高收缩聚丙烯纤维研究 Ⅰ.纤维热收缩机理

运用Ｘ－光衍射仪、偏光显微镜及其复合测试技术，对高收缩聚丙烯纤维热处理前后超分子结构变化和纤维热收缩机理进行了研究，结果表明：高收缩聚丙烯纤维必须具有大量高取向非晶区，少量结晶区，结晶度低，晶粒尺寸小，近晶型晶胞。纤维热收缩机理是在热处理过程中，高取向的非晶区发生了大量解取向，同时伴随着结晶晶型从近晶向α晶转变，结晶度大幅度提高，晶粒尺寸成倍增长。     

高收缩聚丙烯纤维研究I.纤维热收缩机理

运用Ｘ－光衍射仪、偏光显微镜及其复合测试技术，对高收缩聚丙烯纤维热处理前后超分子结构变化和纤维热收缩机理进行了研究，结果表明：高收缩聚丙烯纤维必须具有大量高取向非晶区，少量结晶区，结晶度低，晶粒尺寸小，近晶型晶胞。纤维热收缩机理是在热处理过程中，高取向的非晶区发生了大量解取向，同时伴随着结晶晶型从近晶向α晶转变，结晶度大幅度提高，晶粒尺寸成倍增长。     

高模低缩涤纶工业丝的结构与性能比较

高模低缩(HMLS)涤纶工业丝具有弹性模量高、干热收缩小、尺寸稳定性好等优点,是子午线轮胎的重要骨架材料。本文利用同步辐射广角X射线衍射和小角X射线散射技术研究了5种HMLS涤纶工业丝的晶区结构、非晶区取向和片层散射体结构的主要差异。相比于D和E公司的产品,A,B,C公司产品的结晶度较高、晶粒体积较大,长周期较大,片层倾斜角度较小。高结晶度、高非晶区取向和较小的片层倾斜角度使HMLS涤纶工业丝表现出较高的断裂强度和较好的尺寸稳定性。     

热收缩性聚丙烯纤维的研究

研究了适于纺制高收缩聚丙烯纤维的树脂的性能特点。添加改性组分共混纺丝可以进一步提高所得纤维的热收缩性。对热收缩聚丙烯纤维的聚集态结构特点和热收缩过程中的结构变化进行了研究。结果表明 :结晶速率小的聚丙烯树脂所得纤维的热收缩率高 ,添加适当的改性剂共混纺丝得到了收缩率近 30 %的聚丙烯纤维 ;具有潜在热收缩性的聚丙烯纤维聚集态结构具有结晶度低、晶粒尺寸小、非晶区取向程度高的特点 ,热收缩过程是结晶度变大、晶粒尺寸变大、结构趋于完善的过程。     

热处理温度对高强涤纶工业丝结晶与取向性能的影响

加工过程中的热处理对纤维的聚集态结构变化具有重要的影响。采用二维X射线衍射仪研究了高强涤纶工业丝分别经过25,75,125,175,225℃温度热处理后其结晶度和晶区取向度的变化。结果表明:在较低的热处理温度区域(25～75℃),随着热处理温度升高,高强涤纶工业丝的非晶区分子链段开始活动,晶区结构变得松散,结晶度下降,进一步升高热处理温度至125℃时,纤维晶区发生重结晶现象,结晶度略微增长,而热处理温度升高至175～225℃时,纤维逐渐熔融,结晶度显著下降;随着热处理温度升高,高强涤纶工业丝(010)晶面和(100)晶面的晶区取向度降低,(-110)晶面的晶区取向度增加,但纤维的晶区总取向度随热处理温度的升高而增加,主要是由(-110)晶面的晶区取向度增加导致。     

热定形超喂率对大直径涤纶单丝结构与性能的影响

探究了在热定形过程中超喂率对大直径涤纶单丝结构与力学性能的影响。对制备的单丝进行了拉伸和热收缩性能测试,并通过广角X射线衍射、小角X射线散射及声速取向等方法对微观结构进行了表征。结果表明,随着超喂率的降低,单丝在热定形中受到的张力增大,有利于链段沿着拉伸方向排入晶格,结晶度小幅上升,而在纤维径向上的晶粒尺寸及片晶直径减小。超喂率对单丝非晶区结构影响显著,低超喂率下获得的单丝内部形成的非晶区分子链的取向程度大且含量低,导致纤维断裂强度及初始模量较大且断裂伸长低。此外,低超喂率条件下单丝纤维非晶区取向高,致使热收缩率较大。     

