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Autor     Timothy Dean Fornes
Titel    Polyamide – Layered Silicate Nanocomposites by Melt Processing
Ort    Austin
Jahr    2003
Anmerkung    Dissertation Presented to the Faculty of the Graduate School of The University of Texas at Austin in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy
URL    http://www.lib.utexas.edu/etd/d/2003/fornestd039/fornestd039.pdf

Literaturverz.   

no
Fußnoten    no
Fragmente    7


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[1.] Mrs/Fragment 048 26 - Diskussion
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Some characteristic properties of the α- and γ-forms of polyamide 6 are listed in Table 4.1 [173- 187]. The heats of fusion, ΔHf°, are the values reported by Illers [184]. It should be noted that other values for the α-form have been reported in the literature [180, 184, 186, 188-191] and Wunderlich has suggested a value of 230 J/g based on a compromise of various reports in the literature [192]. The effect of crystallization temperature and time on the formation of the α- versus γ-forms has been widely studied [185, 193, 194]. Gurato and his coworkers have shown that crystallization for extended periods of time below ~130 °C leads only to the γ-crystallites while above ~190 °C only the α-form is produced. Temperatures in between these limits result in a mixture of the two forms, with higher fractions of α-form being [produced at higher temperatures.]

[173] S.M: Aharoni, n-Polyamides [sic], their synthesis, structure, and properties. Chichester; New York: Wiley; 1997.

[174] Arimoto H, Ishibashi M, Hirai M, Chatani Y. Journal of Polymer Science Partt A 1965; 3(1):317–26.

[175] D.R. Holmes, C.W. Bunn, D.J. Smith, Journal of Polymer Science 1955;17:159–77.

[176] N. Murthy, Polymer Communications 1991;32(10):301–5.

[177] F. Rybnikar, Burda J. Faserforsch u Textiltech 1961;12:324–31.

[178] L.G. Roldan, H.S. Kaufman, Polymer Letter 1960;1:603–8.

[179] T. Itoh, H. Miyaji, K. Asai, Japanese Journal of Applied Physics 1975;14(2):206–15.

[180] A. Reichle, A. Prietzschk, Angew Chem 1962;74:562–9.

[181] L.G. Wallner, Monatsh 1948;79:279–95.

[182] K.H. Illers, H. Haberkorn, P. Simak, Makromolekulare Chemie1972;158: 285–311.

[183] K.H. Illers, Makromolekulare Chemie 1978;179(2):497–507.

[184] K.H. Illers, H. Haberkorn, Makromolekulare Chemie 1971;142:31–67.

[185] S. Gogolewski, M. Gasiorek, K. Czerniawska, A. Pennings. Colloid and Polymer Science 1982; 260(9):859–63.

[186] D.C. Vogelsong, J Polymer Science 1963; 1(Pt. A):1055–68.

[187] P. Marx, C. Smith, A. Worthington, M. Dole, Journal of Physical Chemistry; 59: 1015–9.

[188] M. Dole, B. Wunderlich, Makromolekulare Chemie 1959;34:29–49.

[189] M. Inoue, J Polymer Science Part A 1963; 1:2013–20.

[190] J.R. Starkweather, P. Zoller, G.A. Jones, J Polymer Science, Polymer Physics Edition 1984; 22(9):1615–21.

[191] B. Wunderlich, Macromolecular physics, vol. 3. New York: Academic Press; 1973.

[192] G. Gurato, A. Fichera, F.Z. Grandi, R. Zannetti, P. Canal, Makromolekulare Chemie 1974;175(3):953–75.

[193] M. Kyotani, S. Mitsuhashi, J Polymer Science, Part A-2 1972; 10(8): 1497–508.

[194] R.J. [sic] Brill für Praktische Chemie 1942;161:49–64.

Table 9.1 lists characteristic properties of the α- and γ-forms of nylon 6 [6-20]. The heats of fusion, ΔHf°, are the values reported by Illers [17]. It should be noted that other values for the α-form have been reported in the literature [13, 17, 19, 21-25] and Wunderlich has suggested a value of 230 J/g based on a compromise of various reports in the literature [26].

