X‐ray diffraction study of the thermal expansion behavior of cellulose triacetate I

Abstract

AbstractHighly crystalline samples of cellulose triacetate I (CTA I) were prepared from highly crystalline algal cellulose by heterogeneous acetylation. X‐ray diffraction of the prepared samples was carried out in a helium atmosphere at temperatures ranging from 20 to 250 °C. Changes in seven d‐spacings were observed with increasing temperature due to thermal expansion of the CTA I crystals. Unit cell parameters at specific temperatures were determined from these d‐spacings by the least squares method, and then thermal expansion coefficients (TECs) were calculated. The linear TECs of the a, b, and c axes were αa = 19.3 × 10−5 °C−1, αb = 0.3 × 10−5 °C−1 (T < 130 °C), αb = −2.5 × 10−5 °C−1 (T > 130 °C), and αc = −1.9 × 10−5 °C−1, respectively. The volume TEC was β = 15.6 × 10−5 °C−1, which is about 1.4 and 2.2 times greater than that of cellulose Iβ and cellulose IIII, respectively. This large thermal expansion could occur because no hydrogen bonding exists in CTA I. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 517–523, 2009