湿法聚丙烯腈初生纤维表面沟槽的研究

湿法聚丙烯腈初生纤维表面存在沟槽,采用扫描电子显微镜(SEM)和原子力显微镜(AFM)表征纤维表面沟槽形态,研究了纺丝液性质和凝固成型条件对PAN初生纤维表面沟槽的影响。结果表明:随挤出速率、凝固浴浓度的增大,PAN初生纤维表面沟槽变得更加明显,表面粗糙度增大;随纺丝液温度和凝固浴温度的升高,PAN初生纤维表面沟槽变浅,表面粗糙度减小;PAN初生纤维表面粗糙度随凝固牵伸先增大后减小。     

制备聚丙烯腈初生纤维干燥样品研究

通过干喷湿纺纺丝工艺制得聚丙烯腈(PAN)初生纤维,采用不同的干燥方法获得PAN初生纤维干燥样品,考察对比自然晾干、鼓风干燥和冷冻干燥3种方法分别对样品物理特征、表面形貌和内部结构的影响。3种干燥方法均会使初生纤维样品发生收缩,样品截面积和长度均减小,但是变化程度不同。并且3种干燥方法对PAN初生纤维表面形貌、结晶特征、二甲基亚砜(DMSO)残留量以及孔结构产生不同的影响。结果表明冷冻干燥对PAN初生纤维的影响最小,可以有效的保留PAN初生纤维的原始结构,可用于制备聚丙烯腈初生纤维干燥样品。     

干燥法制备聚丙烯腈初生纤维样品的研究

采用湿法纺丝得到聚丙烯腈(PAN)初生纤维,干燥后得到PAN初生纤维样品.利用电阻法确定初生纤维的共晶温度;获得初生纤维的冻干曲线;通过压汞法对初生纤维孔结构进行表征,并对比考察了鼓风干燥、自然风干和冷冻干燥对样品截面形貌的影响.结果表明:初生纤维的共晶温度为-55℃;鼓风干燥会使样品收缩,纤维间发生粘连,原有形貌被破坏;自然风干使样品的截面积和周长分别收缩了20.66%、10.67%,形状系数变化率为3.52%.而冷冻干燥时样品的截面积和周长仅收缩了1.21%、1.15%,形状系数变化率为1.13%.冷冻干燥有效地保留了PAN初生纤维的固有原始结构,可用于制备各种分析的样品.     

聚丙烯腈纤维径向致密结构的光密度法研究

凝固过程聚丙烯腈(PAN)初生纤维在径向上各点的双扩散程度不同,可能会造成PAN纤维在径向上致密结构的差异。首先采用光密度法测定PAN初生纤维径向的致密结构及其差异性的可行性和影响因素,在此基础上采用光密度法研究了凝固浴温度对PAN初生纤维致密性结构差异的影响。结果表明：对于PAN初生纤维,采用纤维切片厚度为4μm、调整入射光强使背景灰度为140时进行PAN初生纤维光密度的测定;保持凝固浴浓度恒定不变,凝固浴温度从25℃升高到65℃会导致PAN初生纤维的灰度降低、光密度值增大、纤维径向皮部与芯部的光密度差值增大,这表明随着凝固浴温度的升高,纤维的致密性降低、径向致密结构差异增大。光密度法可以用来定量表征PAN纤维的径向结构及其差异。     

静电纺丝法制备聚丙烯腈/聚醋酸乙烯酯复合纳米纤维膜

采用静电纺丝法制备了聚丙烯腈(PAN)/聚醋酸乙烯酯(PVAc)复合纳米纤维膜。利用原子力显微镜(AFM)、电子显微镜(SEM)分析了纤维的直径分布、整体形貌及单根纳米纤维的表面形貌;利用傅里叶变换红外光谱(FT-IR)分析了PAN、PAN/PVAc、PVAc纳米纤维膜的化学组成;同时借助热重(TG)分析了PVAc的加入对复合纤维膜热性能的影响。结果表明,当m(PAN)∶m(PVAc)=5∶5、质量分数为10%时,所得纤维膜最有利于制备聚合物电解质膜;PAN与PVAc之间产生配位键,从而提高了纤维膜的热性能。     

