Study On Polyacrylic(Sodium) Molecular Weight And Its Distribution

There is carboxylate radical(-COO-) in sodium polyacrylate molecular, the carboxyl functional groups combine with metal ions which are in the water easy to form scale,such as Ca2 +, Mg 2 +, and so as to achieve scale inhibition dispersing effect. But the molecular weight of sodium polyacrylate from thousands to millions, and its performance not only has close relation with the size of molecular weight, but also influenced by molecular weight distribution index, so the relationship between the sodium polyacrylate molecular weight and its distribution with the performance is of great significance.This article adopts the method of fractional precipitation, realized the uniform classification of sodium polyacrylate, and through the experiment proves that polyacrylic acid molecular weight and its distribution has a great influence on the performance, as the calcium carbonate scale inhibitor the best range of relative molecular mass of polyacrylic acid is less than 1900, and the molecular weight distribution is narrower the scale inhibition performance is better. As dispersing agent for calcium carbonate, when sodium polyacrylate molecular weight Mn = 3400, distribution index D = 3.35 dispersion effect is best; As the zinc ion stabilizer, sodium polyacrylate molecular weight Mn = 5200, distribution index D = 3.35 the stability of zinc ions is best.Explore different polyacrylic acid synthesis system, in which the organic acid salt- isopropyl alcohol compound telomeric system and sodium phosphite as the chain transfer agent system has the batter effect, optimize the process conditions, synthetic of low molecular weight of narrow distribution polyacrylic acid sodium, and the product structure characterization and performance evaluation are also studied.organic acid salt- isopropyl alcohol compound telomeric system synthesis polyacrylic acid, through orthogonal test to determine the best polymerization process as follows: monomer concentration 30%, dropping time is 4h, polymerization temperature 80 ℃, initiator accounting for 12.5% of monomer quality, organic acid salt accounted for 10% of monomer quality, isopropyl alcohol accounted for 25% of the solvent quality.Under the best conditions to get the polyacrylic acid sodium with relative molecular mass 1500, molecular weight distribution index 1.60, the scale inhibition rate for calcium carbonate can reach about 88%.Successively synthetic sodium polyacrylate with sodium hypophosphite as chain transfer agent, investigate the influence of dosage of initiator and sodium hypophosphite, temperature of polymerization on the polymerization, determine the best polymerization process is: concentration of monomer is 30% of the total weight, and dropping time is 2.5 h, the reaction temperature is 80 ℃, dosage of initiator is 8% of monomer mass ratio, dosage of sodium hypophosphite accounts for 10% of monomer mass ratio, polymerization temperature is 80 ℃, obtain the synthesis that relative molecular mass is 1300, molecular weight distribution index is around 1.80, the scale inhibition rate for calcium carbonate can reach about 90.0%.