聚丙烯腈论文：碳纤维用聚丙烯腈溶液共聚合反应研究
【中文摘要】碳纤维自上世纪六十年代开始发展以来,以其比重小、强度高、模量高、耐高温、耐腐蚀等一系列优良特性,成为未来最具发展前景的材料之一。制备碳纤维的前驱体有很多,其中聚丙烯腈(PAN)基碳纤维的产量占到了90%以上。聚丙烯腈基碳纤维的生产可分为两步：聚丙烯腈纺丝原液的制备和原丝的预氧化与炭化。其中的聚丙烯腈往往是丙烯腈和少量其它单体的共聚物,共聚物的合成是制备碳纤维的第一步,也是最为关键的环节,其性能直接影响到碳纤维的性能。本论文采用高浓度的丙烯腈(AN)和少量衣康酸(IA)混合物为共聚单体,低浓度的偶氮二异丁腈(AIBN)为引发剂,在溶剂二甲基亚砜(DMSO)中,进行丙烯腈溶液共聚合,制备高分子量的聚丙烯腈。通过测定不同温度、引发剂浓度、共聚单体含量、总单含量下,经过不同反应时间条件所得到的AN-IA共聚物的转化率,探讨了上述因素对聚合反应速率的影响。以质量计划DMF为溶剂,在30℃条件下,用乌氏粘度计测量各个反应条件下所得共聚物的分子量,探讨聚合条件对分子量的影响。经过上述实验,得到了转化率30%以下,粘均分子量在30-100万的AN-IA员工奖惩制度共聚物。发现不同的条件下,聚合过程中聚合液及共聚物的形态差别较大。经过定量测定,绘制了各个条件下反应的转化率-时间关系曲线。发现反应速率和分子量均随总单浓度的增大而增大,却均随衣康酸含量的增大而减小。温度、引发剂含量的增大均使反应速率显著增大,却
使分子量减小,而反应时间的增大虽使转化率增大,但对分子量却基本没有影响。以衣康酸单正丁酯(MI)为共聚单体,中等浓度的偶氮二异丁腈(AIBN)为引发剂,在二甲基亚砜(DMSO)中,进行AN-MI溶液共聚合。初步探讨了IA的加入对共聚反应的影响,并得到一组转化率-时间关系图。在各个不同温度下,改变AN/MI配比,得到转化率为10%以下的AN-MI共聚物。采用元素分析方法,得到共聚物中两种单体单元的组成。分别采用Fineman-Ross法和Kelen-Tudos法对上述结果进行分析创业企划书少儿儿歌,得到AN-MI共聚体系的竞聚率,并对所得结果进行验证。发现Fineman-Ross法会得到竞聚率为负值的不合理结果,而采用Kelen-Tudos法所得结果与理论相比具有足够高的相符度。在55-65℃下,测得的AN-MI共聚体系的竞聚率的值为劳动法条例rAN=0.66～0.71,rMI= 8.35～7.44悬崖的意思。比较各个温度下的结果,发现温度对于竞聚率有微小的影响,随着温度的升高朱自清春,竞聚率值均向1靠近,表明共聚反应朝着理想共聚方向靠近。
【英文摘要】With the excellent characteristics such as low weight, high strength, high modulus, anti-high temperature, anti-erosion and so on, carbon fiber is widely ud in the field of aeronautical and space technologies, transportation, sports supplies, civil construction, etc., making itlf the most promising material in the coming decades.Several precursors can be ud to produce carbon fibers, among which polyacr
ylonitrile (PAN) bad carbon fibers has the best performance and share 90% in quantity. The production of PAN bad carbon fibers can be divided into two steps:the production of PAN precursor and the pre-oxidation and carbonization of the precursor. The first step is the key point which can determine the quality of carbon fiber.In order to produce high molecular weight polyacrylonitrile, free-radical solution copolymerization of high concentration (about 50 wt%) of acrylonitrile (AN) as first monomer and itaconic acid (IA) as comonomer is carried out in dimethyl sulphoxide (DMSO), using low concentration (about 50 wt%) of azodiisobutyronitrile (AIBN) as initiator. The values of different factors such as temperature, the concentration of monomer, IA content in the monomer, and the concentration of AIBN are changed, the copolymer in tho conditions in different reaction time is produced and the conversion of monomer was measured at each point of condition. Then, the viscosity average molecular weight of poly(AN-co-IA) prepared in each point of condition above was measured by Ubbelohde viscosity meter at 30℃, using DMF as solvent. The copolymer with viscosity average molecular weight of 300～1000 thousand was produced, and the curve of conversion-time at each condition was dr
awn by the experiments above. It has been demonstrated that both reaction rate and viscosity average molecular weight are incread by the increasing of monomer concentration, while the same thing is otherwi with IA content. Reaction rate will increa dramatically with the increading of either temperature or AIBN content, while again, the same thing is otherwi with viscosity average molecular weight. Though conversion increas dramatically along with the polymerization time, viscosity average molecular weight changes slightly.Though the time can make conversion increa, it has little effect on viscosity average molecular weight.Monobutyl Itaconate (MI, also named Itaconic Acid Monobutyl Ester) is also introduced as another potential comonomer in the free-radical solution copolymerization of acrylonitrile, using medium concentration AIBN as initiator and DMSO as solvent under different temperatures of 50℃,55℃,60℃, and 65℃. By using different ratio of AN/MI, a ries of poly(AN-co-MI) are preparared under low conversion (below 10%) at each temperature. The accumulated average composition of the copolymer was determined by elemental analysis, and then both Fineman-Ross method and Kelen-Tudos method were applied to calculate the reactivity ratio of the copo
lymerization system. It shows that the result of Fineman-Ross method is unreasonable becau it has a negative value, while that of Kelen-Tudos method is reasonable becau the practical experimental points coincide with the theoretical curve under each temperature. It shows that temperature has tiny influence on reactivity ratio, the value of reactivity ratio is about rAN=0.66～0.71,rmi=8.35～自我反思作文7.44 in the range of 50～65℃, and with the increasing of the polymerization temperature, the reactivity ratios of AN and MI approach to unity, suggesting that the solution copolymerization of AN/MI has a tendency to ideal copolymerization.
