Structural analysis during creep process of ultrahigh‐strength polyethylene fiber

Structural changes during the creep process of ultrahigh‐strength polyethylene fiber (UHSPE) were investigated using X‐ray and the solid‐state NMR techniques. As the creep strain increases, the quantity of the amorphous phase area estimated by the 13C‐NMR method increases until the final creep rupture. On the other hand, the amorphous quantity estimated by the X‐ray method does not change noticeably. To explain this contrast, we proposed a new model that illustrates how the defects such as chain ends incorporated into the crystalline phase are excluded from the crystallite and agglomerate to generate a new amorphous area, which has a size hardly detected by the X‐ray method. These small amorphous areas are considered to cause a decrease in the tensile strength and the successive final creep rupture.