[...] The effect of crystallization temperature and time on the formation of the α versus γ-forms has been widely studied. For example, three independent investigations [18, 27, 28], have shown that crystallization for extend periods of

[page 254]

time below ~130°C leads solely to the γ-crystallites while above ~190°C only the α-form is produced. Temperatures in between these limits result in a mixture of the two forms, with higher fractions of α produced at higher temperatures. [...] [29]


6. Aharoni, SM, n-Nylons, their synthesis, structure, and properties. New York: J. Wiley & Sons. 1997.

7. Arimoto, H, Ishibashi, M, Hirai, M, Chatani, Y. J Polymer Sci, Part A 1965;3(1): 317-26.

8. Holmes, DR, Bunn, CW, Smith, DJ. J Polymer Sci 1955;17: 159-77.

9. Kohen, MI, ed. Nylon plastics handbook. Hanser: New York. 1995.

10. Murthy, NS. Polym Commun 1991;32(10): 301-5.

11. Rybnikar, F, Burda, J. Faserforsch u Textiltech 1961;12: 324-31.

12. Roldan, LG, Kaufman, HS. Polym Letts 1960;1: 603-8.

13. Itoh, T, Miyaji, H, Asai, K. Jpn J Appl Phys 1975;14(2): 206-15.

14. Reichle, A, Prietzschk, A. Angew Chem 1962;74: 562-9.

15. Wallner, LG. Monatsh 1948;79: 279-95.

16. Illers, KH, Haberkorn, H, Simak, P. Makromol Chem 1972;158: 285-311.

17. Illers, KH. Makromol Chem 1978;179(2): 497-507.

18. Illers, KH, Haberkorn, H. Makromol Chem 1971;142: 31-67.

19. Gogolewski, S, Gasiorek, M, Czerniawska, K, Pennings, AJ. Colloid Polym Sci 1982;260(9): 859-63.

20. Vogelsong, DC. J Polym Sci 1963;1(Pt. A): 1055-68.

21. Rybnikar, F. Chem listy 1958;52: 1042-8.

22. Marx, P, Smith, CW, Worthington, AE, Dole, M. J Phys Chem 1955;59: 1015-9.

23. Dole, M, Wunderlich, B. Makromol Chem 1959;34: 29-49.

24. Inoue, M. J Polymer Sci Pt A 1963;1: 2013-20.

25. Starkweather, HW, Jr., Zoller, P, Jones, GA. J Polym Sci, Part B 1984;22(9): 1615-21.

26. Wunderlich, B, Macromolecular physics (vol 3). New York: Academic Press. 1973.

27. Gurato, G, Fichera, A, Grandi, FZ, Zannetti, R, Canal, P. Makromol Chem 1974;175(3): 953-75.

28. Kyotani, M, Mitsuhashi, S. J Polym Sci, Part A-2 1972;10(8): 1497-508.

29. Brill, R. J prakt Chem 1942;161: 49-64.

Anmerkungen

The source is not mentioned.

Note that most references are -- compared to the source -- moved by one.

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The disappearance of the γ-form at ~190 °C has been commonly referred to as the Brill transition, a phenomenon first observed in polyamide 66 [195]. This transition corresponds to the merging of the two reflections of the α-form into a single peak in plots of X-ray diffraction intensity versus 2 [196-199] as the sample is heated. Kyotani and Mitsuhashi [194] also found that very short crystallization times at either 100 or 200 °C lead to both crystalline forms, while longer times produced predominantly γ- and α-form, respectively. In general, rapid cooling or quenching from the melt produces the γ-form [196, 200-202]. Annealing also affects the crystal structure. For example, annealing of quenched samples or those crystallized between 100 and 150 °C, at 200 °C for extended times leads to the conversion of the γ- into α-form [194]. Gogolewki et al. [186] and Gurato et al. [193] demonstrated similar annealing results. Based on the above, it is clear that, in general, rapid cooling and low temperature crystallization promotes the γ-form of polyamide 6, while higher crystallization temperatures or slow cooling leads to the α-form. Kyotani and Mitsuhashi [194] attribute the temperature dependence to the crystallization rates of the two forms; i.e. at temperatures below 130 °C the rate of formation of γ is faster, while above ~190 °C the crystallization rate of α-form is faster, while at intermediate temperatures, the rates are comparable. Interestingly, the maximum crystallization rate of polyamide 6 occurs at approximately 140 °C [203]. The temperature dependence of the crystallization rate above this maximum is dominated by the driving force for crystallization, i.e. the degree of undercooling, while below, the rate is dominated by the resistance to crystallization, i.e. polymer chain mobility. Therefore, it may be postulated that conditions of limited polymer chain mobility favor the crystallization of the γ-form for polyamide 6.

