Preparation And Characterization Of Polytetrafluoroethylene(PTFE) Fibers

Polytetrafluorethylene (PTFE) fibers are prepared through direct spinning or membrane cutting, where PTFE particle or emulsion was used as raw material. The main spinning methods include:paste extrusion spinning, carrier spinning, melt spinning, etc. PTFE Fibers are widely used in navigation, aerospace, automobile and mechanical industry due to its excellent climate and chemistry resistance, low friction coefficient and excellent biocompatibility.In study, as PVA was used as spinning carrier, PVA/PTFE dry weight ratio has a deep influence on the properties of PVA/PTFE Fiber. So the properties of four kinds membranes made from different dry weight ratio PVA/PTFE spinning solution (1:2,1:4,1:6,1:8) and its sintered PTFE membranes made in different sintering condition were studied to determine the best ratio and the best one was1:6.The die-swell behavior of PVA/PTFE solution was studied on a capillary-rheometer by photographic method. Extrusion die-swell ratio (B) was measured under different dies and extrusion conditions. Extrusion conditions were just as followed,Die length/diameter ratio was varied from3-9, Solution temperature was chosen from15-30℃, extrusion pressure was0.2-0.4MPa, sheer rate was1854s-1,1946s-1,2039s-1,2131s-1and filter layers was3and5. The results showed that B increase with the increase of extrusion pressure,decrease with the increase of solution temperature, the die L/D ratio and the number of filter layers. At the same time, with increasing of sheer rate, activation energy of extrusion die-swell decreased,which has a positive effect on the stabilities of spinning.Then, the effects of spinning solution temperature, coagulation bath temperature, spinneret draw ratio and wet draw ratio on the mechanical properties of as-spun PVA/PTFE fibers, which includes two kinds (1volume and1.5volume) cross linker (H3BO3) content fibers were studied to determine the optimum parameters. The final decided optimum spinning parameters was followed:cross linker content was1.5volume, solution temperature was30℃, coagulation bath temperature was35℃, spinneret draw ratio was-30%, wet draw ratio was3. The breaking strength of PVA/PTFE fiber made in above optimum parameters was0.071cN/dtex, which was improved by19.2%compared to the1volume one.Besides that, the possibilities of using H3BO3+NaOH mixing solution as cogulation bath were verified. But certain parameters should be deeply investigated.Finally, Due to PVA/PTFE fiber should be sintered to prepare PTFE fiber, Thermo gravimetric analysis (TGA), Fourier transform infrared ray (FTIR) and differential scanning calorimetry(DSC) was used to determine sintering temperature range.the comprehensive results showed that the sintering temperature range was330-400℃. Then, the effects of sintering temperature, sintering time,drawing temperature and drawing ratio on the mechanical properties of PTFE fibers were investigated,scanning electron microscopy(SEM) was used to analyzed the surface of PTFE fibers and the anti-corrosion behaviors of PTFE fibes on sulfuric acid and caustic soda were also tested. The final results showed that the optimum sintering temperature and time was360℃and10min. At room temperature, the optimum drawing ratio was1.45, the breaking strength of PTFE Fibers made in1.45was0.7cN/dtex. At200℃, the optimum drawing ratio was0.97, the breaking strength of PTFE fibers made in0.97was0.33cN/dtex. And sulfuric acida and caustic soda has no obvious effect on the mechanical property of PTFE Fibers.