Polymerization

Purpose

Reaction kinetics are measured for the solution polymerization of methyl methacrylate in a batch reactor, showing basic techniques and how variables other than concentration can be used to measure kinetic parameters. The experiment forms the basis for a set of open ended assignments to examine the kinetic mechanism of a free radical chain growth polymerization reaction and the ramifications of physico-chemical phenomena which ,may affect its performance in a continuous reactor.

The parameters that can be varied are:

1. temperature,
2. concentrations of solvent and monomer
3. type and concentration of initiator

The following effects can be studied directly:

1. effective reaction orders for a free radical chain reaction,
2. temperature dependence of the overall rate constant,
3. Tobolsky Dead End polymerization

Kinetics of Polymerization

A brief desciption of the kinetics of poilymerization and of the evolution of the polymer chain length distibution can be found here in pdf format

Experimental Setup

Polymerization in a dilatometer allows measurement of the volume change with time upon polymerization as the lower density monomer forms the higher density polymer. The dilatometer is immersed in a constant temperature bath.

Operational Notes

Monomer, initiator, and solvent are individually weighed and and mixed prior to introduction in the dilatometer. Approximately 100 ml of the mixture is introduced by drawing it into the dilatometer by vacuum, filling it completely. After immersion in a water bath, save for the rising capillary, the dilatometer will equilibrate thermally and some of the solution may spill as expansion forces it out of the capillary. After some delay, the solution will begin to contract as the its volume decreases due to the reaction.

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