The Preparation Of High-strength And High-modulus UHMWPE Monofilament And The Study Of Its Structure And Properties

Ultra high molecular weight polyethylene(UHMWPE)fiber is one of the three high-performance fibers widely used in various fields.Exploring the relationship between structure and properties is important for the preparation of UHMWPE fiber with excellent performance.In this dissertation,self-developed and synthesized UHMWPE resin was used to conduct the gel-spinning test by using various solvents,including good solvents such as turpentine,poly-alpha-olefin,paraffin oil and relatively poor solvents such as paraffin oil/olive oil,paraffin oil/soybean oil.It has been found that UHMWPE gel prepared in poly-alpha-olefin can not be drawn into fibers,UHMWPE gel in turpentine can obtain fiber with total draw ratio of 60,and UHMWPE gel in paraffin oil,paraffin oil/olive oil and paraffin oil/soybean oil can obtain fiber with total draw ratio of 180.Fiber obtained using the 5:5 mixture of paraffin oil and olive oil(pe-bg5:5-fiber)has the best mechanical properties,with a breaking strength of 43.9 c N/dtex and an initial modulus of 1887 c N/dtex;the fiber obtained using turpentine presented the worst mechanical properties,with a breaking strength of 25.6 c N/dtex and an initial modulus of 1025 c N/dtex.Microstructure analaysis indicates that,higher crystallinity and orientation,smaller grain size,larger thickness of the piled lamellae and smoother surface,contribute to the better the mechanical properties of the resultant fiber.The results of microstructure characterization showed that the entanglement molecular weight of UHMWPE/poly-a-olefin gel was only about one fourth of that of other samples,indicating it has a very high entanglement density.The intermolecular force was too strong and made the gel unable to be drawn.Entangled molecular weights of other gels that can be drawn to higher multiples are in the range of4x10~5-5.5x10~5.The results of DSC,WAXS and SEM indicate that the solvent system which can form smaller grains and stacked platelets,less clusters between the platelets in gels has greater advantages for the subsequent drafting and crystal structure improvement.