Polystyrene multiple emulsions

Four types of phase behavior characteristic of the PS/P(MMA-S) system have been described and illustrated in some detail in the previous section and further, the average particle sizes have been tabulated as a function of molecular weight and weight percent of PS initially present in the PS/MMA-S mixture and of the composition of the final P(MMA-S) copolymer resulting after polymerization. In the section we will discuss these results in terms of the ternary polystyrene/poly(methyl methacrylate-styrene)/methyl methacrylate-styrene phase diagram, dealing with (1) the four types of phase relationships, (2) particle size, and lastly (3) multiple emulsions or subinclusions within the dispersed phase. 

Continuous stirred tank reactors are used commercially for solution, bulk (mass), and emulsion polymerization of vinyl monomers. In bulk homogeneous polymerization processes (e.g., polystyrene), the reactor system usually consists of a single CSTR or multiple CSTRs and an extruder-type devolatilizer to remove unreacted monomer, which is then recycled to the reactor. As monomer conversion increases, the viscosity of the polymerizing fluid increases and the overall heat removal efficiency decreases. When styrene is polymerized in bulk in a stirred tank reactor, monomer conversion is limited to about 30-40% due to an increasing viscosity of the polymerizing fluid above this conversion level. However, the overall monomer conversion can be very high because unreacted monomer is constantly recycled to the reactor. 

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