Effects of stirring prior to starting emulsion polymerization of styrene with nonionic emulsifier on particle formation and its incorporation

Abstract

Emulsion polymerization of styrene with a nonionic emulsifier (polyoxyethylene nonylphenyl ether, E911) and potassium persulfate as initiator was carried out at different stirring rates (240-500 rpm) at 70°C, which was started by the addition of initiator after stirring for 100 min at 70°C. Resulting polystyrene (PS) particles at 240 rpm were 70-nm-sized, spherical particles and incorporated only 5 wt.% of total E911. On the other hand, particles at 500 rpm were 1-μm-sized, nonspherical particles, which were formed by coagulation of small particles, and incorporated above 70 wt.% of E911 in the inside. Before starting emulsion polymerization, E911 and styrene, respectively, transferred from an aqueous phase to a styrene phase and from the styrene phase to the aqueous phase (water and micelles) faster at 500 rpm than 240 rpm. At 240 rpm, there were a lot of almost empty micelles (ca. 5 nm) in the aqueous phase, on the other hand at 500 rpm, 70 wt.% of total E911 transferred to the styrene phase and the micelles were swollen with much monomer (ca. 40 nm) even if the number was smaller. Stirring prior to starting the emulsion polymerization greatly affected partitionings of monomer to the aqueous phase and the nonionic emulsifier to the styrene phase, resulting in the differences in the particle formation and the incorporation of the nonionic emulsifier inside PS particles.

Inline Turbidity Measurements of Batch Emulsion Polymerization

“…The emulsification for droplet generation plays an important role in emulsion polymerization . On the one hand, mass transfer limitation from the monomer phase to the particle phase can occur due to an insufficient dispersion .…”

Semicontinuous Emulsion Copolymerization of Vinyl acetate and Butyl acrylate with Nonionic Surfactants (Triton X Series)

“…As a result, a significant amount of surfactant would be located inside the polymer particles at the completion of the polymerization. Therefore, partitioning of surfactant to monomer phase is of substantial importance for the incorporation . In more hydrophobic monomers stabilization with nonionic surfactant occur this situation and the particle sizes of hydrophobic latexes are increased, especially in the presence of styrene.…”

Incorporation Behavior of Nonionic Emulsifiers inside Particles and Secondary Particle Nucleation during Emulsion Polymerization of Styrene

“…Suppression of the incorporation could be achieved by setting conditions that no monomer droplets nor monomer layer exists in the system, in which the monomer concentration in polymerizing particles remains at a low level during the emulsion polymerization by suitable adjustment of the monomer-feed rate . When MAA content in emulsion copolymerization of styrene with MAA was increased, the amount of incorporated E911 increased and, surprisingly, reached 74% of total amount of E911 used at 10 mol % MAA. , Moreover, we reported that there was an obvious stirring effect prior to the emulsion homopolymerization of styrene (or methyl methacrylate) upon the incorporation of nonionic emulsifier inside particles. , The incorporation phenomenon has been so far studied by examining the amount of nonionic emulsifiers incorporated in the interior of PS or P­(S-MAA) particles obtained at the completion of their emulsion polymerizations. The incorporation gives negative images as described above, but recently we reported that it contributed to form hollow PS or P­(S-MAA) particles having high hollow volumes, , although sulfate end-groups, which were derived as fragments of the KPS initiator, buried inside particles during emulsion polymerization, were a main factor .…”

“…6,7 Moreover, we reported that there was an obvious stirring effect prior to the emulsion homopolymerization of styrene (or methyl methacrylate) upon the incorporation of nonionic emulsifier inside particles. 8,9 The incorporation phenomenon has been so far studied by examining the amount of nonionic emulsifiers incorporated in the interior of PS or P(S-MAA) particles obtained at the completion of their emulsion polymerizations. The incorporation gives negative images as described above, but recently we reported that it contributed to form hollow PS or P(S-MAA) particles having high hollow volumes, 10,11 although sulfate end-groups, which were derived as fragments of the KPS initiator, buried inside particles during emulsion polymerization, were a main factor.…”