No abstract

No abstract

The crystal lattice moduli of cellulose I and II were measured by X-ray diffraction using ramie and mercerized ramie. The measured crystal lattice moduli were in the range from 120 to 135 GPa and from 106 to 112 GPa for cellulose I and II, respectively. These values were different from recent theoretical estimates of 167 and 163 GPa for cellulose I and II, respectively, reported by Tashiro and Kobayashi. To study the origin of this difference, a numerical calculation of the crystal lattice modulus, as measured by X-ray diffraction, was carried out by considering effects of the orientation factors of crystal and amorphous chains and crystallinity. In this calculation, a previously introduced model was employed, in which oriented crystalline layers are surrounded by oriented amorphous phases and the strains of the two phases at the boundary are identical. The theoretical results indicate that the crystal lattice modulus measured by X-ray diffraction is different from the intrinsic lattice modulus when a parallel coupling between amorphous and crystalline phases is predominant, while the values of both moduli are almost equal when a series coupling is predominant. Thus, the crystal lattice moduli of cellulose I and II measured by X-ray diffraction are predicted to be dependent upon the morphological properties of the bulk specimens. The numerical calculations, however, indicate that the morphological dependence is less pronounced with increasing degree of molecular orientation and crystallinity. Thus, it is concluded that fibers and films with a high degree of molecular orientation and a high crystallinity should be used as test specimens for measuring crystal lattice moduli by X-ray diffraction.

Specifically substituted O-methylcelluloses, 2,3-di-O-methylcellulose and 6-O-methylcellulose (parts B and C of Figure 1, respectively), were used as cellulosic components in blends with poly (ethylene oxide) (PEO) and poly(vinyl alcohol) (PVA). Since their hydroxyl groups (OH) form controlled intraand intermolecular hydrogen bonds, the cellulose derivatives are useful as model compounds to investigate the effect of hydrogen bonding in cellulose-synthetic polymer blend systems. FTIR (Fourier transform infrared spectroscopy) spectra of the cellulosic-PEO blend films revealed that, while the primary hydroxyl groups at the C-6 position of cellulose interact strongly with ether oxygen in PEO, the secondary hydroxyl groups at the C-2 and C-3 positions show no evidence for polymer-polymer interactions. In the cellulosic-PVA blend films the FTIR analyses suggested that the secondary hydroxyl groups between the cellulose and the PVA were engaged in hydrogen bonds, and, in addition, a hydrogen bond between the anhydroglucose ring oxygen (0-5) of the cellulose and the hydroxyl groups of the PVA was formed. Thus, these results showed the specific regiochemistry of hydroxyl groups in cellulose and its importance to the study of the miscibility in cellulosesynthetic polymer blends.

The crystal lattice modulus of polyethylene was measured by X-ray diffraction using ultradrawn films that were produced by gelation/crystallization from dilute solution. The measurement was carried out at 20 "C for specimens with various elongation ratios beyond 50. The measurable crystal lattice modulus was in the range from 213 to 229 GPa and these values were independent of elongation ratios. This independence supports the assumption that the stress within a specimen is homogeneous. Furthermore, an effort was made to produce specimens whose Young's modulus is almost equal to the theoretical value. Through trial and error, it turned out that Young's modulus approached 216 GPa, nearly the theoretical limit of hardness, in the case that the dry gel films could be consistently elongated to the remarkably high draw ratio of 400.