- Email: [email protected]
clay nanocomposites
July 2001
Materials Letters 49 Ž2001. 327–333 www.elsevier.comrlocatermatlet
Mechanical, thermal and morphological properties of glass fiber and carbon fiber reinforced polyamide-6 and polyamide-6rclay nanocomposites Shang-Han Wu, Feng-Yih Wang, Chen-Chi. M. Ma) , Wen-Chi Chang, Chun-Ting Kuo, Hsu-Chiang Kuan, Wei-Jen Chen Department of Chemical Engineering, National Tsing Hua UniÕersity, Hsin-Chu 30043, Taiwan Received 6 October 2000; accepted 7 November 2000
Abstract Carbon fiber and glass fiber reinforced polyamide-6 and polyamide-6rclay nanocomposites were prepared. Results show that the mechanical and thermal properties of the polyamide-6rclay nanocomposites are superior to those of polyamide-6 composite in terms of the heat distortion temperature, tensile and flexural strength and modulus without sacrificing their impact strength. This may be due to the nanoscale effects, and the strong interaction force existed between the polyamide-6 matrix and the clay interface. The mechanical properties of neat polyamide-6rclay nanocomposites are better than those of 10 wt.% glass fiber or carbon fiber reinforced polyamide-6. The effect of nanoscale clay on toughness is more significant than that of the fiber. q 2001 Elsevier Science B.V. All rights reserved. Keywords: Polyamide-6; Polyamide-6rclay; Glass fiber; Carbon fiber; Nanocomposites
1. Introduction In recent years, polyamide-6rclay nanocomposites have been commonly used in engineering plastics. There are five methods to prepare polyamide-6rclay: Ž1. intercalation methods, Ž2. in-situ methods, Ž3. solution mixing methods, Ž4. direct dispersion methods, and Ž5. other methods w1–10x. Polyamide-6rclay nanocomposites prepared by me-
)
Corresponding author. Fax: q886-3-5715-408.
chanical blending polyamide-6 and montmorillonite may cause a phase separation in a twin-screw extruder. For the past decades, polyamides have been successfully reinforced by glass fiber, carbon fiber and other inorganic reinforcements w1x. In these composites, reinforcements may not dispersed homogeneously in microscopic level. However, polyamide6rclay nanocomposites is a molecular composite in which the silicate monolayers of montmorillonite is 1 nm in thickness and 100 nm in width which are uniformly dispersed in the polyamide-6 matrix w2–5x.
00167-577Xr01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 5 7 7 X Ž 0 0 . 0 0 3 9 4 - 3
S.-H. Wu et al.r Materials Letters 49 (2001) 327–333
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Polyamide-6 molecules and the silicate layers are bonded through ionic bonds. Polyamide-6 is in molten state by injection molding or extrusion process. Injection-molded polyamide-6rclay shows excellent strength, elastic modulus, heat distortion temperature w4–6x, and water barrier properties, compared with neat polyamide-6 resin w7x. Polyamide6rclay films prepared from the molten pellets using an extruder show excellent gas barrier properties w8x. A high extensional flow caused typically by the fiber drawing operation, the molecular chain axis of the polymer is oriented along the drawing direction w9x. In the thin polyamide-6 film prepared from the molten pellets using an extruder with a T-die, the silicate layers have planar orientation and the chain axis of polyamide-6 crystallites Ž g form. were parallel to the film surface while within this film plane, they were randomly oriented w10x. In contrast, the crystallites in the pure polyamide-6 film were three-dimensionally randomly oriented. The orientation of polyamide-6 crystallites in polyamide-6 was also assumed to be promoted by the presence of anisotropy silicate monolayers dispersed separately. Although the high aspect ratio of silicate nanolayers is ideal for reinforcement, the nanolayers are not easily dispersed in most polymers due to their preferred face-to face stacking in agglomerated tactics w11x. Dispersion of the clay into discrete monolayers is further hindered by the intrin-
sic incompatibility of hydrophilic layered silicates and hydrophobic engineering plastics w11x. As was first demonstrated by the Toyota group more than 10 years ago, the replacement of inorganic exchange cations in the galleries of the native clay by alkylammonium surfactants can compatibilize the surface chemistry of the clay. The complete dispersion of clay nanolayers in a polymer optimizes the number of available reinforcing elements for carrying an applied load and deflecting cracks. The coupling between the tremendous surface area of the clay and the polymer matrix facilitates stress transfer to reinforcement phase, allowing for such tensile, flexural strength, elongation and toughness w11x. In this study, mechanical, thermal and morphological properties of polyamide-6 and polyamide-6rclay Ž3 wt.% clay. reinforced with different weight percents of glass fiber and carbon fiber were investigated. The effects of glass fiber and carbon fiber on the properties of polyamide-6 composites and polyamide-6rclay nanocomposite were also discussed. 2. Experiment 2.1. Materials and sample preparation The polyamide-6 pellets ŽM7536A. were received from BASF, USA. The polyamide-6rclay pellets
Table 1 Mechanical properties of polyamide-6rclay ŽPA-6rclay. and polyamide-6 ŽPA-6. reinforced by glass fiber ŽGF. and carbon fiber ŽCF.
