Study On The Preparation Of Rope Used High Strength Uhmwpe Fibers

Ultra-high molecular weight polyethylene(UHMWPE)fibers have excellent mechanical properties and other excellent performance,they are widely used in military bulletproof,safety protection,marine engineering,fisheries and other fields.With the attention and development of marine resources around the world,the demand for UHMWPE fibers of marine ropes is increasing at an unprecedented rate.However,the commercial UHMWPE fiber monofilament is thin,and its breaking force is very low.The fibers are easy to be broken when they are used.In this thesis,large denier UHMWPE fibers were prepared by increasing the spinning concentration.Although fiber strength is slightly low,but the tensile breaking force of single filament is obviously improved,and the wear resistance of fibers will be improved too.The polyethylene powder with viscosity average molecular weight(M?)of 1.3 million,1.8 million and 4.5 million were used in preparation of UHMWPE fibers.UHMWPE gel fibers were prepared by gel spinning through twin-screw extruder swelling,dissolving and extruding technique.The effects of gel spinning and hot drawing technology on the gel fiber's M? were discussed in details.The relationships between the M? of UHMWPE fibers and the drawability,mechanical properties,thermal and crystalline properties,creep and wear resistance of resultant fibers were investigated.Nano-Si C particles were dispersed in the extracting solvent and were used to extracting modify UHMWPE gel fibers during their extracting process.The structure and properties of UHMWPE fibers before and after modification were compared and studied.The results showed that the degradation of UHMWPE molecules cannot be ignored in the preparation of UHMWPE fibers.The molecules degradation mainly occurred in the stage of UHMWPE's dissolving and spinning stage,while it was not obvious during fiber 's ultra-drawing process.During the dissolving and spinning process,the screw rotation speed,spinning temperature and UHMWPE concentration had great influences on the degradation of UHMWPE.With the increasing of screw rotation speed,the screw shearing strength was enhanced and amplified the degradation of PE molecules,while the residence time of UHMWPE solution in the screw extruder became shorter and so reduced the high temperature thermal degradation degree of PE molecules,meanwhile,the thermal degradation degree of PE molecules was also affected by the dissolving temperature.Therefore,the influence of screw speed and solution temperature on the molecular weight of the UHMWPE fiber was complicated under the comprehensive consideration of above three factors.With the increase of UHMWPE concentration,the trend of UHMWPE degradation increased.In addition,the effect of concentration was more obvious when the screw rotation speed increased.After the swelling,dissolving and extruded spinning through twin screw extruder,the degradation degree of UHMWPE with different initial molecular weight reached 20% to 90%,and so greatly influenced fiber's mechanical properties.The drawability,mechanical strength,creep and wear resistance of UHMWPE fibers increased with increasing of the fiber's M? in the case of uniform UHMWPE dissolving,the melting and crystallizing peaks became wider,and the melting temperature and crystallinity of UHMWPE fibers became larger finally,while the crystallizing temperature decreased.The surface morphologies of fibers were not neat when the poor dissolving of UHMWPE happened,the M? of resultant fibers was higher,while the fiber's drawability and comprehensive performance became worse.The dispersion and anti-aggregation ability of nano Si C became stronger in dichloromethane after treated with silane coupling agent and the nano-Si C could be diffused into UHMWPE gel fibers during their extraction process and uniformly distributed inside the fibers.After extraction modified with nano Si C,the crystallinity of fibers became larger,the melting and crystallizing temperature became slightly higher,and the crystal size was decreased.The crystallizing performance was the best when the content of nano Si C in extracting solvent was 10g/L.The addition of nano Si C particles was benefit to the sound wave transmission along fiber axis and the orientation of modified UHMWPE fibers became higher,but as the nano Si C content increased,the orientation of fibers began to decrease.Compared with unmodified fibers,the heat resistance of nano Si C modified fibers became higher,the degradation temperature at 5% weight loss and Tmax were increased by about 8?.With the increasing of the nano Si C concentration in extraction solution,the strength,modulus,creep and wear resistance of the final fibers became stronger.When the nano Si C concentration was 10g/L,the mechanical properties and the creep resistance of modified UHMWPE fibers were increased by 25% and 37%,compared with unmodified fibersrespectively.