Ethylene-propylene-diene terpolymer (EPDM)/wheat husk fibers (WHFs) composites were prepared using a laboratory size two-roll mill. Cure characteristics and some physical properties such as swelling, mechanical, and thermal properties of the vulcanizates were studied. The adhesion status between the WHF and rubber matrix is lacked in general, but it started to reinforce the matrix at higher WHF contents where a higher restriction to molecular motion of the macromolecules with uniformed stress distribution of the fibers is produced. From the TGA analysis, a thermally stable property is exhibited, which in turn partially enhanced the reinforcement of the WHF-EPDM composites due to the natural adhesion during vulcanization. 1. Introduction Natural fibers are subdivided based on their origins, coming from plants, animals, or minerals. Natural Plant-fibers are grouped into four types: seed hairs (cotton, kapok), bast-fibers (flax, hemp, jute, ramie), leaf-fibers (sisal, henequen, coir, abaca), and wood flour (wheat husk, rice husk) [1–5]. It is well known that wheat husk fibers were employed in Egypt [1] for a very long time ago for buildings as construction materials mixed with clay. Generally, the different types of natural fibers are used to reinforce plastics (thermosets as well as thermoplastics) and reach the mechanical properties of glass-fiber composites, and they are already applied, for example, in automobile and furniture industries due to their relative high strength and stiffness and low density [5]. Composites can be tailored to have the desired properties by incorporating particulate fillers into a polymer matrix to suit different applications [6]. For economic and environmental reasons [7, 8], there is an increasing use of polymer composites filled with lignocellulosic materials such as wood flour, rice husk, wheat husk, jute, and sisal [9–12]. The main disadvantage encountered during the incorporation of natural lignocellulosic materials into polymers is the lack of good interfacial adhesion between the two components, especially in the case of rubbers, due to the incompatibility of hydrophilic natural fibers that are to be used as reinforcement with hydrophobic polymer matrix [13, 14]. Furthermore, these composites are often associated with agglomeration as a result of insufficient dispersion, caused by the tendency of fillers to also form hydrogen bonds with each other during processing [13–15]. Moreover, the polar hydroxyl groups on the surface of the lignocellulosic materials have difficulty in forming a well-bonded interface with a
References
[1]
A. K. Bledzki, J. Izbicka, and J. Gassan, Kunststoffe-Umwelt-Recycling, Stettin, Poland, 1995.
[2]
W. Witting, Kunststoffe in Automobilbau, VDI, Dusseldorf, Germany, 1994.
[3]
P. K. Pal, “Jute reinforced plastics: a low cost composite material,” Plastics and Rubber Processing and Applications, vol. 4, no. 3, pp. 215–219, 1984.
[4]
A. G. Winfield, “Jute reinforced polyester projects for UNIDO/government of India,” Plastics and Rubber International, vol. 4, no. 1, pp. 23–28, 1979.
[5]
J. Gassan and A. K. Bledzki, “Einflu？ von haftvermittlern auf das feuchteverhalten naturfaserverst？rkter kunststoffe,” Die Angewandte Makromolekulare Chemie, vol. 236, pp. 129–138, 1996.
[6]
A. K. Bledzki and J. Gassan, “Composites reinforced with cellulose based fibres,” Progress in Polymer Science, vol. 24, no. 2, pp. 221–274, 1999.
[7]
V. G. Geethamma, K. Thomas Mathew, R. Lakshminarayanan, and S. Thomas, “Composite of short coir fibres and natural rubber: effect of chemical modification, loading and orientation of fibre,” Polymer, vol. 39, no. 6-7, pp. 1483–1491, 1998.
[8]
H. Ishida, Interfacial Phenomena in Polymer, Ceramic and Metal Matrix Composites, Elsevier, New York, NY, USA, 1988.
[9]
S.-Y. Lee, H.-S. Yang, H.-J. Kim, C.-S. Jeong, B.-S. Lim, and J.-N. Lee, “Creep behavior and manufacturing parameters of wood flour filled polypropylene composites,” Composite Structures, vol. 65, no. 3-4, pp. 459–469, 2004.
[10]
H.-S. Kim, H.-S. Yang, H.-J. Kim, and H.-J. Park, “Thermogravimetric analysis of rice husk flour filled thermoplastic polymer composites,” Journal of Thermal Analysis and Calorimetry, vol. 76, no. 2, pp. 395–404, 2004.
