窄分子量分布的聚丙烯酸的合成及其阻垢性能

Synthesis and Scale Inhibition Performance of Poly(acrylic acid) with Narrow Molecular Distribution

以水为溶剂,采用可逆加成-断裂链转移自由基聚合(RAFT)方法,合成了分子量2400～9000的聚丙烯酸。GPC分析表明,所合成的聚丙烯酸具有很窄的分子量分布(多分散系数PDI约为1.2)。阻垢性能测定结果表明,用RAFT方法合成的聚丙烯酸比采用普通自由基聚合得到的商品聚丙烯酸阻垢剂具有更好的阻垢性能。如当分子量约为2400的聚丙烯酸的质量浓度分别为2和10mg/L时,其阻碳酸钙垢的阻垢率分别为83.8%和97.5%,而在相同质量浓度下商品聚丙烯酸阻垢剂的阻碳酸钙垢的阻垢率则仅分别为21.3%和42.9%。阻垢作用随温度升高(50～90℃)而降低的幅度也明显小于商品聚丙烯酸阻垢剂,80℃时二者的阻垢作用差别最大,而这正是一般冷却水达到的最高温度。在所研究的分子量范围内,所合成的聚丙烯酸分子量愈小则其阻垢性能愈好。

Poly（ acrylic acid） （Mn 2 400 -9 000） was prepared by reversible addition-fragmentation chain transfer（RAFT） polymerization with water as the solvent. GPC analysis indicats that the polymer possesses narrow molecular distribution（ the polydispersity index PDI was - 1.2）. Scale inhibition test indicates that the poly（ acrylic acid） prepared by RAFT has better scale inhibition performance than a commercial poly （acrylic acid） scale inhibitor, which was prepared by traditional radical polymerization. For example, when the concentration of poly （ acrylic acid） with a molecular mass of - 2 400 was 2 mg/L or 10 mg/L, the scale inhibition against CaCO3 was 83.8% or 97.5%, respectively, while the scale inhibition against CaCO3 of the commercial poly（ acrylic acid） scale inhibitor was 21.3% or 42.9% , respectively, at the same concentration.The scale inhibition performance decreases with temperature raising （ 50 - 90 ℃ ）. However, the decreased extent for poly（ acrylic acid） prepared by RAFT was markedly less than that for the commercial poly（ acrylic acid） scale inhibitor. The difference between scale inhibition performances of the two inhibitors is maximal at 80 ℃, which is usually the maximal temperature in the practical cooling systems. The smaller the molecular mass of the poly（ acrylic acid） in the range studied, the better the scale inhibition performance.