粉煤灰复合聚丙烯酸钠凝胶的制备及其溶胀性能

粉煤灰(CFA)存在的情况下,采用自由基溶液聚合法,以过硫酸钾(KPS)为引发剂,N,N'-亚甲基双丙烯酰胺(NNMBA)为交联剂,制备了粉煤灰复合聚丙烯酸钠凝胶(CFAPAANa)。 以丙烯酸单体质量为基准,当交联剂用量为0.08%,引发剂用量为0.4%,粉煤灰用量为3%,丙烯酸中和度为70%,聚合温度为70 ℃时,所合成的粉煤灰复合聚丙烯酸钠凝胶在蒸馏水和生理盐水中平衡溶胀比最高,分别为1556(g/g)和168(g/g)。 考察了复合凝胶在不同介质溶液中的溶胀动力学,保水性能以及在土壤中的降解行为。 溶胀动力学研究表明,蒸馏水中溶胀初期复合凝胶聚合物链段的扩散运动能够调控凝胶溶胀的快慢及程度,而生理盐水中水分子的平移和对流运动在凝胶的溶胀过程中起着关键性作用。 保水和降解实验结果表明,25 ℃时,50 h凝胶保水率为64%,土壤中50 d时降解率达60%。 相比于聚丙烯酸钠凝胶,粉煤灰复合凝胶保水率提高了8%。

Preparation and Swelling Properties of Coal Fly Ash Composited Sodium Polyacrylate Hydrogel

Coal fly ash composited sodium polyacrylate superabsorbent polymer hydrogel(CFAPAANa) was prepared by free radical solution polymerization of acrylic acid(AA) using potassium persulfate(KPS) as an initiator and N,N'-methylene-bis-acrylamide(NNMBA) as a crosslinker in the presence of coal fly ash(CFA). The CFAPAANa gel has the highest equilibrium swelling degree of 1556 g/g and 168 g/g in distilled water and physiological saline, respectively, when the mass ratio of cross linker to AA is 0.08%, initiator to AA is 0.4%, fly ash to AA is 3%, the neutralization degree of acrylic acid is 70% and polymerization temperature is 70 ℃. The swelling kinetics of gel in different media solution, the water retention properties and degradation behavior in soil were also studied, respectively. Results of the swelling kinetics show that the water absorbent capacity and rate are limited by the expanding polymer segment in distilled water, but the translation and convective diffusion of water play an important role during the swelling process in saline. The results obtained from tests of water retention and degradation show that water retention ratio of hydrogel is 65% after 50 h at 25 ℃, and the degradation percent is about 60% after 50 days in soil. Water retention ratio increases by 8% compared with that of PAANa hydrogel.