Influence of polymerization conditions on the viscosity of polyacrylamide via experimental design

Polyacrylamide was synthesized by a free‐radical inverse emulsion technique and optimized via statistical experimental design, with the objective of developing a polymer with a high viscosity within this synthesis technique. The factors considered to affect the response variable, the viscosity of the polymer, were initiator (K₂S₂O₈) concentration (c), reaction temperature (T), stirring rate (r), and initiator addition method (s, batch or dropwise). An experimental design of the four factors at two levels (2⁴) was carried out to study the effect of these process variables on the viscosity of the polymer. The results show that the main factor having an effect on the viscosity was T, with smaller contributions from r and cs. The optimum combination of values for the factors yielding maximum viscosity was T = 65°C, c = 1 mM, r = 230 rpm, and s = dropwise addition. A close fit was obtained between the experimental and predicted values of the viscosity of the polymer solution. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5719–5724, 2006