Research and Analysis on Polypropylene Fiber Orientation Crystallization Technology and Its Impact on Material Strength Properties

Polypropylene (PP) fiber is widely used in textiles, medical applications, geotechnical construction, and composite materials due to its excellent characteristics such as light weight, low cost, and chemical resistance. The final performance of the fiber, especially mechanical properties like strength and modulus, largely depends on its internal microstructure, including crystallinity, crystal morphology, and the degree of molecular chain orientation. Orientation crystallization technology is a key means to regulate the microstructure of polypropylene fibers, thereby significantly enhancing their mechanical properties. This paper systematically reviews the technical principles and development of inducing orientation crystallization in polypropylene fibers through processes such as high-speed spinning and electrospinning. First, the paper elaborates on the crystallographic fundamentals of polypropylene, including crystal forms, crystallization kinetics, and their relationship with molecular chain structure. Secondly, it focuses on analyzing the induction mechanisms of flow fields and stretch fields during spinning on polypropylene molecular chain orientation, nucleation, and crystal growth, discussing the influence of molecular weight and its distribution, and spinning process parameters (such as spinning speed, cooling conditions) on orientation crystallization behavior. Subsequently, the paper summarizes various methods used to characterize the crystalline structure and mechanical properties of polypropylene fibers, such as density gradient column, inverse gas chromatography, X-ray diffraction, and mechanical testing. Based on existing literature research, this paper deeply discusses the formation conditions of the highly oriented shish-kebab structure and its decisive contribution to fiber strength. The results indicate that by optimizing the orientation crystallization process, the crystallinity and crystal orientation of polypropylene fibers can be effectively improved, leading to an order of magnitude increase in tensile strength and elastic modulus. Finally, this paper prospects future research directions for polypropylene fiber orientation crystallization technology, such as multi-component system induced crystallization and green processing technologies.