拉伸对聚丙烯腈原丝结构和性能的影响

在生产碳纤维原丝的过程中 ,各种工艺条件 ,如含固量、拉伸倍数、凝固浴浓度、温度、预热浴温度等对聚丙烯腈原丝结构与性能影响较大 ,根据近几年的探索和实践 ,在其他条件固定不变的情况下讨论了拉伸倍数对原丝结构和性能的影响 ,并用SEM进行了不同的拉伸倍数下原丝的横、纵截面的分析。结果表明 :拉伸倍数越大 ,原丝纤度越小 ,强度越大 ;最佳拉伸倍数为 6.5～ 7.5倍。     

二次拉伸对干湿法PAN原丝结构性能的影响

讨论了二次高温拉伸过程中拉伸介质、拉伸倍数、拉伸温度、拉伸速度等工艺条件对干湿法聚丙烯腈原丝的物理机械性能和形态结构的影响。结果表明 ,165℃下 2倍过热蒸汽拉伸得到的纤维强度最高 ,可达 7cN/dtex左右。干热拉伸有利于纤维取向结构的形成 ,蒸汽拉伸有利于纤维结晶结构的形成。经过二次高温拉伸 ,纤维的强度及模量较大幅度提高 ,而断裂伸长率下降很多。     

湿法纺丝中凝固成形和拉伸对聚丙烯腈原丝结构和性能的影响

凝固成形和拉伸是原丝生产过程中两个十分关键的工序,它们对聚丙烯腈原丝的结构和性能有着重要的影响。纤维的拉伸强度在凝固成形过程中受到凝固浴浓度、温度和负拉伸的影响,同时在纤维的拉伸中拉伸的倍数、温度和介质等也影响着纤维的结构和性能。     

蒸汽牵伸对原丝制备及后续碳纤维生产的影响

结合原丝性能、取向度、沸水收缩、以及表面形貌表征,研究了蒸汽牵伸对原丝以及碳化生产状态的影响。结果表明:牵伸提高了原丝的强度和取向度;当牵伸倍数超过4.5时会影响原丝生产,当牵伸倍数超过3.5时会影响后续碳纤维的生产;同时,牵伸倍数受纤维表面油剂覆盖状态的制约。     

湿法纺丝制备PTFE纤维的后处理工艺研究

以聚乙烯醇(PVA)为载体采用湿法纺丝制备聚四氟乙烯(PTFE)/PVA初生纤维,然后进行烧结、拉伸后处理得到PTFE纤维,考察了烧结温度、烧结时间和拉伸倍数对PTFE纤维力学性能的影响,讨论了强酸和强碱对PTFE纤维的腐蚀作用。结果表明:较佳的后处理工艺是烧结温度380℃,烧结时间30 min,拉伸倍数5,制得的PTFE纤维的线密度为14.60 dtex,断裂强度为0.871cN/dtex,断裂伸长率为261.26%,模量为0.525 cN/dtex;PTFE纤维具有优异的耐酸碱腐蚀性能。     

浅谈影响83 dtex/36 f涤纶全拉伸丝染色的因素

以规格为83 dtex/36 f的涤纶全拉伸丝(FDY)为研究对象，讨论了侧吹风风速、热辊温度、牵伸倍数等因素对FDY染色性能的影响。通过优化工艺，选择合适的侧吹风速度、热辊温度、牵伸倍数，从而有效提高FDY的染色性能，改善产品质量。结果表明：侧吹风风速为0.30～0.50 m/s、一辊温度为81～90℃、二辊温度为126～138℃、牵伸倍数为1.3～1.5时，产品染色均匀性较好。     

830 dtex/264 f平行型ATY工艺探讨

介绍了 830dtex/ 2 6 4f平行型ATY的生产工艺 ,讨论了原丝、加工速度、变形区超喂率、芯纱皮纱的拉伸倍数和拉伸温度、压缩空气压力、给湿量、热定型工艺、卷绕超喂等工艺参数对 830dtex/ 2 6 4f平行型ATY生产运行和质量的影响     

提高PA6帘子线原丝断裂强度的探讨

讨论了影响ＰＡ６帘子线原丝断裂强度的主要因素，试验表明：提高拉伸倍数、增加纺丝速度及切片粘度均可提高原丝断裂强度。生产中，纺丝总拉伸倍数控制在５．０左右，纺丝速度２．４６～２．８０ｋｍ／ｍｉｎ，切片相对粘度约３．５１，原丝的断裂强度指标可达标，原丝质量优级品率达８５％以上     

