| As an important module form of membrane,hollow fiber membrane has the traits of higher loading density,smaller footage area,lower operating cost,good energy saving,easy enlargement,installing and cleaning,which has been widely used in microfiltration,ultrafiltration,reverse osmosis,gas separation membrane contactor and membrane reactor and other traditional and new type of membrane separation technologies.Since PTFE hollow fiber membrane has high strength,high acid,alkali,and temperature resitance,and lower surface frictional coefficient,it is widly used into the areas of special filtering,gas absorption,ozone dissolution,membrane distillation,etc.In this paper,PTFE hollow fiber membrane was obtained by using the method of paste extrusion and mechanical stretching through using PTFE dispersion resin as raw material and the alkane Exxon Mobil Isopar series solvents as lubricants.Using the tests of pore size,bubble point,porosity,water flux,contact angle,SEM and DSC represents the structure and property of PTFE hollow fiber membrane The effects of lubricant type and proportion,extrusion process,stretching and sintering on structure and properties of PTFE hollow fiber membrane were studied.The main research contents are as follows:(a)The PTFE hollow fiber membrane was obtained through changing the parameters of lubricant,including type and proportion,by the process of mixing,preforming,extrusion,stretching,sintering and cooling.The effects of lubricant type and proportion on the structure and property of PTFE hollow fiber membrane were experimentally investigated and optimized.(b)The effects of reduction ratio RR,length to diameter ratio L/D and cone angle α of the extrusion die on extrusion pressure,breaking strength,pore size,bubble point,porosity and water flux of PTFE hollow fiber membrane were studied,and the best extrusion die parameters were obtained.(c)The effects of strecting and sintering conditions,including strecting ratio,strecting temperature,sintering temperature and sintering duration on the structure and performance of PTFE hollow fiber membrane were studied.The obtained results are as follows:(1)PTFE hollow fiber has smaller pore size,higher breaking strength and bubble point pressure,bigger contact angel,higher porosity,bigger water flux and lower extrusion pressure during the process of extrusion when the type of lubricant was IsoparG and the proportion was 20%.Too high or too low proportion has an adverse effects on structure and performance of PTFE hollow fiber.(2)PTFE hollow fiber has lower extrusion pressure during extrusion process,higher breaking strength,smaller pore size,bigger bubble point pressure and porosity,higher water flux when the die parameter was recuction ratio RR=185,length to diameter ratio L/D=20 and cone angle α=40°.(3)The influences of stretching and sintering on PTFE hollow fiber membrane are as follows: The pore size,water flux and porosity of PTFE hollow fiber membrane increased but bubble point pressure changed on the oppsite trend when the stretching ratio increased.The pore size,porosity and water flux of PTFE hollow fiber membrane rised but bubble point pressure changed on the oppsite trend when the stretching temperature was increased.The pore size,bubble point pressure and water flux of PTFE hollow fiber membrane decreased but porosity had no obvious change when the sinter temperature was increased.The pore size,porosity and water flux of PTFE hollow fiber membrane were increased but the bubble point pressure was decreased when the sinter time was increased.The crystallinity of PTFE products will obviously decrease after being stretched,and it was further decresed after being sintered.PTFE hollow fiber membrane has smaller pore size,higher bubble point pressure,porosity and water flux when stretching at 100% ratio,stretching temperature at 300 oC,sintering temperature at 320 oC and sintering time at 5 seconds. |
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