Neat PA-6rclay 10% GF-PA-6rclay 20% GF-PA-6rclay 30% GF-PA-6rclay 10% CF-PA-6rclay 20% CF-PA-6rclay 30% CF-PA-6rclay Neat PA-6 10% GF-PA-6 20% GF-PA-6 30% GF-PA-6 10% CF-PA-6 20% CF-PA-6 30% CF-PA-6
Tensile properties Strength ŽMPa. Modulus ŽMPa.
Elongation Ž%.
Flexural properties Strength ŽMPa. Modulus ŽMPa.
Notched Izod impact ŽJrm.
73.7 85.3 99.2 106.7 97.4 123.3 146.7 51.8 60.7 78.9 96.2 70.9 111.3 135.5
3.85 2.98 2.49 2.37 2.19 2.07 1.90 276.3 20.3 7.93 5.63 5.00 3.37 2.78
113.8 137.7 149.7 157.4 145.0 184.0 221.3 68.5 86.3 119.6 143 103.3 172.3 214.4
338.1 275.7 258.2 243.7 268.9 253.5 145.1 – 425.2 328.3 313.7 355.7 238.4 139.34
2843 4373 5282 6145 6507 9433 11 946 1073 2164 3158 4321 3261 6379 8942
3278 5265 6025 6498 6340 10 082 14 159 769 1927 2830 3589 2869 6643 9048
S.-H. Wu et al.r Materials Letters 49 (2001) 327–333
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Table 2 Tensile properties of polyamide-6rclay ŽPA-6rclay. and polyamide-6 ŽPA-6. Tensile properties
Neat PA-6rclay Neat PA-6 10% GF-PA-6rclay 10% GF-PA-6 20% GF-PA-6rclay 20% GF-PA-6 30% GF-PA-6rclay 30% GF-PA-6 10% CF-PA-6rclay 10% CF-PA-6 20% CF-PA-6rclay 20% CF-PA-6 30% CF-PA-6rclay 30% CF-PA-6
Strength ŽMPa.
Modulus ŽMPa.
Elongation Ž%.
Strength enhanced ratio
Modulus enhanced ratio
73.7 51.8 85.3 60.7 99.2 78.9 106.7 96.2 97.4 70.9 123.3 111.3 146.7 111.3
2843 1073 4373 2164 5282 3158 6145 4321 6507 3261 9433 6379 11 946 6379
3.85 276.3 2.98 20.3 2.49 7.93 2.37 5.63 2.19 5.00 2.07 3.37 1.90 3.37
42
165
41
102
23
67
11
42
37
100
11
48
8
34
contain 3.0 wt.% Ž1.6 vol.%. montmorillonite ŽM1030D. were obtained from Unitka, Japan. Sample were prepared by the following procedures: polyamide-6 and polyamide-6rclay were mixed mechanically with E-glass fiber Ža473, 6-mm long, Taiwan Glass Industry, Taiwan. and carbon fiber ŽPA6-2, 6-mm long, GRAFIL, USA., separately. Samples were extruded by a twin-screw extruder at a rotational speed 20 rpm. The temperature profiles of the barrel were 190–210–230–2208C from the hopper to the die. The extrudate was pelletized, dried, and injection molded into standard test samples for mechanical properties test. The injection-molding temperature and pressure were 2308C and 13.5 Mpa, respectively.
