Carbon nanofibers (CNFs) are used as both the nucleants and the reinforcements for polystyrene (PS) foams in both batch and continuous extrusion processes with CO2 as the blowing agent. The inclusion of CNFs exhibits substantial impact on the morphology and properties of PS foams. The presence of CNFs results in a decrease in the cell size and an increase in the cell density. Macroscopic strength enhancement of PS foams due to the incorporation of CNFs is experimentally observed. These results are qualitatively explained via a series of nanoscaled observations. Through scanning electron microscopy (SEM), the alignment of CNFs and the polymer-sheathing phenomenon are identified. The protective CNF layers around the cell wall and the substantial polymer-fiber interactions resulted in the enhancement of foam strengths. Thermal properties (heat conductivity, infrared transmission, and thermal expansion coefficient) of the PS foams can also be influenced by CNFs. Intensive shear force exerted by the twin-screw extruder broke the fibers in lengths. The impact of the fiber length on the foam structures (cell size and cell density) is also studied.
Okamoto, M. , Nam, P.H. , Maiti, P. , Kotaka, T. , Nakayama, T. , Takada, M. , Ohshima, M. , Usuki, A. , Hasegawa, N. and Okamoto, H. (2001). Biaxial Flow-Induced Alignment of Silicate Layers in Polypropylene/Clay Nanocomposite Foam , Nano Letters, 1(9): 503-505 .
2.
Okamoto, M. , Nam, P.H. , Maiti, P. , Kotaka, T. , Hasegawa, N. and Usuki, A. (2001). A House of Cards Structure in Polypropylene/Clay Nanocomposites under Elongational Flow , Nano Letters, 1(6): 295-298 .
3.
Nam, P.H. , Maiti, P. , Okamoto, M. , Kotaka, T. , Nakayama, T. , Takada, M. , Ohshima, M. , Usuki, A. , Hasegawa, N. and Okamoto, H. (2002). Foam Processing and Cellular Structure of Polypropylene/Clay Nanocomposites , Polymer Engineering and Science, 42(9): 1907-1918 .
4.
Fujimoto, Y. , Ray, S.S. , Okamoto, M. , Ogami, A. , Yamada, K. and Ueda, K. (2003). Well-controlled Biodegradable Nanocomposite Foams: from Microcellular to Nanocellular , Macromolecular Rapid Communications, 24(7): 457-461 .
5.
Han, X. , Zeng, C. , Lee, L.J. , Koelling, K.W. and Tomasko, D.L. (2003). Extrusion of Polystyrene Nanocomposite Foams with Supercritical CO2 , Polymer Engineering and Science, 43(6): 1261-1275 .
6.
Zeng, C. , Han, X. , Lee, L.J. , Koelling, K.W. and Tomasko, D.L. (2003) Polymer-clay Nanocomposite Foams Prepared Using Carbon Dioxide , Advanced Materials (Weinheim, Germany), 15(20): 1743-1747 .
7.
Abiko, T. (2003). Polymer-clay Nanocomposites and MuCell Foaming , Idemitsu Giho, 46(3): 281-287 .
8.
Mitsunaga, M. , Ito, Y. , Ray, S.S. , Okamoto, M. and Hironako, K. (2003). Intercalated Polycarbonate/Clay Nanocomposites: Nanostructure Control and Foam Processing , Macromolecular Materials and Engineering, 288(7): 543-548 .
9.
Ray, S.S. and Okamoto, M. (2003). New Polylactide/Layered Silicate Nanocomposites. Part 6. Melt Rheology and Foam Processing , Macromolecular Materials and Engineering, 288(12): 936-944 .
10.
Kharbas, H. , Nelson, P. , Yuan, M. , Gong, S. and Turng, L.-S. (2003). Effects of Nano-fillers and Process Conditions on the Microstructure and Mechanical Properties of Microcellular Injection Molded Polyamide Nanocomposites , Polymer Composites, 24(6): 655-671 .
11.
Chandra, A. , Gong, S. , Yuan, M. , Turng, L.-S. , Gramann, P. and Cordes, H. (2004). Microstructure and Crystallography in Microcellular Injection-molded Polyamide-6 Nanocomposite and Neat Resin , Polymer Engineering and Science, 45(1): 52-61 .
12.
Strauss, W. and D’Souza, N.A. (2004). Supercritical CO2 Processed Polystyrene Nanocomposite Foams , Journal of Cellular Plastics, 40(3), 229-241 .
13.
Yuan, M. , Turng, L.-S. , Gong, S. , Caulfield, D. , Hunt, C. and Spindler, R. (2004). Study of Injection Molded Microcellular Polyamide-6 Nanocomposites , Polymer Engineering and Science, 44(4): 673-686 .
14.
Cao, X. , Lee, L.J. , Widya, T. and Macosko, C. (2004). Structure and Properties of Polyurethane/Clay Nanocomposites and Foams , 62nd Annual Technical Conference - Society of Plastics Engineers, Vol. 2, pp. 1896-1900 .
15.
Lee, M., Lee, B.-K. and Choi, K.-D. (2004). PCT Int. Appl., (LG Chem Ltd., South Korea, WO, p. 27.
16.