方位角不对称的PAN/CNT复合纤维的晶态结构与性能

通过原位聚合法合成聚丙烯腈(PAN)/碳纳米管(CNT)复合溶液,经过湿法纺丝技术制备了PAN/CNT复合原丝。通过X射线衍射仪,扫描电子显微镜和单丝拉伸仪研究了CNTs对PAN纤维晶态结构及力学性能的影响。结果表明,在方位角扫描图中,随着PAN/CNT复合纤维的制备过程,其双峰的不对称性逐渐增加,其强度比从1.054增加到1.258;复合原丝的结晶度(53.10%)高于PAN原丝的结晶度(51.89%);在赤道扫描图中,PAN/CNT复合原丝的斜方晶系200晶面峰比PAN原丝明显,且晶粒尺寸高于PAN原丝;复合原丝的断面形貌出现更多的微纤结构,且比PAN原丝具有更高的拉伸模量。     

磷虾蛋白对聚丙烯腈的修饰改性

以水为反应介质,用马来酸酐对磷虾蛋白进行活化后再与丙烯腈共聚,得到磷虾蛋白马来酸酐酯接枝聚丙烯腈共聚物(AKPM-g-PAN),然后用湿法纺丝制备AKPM-g-PAN纤维并研究其力学性能和热性能。结果表明:制备AKPM-g-PAN的最佳配方和条件是:AKP、马来酸酐与PAN的配比为2∶2∶12.5,引发剂的质量为PAN质量的10%,反应温度为60℃。按照最佳工艺条件进行接枝聚合反应,得到的聚合物分子量为15.8万。AKPM-g-PAN纤维的断裂强度随着纺丝液浓度的增加而增大,随着凝固浴浓度和凝固浴温度的增加先增大后减小;而AKP的加入导致复合纤维的保水率提高,但是影响聚丙烯腈原有的分子链规整性并失去了部分结晶能力。     

聚丙烯腈基纳米炭纤维无纺布的制备与表征

以聚丙烯腈(PAN)为先驱体,N,N-二甲基甲酰胺(DMF)为溶剂配置质量分数10%的PAN溶液进行静电纺丝,输出电压为18 kV,注射流量为3 mL/h,收丝距离为15 cm,得到纳米PAN纤维无纺布,纤维直径为200nm～280nm,所得纤维布柔软有韧性。随后,无纺布经过280℃氧化交联和850℃氮气气氛热解处理,得到质轻柔软的纳米炭纤维无纺布,直径为100nm～200 nm。通过扫描电镜(SEM)、红外光谱(FT-IR)、电子探针显微分析(EPMA)、X射线衍射(XRD)等手段对纳米PAN和炭纤维布的形貌、成分和结构进行了表征。热重(TGA)分析结果表明,PAN基纳米炭纤维最终收率为51%。     

氨化方式对聚丙烯腈原丝结构和性能的影响

氨化的聚丙烯腈溶液(PAN)是获得均质致密结构、优良理化性能原丝的必要手段。通过丙烯腈(AN)聚合体系加入氨水和聚合结束后在聚合原液中通入氨气,得到不同氨化程度的PAN原液,经干喷湿纺纺丝制成PAN初生纤维和原丝,研究两种氨化方式对PAN纤维截面、初生纤维膨润度和原丝体密度、原丝强度和模量的影响。结果表明,氨化原液容易获得圆形截面的PAN纤维,且聚合体系氨化的原液在氨化度达到16%时,即可获得圆度为0.91的圆形截面,而聚合原液氨化其氨化度需达到28%,才可获得相同圆度(0.91)的截面。氨化后PAN纤维更致密,表现为初生纤维膨润度更低、原丝体密度更高;氨化度小于28%时,聚合体系氨化的原液比聚合原液氨化的原液得到的PAN初生纤维膨润度低、原丝体密度高。氨化度在20%~24%适宜范围,氨化后原丝强度和模量均值较高,且原丝强度和模量CV值明显减少。PAN纤维如需达到相同膨润度、体密度以及强度和模量CV值,聚合体系氨化原液所需的氨化度更低。     

