少量共单体对丙烯腈在DMF中溶液聚合的影响

Influence of Small Amount of Co-Monomers on Acrylonitrile Polymerization in Dimethylformamide (DMF) Solution

研究了丙烯腈与少量衣康酸、丙烯酸、丙烯酸甲酯、甲基丙烯酸甲酯、丙烯酰胺等共单体在N,N-二甲基甲酰胺(DMF)中溶液共聚时的云点阈值。提出共单体云点迹线斜率的概念,用以比较不同共单体对丙烯腈聚合物的改性作用,发现相比其他几种烯类单体衣康酸更适合于用作碳纤维原丝的共单体。同时考察了衣康酸与丙烯腈在DMF中溶液共聚时,其含量对聚合动力学的影响。发现随衣康酸用量的增加,聚合速率与分子量都降低。分析了间歇共聚中共单体含量随转化率的变化,并拟合了该单体对溶液共聚时的竞聚率,发现接近于理想共聚:rIA=2.0、rAN=0.5;且在低共单含量时,共聚物的累积平均共单组成随转化率线性地下降。

Polymerization of acrylonitrile （AN） on the presence of small amount of co-monomers such as, itaconic acid （IA）, acrylic acid （AA）, methacrylic acid （MA）, methyl methacrylate （MMA） and acrylamide（AM）, were conducted in N,N-dimethylformamide （DMF） solution. The cloudy threshold at which the polymerized mixture becomes heterogeneous was determined for different co-monomer feeds. The cloudy line slope indicates the effect of co-monomer on polyacrylonitrile （PAN） modification. The favorable PAN modification of carbon fiber precursors are ordered as IA 〉 AM 〉 MMA 〉 MA 〉 AA. Then, the co-polymerization kinetics of IA was further studied. With the increase of IA feeding amount, the polymerization rate and polymer molecular weight are both reduced. The reactivity ratio of IA and AN was estimated from experimental data of co-monomer content at different conversion state in a batch reactor by non-linear optimization method. It is found that the co-polymerization of IA-AN in DMF is approximately to be ＂ideal＂ with rLA 2.0 and rAN 0.5. The accumulated amount of IA in co-polymer declines linearly with conversion when the IA feeding amount is low as demanded by carbon fiber precursors.