PAN原丝成形工艺与碳纤维晶体结构和性能的关联性研究

采用广角X射线衍射方法对不同成形工艺的PAN原丝与碳纤维晶体结构和性能的关联性进行了实验和分析。研究表明:PAN原丝的晶体结构与凝固浴成形和纺丝牵伸工艺有直接关联性,由干喷湿纺成形和高倍纺丝牵伸制备的原丝具有晶粒尺寸较大、晶面间距较小和结晶度较高的特点。干喷湿纺成形工艺制备的原丝在碳化过程中石墨晶体的生长速率大于湿法纺丝,且原丝的PAN准晶体结构对碳纤维乱层石墨晶体结构具有遗传型。干喷湿纺成形和高倍数纺丝牵伸更容易获得兼具较高拉伸强度和较高拉伸模量的碳纤维。     

干喷湿纺中聚丙烯腈初生纤维断裂行为研究

为了系统研究干喷湿纺中聚丙烯腈初生纤维的拉伸行为,利用SEM、纤维强伸度仪、XRD等手段,分析了凝固浴拉伸比、拉伸速率、微观结构和缺陷等对初生纤维断裂行为的影响。结果表明,干喷湿纺中,凝固浴拉伸比的提高有利于增加初生纤维的结晶度和断裂延伸率;同时发现,初生纤维内外部的缺陷以及拉伸的速率对初生纤维的断裂行为有重要影响。     

干湿法制备异形PAN原丝及其力学性能的研究

对二甲基亚砜(DMSO)干湿法制备三角形截面聚丙烯腈(PAN)基碳纤维原丝的截面形成因素进行了研究,并比较了不同条件下纤维的性能。结果表明:在干湿法纺制三角形截面PAN基碳纤维原丝过程中,凝固浴条件对PAN纤维的截面影响非常明显,同时凝固浴条件和拉伸条件对纤维的力学性能也有非常显著的影响。     

DMSO法PAN原丝湿法纺丝工艺研究

通过实验对二甲基亚砜（DMSO）法聚丙烯腈（PAN）原丝的纤维凝固成形、水洗、牵伸、干燥定型条等湿法纺丝工艺对纤维性能的影响进行了研究,实验结果表明：增大喷丝板孔径,有利于提高原丝的取向度和干燥收缩率;调节凝固浴质量分数和温度,可生产出综合性能较好的原丝;提高水洗温度有利于制得性能好的原丝;热水、沸水和蒸汽3级牵伸工艺...     

影响PAN基碳纤维原丝取向因素的探究

采用正交试验法,应用干湿纺工艺,系统研究了碳纤维原丝加工过程中凝固浴、喷出速度、喷头拉伸、预牵伸和水浴牵伸对取向度的影响。结果表明:采用干湿法纺制的PAN纤维,在较小的喷头速度下进行正拉伸喷出,并给予纤维适当的预牵伸比和高倍热水牵伸比,取向度较高,可制得的纤维强度也较高。     

纺丝方式对PAN基碳纤维原丝形貌、结构及性能的影响

采用三种方式制备了PAN原丝,并利用扫描电镜、X射线衍射、 单丝拉力机等设备对纤维的形貌和结构进行了研究.实验结果表明,湿法纺丝工艺喷丝后即凝固,表面沟槽现象明显;干湿法和"准干湿法"工艺在非凝固相中完成巴拉斯挤出胀大效应才进入凝固浴,纤维表面光滑.湿法初生纤维的结晶度和取向程度高于其他工艺,随着后续牵伸和干燥致密化过程的进行,各种工艺制备的纤维的凝聚态结构趋于一致.干湿法PAN原丝的致密性明显高于其他两种工艺.     

凝固条件对PAN初生纤维微结构的影响

通过湿法纺丝工艺制备聚丙烯腈(PAN)初生纤维,借助于X射线衍射仪、声速仪、扫描电子显微镜、小角X光散射仪等,研究了凝固浴温度、凝固浴浓度、喷丝头拉伸等凝固条件对初生纤维晶态结构、取向结构、形态结构的影响。结果表明:PAN纤维的凝聚态结构和形态结构在初生纤维形成时已基本形成;PAN初生纤维的结晶度达40%以上,其结晶度和结晶尺寸受凝固浴温度和浓度的影响;PAN初生纤维和原丝的晶区取向和全取向随着喷丝头拉伸的增大而增大;PAN初生纤维具有沿纤维轴向高度取向的沟槽,通过改变成形条件,可以获得沟槽浅且规整性完美的纤维表面;提高凝固浴浓度,可以形成结构均质、致密的PAN初生纤维,避免皮芯结构及芯部出现较多孔洞。     

PAN原丝至碳纤维缺陷的形成与遗传性

利用扫描电镜（SEM）研究了聚丙烯腈（PAN）原丝至碳纤维结构形态转化过程中缺陷的形成与遗传,结果表明,PAN初生纤维,原丝,预氧化纤维和碳纤维的表面缺陷主要包括沟槽,横纹,粘丝、并丝、杂质、划伤和孔洞等,PAN初生纤维和原丝的内部缺陷主要是皮芯结构、芯部疏松和孔洞,皮芯结构由凝固浴中纤维的双扩散所导致,一直保留到原丝、预氧化纤维直到碳纤维中,可以通过调整凝固的工艺参数增大原丝皮层比例,提高芯部致密性,内部孔洞的形成与扩散和相分离速率有关,可以通过改善致密化和蒸汽拉伸工艺来减少孔洞和减小孔洞尺寸,预氧化纤维中的皮芯结构的形成归因于原丝的遗传和氧的不均匀扩散.     

