SynopsisA new method is developed to estimate the reactivity ratios from composition-conversion data based on nonlinear regression. Previously published experimental data for the copolymerization of acrylic acid and acrylamide are analyzed by the new method and the results compared to those reported by the original investigators. Composition-conversion data were collected for this copolymerization system at intermediate conversion levels and over a limited range of compositions. Values for the reactivity ratios a t 40°C were obtained from these data by the new algorithm and compared to the literature values.

SynopsisThe rheological response of dilute solutions of high molecular weight polyacrylamides a t low shear rates has been measured using a capillary viscometer that provided for a fivefold variation in shear rate at each concentration. The non-Newtonian effects were found to be significant for polyacrylamides with number-average molecular weights exceeding lo6. The molecular weight averageintrinsic viscosity relationship most widely used in the literature, [77] = 6.80 X 10-4%?,,0.66, was found to be valid,when [v] was measured a t high shear rates where the polymer solutions approached Newtonian behavior. A new relationship was developed relating a,, to the intrinsic viscosity extrapolated to zero shear rate.

SynopsisAn experimental investigation on the aqueous polymerization of acrylamide with potassium persulfate initiator is reported. Molecular weight averages were measured by viscometry. NonNewtonian effects were accounted for by extrapolation to high shear rates where the polymer solutions approximated Newtonian behavior. Values for the transfer constants to the acrylamide monomer and to the persulfate initiator were estimated a t 25 and 4OoC and compared to literature values.