TMI Testing Machine was used. The dimensions of these samples were 25.0 = 10.0 = 1.4 mm Žlength = width =thickness.. The morphology of the fracture surface of the specimens was examined by a scanning electron microscope ŽJEOL, JSM 840A, Japan.. 2.3. Heat distortion temperature (HDT) The heat distortion temperature of the specimens was examined by a heat distortion temperature ma-
2.2. Mechanical and morphology properties Three-point bending tests with a span-to-depth ratio of 40 and a crosshead speed of 1.0 mmrmin were performed in an Instron test machine Žmodel 4468. at room temperature. Samples were measured according to ASTM D638. The flexural strength and flexural modulus of the specimens were measured by a Testometric Micro 500 machine and samples were measured according to ASTM D790. Notched impact strength were tested according to ASTM D256 and a
Fig. 1. Tensile strength enhanced ratio of GF and CF reinforced polyamide-6rclay and polyamide-6 ŽPA-6..
S.-H. Wu et al.r Materials Letters 49 (2001) 327–333
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Fig. 2. Tensile modulus enhanced ratio of GF and CF reinforced polyamide-6rclay and polyamide-6 ŽPA-6..
chine ŽCS-107, Costom Scientific Instruments, USA.. Specimens were measured according to ASTM D648-95.
3. Results and discussion 3.1. Mechanical properties In this study, polaymide-6 and polyamide-6rclay were prepared by mixing with different weight per-
cents Ž10, 20 and 30 wt.%. of glass fiber and carbon fiber. All results are listed in Table 1. Table 1 shows that the tensile and flexural strength of neat polysmide-6rclay is higher than those of neat polyamide-6, but the notched Izod impact strength of neat polyamide-6 is higher than that of neat polyamide-6rclay. Tensile and flexural strength and modulus of the both composite systems increased with fiber content, while impacting strength of the composites decreased with fiber content. Table 2 shows that the tensile properties of glass and carbon fiber reinforced polyamide-6 and polyamide-6rclay. Compare these two systems, tensile properties of polaymide-6rclay nanocomposites are superior to those of polyamide-6 composites with the same fibers content. Table 2 also shows that the tensile properties of neat polyamide-6rclay are close to polyamide-6 blends with 20 wt.% glass fiber and also close to polyamide-6 prepared with 10 wt.% carbon fiber. Figs. 1 and 2 show that the effect of montmorillonite and fiber reinforced on the tensile properties of both systems. Because of aspect ratio of fiber is larger than montmorillonite, fibers contribute more to tensile properties. From Fig. 1 and Table 2, one can find that the tensile strength of polyamide6rclay containing 30 wt.% glass fiber is 11% higher than polyamide-6 containing 30 wt.% glass fiber. Fig. 1 shows that the tensile modulus of polyamide6rclay is 42% higher than that of polyamide-6.
Table 3 Flexural properties of polyamide-6rclay ŽPA-6rclay. and polyamide-6 ŽPA-6. Flexural Properties
Neat PA-6rclay Neat PA-6 10% GF-PA-6rclay 10% GF-PA-6 20% GF-PA-6rclay 20% GF-PA-6 30% GF-PA-6rclay 30% GF-PA-6 10% CF-PA-6rclay 10% CF-PA-6 20% CF-PA-6rclay 20% CF-PA-6 30% CF-PA-6rclay 30% CF-PA-6
Strength ŽMPa.
Modulus ŽMPa.
Strength enhanced ratio Ž%.
Modulus enhanced ratio Ž%.
113.8 68.5 137.7 86.3 149.7 119.6 157.4 143.0 145.0 103.3 184.0 172.3 221.3 214.4
3278 769 5265 1927 6025 2830 6497 3589 6340 2869 10 082 66 433 14 159 9048
66
326
60
173
25
112
10
81
40
120
7
57
3
56
S.-H. Wu et al.r Materials Letters 49 (2001) 327–333
Fig. 3. Flexural strength enhanced ratio of GF and CF reinforced polyamide-6rclay and polyamide-6 ŽPA-6..
Therefore, the tensile properties of polyamide-6 will be increased by adding carbon, glass fiber or montmorillonite. Table 3 shows that the flexural properties of fiber reinforced polyamide-6rclay nanocomposites are better than those of polyamide-6 composites. In other words, the flexural properties of polyamide-6rclay nanocomposite are better than those of polyamide-6 composite with the same fiber content. As can be seen in Figs. 3 and 4, the flexural strength and flexural modulus of neat polyamide-6rclay are close to polyamide-6 containing 20 wt.% glass fiber. The
Fig. 4. Flexural modulus enhanced ratio of GF and CF reinforced polyamide-6rclay and polyamide-6 ŽPA-6..
