14—On the Technique of Measuring Orientation in Cotton by X-Rays

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Abstract
The degree of crystallite orientation has been measured for 14 cottons by X-rays and has been expressed in three ways. First, by the angular displacement from the point of maximum blackening on the (002) diffraction arc to the point where the absorption is 40 per cent, of the maximum; this was first used by berkley and Woodyard and is standard practice in America. Corrections have to be applied for those experimental conditions which cannot be held constant. A second method, developed by the author, employs a calibration strip on each film, which allows transmitted intensity readings to be converted directly into the corresponding X-ray intensities, independent of the opacity of the film or of the particular characteristics of the microphotometer used. The third method gives the average angle of inclination to the fibre axis of the chain molecules in the crystalline regions; it has been used by Hermans et al mainly for viscose rayon, and takes into account the distribution of X-ray intensity around the (002) arc instead of depending on the intensity at an arbitrary point on the arc. By making corrections it has been found possible to obtain 40 per cent, angles by the first method which are not significantly different from those obtained by Berkley on the same samples. The second method requires less rigid standardisation of experimental conditions and gives angles which are highly correlated with those given by the first method. The average orientation angle does not correlate so well with the 40 per cent. X-ray angle due to differences in the shape of the X-ray intensity distribution curves for the (002) arcs of different cottons, but this average angle is measured because it may correlate better with physical properties.

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