高聚物修饰CNTs改性含氟聚氨酯的制备与性能研究

采用等离子体诱导接枝聚合技术修饰碳纳米管(CNTs),进而与含氟聚氨酯(FPU)预聚体反应后,获得CNTs/FPU复合弹性体.结果表明,CNTs/FPU复合弹性体具有优良的低表面能特性(对水的接触角～130°),其拉伸强度为19～32MPa,断裂伸长率为350%～550%.FPU弹性体经聚合物修饰后的CNTs改性后,其...     

PAN预氧化纤维的炭化过程

采用Raman光谱、XRD、AE、XPS和TG-MS方法分析PAN预氧化纤维在连续炭化过程中纤维结构参数和C、N、O含量的变化,以及反应中小分子的释放情况.Raman光谱分析表明:在炭化过程中纤维内sp2杂化的C-C原子键距逐渐变大,晶体尺寸增大,石墨化度也随之提高,乱层石墨结构趋于完善;XRD分析结果表明:炭化过程巾纤维的择优取向性提高,微孔含量减小是炭纤维体密度增大和强度逐步提高的原因所在;从预氧化纤维、低温炭化和高温炭化纤维的表面和本体元素分析的结果发现:炭化过程中碳元素的富集和非碳元素的脱除是由外向内的过程;TG-MS分析表明:小分子的释放主要发生在低温炭化的过程中,而高温炭化过程主要是大的梯形分子链交联脱除N2的反应.     

聚丙烯腈超滤基膜的水解改性

通过在不同水解程度的PAN基膜上组装聚电解质复合物膜,发现PAN基膜水解程度对聚电解质复合物膜的渗透汽化性能有重要影响.基于此,对PAN超滤基膜的碱性水解条件进行了筛选.通过对不同水解条件下改性前后基膜通量、截留率的测定,确定较为适宜的水解条件:NaOH浓度2 mol/L,水解温度60～70℃,水解时间1 h.润湿角和红外光谱检测证实,改性后基膜表面亲水性和荷电性增强利于后续的聚电解质复合物膜组装.此外,采用不同的碱性水解剂对PAN超滤进行水解,发现碱性越强的水解剂,PAN基膜水解程度越高.实验结果对改进PAN超滤膜亲水性,改变超滤膜的截留率和对荷负电溶质的耐污染性有所参考.     

Plasma modification of polyacrylonitrile ultrafiltration membrane

Polyacrylonitrile (PAN) ultrafiltration (UF) membranes were modified by plasma treatments and plasma polymerization. Influences of plasma modifications on membrane characteristics were investigated. The obtained results indicated that plasma treatments using non-polymer-forming plasma gases such as Ar, He and O₂ led to the increase of membrane surface hydrophilicity and membrane permeability. By using O₂ plasma treatment, UF property of PAN membranes could be improved with the enhancement of membrane flux meanwhile its albumin rejection was almost maintained. The experimental results also showed that plasma polymerization using acrylic acid vapor as monomer and PAN UF membrane as a substrate led to the formation of reverse osmosis membrane due to the deposition of plasma polymer layer onto substrate membrane surfaces. Plasma techniques can control membrane pore size and have a potential to improve the membrane characteristics by using their advantages.     

Formation of an adherent polyacrylonitrile/carbon nanotubes composite film onto a polyacrylonitrile brush electrografted on copper

An adherent polymer film based on a composite of polyacrylonitrile/multiwall carbon nanotubes (PAN/MWNTs) have been elaborated on a copper substrate. The first layer is an electrografted PAN brush on which of a subsequent layer of PAN/carbon nanotubes composite has been deposited by simple dipping from solution in dimethylformamide (DMF). MWNTs have been previously chemically functionalized with 3-cyanopropyltrichlorosilane to promote de-bundling and homogeneous dispersion of the carbon nanotubes in the composite.     

