The Structure and Properties of Natural and Allied Fibres

It has been possible only to outline the structure and some of the physical properties of natural and allied fibres. While such fibres can be regarded as possessing a common basic structure, modifications of this may lead to considerable differences between the different fibres. In wool the chains do not easily fit into a lattice and crystallinity is low. The chains are folded, such folds being maintained by physical forces between chains. These forces are comparatively weak, and unfolding is easy. The fibre has a low strength and, under certain conditions, a high extensibility. In silk, extended chains fit more readily into a lattice, and the fibre is less extensible. In cellulosic fibres the chains fit easily into å lattice, and in native fibres there are relatively strong forces between chains. The fibre is strong with short‐range elasticity. Regenerated cellulose fibres differ from native in a number of ways‐in the dimensions of the unit cell, in the smaller degree of crystallinity and more random orientation of crystallites, and in the possession of a skin, these differences being reflected in differences in physical properties. This outline of structure and properties is based on two concepts‐ the configuration of the chains and the existence, in the fibre, of crystallites and amorphous regions. While this simple picture should possibly be elaborated to include the arrangement of crystallites into fibrils and the surface structures of fibres, it permits the correlation of fibre structure with such important properties as moisture regain, density, birefringence, swelling, extensibility, and crease‐resistance. These are only some of the properties related to fibre structure. Others, such as the diffusion of dyes, the amount of dye absorbed under specified conditions, and the orientation of dyes in fibres, all of importance in dyeing, may also be related to fibre structure.