Studies of polyamide 6-based nanocomposites have caused renewed interest in the factors affecting the crystalline structure. As mentioned above, Kojima et al. [203] and Liu et al. [165] reported that when the one nanometer thick platelets of montmorillonite are dispersed in polyamide 6 the polymer crystallizes in the γ-form. Wu and coworkers [204-207] examined the influence of thermal treatment on the crystallization behavior of melt processed nanocomposites using FTIR, WAXD, and DSC. From FTIR measurements on thin film samples, it has been claimed that the hydrogen bonding in both crystalline forms of polyamide 6 is weakened by the presence of the clay. WAXD analysis revealed that nanocomposites films exhibit both crystalline forms when slowly cooled from the melt; whereas, pure polyamide 6 gave predominantly the α-form. Methods that permit higher cooling rates, e.g. air and water-cooling, have increased the content of the γ-phase especially for the nanocomposite. Further WAXD investigations conducted on samples that had been annealed at different temperatures showed the onset of [the γ- to α- transition, normally observed around 130 °C for p ure polyamide 6, in this case at 120 °C, occurred approximately 40 °C higher for the nan ocomposite.]


[165] L.M. Liu, Z.N. Qi, X.G. Zhu, J Applied Polymer Science 1999, 71, 1133.

[186] D.C. Vogelsong, J Polymer Science 1963; 1(Pt. A):1055–68.

[193] M. Kyotani, S. Mitsuhashi, J Polymer Science, Part A-2 1972; 10(8): 1497–508.

[194] R.J. Brill für Praktische Chemie 1942;161:49–64.

[195] N. Murthy, S.M. Aharoni, A. Szollosi, J Polymer Science, Polymer Physics Edition 1985; 23(12):2549–65.

[196] N.Murthy, S.A. Curran, S.M. Aharoni, H. Minor, Macromolecules 1991; 24(11):3215–20.

[197] C. Ramesh, E.B. Gowd, Macromolecules 2001; 34(10):3308–13.

[198] D.M. Lincoln, R.A. Vaia, Z.G. Wang, B.S. Hsiao, R. Krishnamoorti, Polymer 2001; 42(25):09975–85.

[199] D.R. Salem, R. Moore, H. Weigmann, J. Polymer Science, Part B: Polymer Physics 1987; 25(3):567–89.

[200] I. Campoy, M.A. Gomez, C. Marco, Polymer 1998; 39(25):6279–88.

[201] A. Okada, M. Kawasumi, I. Tajima, J Applied Polymer Science 1989;37(5):1363–71.

[202] J.H. Magill, Polymer 1962; 3:655–64.

[203] Y. Kojima, A. Usuki, M. Kawasumi, A. Okada, J Material Research 1993; 8(5):1185–9.

[204] Q. Wu, X. Liu, L. Berglund, Macromolecular Rapid Communications 2001;22(17): 1438– 40.

[205] X.Liu, Q. Wu, European Polymer Journal 2002;38(7):1383–9.

[206] Q. Wu, X. Liu, Berglund LA. Polymer 2002;43(8):2445–9.

[207] X. Liu, Q. Wu, Polymer 2002;43(6):1933–6.

The disappearance of the γ−form at ~190°C has been commonly referred to as the Brill transition, a phenomenon first observed in nylon 6,6 [29]. This transition corresponds to the merging of the two reflections of the α-form into a single peak in plots of X-ray diffraction intensity versus 2θ [30-33] as the sample is heated.

[page 255]

Kyotani and Mitsuhashi [28] found that very short crystallization times at either 100 and 200°C lead to both crystalline forms, while longer times produced predominantly γ and α , respectively. In general rapid cooling or quenching from the melt produces the γ-form [30, 34-36].

Annealing also affects the crystalline structure. For example, annealing of quenched samples, or those crystallized between 100 and 150 °C, at 200 °C for extended times leads to the conversion of the γ into α [28]. Similar annealing results were demonstrated by Gogolewki et al. [19] and Gurato et al. [27]. [...]

