Preparation Of Large Denier Uhmwpe Fibers

UHMWPE fibers have been widely used in military, industrial, medical, civil and other fields because of their excellent various properties, and the industrialization of UHMWPE f ibers has become very mature with a wide range of fiber goods. The industrialized preparation of UHMWPE fibers generally uses gel spinning method which uauslly needs low concentration and results in a huge waste of solvent and extracting agent. The single f iber of commercial UHMWPE fibers is very thin and the breaking force of single UHMWPE fiber is very low, which results the lower utilization rate when braiding rope with a large numbers of UHMWP E fiber bundles, and the ropes also has bad abrasion resistance. In this thesis, we prepared large denier UHMWPE single f iber with high breaking force via high concentration gel spinning method, from different molecular weight of UHMWPE. The influences of spinning and drawing parameters of different molecular weight of polyethylene on the mechanical, thermal, cr ystallizing and orientational properties, morphological structures, and creep and abrasion resistance of fibers are discussed. The industrial production calculation for preparing UHMWPE fibers are discussed at the end.Firstly, different properties of large denier UHMWPE f ibers were prepared via gel spinning from different viscosity-average molecular weight(Mη) of UHMWPE of 1 million, 2 million and 4 million, the solution concentration was adjusted in the range of 10wt%- 40wt%, the screw rotating speed was changed from 3.43-10.13r/min, and the spinning temperature ranged from 250℃ to 310℃. The experimental results show that the mechanical strength of three kinds molecular weight of fibers decreases with the increasing concentration of spinning solution, the breaking force of fibers from UHMWPE with Mη of 1 million increases with the increasing concentration of spinning solution, and the breaking force of fibers from UHMWPE with Mη of 2 million and 4 million have optimum values, which are 20 wt% and 10 wt%, respectively. The mechanical property of the fiber from UHMWPE with Mη of 1 million decreases with the increasing temperature of dissolving and spinning, while the fibers from UHMWPE with Mη of 2 million has the best mechanical strength at the spinning temperature of 290℃. The mechanical strength of these three kinds of fibers reduce with the increasing of the screw rotating speed, their breaking force reach the highest at the optimal speed of 6.30r/min. The melting points and crystallinities of fibers from UHMWPE with Mη of 1 million and 2million decrease with the increasing of spinning concentration. Instead, the fibers from Mη of 4 million increase. The melting points and crystallinities of fibers from Mη of 1 million increase with the rising of spinning temperature, while the fiber from Mη of 2 million reaches the optimal at 290℃. The melting point and crystallinity of all Mη of fibers increase with the increase of the screw rotating speed. With the increasing of the spinning concentration of UHMWPE from Mη of 1 million and 2 million, the fibers’ degrees of orientation, crystallinity and grain sizes decrease, the interplanar spacing increases, while all above parameters from Mη of 4 million changes on the contrary. The network structure of fibers from Mη of 2 million with solution concentration of 10 wt% is more compact and contributes to a higher crystallinity than that of fibers with concentration of 30 wt%. The maximum drawing ratios of fibers with Mη of 1 million and 2 million have the optimal concentration, the Mη of 1 million matches 30 wt% and the Mη of 2 million corresponds to 20wt%. And the best spinning temperature for the max drawing ratio of the fiber of 2 million is 290℃, the optimal screw speed is 6.30r/min.With the increasing of draw ing ratio, the mechanical property, melting point, crystallinity and degree of orientation of fibers increase with their grain sizes and interplanar spacing decreasing on the other hand. And the uneven entanglement structures of fibers turn out to be straightened out to form highly oriented structures on the surface, but the surfaces gradually form cracks at a higher draw ratio. The creep resistance of fibers appears to be better at a low concentration and small external force. The best creep resistance of fibers matches the best temperature of 290℃. And when the drawing ratio increases, the initial and final creep rate of fiber decrease rapidly.With the increasing of concentration, the wear resistance of drawn fibers becomes better gradually while going down with the higher concentration. Meanwhile with the increase of draw ratio, the wear resistance of fibers increases while the opposite result to the tensile force of testing.The wear resistance, the mechanical property, the breaking force, the crystallinity and the degree of orientation of fibers are well related.The monofilament of lar ge denier UHMWPE fibers should be prepared to improve the wear resistance on the premise of which fibers have excellent mechanical strength.At last, the thesis talks about the industrial production of UHMWPE fibers and how to regulate the metering pump speed to obtain finished fibers with the needed fibre number.When using high concentration of gel spinning to prepare large denier UHMWPE fibers, the capacity of UHMWPE fibers can be improved greately and the cost of production of fibers can reduce sharply under the premise of which other spinning technological parameters stabilize.