Crystallinity and the structure of celluloses

Abstract

Observations on the x‐ray scattering by ball‐milled cellulose and cellulose derivatives, amorphous oligosaccharides, and Fortisan H are reported and an approximate shape is established for the scattering curve of the noncrystalline component of celluloses. Using this shape measurements have been made of the minimum crystallinity which is consistent with the observed x‐ray diagram of regenerated cellulose.From a comparison of this minimum crystallinity with crystallinity determined by the infrared‐deuteration method, it is concluded that at least 14% of the total material cannot be truly described as either perfectly crystalline or perfectly amorphous. This fraction of material of intermediate order is registered as crystalline by x‐ray diffraction, but infrared spectroscopy suggests that it does not possess the precise molecular configuration characteristic of crystalline material. Support for this view of structure is reported from observations of differences in hydrogen‐bonding in amorphous regions of regenerated and bacterial celluloses. Infrared results show that OH groups which lie in the surface of crystallites are hydrogen‐bonded in a random amorphous manner and it is concluded that the material of intermediate order can be accounted for in terms of chains lying in the surface of crystallites of cross‐section 29 A. × 65 A.

Benzylated modification and dyeing of ramie fiber in supercritical carbon dioxide

“…These changes caused by benzylation were very similar to those of cellulose shaped into balls. 25 The XRD pattern of the dyed ramie fiber was quite similar to that of the benzylated fiber without dyeing, which indicated that the dye molecules attached on the fiber had very limited effects on the crystal structure of the benzylated ramie fiber.…”

Effect of surface treatment on the physicomechanical and thermal properties of high‐density polyethylene/olive husk flour composites

“…A second peak corresponds to the thermal degradation of hemicellulose and cellulose, and it is located between 200 and 300 C. More specifically, the thermal decomposition of cellulose occurs mainly by depolymerization from 300 C. 20 Indeed, when subjected to very high temperatures, cellulose absorbs enough energy causing the rupture of the glucosidic link. The depolymerization can also be accompanied by dehydration of the sugar giving rise to unsaturated compounds and the formation of various volatile compounds.…”

Modern methods of determining crystallinity in cellulose

“…This can be examined by measuring the shape of the amorphaus OD band, since, as was mentioned earlier, this is related to the distribution of hydrogen bond strengths (strictly deuterium-band strengths). The amorphaus OD band has been carefully measured for five regenerated and one native cellulose 13 • The bands of the regenerated celluloses were found to be the same within the experimental error but the OD band of bacterial cellulose was found to be significantly different, as shown in Figure 8. Although the shape of the band is very similar to that of the regenerated cellulose bands, the whole band seems to be shifted towards lower frequencies, the maximum being some 20-30 cm-1 lower than with the regenerated celluloses.…”

“…This statement applies to both regenerated and native celluloses, though a complete set of quantitative measurements has only been made on one viscose rayon film 13 • The four types of material are outlined below with reference to this rayon and the percentages of OH groups which show the different types of order.…”