Details of the emulsion polymerization of styrene using a reaction calorimeter

Abstract

An automated reaction calorimeter was used to directly monitor the rate of emulsion polymerization of styrene using different emulsifier (sodium lauryl sulfate) and initiator (potassium persulfate) concentrations. By using this technique in conjunction with off‐line measurements of the evolution of the particle size distributions, important details of the process were observed. The classical constant rate period (Interval II) often reported for the batch emulsion polymerization of styrene was not seen in this work. Instead, the experimental results suggest that the end of nucleation and the disappearance of monomer droplets take place at approximately the same conversion (36–40%). From the polymerization rate data, important parameters such as the monomer concentration in the polymer particles and the average number of radicals per particle were calculated. © 1996 John Wiley & Sons, Inc.

Styrene Emulsion Polymerization above the CMC: New Evidence on Particle Nucleation by means of AFFFF

“…[2] In Figure 4(a), the evolution of conversion and the rate of polymerization (RP), obtained from gravimetric data, are shown. As can be observed the RP curve does not seem to exhibit the classical constant period, in agreement with RPs reported by Varela de la Rosa et al [8] and Gardon. [29] Regarding the evolution of N (Figure 4(b)), the values obtained from AF 4 become approximately constant at around 15% conversion, while those obtained by DLS increase up to approximately 40% conversion.…”

“…These concentrations are similar to those of a typical recipe reported in the literature. [8,19] The polymerizations took place in a cylindrical, roundbottom, glass reactor with jacket, sampling valve and four baffle plates located at 908. A four-pitched-blade (458) impeller, with 7.0 cm diameter was used.…”

“…[4][5][6][7][8][9] Concerning the latter, it is widely accepted [10] that micellar nucleation is the dominant mechanism of particle formation above the critical micelle concentration (CMC), at least for the styrene case. However, it is not clear if the newly-formed (primary) particles coagulate or not, nor to what extent.…”

“…Moreover, the uncertainty about the nucleation mechanism has been extended to Interval II. Varela de la Rosa et al [8] found by the capillary hydrodynamic fractionation (CHDF) technique, that the number of particles (N) increases during this interval, instead of being constant, as reported by Harada et al [19] for the same conditions of polymerization, whose results obtained by TEM agree with the classic conception. Varela de la Rosa et al [8] proposed that during interval II particle formation occurs by homogeneous nucleation, while in interval I, micellar nucleation takes place.…”

Facile synthesis of large scale and narrow particle size distribution polymer particles via control particle coagulation during one-step emulsion polymerization

“…3 × 10 17 per unit mass aqueous phase) during 10-30 min, and the average particle diameter increased from 50 to 85 nm, indicating that obvious particle coagulation occurs in this period. The graph of monomer conversion vs. reaction time provides some extra information about the time of particle coagulation, indicating that particle coagulation lasted for only a very short interval ranged in monomer conversion from 0.13 to 0.21; in contrast, combined with the evolution of the average particle size and number, particle coagulation occurred during the particle nucleation (classical nucleation interval ranged in monomer conversion from 0 to 0.15 [25][26][27]). Thus, the formation of new particle formed in the nucleation period is a major problem in determining particle coagulation feature, thus increasing the particle number and decreasing the average particle size.…”