13—MOLECULAR ORIENTATION AND THE TENSILE PROPERTIES OF COTTON FIBRES

Abstract

Fibre tensile strength and initial Young's modulus have been measured on 36 samples of raw cotton and correlated with the double refraction dete[rdot]mined by the Becke method. About 80 per cent. of the variation in strength and modulus can be attributed to variation in the molecular orientation measured by the double refraction. The higher refractive index varied from 1·573 for short coarse cottons to 1·581 for long fine cottons, whilst the lower refractive index was approximately constant at 1·531. From the higher refractive indices the corresponding angles of the spiral fibrils were calculated to range from 27° for fine Sea Island cottons to 35° for coarse Indian cottons. The initial Young's modulus is almost inversely proportional to the area of cross-section, i.e., approximately the same load is required to extend fibres of different fineness by the same amount. This is accounted for in terms of the spiral structure of the cotton fibre.