Shear-Induced Viscosity Change of Aqueous Polymethacrylic Acid Solution

Abstract

Rheopectic behavior of the aqueous polymethacrylic acid (PMA) solution was investigated with a Zimm-Crothers type viscometer. Measurements were performed for the solutions of PMA ranging in molecular weight from 6 X 10 5 to 16 X 10 5 , at concentration of 0.05-5.0 wt% and shear rate of 0.5-7 .0 s -1 . The solution viscosities of high molecular weight PMA (Mv > lOX 10 5 ) increase linearly with the elapse of shearing time at early stage, reach a maximum and then fall off. Ratio of the maximum viscosity to the initial one, llmaJllinit, decreases with decreasing the concentration of polymer and increasing the rate of shear, indicating that rheopexy is attributed to a competition between growth and disruption of the molecular clusters in the shear field. The influences of four additives (HCl, NaOH, NaCl, and urea) on rheopexy were examined ; it was found that, regardless of the additive species, there is a correlation between rheopexy and the initial rate of shear. These results suggest that a particular balance of hydrophilic and hydrophobic bonding abilities of PMA molecule is essential for the occurrence ofrheopexy in the solution.

Suspension polymerisation of methyl methacrylate using ammonium polymethacrylate as a suspending agent

“…Previous work on PMA indicated that its viscosity follows a shear thickening pattern (Ohoya et al, 2000), and hence it was considered expedient that the response of both APMA and PMA to various shear rates was examined. In Fig.…”

“…The pH increase leads to a greater extent of ionisation, to a more charged coil and to stronger repulsive forces between the charged sites of the polymer coil. These repulsive forces between the carboxyl anions on the polymer chain cause the APMA molecules to occupy a more stretched and extended conformation while also preventing the yielding of intermolecular bonds (Ohoya et al, 2000). This could result in a reduction of the intermolecular frictions and, hence, in a viscosity decrease.…”

Characterization of acrylamide polymers for enhanced oil recovery

“…9 Again, the presence of bulky side chains should assist in the retention of a comparatively higher solution viscosity after the reduction of the solution viscosity by salt than that obtained with smaller side chains.…”

Aggregates of isotactic poly(methacrylic acid) chains in aqueous CsCl solutions: a static and dynamic light scattering study

“…This peak does not represent particles, but is due to so called polyelectrolyte "slow mode" 27,28 originating from electrostatic interactions between highly charged polyions. It is well known [2][3][4][5]14,17,27,29 that this phenomenon leads to low values of the total LS intensity, in contrast to intermolecular association/ aggregation, and to the apparent low diffusion coefficient value measured by DLS. Because the aggregation and the polyelectrolyte slow mode are both associated with a low value of D, a generic name "slow mode" is used for both phenomena in Figure 2.…”

“…However, important differences in the association mechanism exist between the two stereoizomers. For example, the number of aPMA aggregates increases as a result of shearing the solution (a phenomenon known as negative thixotropy 4,17 ), whereas the iPMA ones disintegrate due to shear stress and reform in solutions at rest. 15 In equilibrium, the extent of aggregation is larger for iPMA than it is for aPMA.…”