超拉伸UHMWPE纤维的结晶结构及其形成机理

采用冻胶纺丝-超拉伸技术纺制了超高相对分子质量聚乙烯(UHMWPE)纤维。利用小角X光散射(SAXS)、广角X射线衍射(WAXD)及拉曼光谱等测试手段,研究了拉伸过程中UHMWPE纤维的结晶结构变化。结果表明:随拉伸的进行,纤维非晶区中分子链逐渐参与了结晶,纤维SAXS强度减弱,纤维结构变得紧密规整;纤维结晶长周期及结晶度随拉伸倍数的增加而增大,并趋于平衡,拉伸30倍后,纤维结晶长周期约为50 nm,结晶度约为67.5％;纤维横向晶粒平均尺寸随拉伸倍数的增加而变小,拉伸30倍后,趋于平衡,而纤维晶粒c轴方向的轴向晶粒尺寸随拉伸倍数的增加而变大。     

热处理对聚萘二甲酸乙二酯纤维结晶和力学性能的影响

利用差示扫描量热法(DSC)、X-射线衍射(XRD)和声速取向等测试手段,研究了聚萘二甲酸乙二酯(PEN)纤维加工成为帘子线过程中要经受的高温热处理过程中的内部结构变化,并利用万能材料测试仪研究了纤维的力学性能。试验结果表明:PEN纤维在加工过程中结晶度增大;PEN纤维的α型晶粒尺寸变大,结晶结构趋于完善;纤维在热处理中取向度没有明显的变化;经过热处理后纤维力学强度提高,而断裂伸长率下降。     

国产高强高模聚乙烯纤维的初步研究

通过纤维的力学性能测试、声速取向、晶区取向、广角 X射线衍射 (WAXD)及热分析 (DSC)等测试研究了国产及进口高强高模聚乙烯纤维的结构、性能差异。结果表明 :国产高强高模聚乙烯纤维的力学性能和晶区结构与进口纤维相似 ,但其断裂伸长略偏高 ,非晶区取向偏低 ,说明国产聚乙烯纤维的拉伸倍数还可进一步提高 ,从而可以提高纤维的力学性能。     

梯度热拉伸共聚芳砜酰胺纤维的结构与性能

对共聚芳砜酰胺(PSA)初生纤维进行5级热拉伸,研究了不同拉伸级数下PSA纤维的力学性能、动态力学性能、结晶度、晶区取向度以及片晶结构的变化。结果表明:热拉伸前后的PSA纤维都在425℃左右开始发生分解,热拉伸前后纤维的玻璃化转变温度(Tg)从375℃降为365℃;随着热拉伸的进行,纤维的断裂强度逐步增大,低于Tg进行热拉伸,纤维超分子结构没有明显变化,只发生非晶区的取向;高于Tg进行热拉伸,大分子发生显著的取向和结晶,并形成片晶结构,无定型区沿轴向尺寸增大;纤维经过5级拉伸后,其断裂强度和初始模量分别提高到2.02 cN/dtex和31.88 cN/dtex。     

Insights into process–structure–property relationships of poly(ethylene terephthalate) industrial yarns by synchrotron radiation WAXD and SAXS

Synchrotron radiation wide angle X‐ray diffraction (WAXD) and small angle X‐ray scattering (SAXS) were performed to study the structures of four typical types of poly(ethylene terephthalate) (PET) industrial yarns. Three‐dimensional structural models of the yarns and comprehensive insights into the process–structure–property relationships were gained. High spinning speed, low draw ratio, and high heat‐setting temperatures lead to HMLS yarns with high crystallinity, high amorphous orientation, densely packed lamellar stacks, and a small tilting angle of crystalline lamellae. High draw ratio tends to result in PET industrial yarns with large long period and a large tilting angle of lamellae. Heat‐setting process has a significant influence on the amorphous orientation and crystalline structures, such as crystallinity, crystallite size, as well as crystal grain number. Compared with other structure characteristics, amorphous orientation plays a more important role in determining the tenacity, initial modulus, part load elongation, ultimate elongation, as well as shrinkage of PET industrial yarns. The crystal grain number seems to have an effect on the initial modulus, while the long period influences the elongation of the yarns to some extent. In addition, the small tilting angle of crystalline lamellae may relate to the dimensional stability of PET yarns. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42512.     

