| Polytetrafluoroethylene（PTFE）fibers are prepared by PTFE as raw material through spinning or mading the membrane to cutting or fibrillating.The main spinning technics are matrix spinning,paste extrusion spinning,melt-spinning and films cutting method,etc.PTFE fibers are widely used in national defense,aerospace,petrochemical industry,electronic industry,medicine,textile and other industries because of their excellent chemical resistance,thermal stability,low friction coefficient and good biological compatibility.The homogeneous and stable spinning solution of PTFE emulsion blending with PVA was prepared with the addition of cross linker（H3BO3）.Then the rheological behavior of spinning solution was studied by ARES-RFS Senior Rotary Rheometer.The effects of temperature,PVA:PTFE（dry weight ratio）,shearing rate and angular frequency on the flow curve,non-Newtonian index,activation energy of viscous flow,storage modulus,loss modulus,complex viscosity and loss tangent were investigated.The effects of spinning solution temperature,coagulation bath temperature,spinneret draw ratio and wet draw ratio on the mechnical properties of as-spun fiber were investigated.Optimum coagulation condition and wet draw ratio were determined to lay the foundation for sintering and dry draw ratio.The optimum PTFE/PVA composite as-spun fiber surface was analyzed by scanning electron microscopy（SEM）.The final spinning conditions were:spinning solution temperature was 45°C,coagulation bath temperature was 35°C,spinneret draw ratio was-30%,wet draw ratio was 4.0.The denier,tenacity,elongation and initial modulus of PTFE/PVA composite as-spun fibers under optimum process were 36.50dtex,1.22×10-1cN/dtex,182.48%and 1.14x 10-1cN/dtex respectively.Thermal properties of PTFE/PVA composite as-spun fibers and sintered fibers were analyzed by thermo gravimetric analysis（TGA）and fourier transform infrared ray（FTIR）to determine the sintering temperature range.Comprehensive Analysis of TG,FTIR and thermal decomposition temperature of PTFE,it can be known that the optimum sintering temperature range was between 360°C to 415℃.The effects of sintering temperature,sintering time and dry draw ratio on the mechnical properties and crystallinity of PTFE fibers were investigated,and PTFE fibers’ surface was analyzed by SEM.The corrosion behaviors of concentrated sulfuric acid and caustic soda were studied.The results showed that the optimum sintering temperature was 380°C,sintering time was 30min,dry draw ratio was 5.The denier,tenacity,elongation and initial modulus of PTFEfibers were 14.60dtex,8.71×10-1cN/dtex,261.26%and 5.25×10-1 cN/dtex.The crystallinity decreased significantly after sintering,but increased a little by drawing.And concentrated sulfuric acid and caustic soda have no effects on PTFE fibers.The PTFE fibers were filling modified by adding SiO2 nano-particles into spinning solution.The effects of spinneret draw ratio and wet draw ratio on the mechnical properties and crystallinity of modified as-spun fiber were investigated.The optimum sintering temperature range was determined by TG and FTIR curves.And the effects of sintering temperature,sintering time,dry draw ratio and concentrated sulfuric acid and caustic soda on the mechnical properties of modified PTFE fibers were studied.The modified PTFE fibers surface was analyzed by SEM at last.It is indicated that the optimum spinneret draw ratio was-30%,wet draw ratio was 4.0,sintering temperature was 380°C,sintering time was 30min,dry draw ratio was 5.And the denier,tenacity,elongation and initial modulus of modified PTFEfibers were 15.03dtex,1.07cN/dtex,205.59%and 7.41 ×10-1cN/dtex.The crystallinity decreased significantly after sintering,but increased a little by drawing.The concentrated sulfuric acid and caustic soda have no effects on modified PTFE fibers. |
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