Expansion and shrinkage of fibers

Introduction Fibers are produced worldwide in enormous quantities. More than 20 million tons of synthetic fibers and 20 million tons of natural fibers are manufactured each year. The total length of these fibers corresponds to about 10 000 times the distance from the earth to the sun. A characteristic feature of a fiber is that its length is much greater than its diameter. The great anisotropy of the microstructure and the physical properties originating from spinning and stretching processes are two of the main reasons for the special properties and peculiarities of fibers [1, 2]. Spinning, stretching and annealing are in fact the most important steps in the manufacture of fibers. These processes determine properties such as the modulus of elasticity (Young’s modulus, E) and toughness that are required for the application envisaged. Coloring properties, shrinkage (contraction of fibers) and thermal stability are determined by the size, number and orientation of the crystallites, as well as the molecular structure in the amorphous regions. Thermomechanical analysis (TMA) in particular, as well as DMA, DSC, TGA and TOA are all excellent techniques for the investigation of the effects of temperature and mechanical loading on fibers and yarns. They allow the relationship between structure, properties and the manufacturing process [3] to be investigated. Very often comparative measurements under identical conditions are sufficient to characterize transition temperatures, expansion and shrinking behavior. TMA measurements also yield numerical values such as the coefficient of linear expansion, Young’s modulus, E, and the force of contraction as a function of temperature.