THE EFFECT OF WATER REMOVAL ON THE CRYSTALLINITY OF CELLULOSE

Abstract

The effect of various modes of drying upon the crystallinity of cellulose has been determined by X-ray diffraction.No change in the crystallinity index was observed when previously undried pure cellulose fibers from softwood were dried from water under a wide range of conditions, but a lower value was obtained when they were dried from benzene to which the fibers were accommodated by a series of solvent exchanges. Heat of wetting determinations on the same samples indicated changes in the accessibility with different drying methods. Qualitative variations in the degree of intrafiber bonding were also detected by a differential staining method. The X-ray measurements suggested that drying from water either produces no change in lateral order or that such changes are too small to be detectable by X-rays.The crystallinity of cellulose prepared by dry-milling whole fibers was studied. The crystallinity was substantially reduced in a Wiley mill and obliterated in a ball mill. X-Ray diffraction showed that wetting with water and then drying restored the crystallinity, while similar treatment with other liquids yielded less definite results. However, by following the destruction of the lattice with progressive periods of milling, it was concluded that alcohols reform this lattice to a limited extent depending, among other factors, upon the swelling capacity.