Based on the above, it is clear that, in general, rapid cooling and low temperature crystallization promotes the γ-form of nylon 6, while higher crystallization temperatures or slow cooling leads to the α-form. Kyotani and Mitsuhashi [28] attribute the temperature dependence of the α- and γ-form to their crystallization rates; i.e., at temperatures below 130°C the rate of formation of γ is faster, while above ~190°C the crystallization rate of α is faster, while at intermediate temperatures, the rates are comparable.

[page 256]

Interestingly, the maximization crystallization rate of nylon 6 occurs at approximately 140°C [37]. The temperature dependence of the crystallization rate above this maximum is dominated by the driving force for crystallization, i.e., the degree of undercooling, while below, the rate is dominated by the resistance to crystallization, i.e., polymer chain mobility. Therefore, it may be postulated that conditions of limited polymer chain mobility favor the crystallization of the γ-form for nylon 6.

[page 258]

Studies of nylon 6-based nanocomposites have caused renewed interest in the factors affecting the crystalline structure. As mentioned above, Kojima et al. [1] and Liu et al. [2] reported that when the one nanometer thick platelets of montmorillonite are dispersed in nylon 6 the polymer crystallizes in the γ-form. [...]

Wu and coworkers [49-52] examined the influence of thermal treatment on the crystallization behavior of melt processed nanocomposites using FTIR, WAXD, and DSC. From FTIR measurements on thin film samples, it has been claimed that the hydrogen bonding in both crystalline forms of nylon 6 are weakened by the presence of the clay. WAXD analysis revealed that nanocomposites films exhibit both crystalline forms when slowly cooled from the melt; whereas, pure nylon 6 gave predominantly the α form. Methods that permit higher cooling rates, e.g., air and water-cooling, increased the content of the γ- phase especially for the nanocomposite. Further WAXD investigations conducted on samples that had been annealed at different temperatures showed the onset of

[page 259]

the γ to α transition, normally observed around 130°C for pure nylon 6, in this case 120°C, occurred approximately 40°C higher for the nanocomposite.


1. Kojima, Y, Usuki, A, Kawasumi, M, Okada, A, Fukushima, Y, Kurauchi, T, Kamigaito, O. J Mater Res 1993;8(5): 1185-9.

2. Liu, L, Qi, Z, Zhu, X. J Appl Polym Sci 1999;71(7): 1133-8.

19. Gogolewski, S, Gasiorek, M, Czerniawska, K, Pennings, AJ. Colloid Polym Sci 1982;260(9): 859-63.

27. Gurato, G, Fichera, A, Grandi, FZ, Zannetti, R, Canal, P. Makromol Chem 1974;175(3): 953-75.

28. Kyotani, M, Mitsuhashi, S. J Polym Sci, Part A-2 1972;10(8): 1497-508.

29. Brill, R. J prakt Chem 1942;161: 49-64.

30. Murthy, NS, Aharoni, SM, Szollosi, AB. J Polym Sci, Part B 1985;23(12): 2549-65.

31. Murthy, NS, Curran, SA, Aharoni, SM, Minor, H. Macromolecules 1991;24(11): 3215-20.

32. Ramesh, C, Gowd, EB. Macromolecules 2001;34(10): 3308-13.

33. Lincoln, DM, Vaia, RA, Wang, ZG, Hsiao, BS, Krishnamoorti, R. Polymer 2001;42(25): 9975-85.

34. Salem, DR, Moore, RAF, Weigmann, HD. J Polym Sci, Part B 1987;25(3): 567-89.

35. Campoy, I, Gomez, MA, Marco, C. Polymer 1998;39(25): 6279-88.

36. Okada, A, Kawasumi, M, Tajima, I, Kurauchi, T, Kamigaito, O. J Appl Polym Sci 1989;37(5): 1363-71.

37. Magill, JH. Polymer 1962;3: 655-64.

49. Wu, Q, Liu, X, Berglund, LA. Macromolecular Rapid Comm 2001;22(17): 1438-40.

50. Liu, X, Wu, Q. European Polymer Journal 2002;38(7): 1383-9.

51. Wu, Q, Liu, X, Berglund, LA. Polymer 2002;43(8): 2445-9.

Anmerkungen

The source is not mentioned.