聚丙烯腈原丝氧化工艺的研究

研究了原丝在氧化过程中体密度、线密度、力学性能、环化交联程度、元素组成的变化,结果表明:(1)随着氧化温度的加深,预氧丝交联度和环化指数增加,线密度降低,体密度增加,预氧丝模量、断裂伸长和强度降低。(2)随着氧化程度的加深,纤维致密性增加。(3)随着氧化程度的加深,纤维C、H、N元素含量及H/C、N/C比例逐步降低,预氧丝总体O和O/C增加,在氧化反应初期纤维Si含量迅速减少,然后基本稳定。(4)氧化过程中预氧丝表面的O含量基本恒定,预氧丝表面的含氧量高于中心含氧量。     

Pregelled gel spinning of polyacrylonitrile precursor fiber

A new spinning method - pregelled gel spinning method for polyacrylonitrile (PAN) precursor fiber was reported. The physical and structural properties of the pregelled gel spun PAN precursor fibers as well as dry-jet wet spun PAN precursor fibers were studied. Compared with the dry-jet wet spun fibers, the pregelled gel spun fibers had reduced core-shell difference, circular cross sections and fewer internal pores. The pregelled gel spun fibers were found to have higher crystallinity and larger crystallite size than the dry-jet wet spun fibers. The tensile stress relaxation tests suggested that the pregelled gel spun fibers had higher elasticity and better developed supermolecular structure.     

Synthesis of polyacrylonitrile using AGET-ATRP in emulsion

The technique of activators generated by electron transfer for atom transfer radical polymerization (AGET-ATRP) of acrylonitrile (AN) has been first attempted in emulsion using the procedure of “one-pot”, “two-step” with polyethylene glycol monooleyl ether (Brij 35) as surfactant, cupric chloride (CuCl₂) as catalyst, hexamethylenetetramine (HMTA) as ligand, carbon tetrachloride (CCl₄) as initiator and ascorbic acid (VC) as reducing agent. The polymerization proceeds in controlled/living manner as indicated by first-order kinetics of the polymerization rate with respect to the monomer concentration, linear increase of the molecular weight of polyacrylonitrile (PAN) with monomer conversion and narrow polydispersity. Monomer conversion increases initially with the increase of ligand HMTA and then decreases. The ratio of [AN1] to [AN2] at 1:3 not only gives better control on the molecular weight and the molecular weight distribution, but also provides a more rapid polymerization rate. The rate of polymerization shows a trend of increase along with CCl₄ content. The apparent activation energy of the polymerization is calculated to be 46.6 kJ/mol. Chain extension of PAN with AN was also carried out and the chain extended PAN with 20520 molecular weight and 1.36 polydispersity was successfully obtained.     

Characteristics of chemo-mechanically driven polyacrylonitrile fiber gel actuators

Pure polyacrylonitrile (PAN) fiber gels, exhibiting effective actuation forces and displacements through muscle-like contractile behavior during the volume change when subjected to environmental stimuli, are prepared by electrospinning, twisting (strand creation) and activation process to investigate performance characteristics of chemo-mechanically driven PAN gel actuators. Single PAN strand (yarn) having a dimension of 210 μm in diameter is used. A typical hysteresis loop is observed for the length change (∼ 38%) of PAN gels with respect to pH variation. Diameter and volume changes are observed as greater than 100% and greater than 720%, respectively, for pH activated systems. Chemically induced force generation of pure PAN fiber gel is completed within a few seconds. The average maximum force is 0.002 N, implying that the force generation of a single PAN filament is 6.7 × 10^{− 6} N. A linear relation between force and strain is observed. It is found that PAN fiber gels in contracted state have stronger force and strain (0.043 N/0.112) than those (0.015 N/0.002) in elongated state. The actuation stress of pure PAN is in the range of moving coil transducer and commercial PAN but the actuation strain is better than moving coil transducer and similar to natural muscle.