ELECTROSTATIC AND STERIC STABILIZATION OF PVC PRIMARY PARTICLES

Problems related to the formation and stability of primary particles i n VCM suspension and bulk polymerization were theoretically analyzed, based on the DLVO (Deryaguin-Landau-Verwey-Overbeek) and HVO (Hesselin k-Vrij-Overbeek) theories of stability of colloidal systems. In the ab sence of secondary stabilizers, PVC primary particles were solely stab ilized by negative electric charges, as a result of the presence of HC I formed by a chain transfer reaction of chloride radicals to PVC poly mer chains. The dependence of the stability of primary particles on th e ionic strength of the medium, temperature, and total particle charge was quantitatively investigated in terms of the stability ratio and t he particle coalescence rate constant. The steric stabilization of pri mary particles, arising from the addition of surfactants or polymers t o the monomer phase, was examined, using the HVO theory. It was shown that PMMA improved the stability of primary particles and, thus, could alter the particle agglomeration kinetics. The effects of molar mass and the amount of the adsorbed PMMA, as well as the influence of solve nt quality on the steric stabilization of primary particles, were also investigated. The experimental results, published on the electrostati c and steric stabilization of PVC primary particles, were in good agre ement with the theoretical predictions obtained in this study.