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[Further WAXD investigations conducted on samples that had been annealed at different temperatures showed the onset of] the γ- to α- transition, normally observed around 130 °C for p ure polyamide 6, in this case at 120 °C, occurred approximately 40 °C higher for the nan ocomposite. Interestingly, an unexpected higher amount of γ-form was observed after annealing at 200 °C than a t 180 °C. Lastly, non-isothermal crystallization surprisingly showed that the degree of crystallinity increased with increasing cooling rate for the nanocomposites, in contrast to what is observed in pure polyamide 6 and other polymers.

Table 4.1 Miscellaneous data for the α- and γ-crystalline forms of polyamide 6

Mrs 050a diss.png

a Hexagonal lattice constants were calculated based on the monoclinic parameters a=0.933nm, b=1.688nm, and c=0.478nm and β=121°. The hexagonal lattice constant, a, was taken as the average of a and half of b of the monoclinic unit cell. The constant c representing the fiber axis remained fixed [161].


[161] T.D. Fornes, D.R. Paul, Polymer 2003, 44, 3945.

[173] S.M: Aharoni, n-Polyamides, their synthesis, structure, and properties. Chichester; New York: Wiley; 1997.

[174] Arimoto H, Ishibashi M, Hirai M, Chatani Y. Journal of Polymer Science Partt A 1965; 3(1):317–26.

[175] D.R. Holmes, C.W. Bunn, D.J. Smith, Journal of Polymer Science 1955;17:159–77.

[176] N. Murthy, Polymer Communications 1991;32(10):301–5.

[177] F. Rybnikar, Burda J. Faserforsch u Textiltech 1961;12:324–31.

[178] L.G. Roldan, H.S. Kaufman, Polymer Letter 1960;1:603–8.

[179] T. Itoh, H. Miyaji, K. Asai, Japanese Journal of Applied Physics 1975;14(2):206–15.

[180] A. Reichle, A. Prietzschk, Angew Chem 1962;74:562–9.

[181] L.G. Wallner, Monatsh 1948;79:279–95.

[182] K.H. Illers, H. Haberkorn, P. Simak, Makromolekulare Chemie1972;158: 285–311.

[183] K.H. Illers, Makromolekulare Chemie 1978;179(2):497–507.

[184] K.H. Illers, H. Haberkorn, Makromolekulare Chemie 1971;142:31–67.

[185] S. Gogolewski, M. Gasiorek, K. Czerniawska, A. Pennings. Colloid and Polymer Science 1982; 260(9):859–63.

[186] D.C. Vogelsong, J Polymer Science 1963; 1(Pt. A):1055–68.

Table 9.1 Miscellaneous data for the α and γ crystalline forms of nylon 6.

Mrs 050a source.png

(a) Hexagonal lattice constants were calculated based on the monoclinic parameters a = 0.933 nm, b = 1.688nm, and c = 0.478nm and β = 121°. The hexagonal lattice constant, a, was taken as the average of a and half of b of the monoclinic unit cell. The constant c representing the fiber axis remained fixed.

[page 258]

Further WAXD investigations conducted on samples that had been annealed at different temperatures showed the onset of

[page 259]

the γ to α transition, normally observed around 130°C for pure nylon 6, in this case 120°C, occurred approximately 40°C higher for the nanocomposite. Interestingly, an unexpected higher amount of γ-form was observed after annealing at 200°C than at 180°C. Lastly, non-isothermal crystallization surprisingly showed that the degree of crystallinity increased with increasing cooling rate for the nanocomposites, counter to what is observed in pure nylon 6 and other polymers.


