Structural development of ultra‐high strength polyethylene fibers: Transformation from kebabs to shishs through hot‐drawing process of gel‐spun fibers

Abstract

Structural development of ultra-high strength polyethylene fibers via hot-drawing processes of as-spun gel fibers was investigated by means of transmission electron microscopy. It is found that the shish-kebabs developed in both the as-spun and drawn fibers can be transformed continuously into the micro-fibril structure composed mostly of the shish structure through the hot-drawing process. The structure transformation involves a drastic decrease in diameter of the kebab plus the shish but almost no change in the shish diameter. This result suggests that the chains in the kebabs are incorporated into the shishs and consumed to extend the longitudinal dimension of the shishs during the drawing process. The proposed new deformation model well explains the relationship between the fiber morphology and their mechanical properties: the tensile strength and modulus of the fibers can be determined by the number of the shish in the fiber and the macroscopic diameter of the fiber, which are apriori determined at the spinning process.

Structural transformation from shish‐kebab crystals to micro‐fibrils through hot stretching process of gel‐spun ultra‐high molecular weight polyethylene fibers with high concentration solution

“…Little attention has been paid to crystallization and crystalline phase transition of polymer in hot stretching process with high deformation, especially few in‐depth studies have been made on the further evolution of shish‐kebab crystals. Ohta et al investigated the structural development during the hot‐stretching process of the as‐spun gel fiber into the UHMWPE fibers by means of transmission electron microscopy, and they found the transformation from the shish‐kebab structure into the micro‐fibril structure mainly composed of shish crystals. Tian et al investigated the transformation from shish‐kebab crystals to fibrillar crystals of UHMWPE fibers during the hot stretching at 80, 90, and 100 °C by in situ SAXS, and they thought that shish structures developed accompanied by the break‐reorganization of the shish‐kebab structures and melting recrystallization at 80 and 90, 100 °C, respectively, but the temperature of hot stretching is lower than the temperature in actual product line.…”

Two‐stage drawing process to prepare high‐strength and porous ultrahigh‐molecular‐weight polyethylene fibers: Cold drawing and hot drawing

“…However, the porosity of the ultimate fibers in previous works appeared rather low, although a high strength and modulus were achieved . Until now, related studies have placed almost all of their emphasis on the ultimate mechanical performance and mechanism of structural development of the UHMWPE fibers . Little attention has been paid to the balance of the mechanical performance and porous structure or to the mechanism of void formation in porous UHMWPE fibers.…”

An in situ small-angle X-ray scattering study of the structural effects of temperature and draw ratio of the hot-drawing process on ultra-high molecular weight polyethylene fibers

“…The decrease of kebab lateral size at later hot-drawing process corresponds to the previous study results. 19,31,32 The average shish length (hL shish i) and the shish misorientation (B f ) of UHMWPE gel bers hot-drawing at different temperature and DR 1 are shown in Fig. 11.…”