Kinetics of Addition Polymerization to Polydimethylsiloxane

The system is controlled by running control sequences PS1-PS5 on a standard industrial distributed control system that is operated from a PC. The sequences open/close/adjust valves in the proper sequence and inform when and how to add components to the reactor.

1. Reactor Set-up

1. Open the N₂ cylinder connected to the reaction vessel.
2. Run the control sequence PS1 to test the equipment.
3. Then, close the manual valve to the vacuum pump to check that the system is leak-free.
4. Wait 5 min and verify that the pressure does not exceed 600 mm Hg.
5. Fill the system with N₂. Nitrogen is needed for both safety and kinetics reasons. O₂ inhibits many polymerizations, and can lead to explosions.
6. Run the control sequence PS3 to add monomer to the reactor.
7. When prompted by the sequence, add the catalyst solution and endblocker. through a small funnel called the "adder tank".

2. Polymer Fabrication

1. Start the PS4 sequence and monitor the reaction temperature.
2. Once the temperature reaches >105 °C, frequently collect liquid samples (at least every 8 min) from the sample draw point (caution: HOT, wear thermal gloves).
3. Allow the polymerization reaction to run until near equilibrium. Monitor the power usage of the agitator to confirm the reaction has reached equilibrium. Once power has stopped increasing, then the reaction is close to equilibrium.
4. Make sure to collect at least 7 samples.
5. When done, open the CO₂ tank valve and press "RXN COMPLETE" to neutralize the catalyst with CO₂. This will occur as part of the PS4 sequence.
6. Begin the PS5 stripping sequence.
   1. Open the manual valve to the vacuum pump and allow stripping to run for 15 min.
   2. Select "STRIPPING COMPLETE".
7. Collect the low boilers from the reaction into a flask.
8. Cool the reactor using the automatic cooldown process. Pumpout will be performed much later.
9. Follwong the manufacturer's instructions, measure the collected samples with a rotational (cup and bob) viscometer.
   1. If the rotational speed is set too high, no viscosity reading will be obtained, and a lower speed is chosen. These viscosity values will be used to determine the molecular-weight distribution of the polymer.