331
Fig. 5. Notched Izod impact strength of GF and CF reinforced polyamide-6rclay and polyamide-6 ŽPA-6..
flexural properties of neat polyamide-6rclay are also close to polyamide-6 containing 10 wt.% carbon fiber. However, Table 3 shows that the effect of montmorillonite is unclear when adding fiber. Because both fibers are longer than montmorillonite, adding montmorillonite may enhance the flexural strength and flexural modulus, which fibers contribute much more in flexural properties. Energy of crack propagation was obtained from the notched Izod impact test. Since polyamide-6 possesses very high toughness, polyamide-6 reinforced by glass fiber or carbon fiber required more strength and energy to break. In microscopic aspect,
Fig. 6. Heat distortion temperature of GF and CF reinforced polyamide-6rclay and polyamide-6 ŽPA-6..
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S.-H. Wu et al.r Materials Letters 49 (2001) 327–333
Fig. 7. SEM photograph of polyamide-6rclay and polyamide-6 ŽPA-6. reinforced with GF and CF. Ža. Neat polyamide-6, Žb. neat polyamide-6rclay, Žc. polyamide-6r30 wt.% C.F., Žd. polyamide-6–clayr30 wt.% C.F., Žf. polyamide-6–clayr30 wt.% G.F. Žarrow indicates the crack area..
S.-H. Wu et al.r Materials Letters 49 (2001) 327–333
montmorillonite is a layered mineral clay and which will promote the rigidity of polyamide-6rclay. Fig. 5 shows that notched Izod impact strength of composites decrease with the fiber content. 3.2. Heat distortion temperature Fig. 6 shows that the heat distortion temperature of composites increases with the fiber content. The heat distortion temperature of neat polyamide-6rclay is much higher than that of neat polyamide-6. Consequently, the heat distortion temperature of fiber reinforced polyamide-6rclay nanocomposite is much higher than that of fiber reinforced polyamide-6 composite. The heat distortion temperature of carbon fiber reinforced system is higher than that of glass fiber reinforced system. The glass fiber and carbon fiber are highly crystalline material that can even improve the heat distortion temperature of the polymer matrix.
333
polyamide-6rclay are similar to polyamide-6 reinforced with 20 wt.% glass fiber. Ž2. Heat distortion temperatures of polyamide6rclay and polyamide-6 are 1128C and 628C, respectively. Consequently, the heat distortion temperature of fiber reinforced polyamide-6rclay system is almost 208C higher than that of fiber reinforced polyamide-6 system. Ž3. Notched Izod impact strength of the composites decreased with the addition of the fiber. The SEM microphotographs show that the wet-out of glass fiber is better than carbon fiber in Fig. 7Žb–f..
Acknowledgements This research was supported by the National Science Council, Taiwan, Republic of China, under the Contract No. NSC-89-2216-E-007-016.
3.3. Morphological properties References The SEM microphotographs in Fig. 7 show the crack propagation under cleavage fracture. There is a clear crack propagation in polyamide-6rclay as shown in Fig. 7Žb., while that in neat polyamide-6 is smooth as shown in Fig. 7Ža., implying that the toughness of the matrix increased with the addition of clay. The mechanical properties depend on the fiber content and interaction force between matrix and fiber. The notched Izod impact strength and flexural modulus of the composites increased with the addition of the fiber. The SEM microphotographs show that the wet-out of glass fiber ŽFig. 7Žd., Fig. 7Žf.. is better than that of carbon fiber as can be seen in Figs. 7Žc., 7Že..
4. Conclusions Ž1. Tensile strength of polyamide-6rclay containing 30 wt.% glass fiber is 11% higher than that of polyamide-6 containing 30 wt.% glass fiber, while the tensile modulus of nanocomposite increases by 42%. Flexural strength and flexural modulus of neat
w1x M.I. Kohen et al., Nylon Plastics, Wiley, New York, 1973. w2x A. Okada, M. Kawasumi, A. Usuki, Y. Kojima, T. Kurauchi, O. Kamigaito, Mater. Res. Soc. Symp. Proc. 171 Ž1990. 45. w3x A. Usuki, Y. Kojima, O. Kamigaito, J. Mater. Res. 8 Ž1993. 1179. w4x Y. Kojima, A. Usuki, M. Kawasumi, A. Okada, T. Kurauchi, O. Kamigaito, J. Polym. Sci., Part A: Polym. Chem. 31 Ž1993. 983. w5x Y. Kojima, A. Usuki, M. Kawasumi, A. Okada, T. Kurauchi, O. Kamigaito, J. Polym. Sci., Part A: Polym. Chem. Ž1993. 1755. w6x Y. Kojima, A. Usuki, M. Kawasumi, Y. Fukushima, A. Okada, T. Kurauchi, O. Kamigaito, J. Mater. Res. 8 Ž1993. 1185. w7x Y. Kojima, A. Usuki, M. Kawasumi, A. Okada, T. Kurauchi, O. Kamigaito, J. Appl. Polym. Sci. 49 Ž1993. 1259. w8x Y. Kojima, A. Usuki, M. Kawasumi, A. Okada, T. Kurauchi, O. Kamigaito, K. Kaji, J. Polym. Sci., Part B: Polym. Phys. 32 Ž1994. 623. w9x C.J. Heffelfinger, R.L. Burston, J. Polym. Sci. 47 Ž1960. 289. w10x Y. Kojima, A. Usuki, M. Kawasumi, A. Okada, T. Kurauchi, O. Kamigaito, K. Kaji, J. Polym. Sci., Part B: Polym. Phys. 32 Ž1994. 623. w11x P.C. Lebaron, Z. Wang, T.J. Pinnavaia, J. Appl. Clay Sci. 15 Ž1999. 11.
