Two-stage drawing process to prepare high-strength and porous ultrahigh-molecular-weight polyethylene fibers: Cold drawing and hot drawing
writer：Hongli Liu, Fei Lv, Jing Li, Tian Cao, Wenhua Zhang, Liangbin Li, Guoqiang Zheng(通訊作者), Changyu Shen
keywords：morphology, polyolefins, porous materials, synthesis and processing, structure–property relations
source：期刊
Issue time：2016年
High-strength and porous ultrahigh-molecular-weight polyethylene (UHMWPE) fibers have been prepared through a two-stage drawing process. Combined with tensile testing, scanning electron microscopy, and small-angle X-ray scattering, the mechanical properties, porosity, and microstructural evolution of the UHMWPE fibers were investigated. The first-stage cold drawing of the gel-spun fibers and subsequent extraction process produced fibers with oriented lamellae stacks on the surface and plentiful voids inside but with poor mechanical properties. The second-stage hot drawing of the extracted fibers significantly improved the mechanical properties of the porous fibers because of the formation of lamellar backbone networks on the surface and microfibrillar networks interwoven inside to support the voids. With various processing conditions, the optimized mechanical properties and porosity of the prepared UHMWPE fibers were obtained a tensile strength of 1.31 GPa, a modulus of 10.1 GPa, and a porosity of 35%. In addition, a molecular schematic diagram is proposed to describe structural development under two-stage drawing, including void formation and lamellar evolution.