Structural evolution from shish-kebab to fibrillar crystals during hot-stretching process of gel spinning ultra-high molecular weight polyethylene fibers obtained from low concentration solution

Abstract

The pre-stretched gel-spinning ultra-high molecular weight polyethylene fibers with low concentration solution obtained from industrial production line were used to study the structural transition from shish-kebab to fibrillar crystals during hot-stretching process via in-situ small-angle X-ray scattering, wide-angle X-ray diffraction measurements, and scanning electron microscopy. With the increase of hot-stretching strain, the kebab crystals (lamellae) undergo stress-induced fragmentation and recrystallization at 90, 100, and 110 °C and melting and recrystallization at 120 °C to transform to fibrillar crystals. Furthermore, the shish length of pre-stretched fibers at all stretching temperatures first increase and then gradually decrease with the strain, but the number of shish continuously increase and the shish diameter increase firstly and finally keep almost constant. The degree of crystal orientation for all stretching temperatures is as high as above 0.9 during the whole stretching process. These results indicate that the shish-kebab crystals of ultra-high molecular weight polyethylene fibers prepared from low concentration solution can smoothly transform to fibrillar crystals through the hot stretching process.