Do salts elongate the gelation time of Pam/PEI system?

The effects of salts [sodium chloride (NaCl) and ammonium chloride (NH4Cl)] on the degree of hydrolysis (DH) of PAM were investigated. These salts were used as retarders to elongate the gelation time of the PAM/PEI system. The data obtained from 13C-NMR was used to understand the retardation mechanisms by salts.

What is the acceleration effect of polyacrylamide hydrolysis?

(ii) Constant pH. In Figure 14 some predictions of hydrolysis kinetics of polyacrylamide are given for different constant pH and three values of Z. These simulations correspond to a polymer concentration of 8 x 10-4gcm-3 and T= 80. The acceleration effect is significant for pH up to 7 and becomes negligible for higher pH.

How does salt affect gel formation?

Generally, salts work as retarders to the gelation of the crosslinked gels [26, 38]. Adding 0.1% NaCl decreased the storage modulus of the gel formed of 3.5% CoAc/9% PaM by 70% to about 360 Pa (Figure 14), whereas no gels were identified at higher salt concentrations and when seawater was used. …

How do salts affect gelation?

In this case, the presence of salts affects the gelation through the sodium ions (Na + ) which tend to screen the negatively charged carboxylate groups (COO − ) through the charge shielding effect reducing consequently the hydrodynamic volume of the polymer.

Is polyethylenimine a crosslinker for Pam alkaline hydrolysis?

Polyacrylamide (PAM) and its derivatives are the most commonly used polymers in the preparation of polymeric gels for water control in petroleum reservoirs. This study involved the use of polyethylenimine (PEI) as a crosslinker for PAM. In this study, we investigated PAM alkaline hydrolysis at high temperatures.

Can Pam be hydrolyzed into a co-polymer?

It is well-known that the PAM can be partially hydrolyzed into a co-polymer of PAM-PAA (or PAM-PANa in alkaline, Supplementary Fig. 38) at elevated temperatures 39, 40 , which provides an ideal approach to compare the intrinsic activity of the two hydrogels. As such, we hydrolyzed the PAM (kept at 70°C for 1 h in 6 M KOH, marked as HPAM,). … …