[11]
S. Y. Lee, I. A. Kang, G. H. Doh, W. J. Kim, J. S. Kim, H. G. Yoon, and Q. Wu, “Thermal, mechanical and morphological properties of polypropylene/clay/wood flour nanocomposites,” Express Polymer Letters, vol. 2, no. 2, pp. 78–87, 2008.
[12]
K. Jayaraman, “Manufacturing sisal-polypropylene composites with minimum fibre degradation,” Composites Science and Technology, vol. 63, no. 3-4, pp. 367–374, 2003.
[13]
D. N. Saheb and J. P. Jog, “Natural fiber polymer composites: a review,” Advances in Polymer Technology, vol. 18, no. 4, pp. 351–363, 1999.
[14]
A. I. Medalia and G. Kraus, “Reinforcement of elastomers by particulate fillers,” in Science and Technology of Rubber, J. E. Mark, B. Erman, and F. R. Eirich, Eds., Academic Press, San Diego, Calif, USA, 2nd edition, 1994.
[15]
E. M. Dannenberg, “Filler choices in the rubber industry the incumbents and some new candidates,” Elastomerics, vol. 113, no. 12, pp. 30–50, 1981.
[16]
V. Tserki, P. Matzinos, S. Kokkou, and C. Panayiotou, “Novel biodegradable composites based on treated lignocellulosic waste flour as filler—part I: surface chemical modification and characterization of waste flour,” Composites Part A, vol. 36, no. 7, pp. 965–974, 2005.
[17]
G. Beaucage, S. Rane, D. W. Schaefer, G. Long, and D. Fischer, “Morphology of polyethylene-carbon black composites,” Journal of Polymer Science, Part B, vol. 37, no. 11, pp. 1105–1119, 1999.
[18]
Z. H. Li, J. Zhang, and S. J. Chen, “Effects of carbon blacks with various structures on vulcanization and reinforcement of filled ethylene-propylene-diene rubber,” Express Polymer Letters, vol. 2, no. 10, pp. 695–704, 2008.
[19]
D. Qian, E. C. Dickey, R. Andrews, and T. Rantell, “Load transfer and deformation mechanisms in carbon nanotube-polystyrene composites,” Applied Physics Letters, vol. 76, no. 20, pp. 2868–2870, 2000.
[20]
S. V. Joshi, L. T. Drzal, A. K. Mohanty, and S. Arora, “Are natural fiber composites environmentally superior to glass fiber reinforced composites?” Composites Part A, vol. 35, no. 3, pp. 371–376, 2004.
[21]
C. Klason, J. Kubat, and H.-E. Stromvall, “The efficiency of cellulosic fillers in common thermoplastics—part 1: filling without processing aids or coupling agents,” International Journal of Polymeric Materials, vol. 10, no. 3, pp. 159–187, 1984.
[22]
B. Das, “Restricted equilibrium swelling—a true measure of adhesion between short fibers and rubber,” Journal of Applied Polymer Science, vol. 17, no. 4, pp. 1019–1030, 1973.
[23]
H. Ismail, U. S. Ishiaku, A. R. Arinab, and Z. A. Mohd Ishak, “The effect of rice husk ash as a filler for epoxidized natural rubber compounds,” International Journal of Polymeric Materials, vol. 36, no. 1-2, pp. 39–51, 1997.
[24]
V. M. Murty and S. K. De, “Effect of particulate fillers on short jute fiber-reinforced natural rubber composites,” Journal of Applied Polymer Science, vol. 27, no. 12, pp. 4611–4622, 1982.
[25]
D. K. Setua and S. K. De, “Short silk fiber reinforced natural rubber composites,” Rubber Chemistry and Technology, vol. 56, no. 4, pp. 808–826, 1983.
[26]
E. A. Dzyura, “Tensile strength and ultimate elongation of rubber-fibrous compositions,” International Journal of Polymeric Materials, vol. 8, no. 2-3, pp. 165–173, 1980.
[27]
S. Siriwardena, H. Ismail, and U. S. Ishiaku, “Effect of mixing sequence in the preparation of white rice husk ash filled polypropylene/ethylene-propylene-diene monomer blend,” Polymer Testing, vol. 20, no. 1, pp. 105–113, 2001.
