PROCEDURES FOR VACUUM MODLING FILTER SAMPLES 10.08.2002 Chan CHECKLIST OF OPERATION 1. Checklist for preparation of filter media (glass fiber only) 1) Take 6 lit. of water in container. 2) Add dilute solution of 10% H 2 SO 4 in water. Adjust the ph of solution between 2.5 and 3.0. 3) Mount the stirrer and check it s operation in both directions. 4) Weigh the required amount of fiber for cake preparation. 5) Disperse the fibers uniformly in the container. 6) Start the stirrer. Increase the speed gradually. After every 10 minutes reverse the direction of rotation of stirrer. To reverse the direction of rotation of stirrer, reduce the speed first. Switch off the power. Change the direction of stirrer. Restart. 7) Continue stirring for about 30 minutes. Confirm uniform dispersion of fiber visually. Do manual stirring if required. 8) Assemble fiber media holder. Put the wire mesh between two disks. Tighten the screws. Put cellophane tape on the periphery to minimize air ingress. 9) Make sure that the vacuum vessel is empty. Close the lid and tighten the nuts on the periphery. Make connections to vacuum pump. Also connect fiber media holder. 10) Stop the stirrer after fibers are uniformly dispersed.
11) Add the calculated amount of Carboset 560 to the slurry. Stir to uniformly disperse the binder. Allow the slurry to settle for 24 hours. 12) Stir the slurry to a uniform dispersion after 24 hours. 13) Start the vacuum pump. Wait for some time to remove air from vacuum vessel and associated piping. (see procedures for vacuum tank operation below). 14) Dip the holder in the container. Gradually lower the holder as water level goes down. Manual stirring is required at this stage. 15) Continue till all water is removed from the container and cake is formed in the holder. 16) Take the holder out from the container. Keep the vacuum pump running for some time to remove the water in piping. Remove the holder. Stop vacuum pump. 17) Dissemble the holder. Remove the filter media in the watch glass. 18) Dry the cake in oven at 150 0 C for 30 minutes (The temperature selected is based on the binder. Check periodically to confirm that the binder does not decompose at that temperature.) 19) Remove the cake from oven after is dried completely.
Vacuum Collection Tank Operation 1. Make sure collection tank is empty. Make sure amount of fluid to be collected does not exceed the capacity of the collection tank (do not suck liquid into the vacuum pump). Close all valves. 2. Connect vacuum hose H2 to mold. 3. Turn on vacuum pump. Crack open vent valve [V1] to control pressure in collection tank to about 2 psi. 4. Open valve V2 to pull vacuum on mold. 5. After mold is filled, close valve V2. Turn off vacuum pump. 6. Remove hose from mold. Be careful to not spill the acidic water. 7. Place hose end in floor drain. 8. Turn on sink water (valves V4 and V6, close V5) to dilute the acid solution that drains from the collection tank. 9. Open valve V2 to drain the collection tank. Open valve V1 to vent the collection tank. 10. When the tank is drained, close all valves. V4 V6 V5 V1 H1 H3 Sink Mold Collection Tank Vacuum Pump H2 Floor Drain V2 V3
2. Checklist for production of nanofiber filter media ( Sparge pipe method) 1) Prepare the slurry of glass fibers as described previously (steps 1 12). 2) Setup the electrospinning apparatus. Connect the air pipe to the tank. 3) Connect the power supply. Properly ground the system. 4) Pour the slurry in the tank and start the air supply. 5) Take the polymer solution in the pipette upto the graduated mark. 6) Arrange the pipette such that the nanofibers will fall on the surface of the slurry. 7) Put one electrode in the pipette. Make sure the wire touches the surface of the polymer. 8) Start the voltage supply. Adjust the voltage to 20 KV. 9) Observe the nanofibers forming and falling on the slurry free surface. 10) Continue till the desired amount of polymer is consumed. 11) Switch off the voltage supply. 12) Switch off the air supply after 2-3 minutes. 13) Transfer the slurry in the vacuum media-forming container. 14) Follow steps 13 19 as described previously for vacuum forming the media.
3. Checklist for production of nanofiber filter media (Combined Mixing and vacuuming method in the mixing tank). 1) Prepare the slurry as suggested in the previous method. 2) Setup the electrospinning apparatus. Connect the air system and the mold to the bottom of the mixing tank. 3) Ground the system and connect the electrode to the bottom of the tank. 4) Take the polymer solution in the pipette and make sure to connect the other electrode to the solution in the pipette. 5) Adjust the voltage supply to 20 KV. 6) The nanofibers fall on the surface of the slurry and get mixed well with the glass fibers. 7) Continue till all the polymer solution has been spun into the slurry 8) Let the air agitate the slurry. Open the valve letting the vacuuming take place. 9) Once all the vacuuming has been done, switch off the air supply and remove the filter media.