牵伸倍数分配对PAN原丝及其碳纤维力学性能影响

通过单变量试验,并结合取向度、表面电镜等对丝束性能检测,分析了PAN原丝生产中牵伸倍数分配对原丝及其碳纤维力学性能的影响。结果表明:原丝取向度的提高,主要取决于蒸汽牵伸倍数。随着蒸汽牵伸倍数的增加,分子链取向规整性增强,原丝的取向度得到提高,原丝的整体强度就会上升,其碳纤维的强度及模量也会随之提升。     

热拉伸倍数对芳砜纶结构和性能的影响

通过应力—应变和动态力学热分析研究了热拉伸倍数对芳砜纶力学性能和动态热力学性能的影响,同时利用广角X-射线衍射(WAXD)对不同热拉伸倍数的芳砜纶的结晶度和晶区取向度进行了分析。结果表明:随着热拉伸倍数的增加,纤维的断裂强度提高,在拉伸倍数为2.6倍时,断裂强度达到3.83 cN/dtex;纤维的玻璃化较变温度随拉伸倍数的增加变化不大,而结晶度和晶区取向度则显著增加。     

以环丁砜为溶剂制备聚丙烯腈纤维的初步研究

环丁砜是一种高沸点、低毒性、强极性的环保溶剂。对以环丁砜为溶剂用干湿法制备的聚丙烯腈(PAN)纤维进行初步研究,得到了断裂强度为3.48 cN/dtex的PAN纤维。结果表明,拉伸倍数的增加使PAN纤维的结晶度结晶取向因子增加,而结晶尺寸出现先升后降的现象,纤维的断裂强度和断裂功的变化与结晶尺寸相似。合理的拉伸倍数有利于得到较好力学性能的纤维。     

聚丙烯腈原丝细旦化牵伸工艺

对通过蒸汽牵伸实现了聚丙烯腈(PAN)原丝细旦化的牵伸工艺进行了研究,结果表明:PAN原丝经致密化后再进行蒸汽牵伸,其强度、模量及取向度等显著提高,这表明致密化再牵伸工艺符合高性能原丝制备的需要。此外,还对牵伸温度、牵伸倍数、停留时间、纤维加湿及预热等条件对纤维力学性能的影响进行了研究。     

聚丙烯腈纤维热物理收缩行为的研究

利用动态力学分析、热机械分析以及X射线衍射分析等方法对聚丙烯腈(PAN)纤维在不同拉伸条件下的热物理收缩行为进行了研究。结果表明:拉伸有利于PAN纤维非晶区的取向,在热环境条件下,随着分子链运动活性的提高而生产解取向;拉伸倍数越大,PAN纤维解取向越容易发生,物理收缩量越大;沸水处理后,PAN纤维的物理收缩量随拉伸倍数的增加而减小,纤维晶态结构完善,非晶区相对含量减少。     

干纺与湿纺腈纶大丝束预氧化工艺研究

对 3 .3 3dtex民用干纺与湿纺腈纶大丝束的预氧化工艺进行了研究。结果表明 ,预氧化温度和铺丝厚度是影响纤维性能的关键因素。预氧化温度 2 60～ 2 70℃ ,每 10min升温 10℃ ,制备的干纺与湿纺腈纶预氧纤维都能达到强度 1.6～ 1.7cN/dtex ,伸长 11%～ 16% ,极限氧指数大于 40 .5 %的纺丝用预氧纤维的质量要求。     

干-喷湿纺聚丙烯腈纤维拉伸工艺研究

研究了干 -喷湿纺聚丙烯腈 (PAN)初生纤维的喷丝头拉伸比和三级拉伸 (空气拉伸、DMF浴拉伸、热水和沸水拉伸、干热拉伸 )工艺中各拉伸比对纤维性能的影响。结果表明 :提高喷丝头拉伸比可明显地降低初生纤维的线密度 ,提高强度 ;三级拉伸工艺中各拉伸比的提高均有利于PAN纤维线密度的减小及其强度、声速取向度和抗张模量的提高 ;合理调配三级拉伸中各拉伸比可制得强度超过 7.0cN/dtex的PAN纤维     

