Suspension stabilizers for PVC production III: Control of resin porosity

Suspension PVC resins were prepared using dispersant systems based on a cellulose derivative, Methocel F50, and two poly(vinyl alcohol)s; Gohsenol GH20 and Rhodoviol 5/270. Ammonium laurate and Span 20 were tested as secondary dispersants. The resins were characterized by mercury porosimetry. The results showed that the porosity of the resins increased in the series Gohsenol < Methocel < Rhodoviol. This order seems to follow the order of increasing surface activity. A closer analysis of the data clearly showed, however, that porosity control in S-PVC manufacture is not due to a pure interfacial tension mechanism, not even in those cases where the dispersant systems do not contain any monomer-soluble components. Other possible mechanisms by which suspension stabilizers may affect resin porosity are briefly commented upon.