干喷湿纺法制备T700级聚丙烯腈基碳纤维

采用丙烯腈、氨化试剂A、丙烯酸甲酯为聚合单体,以偶氮二异丁腈为引发剂,在溶剂二甲基亚砜中合成了聚丙烯腈原丝纺丝液,经干喷湿纺法纺丝制得聚丙烯腈原丝,经预氧化和炭化得到了T700级高性能聚丙烯腈基碳纤维。采用扫描电子显微镜,差示扫描量热仪,电子万能材料试验机对纤维的性能进行了研究。研究了空气层距离、喷丝头长径比、凝固浴浓度、空气拉伸比对干喷湿纺法制备纤维性能的影响。在空气层距离为40mm、凝固浴浓度为70%、喷丝头长径比为10.0、空气拉伸比为1.8条件下,采用干喷湿纺法制得的T700级聚丙烯腈基原丝及碳纤维的表面光滑、无沟槽,截面形貌为圆形;原丝的拉伸强度可达8.7cN/dtex,拉伸弹性模量可达154.7cN/dtex,碳纤维的拉伸强度可达5 750MPa,拉伸弹性模量可达220GPa。     

PAN基碳纤维原丝表面形态控制研究

采用扫描电子显微镜(SEM)表征PAN原丝表面沟槽形态,通过凝固浴φ(二甲基亚砜)、温度、pH值、负牵伸倍数的变化对PAN原丝的表面沟槽形态进行控制。结果表明在一定范围内凝固浴φ(二甲基亚砜)的提高、凝固浴温度的降低、凝固浴pH值的提高、凝固浴负牵伸倍数的增加都有利于制备表面沟槽更深的PAN原丝。碳纤维表面沟槽一方面对纤维表面造成一定的机械损伤,另一方面可以提高碳纤维的界面结合力,所以适宜的表面沟槽才能使碳纤维的力学性能得以充分发挥。     

Force field in coagulation bath at low temperature induced microfibril evolution within PAN nascent fiber and precursor fiber

The coagulation process was vital for the microfibril evolution and mechanical properties of polyacrylonitrile (PAN) fibers. The PAN nascent fibers and precursor fibers were prepared by controlling drawing ratio of coagulation bath at low temperature during the dry-jet wet spinning process. The microfibril morphological changes induced by force fields in coagulation bath were investigated by scanning electron microscopy and high-resolution transmission electron microscopy. During the coagulation process, the spinning solution evolved into an interconnected network composed of random microfibrils and tie joints as a building block of the network. At low drawing ratio, the random interconnected network existed in nascent fibers. Increasing drawing ratio, the fiber filaments underwent shrinkage and the network was transformed into the transverse lamellae. Furthermore, the lamellar thickness also decreased. After the treatment of post-spinning, similar transverse lamellae were formed in all of precursor fibers, and random microfibrillar network was stretched and oriented to develop into the aligned microfibrils in precursor fibers. The transverse fold-chain crystal layers were densely stacked in the microfibrils. Increasing drawing ratio, the lamellae and microfibrils in precursor fibers were packed more densely and orderly. Consequently, the order and homogeneity of microfibrils in nascent fibers and precursor fibers were improved by increasing drawing ratio, which were benefit to increase fiber tensile strength and modulus.     

Effect of DMSO/H2O coagulation bath on the structure and property of polyacrylonitrile fibers during wet‐spinning

The effect of coagulation bath condition on the structure and property of the nascent fibers and polyacrylonitrile fibers during wet‐spinning is studied. The best coagulation condition to produce polyacrylonitrile fibers has been found by examination of EA, XRD, SEM, and so on. The results indicated that when the coagulation bath was DMSO/H₂O system, the temperature was 60°C, the concentration was 65%, the minus stretch ratio was ?10%, fine crystallites and high degree of crystallization in the nascent fibers and polyacrylonitrile fibers could be achieved, and less solvents remained in the nascent fibers with circular cross section morphology. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

沸水再拉伸速率对聚丙烯腈纤维结构与性能的影响

以1-丁基-3-甲基咪唑氯盐([BMIM]Cl)为溶剂溶解聚丙烯腈(PAN)制成PAN纺丝原液,采用干喷湿法纺丝,经过凝固、预拉伸、沸水拉伸制得PAN纤维,对所得PAN纤维进行沸水再拉伸处理,研究了沸水再拉伸速率对PAN纤维结构和性能的影响。结果表明:PAN纤维中残留质量分数为4.38%的离子液体,为沸水再拉伸起到了增塑作用;随着沸水再拉伸速率的增大,PAN纤维的力学性能提高,断裂强度由2.69cN/dtex提高到4.33 cN/dtex,而断裂伸长率由26%减小到20%,纤维的玻璃化转变温度、晶区取向度、双折射率、结晶度、晶粒尺寸均增大。     