Materials Letters 49 Ž2001. 327–333 www.elsevier.comrlocatermatlet
Mechanical, thermal and morphological properties of glass fiber and carbon fiber reinforced polyamide-6 and polyamide-6rclay nanocomposites Shang-Han Wu, Feng-Yih Wang, Chen-Chi. M. Ma) , Wen-Chi Chang, Chun-Ting Kuo, Hsu-Chiang Kuan, Wei-Jen Chen Department of Chemical Engineering, National Tsing Hua UniÕersity, Hsin-Chu 30043, Taiwan Received 6 October 2000; accepted 7 November 2000
Abstract Carbon fiber and glass fiber reinforced polyamide-6 and polyamide-6rclay nanocomposites were prepared. Results show that the mechanical and thermal properties of the polyamide-6rclay nanocomposites are superior to those of polyamide-6 composite in terms of the heat distortion temperature, tensile and flexural strength and modulus without sacrificing their impact strength. This may be due to the nanoscale effects, and the strong interaction force existed between the polyamide-6 matrix and the clay interface. The mechanical properties of neat polyamide-6rclay nanocomposites are better than those of 10 wt.% glass fiber or carbon fiber reinforced polyamide-6. The effect of nanoscale clay on toughness is more significant than that of the fiber. q 2001 Elsevier Science B.V. All rights reserved. Keywords: Polyamide-6; Polyamide-6rclay; Glass fiber; Carbon fiber; Nanocomposites
1. Introduction In recent years, polyamide-6rclay nanocomposites have been commonly used in engineering plastics. There are five methods to prepare polyamide-6rclay: Ž1. intercalation methods, Ž2. in-situ methods, Ž3. solution mixing methods, Ž4. direct dispersion methods, and Ž5. other methods w1–10x. Polyamide-6rclay nanocomposites prepared by me-
)
Corresponding author. Fax: q886-3-5715-408.
chanical blending polyamide-6 and montmorillonite may cause a phase separation in a twin-screw extruder. For the past decades, polyamides have been successfully reinforced by glass fiber, carbon fiber and other inorganic reinforcements w1x. In these composites, reinforcements may not dispersed homogeneously in microscopic level. However, polyamide6rclay nanocomposites is a molecular composite in which the silicate monolayers of montmorillonite is 1 nm in thickness and 100 nm in width which are uniformly dispersed in the polyamide-6 matrix w2–5x.