6. Aharoni, SM, n-Nylons, their synthesis, structure, and properties. New York: J. Wiley & Sons. 1997.

7. Arimoto, H, Ishibashi, M, Hirai, M, Chatani, Y. J Polymer Sci, Part A 1965;3(1): 317-26.

8. Holmes, DR, Bunn, CW, Smith, DJ. J Polymer Sci 1955;17: 159-77.

9. Kohen, MI, ed. Nylon plastics handbook. Hanser: New York. 1995.

11. Rybnikar, F, Burda, J. Faserforsch u Textiltech 1961;12: 324-31.

12. Roldan, LG, Kaufman, HS. Polym Letts 1960;1: 603-8.

13. Itoh, T, Miyaji, H, Asai, K. Jpn J Appl Phys 1975;14(2): 206-15.

14. Reichle, A, Prietzschk, A. Angew Chem 1962;74: 562-9.

15. Wallner, LG. Monatsh 1948;79: 279-95.

16. Illers, KH, Haberkorn, H, Simak, P. Makromol Chem 1972;158: 285-311.

17. Illers, KH. Makromol Chem 1978;179(2): 497-507.

18. Illers, KH, Haberkorn, H. Makromol Chem 1971;142: 31-67.

19. Gogolewski, S, Gasiorek, M, Czerniawska, K, Pennings, AJ. Colloid Polym Sci 1982;260(9): 859-63.

20. Vogelsong, DC. J Polym Sci 1963;1(Pt. A): 1055-68.

Anmerkungen

The source is not mentioned. Possibly the table can also be found in the reference [161] (still to be checked), but even if this was the case, this reference would not make clear that the entire page is taken from the source.

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Wu and Liao examined the effect of thermal history and filler concentration on the crystal structure of polyamide 6 nanocomposites formed by in situ polymerization using synthetic saponite and natural montmorillonite [208, 209]. Similar crystalline behavior was observed for the pure and nanocomposite materials when samples were slowly or rapidly cooled from the melt; however, nanocomposites containing a low concentration of saponite, i.e. 2.5 wt. %, favored the formation of the α-form regardless of the cooling conditions, whereas by increasing silica content γ-form is more dominant (Figure 4.5). Annealing studies showed that higher amounts of γ were present in the nanocomposite than in pure polyamide 6 after annealing at high temperatures, except at low saponite contents.

[208] T.M. Wu, C.S. Liao, Macromolecular Chemistry and Physics 2000;201(18):2820–5.

[209] T.M. Wu, E.C. Chen, C.S. Liao, Polymer Engineering Science 2002;42(6):1141–50.

Wu and Liao examined the effect of thermal history and filler concentration on the crystal structure of nylon 6 nanocomposites formed by in situ polymerization using synthetic saponite and natural montmorillonite [53, 54]. Similar crystalline behavior was observed for the pure and nanocomposite materials when samples were slowly or rapidly cooled from the melt; however, nanocomposites containing a low concentration of saponite, i.e., 2.5 weight %, favored the formation of the α-form regardless of the cooling conditions. Annealing studies showed that higher amounts of γ were present in the nanocomposite than in pure nylon 6 after annealing at high temperatures, except at low saponite contents.

53. Wu, T-M, Liao, C-S. Macromolecular Chem Phys 2000;201(18): 2820-5.

54. Wu, T-M, Chen, E-C, Liao, C-S. Polym Engng Sci 2002;42(6): 1141-50.

Anmerkungen

A source is not mentioned. The description from Fornes' thesis is also to be found at Fornes, T.D. & Paul, D. R. (2003). Crystallization behavior of nylon 6 nanocomposites. In Polymer 44, pp. 3945–3961.

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Some studies have explored the differences between polyamide 6 nanocomposites formed by in situ polymerization and by melt processing. Based on DSC and solid state NMR studies, VanderHart et al. [214, 215] concluded that the silicate layers promote the γ-form regardless of the formation technique, and that γ-crystallites reside near the polyamide/clay interface. Lincoln et al. [164] used small angle X-ray scattering, in addition to WAXD and DSC, to infer about the crystalline morphology of these two types of nanocomposites. They concluded that the clay platelets disrupt the formation of crystallites and the extent of platelet-crystallite interactions is dependent upon the technique used to form the nanocomposites. In other words, the nature of the bond between the clay and polyamide chains seems to influence clay-crystallite interactions.

[164] D. Lincoln, R. Vaia, Z. Wang, Hsiao, B. S.; Krishnamoorti, R. Polymer 2001, 42, 9975.

[214] D.L. VanderHart, A. Asano, J.W. Gilman, Chemistry of Materials 2001; 13(10): 3796–809.

[215] D.L. VanderHart, A. Asano, J.W. Gilman, Chemistry of Materials 2001; 13(10): 3781–95.

Some studies have explored the differences between nylon 6 nanocomposites formed by in situ polymerization and by melt processing. Based on DSC and solid state NMR studies, VanderHart et al. [55, 56] concluded that the silicate layers promote the γ-form regardless of the formation technique, and

[page 260]

that γ-crystallites reside near the polyamide/clay interface. Lincoln et al. [57] used small angle X-ray scattering, in addition to WAXD and DSC, to infer about the crystalline morphology of these two types of nanocomposites. They concluded that the clay platelets disrupt the formation of crystallites and the extent of platelet-crystallite interactions is dependent upon the technique used to form the nanocomposites. In other words, the nature of the bond between the clay and polyamide chains seems to influence clay-crystallite interactions.


