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

摘要

Crystalline, orientated fibers of α-chitin were obtained from the tendons of a snow crab (Chionoecetes opilio). The elastic modulus of the crystalline region along the fiber axis (E1) and the thermal expansion coefficients (TECs) of α-chitin were measured using synchrotron X-ray diffraction. The E1 value of α-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: α_a = 6.1 x 10~(-5)oC~(-1),α_b, = 7.3 x 10~(-5)oC~(-1),and α_c = 2.1 x 10~(-5) °C~(-1), respectively. This anisotropic thermal expansion behavior, α_b >α_a>α_c, was ascribed to the crystal structure and hydrogen bonding system of α-chitin. In addition, the volume TEC of α-chitin is reported for the first time as β = 15.8 x 10~(-5) °C~(-1).