Elastic modulus in the crystalline region and the thermal expansion coefficients of α-chitin determined using synchrotron radiated X-ray diffraction

Crystalline, orientated fibers of alpha-chitin were obtained from the tendons of a snow crab (Chionoecetes opilio). The elastic modulus of the crystalline region along the fiber axis (E-1) and the thermal expansion coefficients (TECs) of alpha-chitin were measured using synchrotron X-ray diffraction. The E-1 value of alpha-chitin was 59.3 +/- 11.3 GPa, which was slightly larger than the value reported previously. This was because of the higher degree crystallinity of our sample and the use of synchrotron radiation as an X-ray source in this study. The linear TECs of the a-, b-, and c-axes were: alpha(a) = 6.1 x 10(-5) degrees C-1, alpha(b) = 7.3 x 10(-5) degrees C-1. and alpha(c) = 2.1 x 10(-5) degrees C-1, respectively. This anisotropic thermal expansion behavior, alpha(a)> alpha(b) > alpha(c), was ascribed to the crystal structure and hydrogen bonding system of alpha-chitin. In addition, the volume TEC of alpha-chitin is reported for the first time as beta = 15.8 x 10(-5) degrees C-1. (C) 2010 Elsevier Ltd. All rights reserved.