Creep deformation and its correspondence to the microstructure of different polyester industrial yarns at room temperature

The room temperature creep behaviors and related microstructural changes of a high‐tenacity (HT) poly(ethylene terephthalate) (PET) industrial yarn and a super‐low‐shrinkage (SLS) PET industrial yarn were investigated and compared by using wide‐angle X‐ray scattering (WAXS), small‐angle X‐ray scattering (SAXS), birefringence measurements and Fourier transform infrared spectroscopy (FTIR) in order to identify their respective underlying creep mechanisms. The crystal structure including crystalline orientation and crystallinity of fibers did not show obvious changes after the creep process, while the amorphous structures varied with creep stress. The HT yarn creep deformation was mainly elastic, and its creep recovery ratio was high. The amorphous orientation, amorphous layer thickness and degree of conformation change from gauche to trans conformers showed a slight increase. The mechanism of this slight change is that the coiled molecular chains are oriented under tensile loading and most of the extended chains are disoriented under offloading in the small amorphous region. By contrast, the SLS yarn underwent plastic creep deformation with a low recovery ratio. After the creep test, the amorphous orientation and lamellar thickness both increased but the crystallinity remained unchanged. The creep mechanism for the SLS yarn is that the molecular chains in the large amorphous domain are easily extended and oriented subjected to tensile loading, while conformation transition from gauche to trans conformers and the formation of irreversible mesophase take place. © 2018 Society of Chemical Industry     

共混纺丝制备水溶PVA纤维的结构与性能

采用聚合度为500的聚乙烯醇(PVA-0599)与聚合度为1700的聚乙烯醇(PVA-1795)进行共混纺丝,制备水溶PVA纤维,分别对其结晶度、取向度、晶面间距、晶粒尺寸、溶程和水中溶断收缩率进行了测试与表征。结果表明:随着w(PVA-0599)的增加,PVA纤维的结晶度、取向度和晶粒尺寸呈先增大后减小的趋势,而晶面间距则先减小后增大;水中溶断收缩率主要受取向度的影响,随着取向度的增加而变大,最低溶断收缩率为45%;随w(PVA-0599)的增大,纤维在高温下的溶解率变化不大,但在低温下的溶解率先升高后降低,当w(PVA-0599)为7%时,纤维的溶程最窄,为16.9℃。     

High modulus polypropylene fibers. II. Influence of fiber preparation upon structure and morphology

The influence of drawing on the limiting draw ratio upon formation of the morphological structure of fibers spun from binary polypropylene (PP) blends was studied. Fibers were spun from a fiber‐grade CR‐polymer and from the blends of a fiber‐grade CR‐polymer with a molding‐grade polymer in the composition range of 10–50 wt % added. As‐spun fibers were immediately moderately and additionally highly drawn at the temperature of 145°C. The structure and morphology of these fibers were investigated by small‐angle X‐ray scattering, wide‐angle X‐ray scattering, differential scanning calorimetry, scanning electron microscopy, density, birefringence, and sound velocity measurements. It was shown that continuously moderately drawn fibers are suitable precursors for the production of high tenacity PP fibers of very high modulus, because of so called oriented “smectic” structure present in these fibers. With drawing at elevated temperature, the initial metastable structure of low crystallinity was disrupted and a c‐axis orientation of monoclinic crystalline modification was developed. Hot drawing increased the size of crystallites and crystallinity degree, the orientation of crystalline domains, and average orientation of the macromolecular chains and resulted in extensive fibrillation and void formation. It was found that the blend composition has some influence on the structure of discontinuously highly drawn fibers. With increasing the content of the molding‐grade polymer in the blend, the size of crystalline and amorphous domains, density and crystallinity, as well as amorphous orientation decreased. Relationship has been established between the mechanical properties, crystallinity, and orientation of PP fibers. It was confirmed that by blending the fiber‐grade CR‐polymer by a small percentage of the molding‐grade polymer, maximization of elastic modulus is achieved, mainly because of higher orientation of amorphous domains. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1067–1082, 2006     