00167-577Xr01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 5 7 7 X Ž 0 0 . 0 0 3 9 4 - 3
S.-H. Wu et al.r Materials Letters 49 (2001) 327–333
328
Polyamide-6 molecules and the silicate layers are bonded through ionic bonds. Polyamide-6 is in molten state by injection molding or extrusion process. Injection-molded polyamide-6rclay shows excellent strength, elastic modulus, heat distortion temperature w4–6x, and water barrier properties, compared with neat polyamide-6 resin w7x. Polyamide6rclay films prepared from the molten pellets using an extruder show excellent gas barrier properties w8x. A high extensional flow caused typically by the fiber drawing operation, the molecular chain axis of the polymer is oriented along the drawing direction w9x. In the thin polyamide-6 film prepared from the molten pellets using an extruder with a T-die, the silicate layers have planar orientation and the chain axis of polyamide-6 crystallites Ž g form. were parallel to the film surface while within this film plane, they were randomly oriented w10x. In contrast, the crystallites in the pure polyamide-6 film were three-dimensionally randomly oriented. The orientation of polyamide-6 crystallites in polyamide-6 was also assumed to be promoted by the presence of anisotropy silicate monolayers dispersed separately. Although the high aspect ratio of silicate nanolayers is ideal for reinforcement, the nanolayers are not easily dispersed in most polymers due to their preferred face-to face stacking in agglomerated tactics w11x. Dispersion of the clay into discrete monolayers is further hindered by the intrin-
sic incompatibility of hydrophilic layered silicates and hydrophobic engineering plastics w11x. As was first demonstrated by the Toyota group more than 10 years ago, the replacement of inorganic exchange cations in the galleries of the native clay by alkylammonium surfactants can compatibilize the surface chemistry of the clay. The complete dispersion of clay nanolayers in a polymer optimizes the number of available reinforcing elements for carrying an applied load and deflecting cracks. The coupling between the tremendous surface area of the clay and the polymer matrix facilitates stress transfer to reinforcement phase, allowing for such tensile, flexural strength, elongation and toughness w11x. In this study, mechanical, thermal and morphological properties of polyamide-6 and polyamide-6rclay Ž3 wt.% clay. reinforced with different weight percents of glass fiber and carbon fiber were investigated. The effects of glass fiber and carbon fiber on the properties of polyamide-6 composites and polyamide-6rclay nanocomposite were also discussed. 2. Experiment 2.1. Materials and sample preparation The polyamide-6 pellets ŽM7536A. were received from BASF, USA. The polyamide-6rclay pellets
Table 1 Mechanical properties of polyamide-6rclay ŽPA-6rclay. and polyamide-6 ŽPA-6. reinforced by glass fiber ŽGF. and carbon fiber ŽCF.
Neat PA-6rclay 10% GF-PA-6rclay 20% GF-PA-6rclay 30% GF-PA-6rclay 10% CF-PA-6rclay 20% CF-PA-6rclay 30% CF-PA-6rclay Neat PA-6 10% GF-PA-6 20% GF-PA-6 30% GF-PA-6 10% CF-PA-6 20% CF-PA-6 30% CF-PA-6
Tensile properties Strength ŽMPa. Modulus ŽMPa.
Elongation Ž%.
Flexural properties Strength ŽMPa. Modulus ŽMPa.
Notched Izod impact ŽJrm.
73.7 85.3 99.2 106.7 97.4 123.3 146.7 51.8 60.7 78.9 96.2 70.9 111.3 135.5
3.85 2.98 2.49 2.37 2.19 2.07 1.90 276.3 20.3 7.93 5.63 5.00 3.37 2.78
113.8 137.7 149.7 157.4 145.0 184.0 221.3 68.5 86.3 119.6 143 103.3 172.3 214.4
338.1 275.7 258.2 243.7 268.9 253.5 145.1 – 425.2 328.3 313.7 355.7 238.4 139.34
2843 4373 5282 6145 6507 9433 11 946 1073 2164 3158 4321 3261 6379 8942
3278 5265 6025 6498 6340 10 082 14 159 769 1927 2830 3589 2869 6643 9048
S.-H. Wu et al.r Materials Letters 49 (2001) 327–333
329
Table 2 Tensile properties of polyamide-6rclay ŽPA-6rclay. and polyamide-6 ŽPA-6. Tensile properties
Neat PA-6rclay Neat PA-6 10% GF-PA-6rclay 10% GF-PA-6 20% GF-PA-6rclay 20% GF-PA-6 30% GF-PA-6rclay 30% GF-PA-6 10% CF-PA-6rclay 10% CF-PA-6 20% CF-PA-6rclay 20% CF-PA-6 30% CF-PA-6rclay 30% CF-PA-6
Strength ŽMPa.
Modulus ŽMPa.
Elongation Ž%.
Strength enhanced ratio
Modulus enhanced ratio
73.7 51.8 85.3 60.7 99.2 78.9 106.7 96.2 97.4 70.9 123.3 111.3 146.7 111.3
2843 1073 4373 2164 5282 3158 6145 4321 6507 3261 9433 6379 11 946 6379
3.85 276.3 2.98 20.3 2.49 7.93 2.37 5.63 2.19 5.00 2.07 3.37 1.90 3.37
42
165
41
102
23
67
11
42
37
100
11
48
8
34
contain 3.0 wt.% Ž1.6 vol.%. montmorillonite ŽM1030D. were obtained from Unitka, Japan. Sample were prepared by the following procedures: polyamide-6 and polyamide-6rclay were mixed mechanically with E-glass fiber Ža473, 6-mm long, Taiwan Glass Industry, Taiwan. and carbon fiber ŽPA6-2, 6-mm long, GRAFIL, USA., separately. Samples were extruded by a twin-screw extruder at a rotational speed 20 rpm. The temperature profiles of the barrel were 190–210–230–2208C from the hopper to the die. The extrudate was pelletized, dried, and injection molded into standard test samples for mechanical properties test. The injection-molding temperature and pressure were 2308C and 13.5 Mpa, respectively.
