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 α-chitin were obtained from the tendons of a snow crab (Chionoecetes opilio). The elastic modulus of the crystalline region along the fiber axis (El) and the thermal expansion coefficients (TECs) of α-chitin were measured using synchrotron X-ray diffraction. The El 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: αa = 6.1 × 10−5 °C−1, αb = 7.3 × 10−5 °C−1, and αc = 2.1 × 10−5 °C−1, respectively. This anisotropic thermal expansion behavior, αb > αa > αc, 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 × 10−5 °C−1.