Effects of stirring prior to starting emulsion polymerization of styrene with nonionic emulsifier on particle formation and its incorporation |
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Authors: | Nami Matsusaka Toyoko Suzuki Masayoshi Okubo |
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Institution: | (1) Graduate School of Engineering, Kobe University, Rokko, Nada, Kobe 657-8501, Japan;(2) Smart Spheres Workshop Co. Ltd., 2-1-214-122, Koyo-Naka, Higashi-Nada, Kobe 658-0032, Japan; |
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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. |
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Keywords: | |
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