55. VanderHart, DL, Asano, A, Gilman, JW. Chem Maters 2001;13(10): 3796-809.

56. VanderHart, DL, Asano, A, Gilman, JW. Chem Maters 2001;13(10): 3781-95.

57. Lincoln, DM, Vaia, RA, Wang, Z-G, Hsiao, BS. Polymer 2001;42(4): 1621-31.

Anmerkungen

A source is not mentioned. The description from Fornes' thesis is also to be found at Fornes, T.D. & Paul, D. R. (2003). Crystallization behavior of nylon 6 nanocomposites. In Polymer 44, pp. 3945–3961.

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(Hindemith), WiseWoman

[6.] Mrs/Fragment 134 01 - Diskussion
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Non-Isothermal crystallization of polyamide 6 nanocomposites fibers

An extensive analysis of non-isothermal crystallization behavior was carried out on pure polyamide 6 and its nanocomposites. To rightfully compare pure polyamide 6 materials with its nanocomposites, it was necessary to extrude the pure polyamide under the same processing conditions used to form the nanocomposites. Regardless of the molecular weight, the extruded materials exhibit faster crystallization than the virgin samples (Figure 8.12 labeled as (1)). There are several possible reasons why such behavior is observed. Faster crystallization may arise from increased nucleation due to the presence of impurities incorporated in the matrix during processing. Memory effects associated with thermal and stress histories that remain present in the sample after annealing in the melt may also lead to an increased rate of crystallization.

Isothermal Crystallization of Nylon 6 Nanocomposites

An extensive analysis of isothermal crystallization behavior was carried out on pure nylon 6 and its nanocomposites. To rightfully compare pure nylon 6 materials with its nanocomposites, it was necessary to extrude the pure polyamides under the same processing conditions used to form the nanocomposites. Figure 9.4 shows the isothermal crystallization behavior of virgin, i.e., from as-received pellets, and extruded nylon 6 materials. Regardless of the molecular weight, the extruded materials exhibit faster crystallization than the virgin samples. There are several possible reasons why such behavior is observed. Faster crystallization may arise from increased nucleation due to the presence of impurities incorporated in the matrix during processing. Memory effects associated with thermal and stress histories that remain present in the sample after annealing in the melt may also lead to an increased rate of crystallization.

Anmerkungen

A source is not mentioned. The description from Fornes' thesis is also to be found at Fornes, T.D. & Paul, D. R. (2003). Crystallization behavior of nylon 6 nanocomposites. In Polymer 44, pp. 3945–3961. The figures referred to are not the same.

Sichter
(Hindemith), WiseWoman

[7.] Mrs/Fragment 135 01 - Diskussion
Zuletzt bearbeitet: 2015-03-22 13:40:00 WiseWoman
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Numerous studies have shown that the processing history of the polymer, e.g. melting, mixing, cooling, pelletizing, etc. is often not fully erased when the polymer is annealed at high melt temperatures [289,–320-325].

[Figure 8.12]

Figure 8.12 Crystalline temperature of virgin PA6 (1) and pure extruded PA6 (2). Faster crystallization may arise from increased nucleation due to the presence of impurities incorporated in the matrix during processing.

Aharoni [173] reports that any shearing imposed on the polymer during melt processing may facilitate the production of aligned arrays of bridged H-bonded sections that act as stable nuclei, capable of remaining intact in the melt state for long periods of time. These arrays ultimately act as crystallization sites upon cooling from the melt. Indeed, Khanna et al. [321] showed that extruded polyamide 6 leads to faster crystallization than virgin polyamide 6 under both isothermal and non-isothermal conditions. The temperature of melting and the length of time held in the molten state will also determine the amount of stable nuclei remaining prior to recrystallization; this issue has been the topic of many investigations [325-330]. The above demonstrates that processing alone significantly affects the crystallization behavior of polyamide 6; therefore, for proper comparison between pure polyamide 6 and the nanocomposites, the 0 wt. % SiO2 data presented in the remaining plots represent the extruded version of polyamide 6.


[173] S.M: Aharoni, n-Polyamides, their synthesis, structure, and properties. Chichester; New York: Wiley; 1997.

