The Study On Technology Of Producing Submicro PET Track Etched Membrane

The Polyethylene terephthalate (PET) membranes are irradiated by32S and79Brproduced by the HI-13tandem accelerator in China Institute of Atomic Energy. After agingin air for three months, the PET membranes are etched in the particular device.15μm and12μm thick PET films irradiated by32S and79Br were sensitized for3h on both sides by UVlight with a peak wavelength of365nm. Sodium hydroxide solution is used as etchant.The small-scale production etching equipment has a high-precision temperature controlsystem and a wall insulation,reducing temperature fluctuations. The effect of differentconcentration of sodium hydroxide solution and etching temperature on the pore shape hasbeen studied.The PET track etched membranes with0.2-0.93μm pore diameter have beenproduced and were frozen in liquid nitrogen to make film cross section.The sample wereobserved by scanning electron microscope.Then based on the actual hole photo holesectional cone angle calculation model was established to calculate cone angle size indifferent etching condition. As pore diameter, etchant concentration and etchingtemperature changed, the changing trend of taper angle have been obtained.The suitableetching condition for producing has been concluded.The conductance method was applied to monitor the current changes with etchingtime. The breakthrough time of the samples etched by sodium hydroxide solution with andwithout different surfactants was measured. The bulk-etch velocity in sodium hydroxidesolution and sodium hydroxide solution added Dowfax2A1surfactant was calculated. Thechange trend of pore size growth as the etching time increases was obtained while sodiumhydroxide solution was added and without Dowfax2A1surfactant. The effects ofultraviolet sensitizition and Dowfax2A1surfactant,polyvinyl pyrrolidone homopolymerPVP K17and PVP K25was studyed respectively.In addition,the effects of ultravioletsensitizition combined with Dowfax2A1surfactant was studyed. The suitable etching conditions for the production, to improve the quality of the microporous film wereobtained.Surfactant added to an alkaline etching solution adsorb on the polymer surface at thepore entrances. This reduces taper angle, the etch velocity, the rate of current increase andincrease of pore diameter without changing breakthrough time. Bulk-etch velocity can bereduced by Dowfax2A1surfactant added to sodium hydroxide solution. The taper angle isnot observed after PET membrane Sensitizitied by UV first and then etched in sodiumhydroxide solution added Dowfax2A1surfactant. PVP surfactant can adsorb on thepolymer surface at the pore entrances thus reduced the etching process, extendingbreakthrough time, reduced the taper angle. It has been show that low concentrations ofsodium hydroxide solution with high temperature makes the pore taper angle and pore sizerelatively smaller and the pores close to cylindrical. Pore taper angle was relatively minimalon0.5mol/L sodium hydroxide solution, at90℃with etching time in2hours.According to the results of a large number of experiments, the etching methods toenhance the quality of sub-micron pore size PET track-etched membrane were obtained.The etching conditions suitable for the production were obtained. This lay the foundationfor putting the sub-micron pore size PET track-etched membrane into practical application.