TMI Testing Machine was used. The dimensions of these samples were 25.0 = 10.0 = 1.4 mm Žlength = width =thickness.. The morphology of the fracture surface of the specimens was examined by a scanning electron microscope ŽJEOL, JSM 840A, Japan.. 2.3. Heat distortion temperature (HDT) The heat distortion temperature of the specimens was examined by a heat distortion temperature ma-
2.2. Mechanical and morphology properties Three-point bending tests with a span-to-depth ratio of 40 and a crosshead speed of 1.0 mmrmin were performed in an Instron test machine Žmodel 4468. at room temperature. Samples were measured according to ASTM D638. The flexural strength and flexural modulus of the specimens were measured by a Testometric Micro 500 machine and samples were measured according to ASTM D790. Notched impact strength were tested according to ASTM D256 and a
Fig. 1. Tensile strength enhanced ratio of GF and CF reinforced polyamide-6rclay and polyamide-6 ŽPA-6..
S.-H. Wu et al.r Materials Letters 49 (2001) 327–333
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Fig. 2. Tensile modulus enhanced ratio of GF and CF reinforced polyamide-6rclay and polyamide-6 ŽPA-6..
chine ŽCS-107, Costom Scientific Instruments, USA.. Specimens were measured according to ASTM D648-95.
3. Results and discussion 3.1. Mechanical properties In this study, polaymide-6 and polyamide-6rclay were prepared by mixing with different weight per-
cents Ž10, 20 and 30 wt.%. of glass fiber and carbon fiber. All results are listed in Table 1. Table 1 shows that the tensile and flexural strength of neat polysmide-6rclay is higher than those of neat polyamide-6, but the notched Izod impact strength of neat polyamide-6 is higher than that of neat polyamide-6rclay. Tensile and flexural strength and modulus of the both composite systems increased with fiber content, while impacting strength of the composites decreased with fiber content. Table 2 shows that the tensile properties of glass and carbon fiber reinforced polyamide-6 and polyamide-6rclay. Compare these two systems, tensile properties of polaymide-6rclay nanocomposites are superior to those of polyamide-6 composites with the same fibers content. Table 2 also shows that the tensile properties of neat polyamide-6rclay are close to polyamide-6 blends with 20 wt.% glass fiber and also close to polyamide-6 prepared with 10 wt.% carbon fiber. Figs. 1 and 2 show that the effect of montmorillonite and fiber reinforced on the tensile properties of both systems. Because of aspect ratio of fiber is larger than montmorillonite, fibers contribute more to tensile properties. From Fig. 1 and Table 2, one can find that the tensile strength of polyamide6rclay containing 30 wt.% glass fiber is 11% higher than polyamide-6 containing 30 wt.% glass fiber. Fig. 1 shows that the tensile modulus of polyamide6rclay is 42% higher than that of polyamide-6.
Table 3 Flexural properties of polyamide-6rclay ŽPA-6rclay. and polyamide-6 ŽPA-6. Flexural Properties
Neat PA-6rclay Neat PA-6 10% GF-PA-6rclay 10% GF-PA-6 20% GF-PA-6rclay 20% GF-PA-6 30% GF-PA-6rclay 30% GF-PA-6 10% CF-PA-6rclay 10% CF-PA-6 20% CF-PA-6rclay 20% CF-PA-6 30% CF-PA-6rclay 30% CF-PA-6
Strength ŽMPa.
Modulus ŽMPa.
Strength enhanced ratio Ž%.
Modulus enhanced ratio Ž%.
113.8 68.5 137.7 86.3 149.7 119.6 157.4 143.0 145.0 103.3 184.0 172.3 221.3 214.4
3278 769 5265 1927 6025 2830 6497 3589 6340 2869 10 082 66 433 14 159 9048
66
326
60
173
25
112
10
81
40
120
7
57
3
56
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Fig. 3. Flexural strength enhanced ratio of GF and CF reinforced polyamide-6rclay and polyamide-6 ŽPA-6..
