How does polyacrylonitrile with different degrees of polymerization and molecular weight distribution affect the performance of the fiber?
Publish Time: 2024-07-12
The performance of polyacrylonitrile fiber is significantly affected by its degree of polymerization and molecular weight distribution.
The degree of polymerization directly determines the length of the polyacrylonitrile molecular chain. When the degree of polymerization is low, the molecular chain is short, and the strength and modulus of the fiber are relatively low. This is because when the short molecular chain is subjected to force, the interaction force between molecules is weak, and it is easy to slip, resulting in insufficient ability of the fiber to resist external forces. On the contrary, a higher degree of polymerization makes the molecular chain longer, and the chances of mutual entanglement and interaction between molecules increase, which enhances the cohesion of the fiber, thereby showing higher strength, modulus and toughness.
Molecular weight distribution also plays a key role in the performance of polyacrylonitrile fiber. A narrow molecular weight distribution means that the size of the polymer molecules is relatively uniform. In this case, the physical properties of the fiber are more uniform and stable, and the crystallinity and orientation are easy to control, which helps to obtain consistent and excellent mechanical and thermal properties. For example, during the stretching process, the molecular chains can be arranged more neatly to form a more complete crystalline structure, giving the fiber better strength and dimensional stability.
However, a wider molecular weight distribution will make the fiber performance complex. The high molecular weight part helps to improve the strength of the fiber, but may cause poor processing fluidity; although the low molecular weight part helps to improve the processing performance, the excessive presence will reduce the overall strength and durability of the fiber.
In summary, in the preparation process of Polyacrylonitrile Fiber, reasonable control of the degree of polymerization and molecular weight distribution is crucial to obtain fiber products with excellent performance and stable quality. In-depth research and optimization of these parameters will help promote the wider application and performance improvement of Polyacrylonitrile Fiber in various fields.
