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Synthetic Organic Polymer
Polymers are large molecules made up of repeating units called Monomers. The molecules are composed of smaller subunits or monomers to form linear or branched chains. If the monomer has ionizable groups, the polymer is called polyelectrolyte, and the type of ionizable group can be cationic (positively charged), anionic (negatively charged) or ampholytic (positive and negative charge). There are other no ionizable groups called nonionic, capable of destabilizing the colloids by intraparticle bridge links polyelectrolytes. Polymers are large molecules made up of repeating units called Monomers.
The higher or lower affinity to bind to the surface of colloids presenting a polymer determines its ability to act as a coagulant, and these very specific compounds. The ph of the system can affect load polyelectrolyte.
The cationic polyelectrolytes are polyamides which is hydrolysed in water as follows:
R1 R2 NH + H2O →R1 R2 NH2+ + OH-
Since OH- hydrolysis, at high ph is the reaction force on the left and the nonionic polymer becomes. The mechanism of destabilization for these polyelectrolytes can be bridge bonding, by charge neutralization, or both. Due to the ability of cationic polymers specifically adsorbed on colloids and neutralize negative primary charge, these polymers need not have a high molecular weight to produce effective destabilization. In contrast, anionic or nonionic polymers need their compounds pose minimal molecular weight as possible to overcome the potential energy barrier between two negative colloidal particles. The value of this minimum molecular weight is given by the charge of the particles to destabilize, the ionic strength of the solution and the number of charged groups and degree of branching of the polymer. Destabilization by these polyelectrolytes is given by adsorption - bridge link. Similarly, the anionic polymers incorporated into its structure a carboxyl group which is ionized in water as follows:
RCOOH- →RCOO- + H+
Low ph forces the anionic polymer transforms nonionic. Accordingly, cationic polymers usually used at low ph, and anionic at high ph. This does not mean stop working, what happens is that they become non-ionic, which will vary somewhat effective in the particular treatment to which they apply.
In the chemical physical treatment, first salts is usually added to improve the process polymers are added. Are more effective high molecular weight polyelectrolytes with high charge density and because they produce longer chains and drag more clots.
The presence of cations (Ca2+, Mg2+) helps absorption of negative particles wing of anionic polymers and reduce the repulsive forces because they link to the colloid. Links also help bridge between particles and charge neutralization.
If stirring rapidly, can break flocs formed overdosing and if not more active sites remain available so they will not be able to link the colloids and no destabilization occurs.