Investigating the jet stretch in the wet spinning of PAN fiber

The jet stretch of wet‐spun PAN fiber and its effects on the cross‐section shape and properties of fibers were investigated for the PAN‐DMSO‐H₂O system. Evidently, the spinning parameters, such as dope temperature, bath concentration, and bath temperature, influenced the jet stretch. Also, under uniform conditions, the postdrawing ratio changed as well as that of jet stretch. When coagulation temperature was 35°C simultaneously with bath concentration of 70%, jet stretch impacted obviously the cross‐section shapes of PAN fiber, but had little effect when the temperature was below 10°C or above 70°C. As the jet stretch ratio increased, the crystallinity, crystal size, sonic orientation, and mechanical properties of the as‐spun fiber changed rapidly to a major value for jet stretch ratio of 0.9 where the cross section of as‐spun fiber was circular. With further increasing of jet stretch ratio, the properties changed slightly but the fiber shape was not circular. The results indicated that appropriate jet stretch, under milder formation conditions in wet‐spinning, could result in the higher postdrawing ratio and circular profile of PAN fiber, which were helpful to produce round PAN precursor with minor titer and perfect properties for carbon fiber. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Investigation the jet stretch in PAN fiber dry‐jet wet spinning for PAN‐DMSO‐H2O system

The jet stretch of dry‐jet wet spun PAN fiber and its effects on the cross‐section shape of fibers were investigated for a PAN‐DMSO‐H₂O system. Clearly, the spinning parameters, such as dope temperature, bath concentration, bath temperature, and air gap, all influenced the jet stretch. Also, under uniform conditions, the postdrawing ratio as well as that of jet stretch changed. Under given conditions, as the bath temperature was below 30°C or above 45°C, jet stretch had little effect on the cross‐sectional shapes of PAN fiber. Within the temperature of 30–45°C, fiber's cross‐section shapes change obviously from round over an approximate circular shape into to an elliptical or a flat shape. The scope of jet stretch produced PAN fiber with circular cross‐section was bigger than that in wet spinning. These results indicated that appropriate air gap height, under milder formation conditions in dry‐jet wet spinning, could result in higher jet stretch and higher postdrawing ratio. The appropriate jet stretch and postdrawing ratio could result in circular profile of PAN fiber, which were helpful to produce round PAN precursor with finer size and better properties for carbon fiber. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of the drawing process on the wet spinning of polyacrylonitrile fibers in a system of dimethyl sulfoxide and water

The effect of the drawing process on the structural characteristics and mechanical properties of polyacrylonitrile (PAN) fibers was comparatively studied. The protofibers extruded from the spinneret were the initial phase of stretching, which involved the deformation of the primitive fiber with the concurrent orientation of the fibrils. Wet‐spun PAN fibers observed by scanning electron microscopy exhibited different cross‐sectional shapes as the draw ratio was varied. X‐ray diffraction results revealed that the crystalline orientation of PAN fibers increased with increasing draw ratio; these differences in the orientation behaviors were attributed to the various drawing mechanisms involved. The crystalline and amorphous orientations of the PAN fibers showed different features; at the same time, the tensile properties were strongly dependent on the draw ratio. However, the stream stretch ratio had most influence on the tensile strength and the orientation of PAN fibers for the selected process parameters. Electron spin resonance proved that the local morphology and segmental dynamics of the protofibers were due to a more heterogeneous environment caused by the sequence structure. Differential scanning calorimetry indicated that the size and shape of the exotherm and exoenergic reaction were strongly dependent on the morphology and physical changes occurring during fiber formation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1026–1037, 2007     

Investigation of post-spinning stretching process on morphological, structural, and mechanical properties of electrospun polyacrylonitrile copolymer nanofibers

Electrospun polyacrylonitrile (PAN) copolymer nanofibers with diameters of ∼0.3 μm were prepared as highly aligned bundles. The as-electrospun nanofiber bundles were then stretched in steam at ∼100 °C into 2, 3, and 4 times of the original lengths. Subsequently, characterizations and evaluations were carried out to understand morphological, structural, and mechanical properties using SEM, 2D WAXD, polarized FT−IR, DSC, and mechanical tester; and the results were compared to those of conventional PAN copolymer microfibers. The study revealed that: (1) the macromolecules in as-electrospun nanofibers were loosely oriented along fiber axes; although such an orientation was not high, a small extent of stretching could effectively improve the orientation and increase the crystallinity; (2) most of macromolecules in the crystalline phase of as-electrospun and stretched nanofibers possessed the zig-zag conformation instead of the helical conformation; and (3) the post-spinning stretching process could substantially improve mechanical properties of the nanofiber bundles. To the best of our knowledge, this study represented the first successful attempt to stretch electrospun nanofibers; and we envisioned that the highly aligned and stretched electrospun PAN copolymer nanofibers could be an innovative type of precursor for the development of continuous nano-scale carbon fibers with superior mechanical strength.