[289] T.D.Fornes, D.R.Paul, Polymer 44 (2003) pp. 3945-3961

[320] Y.P. Khanna, R. Kumar, A.C. Reimschuessel, Polym Eng Sci 1988; 28(24):1607–11.

[321] Y.P. Khanna, A.C. Reimschuessel, A. Banerjie, Polym Eng Sci 1988; 28(24):1600–6.

[322] Y.P. Khanna, R. Kumar, A.C. Reimschuessel, Polym Eng Sci 1988; 28(24):1612–5.

[323] Y.P. Khanna, A.C. Reimschuessel, J Appl Polym Sci 1988; 35(8): 2259–68.

[324] Y.P. Khanna, Polym Eng Sci 1990; 30(24):1615–9.

[325] N. Avramova, Polym Polym Compos 1993; 1(4):261–74.

[326] JH. Magill, Polymer 1962; 3(No. 1):43–51.

[327] E. Turska, S. Gogolewski, Polymer 1971;12(10):616–28.

[328] E. Turska, S. Goglewski, J Appl Polym Sci 1975;19(3):637–44.

[329] N. Avramova, S. Fakirov, I. Avramov, J Polym Sci, Polym Phys 1984; 22(2):311–3.

[330] N. Avramova, S. Fakirov, J Polym Sci, Polym Phys 1986; 24(4):761–8.

Faster crystallization may arise from increased nucleation due to the presence of impurities incorporated in the matrix during processing. [...] Numerous studies have shown that the processing history of the polymer, e.g., melting, mixing, cooling, pelletizing, etc., are often not fully erased when the polymer is annealed at high melt temperatures [6, 58-63]. Aharoni reports that any shearing imposed on the polymer during melt processing may facilitate the production of aligned arrays of H-bonded sections that act as stable

[page 266]

nuclei, capable of remaining intact in the melt state for long periods of time [6]. These arrays ultimately act as crystallization sites upon cooling from the melt. Indeed, Khanna et al. showed that extruded nylon 6 leads to faster crystallization than virgin nylon 6 under both isothermal and non-isothermal conditions [59]. The temperature of melting and the length of time held in the molten state will also determine the amount of stable nuclei remaining prior to recrystallization; this issue has been the topic of many investigations [63-68].

[page 267]

The above demonstrates that processing alone significantly affects the crystallization behavior of nylon 6; therefore, for proper comparison between pure nylon 6 and the nanocomposites, the 0 wt% MMT data presented in the remaining plots represent the extruded version of nylon 6.


6. Aharoni, SM, n-Nylons, their synthesis, structure, and properties. New York: J. Wiley & Sons. 1997.

58. Khanna, YP, Kumar, R, Reimschuessel, AC. Polym Engng Sci 1988;28(24): 1607-11.

59. Khanna, YP, Reimschuessel, AC, Banerjie, A, Altman, C. Polym Engng Sci 1988;28(24): 1600-6.

60. Khanna, YP, Kumar, R, Reimschuessel, AC. Polym Eng Sci 1988;28(24): 1612-5.

61. Khanna, YP, Reimschuessel, AC. J Appl Polym Sci 1988;35(8): 2259-68.

62. Khanna, YP. Polym Engng Sci 1990;30(24): 1615-9.

63. Avramova, N. Polymers & Polymer Composites 1993;1(4): 261-74.

64. Magill, JH. Polymer 1962;3(No. 1): 43-51.

65. Turska, E, Gogolewski, S. Polymer 1971;12(10): 616-28.

66. Turska, E, Goglewski, S. J Appl Polym Sci 1975;19(3): 637-44.

67. Avramova, N, Fakirov, S, Avramov, I. J Polym Sci, Part B 1984;22(2): 311-3.

68. Avramova, N, Fakirov, S. Journal of Polymer Science, Part B 1986;24(4): 761-8.

Anmerkungen

A source is not mentioned.

The description from Fornes' thesis is also to be found at Fornes, T.D. & Paul, D. R. (2003). Crystallization behavior of nylon 6 nanocomposites. In Polymer 44, pp. 3945–3961. The figures referred to are not the same. This reference is given as number 289 by Mrs and referenced here, but it would only cover the sentence before the reference, not the entire page including all referenced work. Thus, this fragment is marked as a "BauernOpfer" (pawn sacrifice).

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(Hindemith), WiseWoman

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