[28]
S. Siriwardena, H. Ismail, and U. S. Ishiaku, “Mechanical properties and recyclability of thermoplastic elastomer composites of white rice husk ash-ethylene/propylene/diene terpolymer-polypropylene,” Plastics, Rubber and Composites, vol. 31, no. 4, pp. 167–176, 2002.
[29]
H. Ismail, J. M. Nizam, and H. P. S. Abdul Khalil, “Effect of a compatibilizer on the mechanical properties and mass swell of white rice husk ash filled natural rubber/linear low density polyethylene blends,” Polymer Testing, vol. 20, no. 2, pp. 125–133, 2001.
[30]
H. Ismail, J. M. Nizam, and H. P. S. Abdul Khalil, “White rice husk ash filled natural rubber/linear low density polyethylene blends,” International Journal of Polymeric Materials, vol. 48, no. 4, pp. 461–475, 2001.
[31]
G. R. Hamed, “Reinforcement of rubber,” Rubber Chemistry and Technology, vol. 73, no. 3, pp. 524–533, 2000.
[32]
M. S. Sobhy, D. E. El-Nashar, and N. A. Maziad, “Cure characteristics and physicomechanical properties of calcium carbonate reinforcement rubber composites,” Egyptian Journal of Solids, vol. 26, no. 2, p. 241, 2003.
[33]
L. Ibarra and C. Chamorro, “Short fiber-elastomer composites. Effects of matrix and fiber level on swelling and mechanical and dynamic properties,” Journal of Applied Polymer Science, vol. 43, no. 10, pp. 1805–1819, 1991.
[34]
M. S. Sobhy, M. M. M. Mahdy, M. A. K. El-Fayoumi, and E. M. Abdel-Bary, “Effect of waste rubber powder in SBR formulations on the swelling of different organic solvents,” Polymer Testing, vol. 16, no. 4, pp. 349–362, 1997.
[35]
D. M. Bigg, “Mechanical properties of particulate filled polymers,” Polymer Composites, vol. 8, no. 2, pp. 115–122, 1987.
[36]
D. W. Brazier, “Applications of thermal analytical procedures in the study of elastomers and elastomer systems,” Rubber Chemistry and Technology, vol. 53, no. 3, pp. 437–509, 1980.
[37]
T. Ozawa, “A new method of analyzing thermogravimetric data,” Bulletin of the Chemical Society of Japan, vol. 38, no. 11, pp. 1881–1886, 1965.
[38]
W. L. Chang, “Decomposition behavior of polyurethanes via mathematical simulation,” Journal of Applied Polymer Science, vol. 53, no. 13, pp. 1759–1769, 1994.
[39]
J. Guo and A. C. Lua, “Kinetic study on pyrolysis of extracted oil palm fiber. Isothermal and non-isothermal conditions,” Journal of Thermal Analysis and Calorimetry, vol. 59, no. 3, pp. 763–774, 2000.
[40]
S. Kohjiya and Y. Ikeda, “Reinforcement of general-purpose grade rubbers by silica generated in situ,” Rubber Chemistry and Technology, vol. 73, no. 3, pp. 534–550, 2000.
[41]
M. P. Wagner, Rubber Chemical Technology, vol. 48, p. 271, 1975.
[42]
R. G. Raj, B. V. Kokta, and C. Daneault, “Comparative study on the effect of aging on mechanical properties of LLDPE-glass fiber, mica, and wood fiber composites,” Journal of Applied Polymer Science, vol. 40, no. 5-6, pp. 645–655, 1990.
[43]
R. G. Raj, B. V. Kokta, and C. Daneault, “The use of Isocyanate as a Bonding Agent to Improve the Mechanical Properties of Polyethylene-Wood Fiber Composites,” International Journal of Polymeric Materials, vol. 14, p. 223, 1990.
[44]
P. J. Flory and J. Rehner Jr., “Statistical mechanics of cross-linked polymer networks I. Rubberlike elasticity,” The Journal of Chemical Physics, vol. 11, no. 11, pp. 512–520, 1943.
[45]
A. S. Deuri and A. K. Bhowmick, “Ageing of rocket insulator compound based on EPDM,” Polymer Degradation and Stability, vol. 16, no. 3, pp. 221–239, 1986.
