Studies on poly(vinyl chloride). III. The role of the precipitated polymer in the kinetics of polymerization of vinyl chloride

Abstract

In polymerization of vinyl chloride monomer, free radicals precipitate on or within aggregatm of partidy swollen dead polymer. Polymerization on the solid polymer is characterized by autoaccelerating rates due to a progressive reduction in termination rate.This reduction in termination rate is due to the fact that as the reaction progresses and more polymer accumulates there is a decrease in probability that chain transfer of polymer radicals to monomer will generate a mobile radical, which can readily terminate an occluded or stuck free radical. From the appearance of the particles of solid polymer in the system, it has been concluded that free radicals precipitate both on polymer particle surface and inside the open structure of polymer particles.

Heterogeneous suspension polymerization of vinyl chloride: Phase distribution and evolution

“…Equation 9 indicates that the monomer phase is practically pure. In agreement with original state ments by Cotman, et aL (12), polymer chains having about 25 monomer units become insoluble and disappear from the liquid phase by coalescence with larger particles. A similar qualitative description of phase, partition has been described in Ref.…”

On the modeling of bulk poly(vinyl chloride) reactors

“…( size range. This hypothesis is supported by the data of Cotman et al 5 which show a very large number of these small particles at extremely low conversions (<l%); yet for conversion above 1%, there is a sharp decrease in the number of particles and the mean particle size has increased to 0.5-1 p. Further evidence in support of this mechanism comes from the papers and patent of T h~m a s *~-~l which indicate that a conversion of -7% is required before the polymer particles are structurally stable.…”

The bulk and suspension polymerization of vinyl chloride

“…Many papers in literature deal with the bulk polymerization of vinyl chloride (VC) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In all of them it is reported that the reaction has an accelerated behaviour and that the formed polymer separates as particles swollen by monomer from the onset of the process.…”