【作者】 张静；

【导师】 金日光；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2011， 硕士

【摘要】 作为碳纤维生产最主要的一种前驱体,聚丙烯腈(PAN)的分子量及其分布很大程度上影响纺丝液的性质,对最终碳纤维的质量也起到决定性的作用。因此,为了生产出优质高强的聚丙烯腈基碳纤维前驱体,采用高分子量聚丙烯腈进行纺丝是非常行之有效的途径。在制备高分子量的聚丙烯腈众多方法中,混合溶剂沉淀聚合具有其独特的优势,不仅可以制备出高分子量聚丙烯腈,而且合成时间短,方便实验室操作。本文选择水(H2O)和二甲基亚砜(DMSO)作混合溶剂,合成出了均聚PAN,并从混合溶剂沉淀聚合的微观聚集过程出发,结合宏观上聚合过程中聚合物沉淀量的增加,运用泰勒展开式,建立了沉淀聚合过程中初生态粒子聚集过程模型,进而推导出沉淀过程中PAN的粘均分子量与H2O/DMSO的比例成线性增加的关系,即Mη=K3+K4[H2O/DMSO],并通过实验验证了该理论方程的正确性。随后,本文讨论了水和二甲基甲酰胺(DMF)作混合介质时,H2O/DMF的比例对PAN粘均分子量的影响,进一步证明了沉淀过程中PAN的粘均分子量与H2O/DMSO的比例成线性关系这一结论。研究混合溶剂沉淀聚合过程中,混合介质H2O/DMSO的比例对转化率影响,结果表明：聚丙烯腈的转化率随着H2O/DMSO的比例的增加,呈现一种先上升,达到一个极大值随后下降的趋势。由于聚丙烯腈均聚物结构规整性高,内聚能密度大,不利于预氧化,就有必要选择第二单体,进行共聚合。本文选择丙烯酸甲酯(MA)和衣康酸(IA)作为第二单体。沉淀聚合制备的PAN分子量很高,高分子量PAN制备纺丝液,粘度高,湿纺时易产生挤出胀大效应,不利于制备优质PAN原丝。本文发现用DMSO和H20作混合溶剂时,适量加入C2H5OH, C4H9OH,可以有效的控制PAN的分子量,为工业上制备高性能PAN纺丝液提供了良好的先决条件。随着H20含量的减少,C2H5OH. C4H9OH含量的增加,溶剂极性变小,PAN分子量呈减小的趋势。不同分子量和粒径分布对纺丝液的流变性能有很大的影响,本文运用第四统计力学定量研究不同聚合温度对分子量的影响发现,温度对大分子量PAN影响不大,对小分子量PAN影响显著；研究混合溶剂对粒径分布的影响发现,混合溶剂比为5：5时粒径分布最均匀。这为制备具有优异流变性能的PAN纺丝液提供了依据。更多还原

【Abstract】 As an important precursor to producing carbon fiber, the molecular weight of polyacrylonitrile (PAN) is the key to enhance not only the properties of the spinning solution but also the quality of the final carbon fiber. It is an effective way to use high molecular weight polymer to enhance the strength of PAN precursor fibers. It is convenient to prepare high molecule weight of PAN with mixed solvent in the precipitation polymerization more than other methods. It is not only for little time to prepare but also convenient for normal experiment. The precipitation polymerization of acrylonitrile (AN) was carried out in a mixture solution of dimethyl sulfoxide (DMSO) and water at 50～65℃usingα,α’-azobisisobutyronitrile (AIBN) as an initiator. The model was proposed from the sub-micro process of precipitation polymerization. An equation was then deduced by using the concept of total ways of the primary precipitate aggregates F[P]. The final equation of the precipitation polymerization: Mη=K3+K4[H2O/DMSO] Where, Mη:represented molecule weight, H2O/DMSO:the ratio of water in the mixed solvent. The equation was based on the relation between F(P) and precipitation amount and Taylor series expansion of F(P). The theoretical equation derived from the mechanisms was well coincided with the experimental results showing the linear relationship between the viscosity average molecular weight and the ratio of H2O/DMSO.In this paper, it was discussed that the influence of H2O and N,N-Dimethylformamide (DMF) to the viscosity molecule weight. The viscosity average molecular weight of H2O/DMSO solvent was larger than that of H2O/DMF solvent. The H2O/DMSO solvent system was better than H2O/DMF system in precipitation polymerization due to the far decreased chain transfer effect of DMSO. The relationship between react temperature and the viscosity molecule weight was also discussed. Due to the increasing of the temperature, the capability of precipitation became worse and the termination of free radical chains became easy, finally, the viscosity molecule weight decreased at 50～65℃.The effect of conversion ratio to the ratio of H2O/DMSO was investigated in the precipitation polymerization. The results obtained showed that at first the conversion ratio increased with the ratio of H2O/DMSO, and then reached a maximum value, finally decreased.In order to obtain high molecule weight and high-performanced PAN, we took the methyl acrylate (MA) and itaconic acid (IA) as the second monomer to reinforce the properties of homo PAN. It can be found the molecule weight by copolymerization was higher than the homopolymerization.During the copolymerization process of PAN, the molecular weight of PAN can be effectively adjusted by changing the ratio of mixed solvent. When the mixed solvent consisted with DMSO, H2O and C2H5OH or C4H9OH, the molecular weight of PAN decreased with the increasing of the content of C2H5OH or C4H9OH.According to sub-cluster statistical theory, we studied the reaction temperature affected high molecular weight PAN less than low molecular weight. The diameter of particles was the smallest and well-distributed when DMSO/H2O (C2H5OH or C4H9OH)=50/50.更多还原