Chitin fiber (CHF) and chitosan (CS) 3D composite rods with layer-by-layer structure were constructed by in situ precipitation method. CHF could not be dissolved in acetic acid aqueous solution, but CS could be dissolved due to the different deacetylation degree (D.D) between CHF and CS. CHF with undulate surfaces could be observed using SEM to demonstrate that the sufficiently rough surfaces and edges of the fiber could enhance the mechanical combining stress between fiber and matrix. XRD indicated that the crystallinity of CHF/CS composites decreased and CS crystal plane d-spacing of CHF/CS composites became larger than that of pure CS rod. TG analysis showed that mixing a little amount of CHF could enhance thermal stability of CS rod, but when the content of CHF was higher than the optimum amount, its thermal stability decreased. When 0.5% CHF was added into CS matrix, the bending strength and bending modulus of the composite rods arrived at 114.2？MPa and 5.2？GPa, respectively, increased by 23.6% and 26.8% compared with pure CS rods, indicating that CHF/CS composite rods could be a better candidate for bone fracture internal fixation. 1. Introduction Chitin, a natural polymer from marine resources [1], is found particularly in the shells of crustaceans such as crab and shrimp, the cuticles of insects, and the cell walls of fungi and is one of the most abundant biopolymers next to cellulose [2]. The shells contain 15%–40% chitin and its amount in the whole marine environment has been estimated at 1560 million tons [3, 4]. It has attracted more and more attention nowadays, due to its abundant resources, friendliness to the environment, and potential to substitute some petrochemicals [1]. Commercially, chitin is obtained at a relatively low cost from the wastes of the seafood processing industry. Briefly, the process consists of deproteinization of the raw shell material in a dilute NaOH solution and decalcification in a dilute HCl solution [5]. Chitosan (CS), a fully or partially deacetylated form of chitin, has become important materials in various fields, including medicine, biochemistry, analytical chemistry, and chemical engineering [6]. This derivative product with higher degree of deacetylation (D.D) results from the reaction of chitin with alkali (40%–45% NaOH solution) at elevated temperatures at prolonged exposures [5, 7]. Chitin and CS are polymers consisted of N-acetyl-glucosamine and N-glucosamine units randomly or block distributed throughout the biopolymer chain (Figure 1) [7, 8]. They are characterized by D.D; when D.D is lower than 50%,
References
[1]
L. Chen, Y. Du, H. Wu, and L. Xiao, “Relationship between molecular structure and moisture-retention ability of carboxymethyl chitin and chitosan,” Journal of Applied Polymer Science, vol. 83, no. 6, pp. 1233–1241, 2002.
[2]
D. Suzuki, M. Takahashi, M. Abe et al., “Comparison of various mixtures of β-chitin and chitosan as a scaffold for three-dimensional culture of rabbit chondrocytes,” Journal of Materials Science: Materials in Medicine, vol. 19, no. 3, pp. 1307–1315, 2008.
[3]
K. Kurita, “Chitin and chitosan: functional biopolymers from marine crustaceans,” Marine Biotechnology, vol. 8, no. 3, pp. 203–226, 2006.
[4]
E. Agulló, M. S. Rodríguez, V. Ramos, and L. Albertengo, “Present and future role of chitin and chitosan in food,” Macromolecular Bioscience, vol. 3, no. 10, pp. 521–530, 2003.
[5]
B. Krajewska, “Membrane-based processes performed with use of chitin/chitosan materials,” Separation and Purification Technology, vol. 41, no. 3, pp. 305–312, 2005.
[6]
T. Honma, T. Senda, and Y. Inoue, “Thermal properties and crystallization behaviour of blends of poly(ε-caprolactone) with chitin and chitosan,” Polymer International, vol. 52, no. 12, pp. 1839–1846, 2003.
[7]
K. Van De Velde and P. Kiekens, “Structure analysis and degree of substitution of chitin, chitosan and dibutyrylchitin by FT-IR spectroscopy and solid state13C NMR,” Carbohydrate Polymers, vol. 58, no. 4, pp. 409–416, 2004.
[8]
E. Khor and L. Y. Lim, “Implantable applications of chitin and chitosan,” Biomaterials, vol. 24, no. 13, pp. 2339–2349, 2003.
[9]
R. Jayakumar, N. Selvamurugan, S. V. Nair, S. Tokura, and H. Tamura, “Preparative methods of phosphorylated chitin and chitosan—an overview,” International Journal of Biological Macromolecules, vol. 43, no. 3, pp. 221–225, 2008.
[10]
T. Wu and S. Zivanovic, “Determination of the degree of acetylation (DA) of chitin and chitosan by an improved first derivative UV method,” Carbohydrate Polymers, vol. 73, no. 2, pp. 248–253, 2008.
[11]
M. Rinaudo, “Chitin and chitosan: properties and applications,” Progress in Polymer Science, vol. 31, no. 7, pp. 603–632, 2006.
[12]
V. G. Mir, J. Hein？m？ki, O. Antikainen et al., “Direct compression properties of chitin and chitosan,” European Journal of Pharmaceutics and Biopharmaceutics, vol. 69, no. 3, pp. 964–968, 2008.
[13]
Y.-C. Kuo and I.-N. Ku, “Cartilage regeneration by novel polyethylene oxide/chitin/chitosan scaffolds,” Biomacromolecules, vol. 9, no. 10, pp. 2662–2669, 2008.
[14]
J. Sriupayo, P. Supaphol, J. Blackwell, and R. Rujiravanit, “Preparation and characterization of α-chitin whisker-reinforced chitosan nanocomposite films with or without heat treatment,” Carbohydrate Polymers, vol. 62, no. 2, pp. 130–136, 2005.
[15]
Q. L. Hu, X. Z. Qian, B. Q. Li, and J. C. Shen, “Studies on chitosan rods prepared by in situ precipitation method,” Chemical Journal of Chinese Universities-Chinese, vol. 24, no. 3, pp. 528–531, 2003.
[16]
Z. K. Wang, Q. L. Hu, X. G. Dai, H. Wu, Y. X. Wang, and J. C. Shen, “Preparation and characterization of cellulose fiber/chitosan composites,” Polymer Composites, vol. 30, no. 10, pp. 1517–1522, 2009.
[17]
Z. K. Wang, Q. L. Hu, and L. Cai, “Chitosan and multi-walled carbon nanotube composite rods,” Chinese Journal of Polymer Science. In press.
[18]
Z. K. Wang and Q. L. Hu, “Chitosan rods reinforced by N-carboxyl propionyl chitosan sodium,” Acta Physico-Chimica Sinica. In press.
[19]
A. Yang and R. Wu, “Mechanical properties and interfacial interaction of a novel bioabsorbable chitin fiber reinforced poly (ε-caprolactone) composite,” Journal of Materials Science Letters, vol. 20, no. 11, pp. 977–979, 2001.
[20]
Q. Hu, B. Li, M. Wang, and J. Shen, “Preparation and characterization of biodegradable chitosan/hydroxyapatite nanocomposite rods via in situ hybridization: a potential material as internal fixation of bone fracture,” Biomaterials, vol. 25, no. 5, pp. 779–785, 2004.
[21]
B. Q. Li, D. C. Jia, Y. Zhou, Q. L. Hu, and W. Cai, “In situ hybridization to chitosan/magnetite nanocomposite induced by the magnetic field,” Journal of Magnetism and Magnetic Materials, vol. 306, no. 2, pp. 223–227, 2006.
