【作者】 刘永乐；

【导师】 沈新元； 刘兆峰；

【作者基本信息】 东华大学 ， 材料学， 2005， 硕士

【摘要】 聚丙烯腈(PAN)纤维具有较高的耐热性能,具有对日光和大气、化学试剂等的稳定性及耐霉菌性,使其广泛用于消费纺织品和产业用纺织品。PAN纤维的产品规格也在逐渐走向多样化、差别化,PAN浆粕是其差别化产品之一,与价格昂贵的芳纶(PPTA)浆粕相比具有更大的比表面积,能够更好地与基材进行复合,与具有环境公害的石棉相比,具有竞争优势,被广泛用于密封、摩擦、增强材料领域。 本论文提出了一种制备PAN浆粕的沉析方法,即将一定浓度粘稠的PAN/DMAc浆液注入高速剪切流动的DMAc/水组成的凝固液中,液滴在剪切流动过程中被逐渐拉长发生形变、凝固、原纤化而形成PAN浆粕。PAN浆粕的长径比及比表面积的大小可以通过沉析工艺进行调整,该工艺省去了复杂的纺丝切割帚化过程,为PAN浆粕的制备开辟了新的途径。 首先通过旋转粘度、落球粘度及凝固性能的测定研究了PAN/DMAc浆液的性质。PAN浆液的浓度和粘度对浆液在凝固浴中分散、凝固、细化、浆粕成形有重要影响。随温度升高,浆液粘度呈指数关系下降,凝固值略有上升,凝固条件缓和;氯化锂的加入能在不降低聚合物浓度的情况下显著降低浆液的粘度。 研究了各个工艺参数对PAN浆粕沉析成形的影响。系统地研究了沉析法制备PAN浆粕的工艺条件,包括浆液浓度与温度、凝固浴浓度与温度、剪切速率及剪切时间对浆粕的比表面积和长径比的影响。提高剪切速率、延长剪切时间、提高浆液和凝固浴温度、降低浆液浓度对PAN浆粕的成形有利。沉析法制备得到的PAN浆粕典型参数如下:长度为0.5～2.4mm,宽度(直径)为7～20um,堆积密度为10～25g/L,比表面积达35～80m~2/g。 通过在PAN浆液中加入聚间苯二甲酰间苯二胺(PMIA)对PAN浆粕进行共混改性,利用PAN/PMIA的微观相分离和凝固性能上的差异来提高PAN浆粕的比表面积。研究了PAN/PMIA的相容性,共混浆液的性质以及对浆粕成形的影响,表明PAN、PMIA能共同溶解于DMAc溶剂中,形成透明无分层的稳定浆液;更多还原

【Abstract】 Polyacrylonitrile Fibers (PAN) have been widely used as consumable textiles and industrial textiles with high heat-resistance and stability to sunlight, to atmosphere and to chemical reagents. Varieties of PAN are produced, one of which is PAN-Pulps. PAN-Pulps have higher special surface area(SSA) than aramid pulps like PPTA-Pulps, and can be blended with rubbers or resins. Compared to asbestos and costly PPTA-Pulps, PAN-Pulps are more competitive and can be widely used in sealed material, friction material and reinforced material.A new way to prepare PAN-Pulps was introduced in the thesis-precipitation method. That is: PAN/DM Ac solutions with different concentrations and viscosity were injected into a rapidly stirred coagulant. A proposal mechanism of the process is that the dispersed drops were elongated, deformed, coagulated and fibrillated, and PAN-Pulps with certain length and SSA were obtained. This method left out the complicated spinning, cutting and milling procedures.First, the properties of PAN spinning solutions were studied via rotating cylinder viscosity and coagulating characteristics. The concentration and viscosity are important to the dispersion and distortion of the PAN/DMAc drops, and to the formation of PAN-Pulps. The viscosities fell rapidly and the value of coagulation rose slightly with increasing solution temperature. The addition of lithium chloride (LiCl) could reduce the viscosity dramatically without decreasing the concentration of polymer.Second, the influence of related parameters on the formation of PAN-Pulps was studied, systemically, including the concentration and temperature of the PAN solution, the concentration and temperature of coagulant, stirring speed and precipitation time. The typical PAN-Pulps have a diameter distribution of 7~20μm, alength distribution of 0.5~2.4mm, a SSA distribution of 35~80m2/g.Third, poly (m-phenylene isophthalamide) (PMIA) was added into PAN/DMAc solution. It has been found that PMIA is compatible with PAN dynamically, but it is incompatible with PAN thermodynamically. The SSA of PAN-Pulps can be unproved by 30-50% compared to pure PAN/DMAc solution, due to the microcosmic phase separation and the different coagulating properties between PAN and PMIA.New ideas mainly brought forward in this paper are:1) A new approach of precipitation to produce PAN-Pulps;2) Adding LiCl into the PAN/DMAc solution to reduce the viscosity and improve the SSA of PAN-Pulps;3) Blending PMIA into PAN solution to improve the SSA of PAN-Pulps.Liu Yongle (Major: Material Science) Supervised by: Professor Liu Zhaofeng更多还原