Di, Y. , Iannace, S. , Di Maio, E. and Nicolais, L. (2005). Poly(lactic acid)/Organoclay Nanocomposites: Thermal, Rheological Properties and Foam Processing , Journal of Polymer Science, Part B: Polymer Physics, 43(6): 689-698 .
17.
Cao, X. , Lee, L.J. , Widya, T. and Macosko, C. (2005). Polyurethane/Clay Nanocomposites Foams: Processing, Structure and Properties , Polymer, 46(3): 775-783 .
18.
Shen, J. , Zeng, C. and Lee, L.J. (2005). Synthesis of Polystyrene-Carbon Nanofibers Nanocomposite Foams , Polymer, 46(14): 5218-5224 .
19.
Lozano, K. and Barrera, E.V. (2000). Nanofiber-reinforced Thermoplastic Composites. I. Thermoanalytical and Mechanical Analyses , Journal of Applied Polymer Science, 79(1): 125-133 .
20.
Lozano, K. , Bonilla-Rios, J. and Barrera, E.V. (2001). A Study on Nanofiber-reinforced Thermoplastic Composites (II): Investigation of the Mixing Rheology and Conduction Properties , Journal of Applied Polymer Science, 80(8): 1162-1172 .
21.
Lee, B.O. , Woo, W.J. and Kim, M.-S. (2001). EMI Shielding Effectiveness of Carbon Nanofiber Filled Poly(Vinyl Alcohol) Coating Materials , Macromolecular Materials and Engineering, 286(2): 114-118 .
22.
Ying, Z. , Du, J.-H. , Bai, S. , Li, F. , Liu, C. and Cheng, H.-M. (2002). Mechanical Properties of Surfactant-coating Carbon Nanofiber/Epoxy Composite , International Journal of Nanoscience, 1(5-6): 425-430 .
23.
Ma, H. , Zeng, J. , Realff, M.L. , Kumar, S. and Schiraldi, D.A. (2003). Processing, Structure, and Properties of Fibers From Polyester/Carbon Nanofiber Composites , Composites Science and Technology, 63(11): 1617-1628 .
24.
Xu, J. , Donohoe, J.P. , Pittman, Jr., C.U. (2004). Preparation, Electrical and Mechanical Properties of Vapor Grown Carbon Fiber (VGCF)/Vinyl Ester Composites , Composites, Part A: Applied Science and Manufacturing, 35A(6): 693-701 .
25.
Hammel, E. , Tang, X. , Trampert, M. , Schmitt, T. , Mauthner, K. , Eder, A. and Potschke, P. (2004). Carbon Nanofibers for Composite Applications , Carbon, 42(5-6): 1153-1158 .
26.
Shen, J. and Lee, L.J. (2004). Effects of Carbon Nanofibers on Polystyrene Nanocomposites and Foams , 62nd Annual Technical Conference - Society of Plastics Engineers, Vol. 2, pp. 1836-1840 .
27.
McClurg, R.B. (2004). Design Criteria for Ideal Foam Nucleating Agents , Chemical Engineering Science, 59(24): 5779-5786 .
Barber, A.H. , Cohen, S.R. , Kenig, S. and Wagner, H.D. (2004). Interfacial Fracture Energy Measurements for Multi-walled Carbon Nanotubes Pulled from a Polymer Matrix , Composites Science and Technology, 64(15): 2283-2289 .
30.
Lourie, O. and Wagner, H.D. (1998). Transmission Electron Microscopy Observations of Fracture of Single-wall Carbon Nanotubes under Axial Tension , Applied Physics Letters, 73(24): 3527-3529 .
31.
Bower, C. , Rosen, R. and Lin, J. (1999). Deformation of Carbon Nanotubes in Nanotube-polymer Composites , Applied Physics Letters, 74(22): 3317-3319 .
32.
Cadek, M. , Coleman, J.N. and Barron, V. (2002). Morphological and Mechanical Properties of Carbon-Nanotube-reinforced Semicrystalline and Amorphous Polymer Composites , J. Appl. Phys. Lett., 81(27): 5123-5125 .
33.
Potschke, P. , Frones, T.D. and Paul, D.R. (2002). Rheological Behavior of Multiwalled Carbon Nanotube/Polycarbonate Composites , Polymer, 43(11): 3247-3255 .
34.
Ding, W. , Eitan, A. , Fisher, F.T. , Chen, X. , Dikin, D.A. , Andrews, R. , Brinson, L.C. , Schadler, L.S. and Ruoff, R.S. (2003). Direct Observation of Polymer Sheathing in Carbon Nanotube-Polycarbonate Composites , Nano Letters, 3(11): 1593-1597 .
35.
Holman, J.P. (1981). Heat Transfer, McGraw-Hill, New York .
36.
Van Hattum, F.W.J. and Bernardo, C.A. (1999). A Model to Predict the Strength of Short Fiber Composites , Polymer Composites, 20(4): 524-533 .
37.
Lee, B.O. , Woo, W.J. , Song, H.S. , Jung, S.W. , Lee, J.C. and Kim, M.S. (2001). Carbon’01, An International Conference on Carbon, Lexington, KY, United States, July 14-19, pp. 895-896 .
38.
Ramesh, N.S. (1992). Thesis, Clarkson University, New York, pp. 97-107.
