X-ray measurement of cellulose crystallite orientation in cotton fibers

The orientation of crystallites in a bundle of parallel cotton fibers was studied by x-ray diffraction. The intensity distributions of the 101 and 002 diffraction rings showed the distributions of (101) and (002) planes to be identical within the limits of accuracy. Therefore, the crystallites in the cotton fibers very likely had random orientation about their long axes. The orientation distribution of these axes was calculated by using the intensity distribution of the 002 diffraction ring. The cylindrically symmetrical density distribution J(β) thus obtained was multiplied by sin β to obtain the distribution of relative numbers of crystallites at given angles β to the long axis of the fiber. The average 〈β〉 was found to be in agreement with the value of 〈sin²β〉 measured from the 002 diffraction ring. The intensity distributions on the 101 and 002 diffraction rings showed small fluctuations. These fluctuations appeared much stronger in the J(β) and sin β J(β) distributions, indicating clear discontinuities in the pitch angle distribution.