Therefore, the tensile properties of polyamide-6 will be increased by adding carbon, glass fiber or montmorillonite. Table 3 shows that the flexural properties of fiber reinforced polyamide-6rclay nanocomposites are better than those of polyamide-6 composites. In other words, the flexural properties of polyamide-6rclay nanocomposite are better than those of polyamide-6 composite with the same fiber content. As can be seen in Figs. 3 and 4, the flexural strength and flexural modulus of neat polyamide-6rclay are close to polyamide-6 containing 20 wt.% glass fiber. The
Fig. 4. Flexural modulus enhanced ratio of GF and CF reinforced polyamide-6rclay and polyamide-6 ŽPA-6..
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Fig. 5. Notched Izod impact strength of GF and CF reinforced polyamide-6rclay and polyamide-6 ŽPA-6..
flexural properties of neat polyamide-6rclay are also close to polyamide-6 containing 10 wt.% carbon fiber. However, Table 3 shows that the effect of montmorillonite is unclear when adding fiber. Because both fibers are longer than montmorillonite, adding montmorillonite may enhance the flexural strength and flexural modulus, which fibers contribute much more in flexural properties. Energy of crack propagation was obtained from the notched Izod impact test. Since polyamide-6 possesses very high toughness, polyamide-6 reinforced by glass fiber or carbon fiber required more strength and energy to break. In microscopic aspect,
Fig. 6. Heat distortion temperature of GF and CF reinforced polyamide-6rclay and polyamide-6 ŽPA-6..
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Fig. 7. SEM photograph of polyamide-6rclay and polyamide-6 ŽPA-6. reinforced with GF and CF. Ža. Neat polyamide-6, Žb. neat polyamide-6rclay, Žc. polyamide-6r30 wt.% C.F., Žd. polyamide-6–clayr30 wt.% C.F., Žf. polyamide-6–clayr30 wt.% G.F. Žarrow indicates the crack area..
S.-H. Wu et al.r Materials Letters 49 (2001) 327–333
montmorillonite is a layered mineral clay and which will promote the rigidity of polyamide-6rclay. Fig. 5 shows that notched Izod impact strength of composites decrease with the fiber content. 3.2. Heat distortion temperature Fig. 6 shows that the heat distortion temperature of composites increases with the fiber content. The heat distortion temperature of neat polyamide-6rclay is much higher than that of neat polyamide-6. Consequently, the heat distortion temperature of fiber reinforced polyamide-6rclay nanocomposite is much higher than that of fiber reinforced polyamide-6 composite. The heat distortion temperature of carbon fiber reinforced system is higher than that of glass fiber reinforced system. The glass fiber and carbon fiber are highly crystalline material that can even improve the heat distortion temperature of the polymer matrix.
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polyamide-6rclay are similar to polyamide-6 reinforced with 20 wt.% glass fiber. Ž2. Heat distortion temperatures of polyamide6rclay and polyamide-6 are 1128C and 628C, respectively. Consequently, the heat distortion temperature of fiber reinforced polyamide-6rclay system is almost 208C higher than that of fiber reinforced polyamide-6 system. Ž3. Notched Izod impact strength of the composites decreased with the addition of the fiber. The SEM microphotographs show that the wet-out of glass fiber is better than carbon fiber in Fig. 7Žb–f..
Acknowledgements This research was supported by the National Science Council, Taiwan, Republic of China, under the Contract No. NSC-89-2216-E-007-016.
3.3. Morphological properties References The SEM microphotographs in Fig. 7 show the crack propagation under cleavage fracture. There is a clear crack propagation in polyamide-6rclay as shown in Fig. 7Žb., while that in neat polyamide-6 is smooth as shown in Fig. 7Ža., implying that the toughness of the matrix increased with the addition of clay. The mechanical properties depend on the fiber content and interaction force between matrix and fiber. The notched Izod impact strength and flexural modulus of the composites increased with the addition of the fiber. The SEM microphotographs show that the wet-out of glass fiber ŽFig. 7Žd., Fig. 7Žf.. is better than that of carbon fiber as can be seen in Figs. 7Žc., 7Že..
4. Conclusions Ž1. Tensile strength of polyamide-6rclay containing 30 wt.% glass fiber is 11% higher than that of polyamide-6 containing 30 wt.% glass fiber, while the tensile modulus of nanocomposite increases by 42%. Flexural strength and flexural modulus of neat
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