1965). 11. J. Lemaire and R. Arnaud, Polymer Photochemistry, Vol. 5, (N. S. Allen, ed.), Elsevier, London, p. 243 (1984). 12. S. F. Shah and R. V. R. Subamanian, Silk Rayon Ind. India, 10, 128 (1967). 13. H. A. Taylor, W. C. Tincher and W. F. Hemmer, J. Appl. Polym. Sci., 14, 141 (1970). 14. L. H. Peebles, Jr., and M. W. Hoffman, J. Polym. Sci., A-1, 9, 1807 (1971). 15. H. H. G. Jellineck and A. K. Chaudhari, J. Polym. Sci., A-1, 10, 1773 (1972). 16. N. S. Allen. J. F. McKeller and G. O. Phillips, J. Polym. Sci., Polym. Lett. Ed., 12, 477 (1974). 17. N. S. Allen, J. F. McKeller and G. O. Phillips, J. Polym. Sci., Polym. Chem. Ed., 12, 1233 (1974). 18. N. S. Allen, J. F. McKeller and G. O. Phillips, J. Polym. Sci., Polym. Chem. Ed., 12, 2623 (1974). 19. S. T. Koenig and C. W. Roberts, J. Appl. Polym. Sci., 19, 1847 (1975). 20. N. S. Allen, J. Homer, J. F. McKeller and G. O. Phillips, Br. Polym. J., 7, 11 (1975). 21. N. S. Allen, J. F. McKeller and D. Wilson, J. Photochem., 6, 337 (1977). 22. N. S. Allen, J. F. McKeller and D. Wilson, J. Photochem., 7, 405 (1977). 37

5 23. N. S. Allen, M. J. Harrison, G. W. Follows and V. Matthews, Polym. Degrad. Stabil., 19, 77 (1987). 24. C. R. Brasing and F. Gadala-Maria, J. Appl. Polym. Sci., 55, 687 (1995). 25. N. S. Allen, M. Ledward and G. W. Follows, J. Photochem., Photobiol. A., 53, 373 (1990). 26. N. S. Allen, M. Ledward and G. W. Follows, Eur. Polym. J., 28, 23 (1992). 27. N. S. Allen, Polym. Degrad. Stabil., 44, 357 (1994). 28. H. S. Freeman and J. S. Gadja, Text. Res. J., 221 (1990). 29. N. S. Allen, M. J. Harrison and G. W. Follows, Polym. Degrad. Stabil., 21, 251 (1988). 30. Deutsche Rhodiaceta A.-G., Ger ,393 (1959). 31. A. F. Strobel, Am. Dyestuff Rep., 50, 583 (1961); 51, 91 (1962). 32. J. R. Geigy, Swiss 3,88,253 (1965). 33. W. Stilz, H. Pommer, L. Buechs and H. Fessmann, Belg. 621,316 (1962). 34. Socite de la Viscose Suissse, Belg. 666,138 (1965). 35. N. Ozaka, T. Usami and M. Imoto, Japan 70 38,431 (1970). 36. V. N. Kochetkov, V. A. Ponomareva and N. V. Morozova, Plasticheskic Massy, 15, (1963). 37. Imperial Chemical Industries Ltd., Fr. 546,069 (1968). 38. N. S. Allen, J. F. McKeller, G. O. Phillips and C. B. Chapman, J. Polym. Sci., Lett. Ed., 12, 723 (1974). 39. N. S. Allen, J. F. McKeller and D. Wilson, J. Photochem., 7, 319 (1977). This chapter is part of the Ph.D thesis of Dr. Paragkumar Thanki. For any query please contact parag_thanki@rediffmail.com 38

Characterization. Chapter 3: Photo-oxidative degradation in Nylon 66 : Chemical. 3.1 Introduction

Characterization. Chapter 3: Photo-oxidative degradation in Nylon 66 : Chemical. 3.1 Introduction Chapter 3: Photo-oxidative degradation in Nylon 66 : Chemical Characterization 3.1 Introduction Aliphatic polyamides have got very good applications as engineering plastic as well as fiber material. During