A Role of Taut Tie Chains in the Heterogeneous Stress Distribution and Mechanical Deformation Behavior of Synthetic and Natural Fibers

The study of the mechanical deformation behavior is indispensable for endowing more excellent mechanical property to the fibers. In particular the information on the behavior of the crystalline region is basically important. One typical experiment is to trace the structural change in the crystalline (and amorphous) region of the fiber subjected to a tensile force by measuring the change of the X-ray scattering pattern, for example. In principle, the mechanical property of the crystalline phase should be constant as an ultimate property of the semi-crystalline polymer materials. However, the actually detected mechanical deformation behavior of the crystalline region is not constant always but it changes sensitively depending on the sample preparation condition or the higher-order structure. This apparently curious behavior comes from the heterogeneous stress distribution in the fiber, which is speculated to be caused by the existence of the highly-tensioned tie chains in the amorphous region passing through the stacked lamellae. In the present article the important roles of the taut tie chains are reviewed concretely from the various aspects including the quantitative evaluation of the Youngʼs modulus along the chain axis (crystallite modulus), the clarification of the stress-induced phase transition, the improvement of the stress cracking property, the interpretation of fracture phenomenon and so on.