Seeded emulsion polymerization of vinyl chloride. A new approach to mechanism and kinetics

Abstract

Some peculiarities concerning the mechanism and the kinetic behaviour of the vinyl chloride emulsion polymerization are described. Seeded emulsion polymerizations in the presence of an adequate mixture of anionic and non‐ionic surfactants were carried out in order to avoid the micellar initiation. New kinetic parameters were determined from the experimental data as follows: (i) MSA, the minimum surface area of polymer seed particles necessary to capture all ion‐oligoradicals generated in aqueous phase at a given initiator concentration; (ii) MCCI, the maximum critical concentration of initiator per unit surface of polymer particle under which the formation of new polymer particles is avoided; (iii) PVR1, the polymer volume per active growing radical, necessary to be within the particle for 1 s. It was found that the average number of propagating radicals per particle, n, depends on the size of the polymer particle, as a resultant of entry and exit and then of the initiation and termination reactions. The practical consequences of the accurate control of the polymer particles growing during seeded emulsion polymerization of vinyl chloride were emphasized.

Particle Formation in Vinyl Chloride Emulsion Polymerization. Experimental Study

“…In sum, the works of Gatta et al 13 and Tauer and Petruschke 14 seem to corroborate each other, as both relate the onset of SPF to a minimum value of the product (Nd j ) seed , although very distinct values are presented for this parameter. The work of Butucea et al, 15 on the other hand, points in a totally different and less evident direction.…”

“…Butucea et al 15 proposed to quantify the onset of SPF in terms of a parameter that they designated "maximum critical concentration of initiator per unit surface of particles" (MCCI). A series of seeded experiments was conducted, at 50 °C, with two seed diameters and a constant concentration of potassium persulfate, from which they determined MCCI ) 2.1 × 10 -6 mol/m 2 .…”