Multiscale Evolution of Chain Orientation and Crystal Structure under the Dual Action of Temperature and Stress
C. Liang, Weilei Huang, Senlong Yu, Qianqian Wang, Zexu Hu, Hengxue Xiang, Meifang Zhu
Abstract
A comprehensive understanding of the multiscale structural evolution that governs fiber properties during polyamide formation is essential for the theoretical development of high-strength fibers. This study systematically investigates the hierarchical structural transformations in high-strength polyamide 66 fibers (H-PA66F) at key stages during high-speed spinning, with a focus on molecular chain conformations, hydrogen bonding networks, crystalline organization, orientation dynamics, and long-period structural features. By constructing a three-phase structural model, the study elucidates the progressive structural-property relationships during fiber processing. The mechanical enhancement observed throughout the formation process is attributed to synchronized structural optimizations: hot drawing enhances fiber strength through crystal perfection and increases the alignment of rigid segments, while subsequent heat setting stabilizes the structure by reducing defects. These findings establish a robust structure-performance framework, providing theoretical insights for the targeted multiscale structural engineering of high-performance polyamide fibers.