Study On Manufacture By Heat Treatment And Distillation Performance Of Low Creep PTFE Microporous Membrane

PTFE microporous membrane is widely used in sealing and membrane distillation fields due to its excellent solvent resistance,high temperature resistance and corrosion resistance.However,the molecular chain of PTFE is highly symmetrical and the intermolecular force is small,which leads to the creep of PTFE microporous membrane and is not conducive to membrane distillation performance.The effects of heat treatment parameters(quenching temperature,annealing temperature,quenching time,annealing time)on crystallinity,orientation,mechanical properties,creep properties and membrane distillation properties were studied by the modification of PTFE microporous membrane,and the intrinsic relationship was discussed to provide a theoretical basis for preparing PTFE microporous membranes with excellent creep resistance.The main research contents and conclusions are as follows:(1)SEM,DSC,sound velocity orientation instrument,universal testing machine,DMA and other research shows: With the increase of heat treatment temperature,the crystallinity of quenching specimen increases first and then decreases,the crystallinity of annealing specimen decreases first,then increases,then decreases,and the orientation of the two specimens increases gradually,influenced by crystallization and orientation,the initial modulus and fracture strength gradually increase,and the elongation at break gradually decreases,and the creep variable first decreases and then increases.When the heat treatment temperature is 320 ?,the creep variable of the two specimens is the least,and the creep resistance is the best.(2)With the extension of heat treatment time,the crystallinity of the two specimens decreased and then increased,the orientation gradually increased,influenced by crystallization and orientation,the initial modulus and breaking strength gradually increased,while the elongation at break gradually decreased and creep variable gradually decreased.The annealing specimen has the advantages of high strength,good toughness and the best creep resistance compared with the three specimens.Therefore,the best technology to improve the creep resistance is: 320 ?,thermal insulation 10 min,annealing treatment.(3)The research of porosity analyzer and mercury porosimetry shows that: With the increase of heat treatment temperature,the average pore size,porosity,water flux of the two specimens increased first and then decreased,but the desalting rate did not change obviously.The average aperture,porosity and water flux are the largest when the heat treatment temperature is 320 ?.The average pore size,porosity and water flux of the Annealed sample are the largest in comparison with the three specimens.(4)With the increase of heat treatment time,the average pore size,porosity and water flux of the two specimens gradually increased,while the desalting rate did not change significantly,and the performance of membrane distillation was less influenced when the heat treatment time was too long.So the best heat treatment conditions are: in 320 ?,insulation 10 min,annealing treatment.