PAN分子取向程度与纤维结构性能的关系

研究了丙烯腈(AN),甲叉丁二酸(ITA)聚合体系中PAN分子取向与纤维结构、性能之间的关系。 结果表明:在一定范围内,PAN分子取向因子的增加有利于提高纤维的结晶度和(100)晶面法线方向上晶粒 尺寸,提高纤维的体积密度和力学性能。但同时增加了纤维内应力,使纤维的沸水收缩率增加。综合考虑取 向因子对纤维结构性能因素的影响,认为PAN原丝晶区取向因子约为0.9、总取向因子约为0.8时,纤维力 学性能较好。     

Structure and properties of MDO stretched polypropylene

Two polypropylene cast films of different crystalline structures (one with coexisting small rows of lamellae and spherulites and the other with only a spherulitic structure) were prepared by extrusion. The produced cast films were uniaxially hot drawn at T = 120 °C using a machine direction orientation (MDO) unit and the changes in structure and morphology were examined and related to barrier as well as tear and puncture properties. Structural changes in terms of the degree of crystallinity and crystal size distribution, orientation of the amorphous and crystalline phases, and the deformation behavior at the crystal lattice and lamellae scales were investigated using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), wide angle X-ray diffraction (WAXD), and small angle X-ray scattering (SAXS), respectively. A significant effect of the original crystal morphology on the alignment of the amorphous and crystalline phases was observed from FTIR and WAXD. The results also revealed that the deformation behavior of the crystal structure was dependent on the draw ratio (DR). Our findings showed that by increasing DR the crystal lamellae first broke up and oriented along the drawing direction and then, at large DR, they were deformed and created a fibrillar structure. Morphological pictograms illustrating the effects of original morphology and draw ratio on the stretched film microstructure are proposed. The tear resistance along the machine direction (MD) decreased significantly with increasing DR whereas the puncture resistance increased drastically. Finally, the oxygen transmission rate (OTR) of the MDO stretched films could be correlated with the orientation parameters as well as the β-relaxation peak magnitude of the amorphous tie chains.     

张力拉伸对PAN纤维热稳定化反应进程的影响

在不同拉伸条件下,对聚丙烯腈(PAN)纤维进行热处理。借助傅里叶变换红外光谱、X射线衍射等表征手段,研究了PAN纤维热稳定化过程中,拉伸张力对纤维分子链聚集态结构及化学反应的影响。结果表明:PAN纤维热处理过程中,施加张力会在一定程度上影响纤维的环化反应。当热处理温度较低(180℃)时,施加张力可抑制环化反应的发生;热处理温度较高(大于200℃)时,拉伸张力有利于环化反应的发生。热处理过程中,施加张力,对PAN纤维结晶度影响较小,晶区取向和全取向度增加,晶粒尺寸增大。这是由于拉伸与温度双重作用影响了纤维的聚集态结构,导致参与环化反应的分子数量发生变化。     

Higher-order structures and mechanical properties of stereocomplex-type poly(lactic acid) melt spun fibers

Equimolar blend of poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) was melt spun into fibers and the relations among the processing conditions, crystalline structures, thermal properties, and mechanical properties were investigated. Drawing and annealing were performed in order to obtain fiber mainly consisting of the stereocomplex crystal phase. Fibers drawn at various temperatures exhibited either amorphous, highly oriented homo crystal, or the mixture of homo and stereocomplex with a fairly low orientation depending on the drawing temperature. Annealing of the drawn fibers at an elevated temperature higher than the melting temperature of homo crystal increased the stereocomplex content significantly. The fractions of the homo and the stereocomplex crystals strongly depended on the higher-order structure of the drawn fibers and the annealing temperature.