BUCHI Encapsulator B-395 Pro - Manual (Page 46)

6 Operation
46 B-395 Pro Operation Manual, Version C
6 .8 Practicing with the Encapsulator, using water
Before working with encapsulation polymers, use water for practicing with the Encapsulator to
become familiar with the effects of the controls. Take the cover plate of the reaction vessel, attach the
bead producing unit and a 200 µm or 300 µm nozzle to it. Place the assembled cover plate on the
control unit. Attach it with the two thumb screws. Put the vibration unit on the bead producing unit.
Place a large beaker (approx. 600 mL) under the nozzle. Connect the electrode with the red wire to
the electrostatic dispersion unit (EDU).
6 .8 .1 Using the syringe pump
1. Fill a 60 mL syringe with distilled water and install it as described in section 5.5. Set the syringe
pump speed to 4 mL/min. Activate the vibration control system and set the vibration at 1500 Hz.
Activate the syringe pump. The water will flow in large drops from the nozzle. Increase the
pumping speed until a continuous liquid jet is formed. Change the pumping speed and observe
the bead chain in the light of the stroboscope. The proper working condition is when the beads
within the bead chain are clearly separated over a length of several centimeters, 3 to 5 mm below
the nozzle. Note the vibration, voltage and syringe pump settings before you stop the pump.
NOTE
If you have difficulty seeing the bead chain, reduce the amount of light around the Encapsulator and
look from a distance of 20 to 30 cm (8” to 12”) into the liquid jet so that the black frame of the stro-
boscope is directly behind the stream.
2. Start the pump again and depress the “turbo” button – the pump will move at double speed and
a continuous liquid jet will be formed. Release the “turbo” button and the jet will soon stabilize
at the preset flow rate. The “turbo” button is very helpful priming the system when using viscous
polymer solutions and in dislodging small occlusions that impede the flow.
3. Increase the vibration frequency until the bead chain becomes unstable and then increase the
pumping speed until a good bead chain is restored. Repeat this procedure in the opposite
direction by decreasing the pumping speed and then decreasing the vibration frequency. After
performing this exercise a few times, you will become familiar with the relationship between these
two parameters. Insert the values you have determined for the optimal bead chain in table 6-1.
NOTE
The pumping speed and the vibration frequency influence each other within a given working range.
The working range itself is mainly determined by the nozzle diameter and the viscosity of the polymer
mixture.
General Rules:
• Higher frequencies generate smaller bead sizes.
• Lower liquid flow rates generate smaller bead sizes.
• The smaller the beads the lower the electrostatic voltage needed to separate the bead
stream.
• Smaller nozzles generate smaller bead sizes. The final bead diameter will be approxi-
mately 2 times the nozzle size.