高强高模聚乙烯醇纤维的生产工艺初探

采用凝胶纺丝,添加硼酸和助剂生产高强高模聚乙烯醇(PVA)纤维,探讨了其生产工艺。结果表明:控制纺丝原液PVA质量分数16%,添加硼酸质量分数1.0%～1.1%;采用Na_2SO_4/NaOH凝固浴体系,其中Na_2SO_4质量浓度为300g/L,NaOH质量浓度为80～100g/L,凝固浴温度45℃,凝固时间25s;选择4段拉伸,湿热拉伸倍数为6,总拉伸倍数为14;生产稳定,得到的高强高模PVA纤维断裂强度达15cN/dtex,模量达320cN/dtex。     

Crystallinity development in polyacrylonitrile nascent fibers during coagulation

This paper has studied the crystal and thermal property of nascent fibers during the polyacrylonitrile coagulation process. A water (H₂O)/dimethyl sulphoxide (DMSO) mixture was used as the coagulation bath for the coagulation process of acrylonitrile(AN)/itaconic acid(IA) copolymer fibers in the study. By transforming the spinning conditions, especially air gap distance between the spinneret and coagulation bath, draw ratios, coagulation time, we received the crystal and thermal properties of nascent fibers under different conditions. The relationship between the property of nascent fibers and the spinning conditions has been studied by use of X-rays, SEM, differential scanning calorimetry (DSC) and so on. The results indicated that the degree of crystallization gradually increased with the rise of coagulation time and tended to a fixed value when reached some time. With the augment of draw ratios, the crystal degree appeared differently, in which it decreased when the air gap distance was 0 mm and it increased when the air gap distance was 1 mm and 2 mm. At the same time, the thermal properties showed little difference in peak position and biggish difference in heat energy, which indicated the ability to endure heat for latter spinning process and thermal stabilization process.     

含氨基螯合纤维的制备 Ⅰ．前驱纤维的制备

将N-乙烯基甲酰胺(NVF)与丙烯腈(AN)的共聚物溶液进行湿法纺丝,制备了含氨基螯合纤维的前驱纤维。研究了凝固条件、纺丝工艺、后处理条件对纤维的结构和性能的影响。结果表明:凝固浴中二甲基甲酰胺溶剂质量分数为20％,湿热拉伸倍数3．0、干热拉伸倍数3．5,纤维断裂强度达3．5 cN／dtex。扫描电镜观察表明纤维为圆形多孔断面,具有较高的孔隙率,适合于制备高效的螯合纤维。     

海藻酸钙/纳米TiO_2共混纤维的制备与表征

将含固体质量分数为5%的海藻酸钠纺丝原液与纳米二氧化钛(TiO2)水分散液均匀混合,制得海藻酸钠/纳米TiO2混合纺丝原液,采用湿法纺丝,通过氯化钙凝固浴,经拉伸、水洗,制备了海藻酸钙/纳米TiO2共混纤维,研究了纳米TiO2含量对共混纤维结构及性能的影响。结果表明:纳米TiO2的加入,提高了共混纤维的力学性能;加入质量分数为0.5%的纳米TiO2,海藻酸钙大分子链上的红外特征吸收峰峰形明显变宽,共混纤维的力学性能最佳,断裂强度为2.93 cN/dtex,断裂伸长率为7.34%,优于海藻酸钙纤维;添加纳米TiO2质量分数为3%时,纳米TiO2在共混纤维中仍能较好的分散,且纤维表面光滑。加入纳米TiO2后,共混纤维的热稳定性提高。     

Impact of the wet spinning parameters on the alpaca-based polyacrylonitrile composite fibers: Morphology and enhanced mechanical properties study

The study examined the effect of different wet spinning parameters (e.g., total solid content, coagulation bath concentration, drawing, and stretching) on the morphology and mechanical properties of the wet spun alpaca/polyacrylonitrile (PAN) composite fibers. The alpaca/PAN composite fibers were wet spun using 10, 20, and 30% of alpaca particles along with the PAN polymer. The shear-thinning or non-Newtonian flow behavior was observed among the dope solutions with different solid content. The cross-sectional fiber morphology showed the bean-shaped characteristic for the control PAN fibers, whereas the alpaca/PAN composite fibers exhibited almost circular shape. “Cavity healing” was observed, where noticeable voids and porous areas were demolished in the cross section of the composite fibers, by changing the total solid content and coagulation bath concentration. Although the control PAN fibers exhibited the highest tenacity with lower fiber diameter, the alpaca/PAN composite fibers showed a gradual deterioration in tenacity while adding alpaca particles into the PAN polymeric matrix. Nevertheless, due to the increment in the total solid content, higher draw ratio, and stretching of the fibers, the tenacity, molecular orientation, and the crystallinity of the composite fibers were increased.